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Università di Torino
THE TREES OF
HISTORY
Protection and exploitation
of veteran trees
Proceedings of the International Congress
Torino, Italy, April 1st-2nd, 2004
Edited by
Giovanni NICOLOTTI
University of Torino
DI.VA.P.R.A. Plant Pathology
Paolo GONTHIER
Regione Piemonte
Università di Torino
THE TREES OF HISTORY
Protection and exploitation of veteran trees
Proceedings of the International Congress
Torino, Italy, April 1st-2nd, 2004
Edited by
Giovanni NICOLOTTI
Paolo GONTHIER
ORGANIZING COMMITTEE
Prof. G. Nicolotti
Dr. M. Palenzona
Dr. P. Gonthier
Dr. R. Martinis
Dr. F. Grisoni
Dr. L. Persio
Ms. S. Ghirardi
Dr. B. Camusso
MAF Servizi (Secretary)
SCIENTIFIC COMMITTEE
Prof. G.P. Cellerino
Prof. F. Ferrini
Dr. P. Gonthier
Dr. D. Lonsdale
Prof. G. Nicolotti
Dr. D. Nowak
Dr. G. Watson
Printed by Centro Stampa - Regione Piemonte
Speakers
Torino, April 1st - 2nd, 2004
3
MONUMENTAL TREES IN HISTORICAL PARKS AND GARDENS AND MONUMENTALITY
SIGNIFICANCE
R. Caramiello1 and P. Grossoni2
1
2
Università di Torino Dipartimento di Biologia Vegetale - Torino
Università di Firenze, Dipartimento di Biologia vegetale - Firenze
Reference to trees is present in all cultures and in all ages as a cosmic symbol and one of
regeneration and resurrection and more in general of life, in its various stages: from the
biblical tree of knowledge of good and evil to that of the garden of Hesperides, from the tree
of liberty to that of fevers which summed up medical knowledge in the first half of the
eighteenth century on the fever which afflicts mankind in a wide range of diseases.
Despite these cultural values the protection of trees and woods in general has undergone
over time periods of more or less marked decline. These have been linked both to a variety
of reasons: a diminished sense of the sacred, reduced control over royal and community
forests, changes in the use of the various species, and finally, to the different importance
given to the question of the landscape.
However, the might of a tree has always caught mans attention and the species which
could more easily reach considerable dimensions or age often acquired a religious meaning or
a social role (for example, the oaks dedicated to Jupiter or Yggdrasil, the huge ash tree
which according to Germanic-Scandinavian cosmogony had given rise to the universe and
from which, after the disappearance of the world and gods, a new universe would be born or,
to cite other examples, the cypress trees linked to the cult of St. Francis, the lime trees of
mediaeval central Europe were often the place where justice was administered, etc.).
Conservation and protection in the past were therefore derived essentially from the
respect of beliefs and traditions which saw in certain trees the symbol of a guarantee,
including a supernatural one, of the daily activities of survival but which, often, were also a
fundamental moment in human activity (trees for fruit production for food and/or for
propagation, trees for shelter, trees as signs or boundary markers and so forth).
A first sign of defence of the territory and tree heritage can be found, for unified Italy, in
the forestry law of 1877 and in 1939 tree heritage was finally considered in several laws
which regarded historical and artistic heritage, at least as far as gardens and parks are
concerned and the whole aspect of panoramic beauty spots considered as natural
pictures without better defining the characteristics. In the last few decades the cultural
debate has led to the drawing up of national and regional legislation which include trees in
programmes which promote the knowledge and protection of such assets.
Furthermore, many of the trees which at present are indicated as monuments are part of
historical parks and gardens, although the practice of safeguarding and allowing trees to
grow in gardens is a relatively recent cultivation technique. In the mediaeval garden and in
formal gardens (in so-called Italian and French gardens) trees of particular size were not
envisaged (it is sufficient to read the theories of Alberti, Colonna, Serlio, Del Riccio, Ferrari
or Dezallier DArgenville, etc.) although the presence of a majestic tree could form an
unusual and striking architectural motif such as Castellos and Pratolinos oak ( una Quercia
di smisurata grandezza nella cui cima si sale per due scalle coperte dalle foglie ove sopra vi
è uno spatio di 16 braccia di circuito cinto di lochi da sedere con una tavola nel cui mezzo
sgorga un fonte chiarissimo [ ... an Oak of huge size to the top of which one can go up by
two stairways cloaked by leaves where above there is a space of 16 braccio in circumference,
about 10 m, surrounded by places to sit with a table in the middle of which gurgles the
lightest of fountains.]. AVR, Cod. Barb. lat., n. 5341, c. 210 r., 1588. In Zangheri, 1979).
For romantics, beauty is not closed in perfection: beautiful is any subject where it is
possible to read the free flow of nature and history. Thus wonder for the unusualness of a
tree (for size, shape, blossom, rarity, location, etc.) becomes a typical artifice of the
romantic garden which is amply recommended by the theoreticians of the period because it
exalts the very meaning of Nature, permanence and resistance: A tree, alone and isolated,
may be noteworthy for its own nature: it can attract attention with its immense stature,
with its fine canopy, and also with its branches, and with its leaves and fruits. The more
isolated the tree is, the less the eye is distracted However the gardener artist will not
offer too frequently a solitary tree, unless it merits particular regard (Silva, 1813).
Certainly sustained and fostered by Romantic aesthetic reasons, admiration for the unusual
tree rapidly acquires momentum, as a motif of exceptionalness, whether the tree is unusual
in itself, or in habit, in colour, in growth. In the woods of our continent, where, in certain
zones, mans action has been uninterrupted for thousands of years, the monumental tree is
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International Congress on The Trees of History
not so much one which reaches the maximum dimensions as such but rather one which, for
the reasons mentioned above, has been able to exceed the time limits (generally reduced)
which man puts on the life of trees and thus it appears to be outsize compared to the
standards of our cultural models.
It is the tree which lives longer than normal which surprises us for its dimensions and
already Horace Walpole in 1771 wrote that one does not often see a really old tree because
the sense of landscape and government inspectors are two incompatible things. Walpole
was certainly not what we would call today an angry environmentalist, so much so that
shortly later he also wrote that in a garden, at Petworth, there are several two-hundredyear-old oaks. According to him, if there is a shortcoming in such a noble, skilfully improved
fragment of nature, it is that the large size of the trees is out of proportion to shrubs and
bushes.
Factors Which Influence The Monumentality
A tree which for age, habit, size, rarity, cultural, historical or geographical value or for a
specific connection with decorative or structural features (buildings, statues, fountains,
etc.) has an intrinsic value which may be defined as a very noticeable plant (Grossoni,
2002). The monumentality of a tree brings immediately to mind the idea of exceptional
dimensions (correctly speaking, monumentality qualifies the very grandeur of a specific
monument); in this sense it is strictly connected to the definition of noticeable plant and it
refers both to specimens of species which, potentially, may reach particular values regarding
height, width of canopy and/or trunk diameter and to trees which are exceptionally outside
the norm for species which are usually of modest size. The factors which can foster a
monumental habit of a determined tree are multiple. They may be intrinsic (in the genome),
correlated to cultivation methods or to environmental conditions.
1) Genotype. Given that a tree which reaches exceptional dimensions for its species is a
clear expression of diversity, obviously the first condition is represented by the characteristics
of that determined genome. The information contained in a genome is seen not only as a
cause/effect relationship (i.e. genes that regulate a superior phenotype) but also as genes
which induce the potentiality to grow very old by determining resistance to otherwise fatal
diseases.
2) Age. It would seem obvious to state that the more a tree ages the greater it can grow
in dimensions until it reaches a monumental value. Actually cultivation practices (in the
woods) and maintenance, restoration or restructuring works (in an urban environment or in
gardens) tend to sharply reduce the life expectancy of a tree.
3) Economic value. For centuries (and, in the Mediterranean area, for thousands of
years) the woods of most of Europe (especially western Europe) have seen constant use, a
fact which necessarily has limited the life of their trees and which defines periods of growth
that are lower or much lower than their biological lifespan. The life expectancy of these
trees has always been tied to the economics of felling. There are several examples but they
regard essentially (more or less sporadic) species whose felling, until the advent of suitable
tools (chain-saws), was particularly difficult and expensive (for example, juniper, yew and
Cornelian cherry) or species whose wood is in little demand (e.g. Pinus heldreichii on Monte
Pollino) or, finally, individual trees or clusters of trees growing in areas which are difficult to
exploit (for example, the beech wood of the Riserva Integrale di Sasso Fratino in the Parco
Nazionale delle Foreste Casentinesi). Likewise, individual trees were conserved when their
products or exploitation determined an economic advantage (examples can easily be found
throughout Italy among chestnuts and oaks with edible acorns) or had a social function
(parks and hunting reserves, but also individual beeches, sycamores, cypresses or holmoaks, linked to forms of veneration or used for shelter or protection). However, it should be
pointed out that in the last few years, for both social and economic reasons, this rule of
cutting any wood has started to give way to the advantage of protectionist choices
(hydrogeological defence, conservation, etc.) Very recently the regulation for applying the
Tuscan forestry law (Regional Law n. 39/2000), sub-section 12 (point 6) orders that In all
felling operations regarding a surface area of one hectare or more, at least one tree per
hectare must be left to destine to indefinite aging for every hectare of wood cut. The
specimens to be left uncut are those with the greatest diameter present in the felling area.
(Regione Toscana, Decree of the President of the Regional Government 48/R, 08.08.03).
4) Planned historical parklands. In the specific case of historical organised green spaces
(historical gardens and green areas) the existence of monumental trees is mainly closely
linked to the kind of arboricultural cares: trees which have not undergone drastic or periodic
pruning are at a strong advantage not only for their dimensions but, above all, for their life
5
expectancy. In this context, historical botanic gardens, for their very aim of conservation,
have undoubtedly played a role in fostering the growth of trees which today have been
qualified for their monumental status.
5) Environmental factors.
(a) location: it is easier to find that an isolated tree is identified and selected as monumental
because the accentuated tapering of the trunk and the greater width and depth of the
canopy make it particularly majestic and hence more easily identifiable.
(b) site conditions (climatic and soil): obviously, environmental conditions which are
conducive to growth favour reaching advanced age and considerable dimensions. Often
isolated trees used as midday shelter for animals have enjoyed the advantage of a constant
supply of fertilizers. Neveertheless, it should be remembered that trees grown in environments
which are more favourable than the natural environment could show greater growth rates,
rapidly reaching considerable dimensions, but they are more open to attack by wood-eating
organisms (fungi and insects).
(c) site conditions (pollution): widespread pollution is a recent factor linked to
industrialisation and motor vehicle traffic. This complex factor is to be considered a negative
element which limits the growth of veteran trees and acts as a debilitating agent which
fosters the successive attack by pathogens. Moreover, the activity of certain pollutants
(greenhouse effect) is attributed as being a cause of global climate change whose negative
action is already clearly visible on many monumental (and ageing) trees.
(d) arboricultural techniques: arboricultural techniques regard especially trees in planned
historical green spaces. They can constitute an advantageous factor in the expression of
genetic potentiality but can have marked negative effects, as in the case of pruning (cfr.
point 4) and the application of fertilizers and irrigation which by extending the vegetative
period can make the trees more open to attack by pathogens. In any case, arboricultural
techniques can be advantageous for the conservation of existing veteran trees.
6) Elements for enhancing monumentality. The acquisition or enhancement of the
monumental aspect may be due also to mostly casual factors, which foster the development
of particular growth features. These are frequently due to the fusion of several trunks, to
the rooting of lower branches and to and to the emission of aerial roots.
(a) fusion of trunks: various trunks (suckers, branches or trunks growing closely together)
fuse and graft; in this way trunks of particular dimensions and shapes are created (for
example, the legendary Etnean chestnut known as the Chestnut of one hundred horses
and the Taxodium mucronatum Ten. of Santa Maria del Tule with a diameter of 12 m, etc.).
(b) rooting of drooping branches at the base: rooting of branches of lower crown leads
to the formation of a cluster of boles which can reach monumentality dimensions.
(c) aerial roots and buttressing: the emission of aerial roots and the development of
buttressed roots are features which can exalt the sense of monumentality of a tree (e.g., in
Palermo the Ficus magnolioides of Piazza Marina and of the Botanic Gardens).
Further factors which intervene in the concept of monumentality and are included in the
definition cited at the beginning of the treatise refer to cultural and historical values which,
very frequently, but not always, accompany the extraordinary dimensions and age of certain
specimens. Indeed some have a precise historical motivation that connates them as
monuments: for example, the Goethe palm in Padua, the date of planting is known (1585) as
is the origin of the name, which dates to 1786 when, almost two centuries later, Goethe
admired it and studied it, drawing inspiration for his evolutionary intuition expressed in the
essay The metamorphosis of plants. Other great trees, even in a historical garden, may
not be accompanied by such a well known written history that documents when the tree
was planted or the reason for the choice or that connects it with personalities and events.
Certainly for this reason the Corpo Forestale dello Stato (National Forestry Service - CFS)
lists that are today available, albeit rich, should be integrated with information that can
come from herbarium or archive studies conducted in Botanic Gardens and similar cultural
and historical contexts.
Monumentability And Botanical Species
It is not easy to make an analysis of the taxa to which Italian monumental trees belong
in that a general official census that is representative of our country has never been
performed. The only inventory on a national scale, decided and performed by an authoritative
and representative organisation, is that conducted by the Corpo Forestale dello Stato which
started in 1982. It is on the basis of this study that a selection was published in the early
1990s (Alessandrini et al., 1990-91) and is available on the official Corpo Forestale dello
Stato website.
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Most Italian regions have drawn up inventories for their own territories; similar initiatives
have been undertaken and implemented also by individual provinces and municipalities.
Therefore there are lists which are more or less comprehensive and more or less correct;
however, even today there is no list that is exhaustive and authoritatively reliable. In fact
the CFS inventory has given relative importance to historical urban and out of town public
green spaces. It is not even possible to complete this list using regional, provincial and
municipal lists in that the criteria of evaluation are different as the fundamental factor in the
decision of giving a tree the title monumental still remains a subjective one linked above all
to the emotion that a certain tree creates in the observer. Moreover the discriminatory
threshold between ordinariness and monumentality tends to be also in function of the
surface area of the territory in hand.
The task of our report is to examine certain aspects of the most common taxa represented
in so-called monumental trees. For this reason our starting place was the only national list
available. Actually, as the list published on the Corpo Forestale dello Stato website is more
comprehensive than that published in the two volumes by Alessandrini and co-workers
(1990-91), we refer to the web version. The inventory has covered 1255 trees belonging to
143 taxa (species, subspecies, cultivars and hybrids) belonging to 76 genera (21 Pinophyta
and 55 Magnoliophyta). Of the 143 taxa 65 are included in Italian flora and 78 are exotic.
In addition to the use, in some cases, of now obsolete nomenclature, the analysis of this
inventory brings up some justifable doubts on the correct taxonomic attribution of some of
the recognised specimens. We refer, for example, to the numerous specimens of Cedrus
libani A. Rich. (58) and Platanus orientalis L. (37) which are a little too abundant compared
to the systematically nearest taxa (Cedrus atlantica Carr. (19), C. deodara G. Don f. (22)
and especially, Platanus x acerifolia (Ait.) Willd. (3).
Quercus pubescens Willd. is the most represented species (211 records); far behind in
second place is Fagus sylvatica L, which is mentioned 98 times (the value would rise to 113
if ornamental varieties were included). There are 99 cedars but 58.6% of these are cedars
of Lebanon; among the other oaks the main species are fairly well represented (holm-oak,
with 52 specimens, sessile oak with 50, turkey oak with 43 and the pedunculate oak with
36). All native deciduous oaks amount to 346 (27.6% of the total): this is certainly linked to
the significance that these species had in the countryside as well as of course, to their
longevity and growth capacity (it is highly probable that there have been errors in taxonomic
attribution between sessile oak and downy oak). Obviously there are quite a few specimens
of plane trees and giant sequoias, while we find the presence, but not in abundance, of two
species which have a considerable importance in the coastal and hill landscapes of our
peninsula: Pinus pinea L. and Cupressus sempervirens L. (the latter is particularly linked to
episodes of devotion and religious tradition) were included in the inventory 22 and 25 times
respectively. Naturally, it is given for granted that certain species are present mainly, or
exclusively, in certain geographical areas; this is due to their chorology or to the fact that
the climatic environmental are such as to prevent or discourage their growth in other
regions. The parameters most used in defining a certain tree as monumental were undoubtedly
the dimensions (height and/or circumference); however, also age, bearing, rarity and cultural
values (historical, social, landscape) are all well represented. Not all the specimens included
in the census are necessarily of exceptional size and several species are represented by
shrubs or arborescent specimens.
In order to check what the most representative taxa were, we had used some other
inventories for comparison/confirmation purposes. As mentioned earlier, we used the inventory
of the Corpo Forestale dello Stato and, for the sake of comparison/completion, a geographically
defined sample, among the other existing lists. For the sake of simplification, we examined
some surveys made in Tuscany, the region where one of the authors lives.
In addition to the CFS inventory (Alessandrini et al., 1991), for the monumental trees of
Tuscany we consulted some surveys made by the Lucca Botanic gardens (Poli et al.; 1992),
Regione Toscana (2001) and a review made by Capodarca (2003). We then examined also
the results of a survey conducted on the territory of the province of Lucca (Giambastiani,
1996). The number of specimens included in the censuses ranged from 176 (Alessandrini et
al., 1991) to 347 (Capodarca, 2003; this author, however, also reports the results for
Tuscany of the national census). In all, 82 taxa were reported in this region; 10 other taxa
are records which have been surveyed by Giambastiani (1996) only in the province of Lucca.
Compared to the taxa identified in the CFS inventory and excluding the province of
Lucca, 37 more taxa have been reported while 7 are missing. On the same tree there are
differences between the inventories and, in some cases, also very considerable ones both
for the dimensions reported and especially for the discordant taxonomic classifications in the
7
genus but also (cfr. the case of Washingtonia/Jubaea) between genera. The distribution of
Tuscan vegetation ranges from a dry Mediterranean to a montane environment, summing
up in a certain sense most Italian forest climatic conditions. Likewise, the frequency trend
for species of monumental trees presents many similarities with the national trend: deciduous
oaks (downy oak, sessile oak, turkey oak, etc.) are the predominant species followed by
cedars, beech and chestnut. Above national average we find holm-oak, cypress and stone
pine in that these species are particularly used in this region as ornamental plants (historical
gardens, etc.), so much so that they characterise much of Tuscan landscapes.
For Piedmont the regional law which governs the census and successive protection of
monumental trees is Law 50 (1995). The Corpo Forestale dello Stato inventory cites 102
monumental trees in Piedmont, of which about twenty are highlighted as specimens of
exceptional value. The data are being updated as part of a wide-scale census and monitoring
operation throughout the region, which has brought about, as a first step, the official
baptism and inclusion in the appropriate regional list of five monumental trees: the Napoleon
Plane in Alessandria, the Mergozzo elm (VB), the Macugnaga lime (VB), the Zelkova in the
Park of Racconigi Castle (CN) and the Moncenisio ash (TO). The last two specimens have
not been cited in the previous lists. The works of the Commission are obviously continuing
and other reports will be arriving, including from the Turin Botanic Gardens, on some specimens
which so far had not been included in the census. In the Aosta Valley 10 monumental trees
have been mentioned, 4 of which particularly noteworthy. They are made up of species such
as Tilia cordata Mill. in Aosta, Picea abies Karst. at Courmayeur, Aesculus ippocastanum L.
at Donnas and Larix decidua Mill. at Morgex. On the other hand, in Liguria, where 18 trees
have been classified as monumental, there is a predominance of exotic species, introduced
into parks and gardens, including Araucaria bidwillii Hook. f. at Villa Groppallo and Jubaea
chilensis Baill. at Villa Serra in the city of Genoa and Sequoiadendron giganteum (lindl.)
Buchholz at Montoggio (GE).
The list for Lombardy reports some 192 specimens and among these we may mention, at
least for a sense of affection, that of the Scopoli Plane, planted in the Botanic Gardens of
Pavia by Giovanni Antonio Scopoli, a man of great scientific repute, who the previous year
had been appointed director of the Gardens. From a brief look at the lists of other regions,
these too need revising, one can observe that all in all species can, if left to grow freely
without the restrictions of management or maintenance, reach such dimensions that
undoubtedly many of them could be classified as monumental trees. Even if we limit our
inquiry to only native species, we could include conifers such as fir, spruce, larch, some
pines and broad-leafed trees such as all Fagaceae (with the exception of kermes oak and a
few others), elms, the nettle-tree, the sycamore maple, limes and the common ash (although
the monumentality of the last two groups is perhaps more tied to Central European culture
than to that of the Mediterranean).
Loudon (1835-39) wrote that thanks to the extreme variability of climatic conditions in
Italy every species on the planet could be grown. The claim is certainly excessive but it
gives a good idea of the possibilities of growth and development of numerous exotic species
in our country which have been able to reach dimensions which justify including them among
monumental trees. Among the Gymnospermae the genera which are most represented and
representative of the very concept of monumentality are undoubtedly Cedrus, Sequoia and
Sequoiadendron; however, we should not forget Ginkgo and Cupressus (Cupressus
semprevirens). The latter is noteworthy not only for the dimensions of certain species but
also for the landscape value which it has in certain regions and in certain climatic environments
(for example, the southern Alpine lakes). Moreover, in general we should remember some
other genera of the Cupressaceae family such as Calocedrus, Thuja and Chamaecyparis
which, although less frequently, are also present with noteworthy specimens. Albeit less
frequent, we should note Arauciariaceae and Taxodiaceae (for example, Araucaria columnaris
(Forster) Hook. and Taxodium distichum in the Reggia park in Caserta).
Tulip trees, planes, ornamental forms of beech, Ficus magnolioides Borzi, Sophora japonica
L. and Carya are exotic Magnoliophyta which can produce specimens of exceptional dimension.
For these taxa we outline some useful aspects for understanding their salient features.
References
ALESSANDRINI A., FAZZUOLI F., MITCHELL A., NIEVO S., RIGONI STERN M., BORTOLOTTI L., 1990-91 Alberi monumentali
dItalia. 2 voll. Edizioni Abete. Roma. (Lelenco completo degli alberi e la loro localizzazione sono
disponibili sul sito del Corpo Forestale dello Stato: www.corpoforestale.it/foreste&forestale/
ricerca&progetti/alberi_m/regioni.htm).
8
CAPODARCA V., 2003 Gli alberi monumentali della Toscana. Regione Toscana e Edifir. Firenze
GIAMBASTIANI M., 1996 Gli alberi monumentali della provincia di Lucca. Inventario e proposte di
conservazione. Tesi di laurea in Scienze forestali. Università di Firenze.
GROSSONI P., 2002 - Metodologie per linventario e larchivio della componente verde dei giardini storici.
In: Grossoni P. (Ed.), Metodologie di studio per i giardini storici, Quaderni dellArchivio n° 8, pp. 1117. Edizioni Don Chisciotte. San Quirico dOrcia (SI).
LOUDON J. CLAUDIUS, 1835-39 Arboretum et Fruticetum Britannicum. London.
POLI R., LIPPI A., BRACCELLI F. (EDS.), 1992 Catalogo degli alberi monumentali dellItalia centrale. I. La
Toscana. Orto Botanico comunale di Lucca & Ministero dellAmbiente. Lucca.
REGIONE TOSCANA, 2001 Elenco regionale degli alberi monumentali (aggiornamento al 8/11/2001).
Documento non pubblicato.
REGIONE TOSCANA, 2003 - Regolamento Forestale della Toscana (decreto Presidente Giunta Regionale
48/R, 08.08.03).
SILVA E., 1813 Dellarte de giardini inglesi. Tomo I. Pietro e Giuseppe Vallardi. Milano. (Nuova
edizione a cura di G. Guerci, C. Nenci e L. Scazzosi, Leo S. Olschki, Firenze,. 2002).
WALPOLE H., 1771 On modern gardening. London. (Saggio sul giardino moderno. Edizione italiana
a cura di G. Franci e E. Zago. Casa Editrice Le Lettere, Firenze, 1991).
ZANGHERI L., 1979 Pratolino. Il giardino delle meraviglie. Vol. II. Edizioni Gonnelli. Firenze
Absolute frequency and percentage of the most represented monumental trees in Italy
and Tuscany (several sources)
9
10
Comparison between various inventories referring to Tuscany and the Province of Lucca
(various sources)
1
2
in the CFS website list it is indicated as 5.65 m
this specimen is not reported in the list on the CFS website
11
EVOLUTION OF TREE LANDSCAPING IN HISTORICAL PARKS AND GARDENS
M. Devecchi
Dipartimento di Agronomia, Selvicoltura e Gestione del Territorio. Università di Torino
1.Foreword
Since the origins of history, man has developed the need to organize and mould the
surrounding space, in both amusing-recreational and utilitarian terms, transforming and
changing it in a pleasantly livable environment. A garden is a space that symbolizes Eden,
where we were born, but from which we were driven away. A garden represents the myth of
the sacred wood, i.e. of the magical place or enchanted and remote microcosm, where
everything is possible and achievable. The tree, as a primary component of the garden, has
always represented the symbol of stability and is associated with the concepts of growth,
development, protection, longevity, radication, and age. Planting a tree has always been an
act full of spiritual meaning, as it is a faithful mirror of mans existence. The big tree invites
to meditation and induces respect and wonder that turned to a deep religious feeling in
many peoples and civilizations. The garden art emerges naturally from this religious thought,
linked to the idea of creation and organization of the natural element in an anthropical
vision, i.e. in a landscape arranged according to a rational criterion. A garden has, thus, the
primacy of being the aesthetical, historical, and cultural identity of a place. Not only a
garden, but the very landscape appears as a metaphor of human deeds, that modify it
continuously following his demands and needs. Each tree, group of plants, avenue, thicket
and spontaneous hedge, as well as the heritage of urban green and country green, holds a
landscaping function of extraordinary importance. A tree characterizes, carves, and determines
the colour and often the shape of landscape. In particular, the trees of monumental interest,
as elements that participate strongly in the characterization of places, represent elements
able to resist to an increasing landscape banalisation and simplification. It is renowned
how the rural landscape even in the Piedmontese reality, has found in the trees the
characteristic features that can be referred to well identifiable plantation and exploitation
models. An example of this are, for instance, the trees around farms, the rows and single
specimens placed to mark the borders between holdings or along water courses and ditches.
Old prints or paintings are of great interest for this purpose, as they depict the landscapes
of some centuries ago, where one can see the frequency with which oaks are illustrated for
the majestic architecture of their trunk and branches. Landscape safeguard and exploitation
can be addressed also towards a field until now not sufficiently explored as that of the tree
heritage, considering the importance of such elements in the characterization of the
landscape, besides of parks and gardens. In a view that does not end only in the aestheticalperceptive consideration of landscape, another aspect of the trees of extraordinary importance
is the fact that they are the result of a whole series of environmental adaptations and of the
capacity to respond to external conditionings that make them the depositary of a remarkable
heritage of scientific knowledge.
2.The use of trees in ancient times
Under the word garden, we usually mean a piece of ground in which ornamental plants
and flowers are grown. Really, the oldest descriptions talk of a garden as a vegetable
garden, or an orchard, thus having utilitarian scopes. In the mythological imagination,
Persian paradises are enclosures and places where tame animals, that do not attack man,
are kept as signs, symbols, and memory of the old sacred wood. In the Egyptian
civilisation, the garden was conceived both as a place of relaxation and as a productive
place for growing grapevines, date palms and vegetables and so, with the typical feature of
the orchard-vegetable garden. The Egyptian garden, known through many paintings
found inside tombs, was characterized by a strictly planned design: around a rectangular
basin, or even more pools, herbaceous and shrubby plants were placed, followed by the tall
trees. Among the evidence found, remarkably important are the paintings on the walls of the
temple of Tuthmosis III at Karnak, illustrating 256 different species, that underline the
particular interest of the Egyptian culture for the study of botany. Among the most common
plants grown there are trees of productive and ornamental interest, such as palms (Phoenix
dactylifera), tamarisks (Tamerix gallica), fig trees (Ficus carica), pomegranate trees (Punica
granatum), olive trees (Olea europaea), almond trees (Prunus amigdalus) and grapevines
(Vitis vinifera). In the civilisation of ancient Greece, the garden was not considered as a
real kind of art, it was characterized instead in a functional and productive way. The old
garden of the literary tradition, handed on from the Greek world, is described in the 7th book
12
of the Odyssey, where Ulysses arrives when he approaches the town of the Phaeacians and
is hosted in the royal palace of Alcinous. It is a meticulously arranged garden, as often this
image of the Greek world is, like a mixture between garden and orchard. It is a fructiferous
place, sprayed with crystal water and decorative elements. Greek mythology refers to the
locus amoenus: a magic place where the genius loci reigns and where one searches the
harmony between man and landscape, inherent in nature. Such were the woods close to the
sanctuaries, where plane trees (Platanus orientalis), elms (Ulmus minor), alders (Alnus
glutinosa), and cypresses (C. sempervirens) are grown, as well as fruit trees. The woods in
the neighbourhoods of the towns were instead different, they were planted in regular rows.
In Athens agora, for example, in correspondence with the temple of Hephaestus, there was
a geometrical garden, in which the rows of small trees repeated the setting of the temples
columns.
The Romans had the custom to name a certain tree species to the divinities, that they
believed were born from trees or under trees, symbolizing with them their attributes; so the
oak (Quercus robur), as the expression of strength and vigour, was consecrated to Jupiter
for its majesty and superiority over the trees of the forests; the holm oak (Q. ilex) was
consecrated to Pan and with this tree the ancients forecasted the deeds of heaven (also
the Etruscans considered the holm oak divining and, with its branches shaken towards the
sky, they called for the rain to make the seed grow); the elm (U. minor) was dedicated to
Morpheus, as it invites to relax, because under its shadow sleeping is sweet; the ash tree
(Fraxinus excelsior) was linked to Mars, as it was useful to make lances; the cypress
(Cupressus sempervirens) was dedicated to Pluto and was put on the front door as a
funeral sign; the white poplar (Populus alba) was connected to the Muses and to Hercules;
the black poplar (Populus nigra) was joined to the Heliades in memory of Phaeton, their
brother; the weeping willow (Salix babylonica) was consecrated to Juno, because she was
born and brought up among these melancholy trees; and finally the laurel (Laurus nobilis)
that, as a symbol of triumph, health, cheerfulness and also safety, was dedicated to Tiberius.
In Italy at the time of the Romans there was no spring, river, famous place, and forking of a
public road that had not its sacrarium with a tree; The most solemn acts of the life of
peoples or of the individuals were made in the shade of big trees. Around certain consecrated
trees a fence was built in which not everybody could enter; the enclosed space became
sacred and the ground a religious place (AA.VV., 1990). Especially starting from the Augustan
age, the gardens in Rome reached the highest forms of artistic expression, also as a
consequence of the fact that the vegetation became architecture, through the practice of
the ars topiaria. The specialists of the ars topiaria tried to make the garden habitat lively,
operating not much with the colours, but with the shapes of the plants (Grimal, 1990). So
these were pruned in the most curious shapes and placed so as to create diverse shades of
green of the foliage of trees and shrubs (Fariello, 1967). The remaining decorativity came
from fruit trees, thanks to their abundant blossoming, such as in the peach trees, a tree
imported from Orient by Lucullus, together with local species, such as cherry and apple
trees. Fundamental is the information handed on to us by Pliny the Elder in Naturalis Historia
about the commonly used plants: oak (Q. robur), holm oak (Q. ilex), and pine (Pinus pinea)
were used in big parks; the cypress was used to make protective curtains in gardens; linden
(T. cordata), plane tree and palm were instead employed mostly in the city; laurel, box
(Buxus sempervirens), myrtle (Myrtus communis) were preferred, because easily shaped;
but there was space also for alder, oleander (Nerium oleander), ivy (Hedera helix), fruit
trees and flowers: roses (Rosa spp.), violets (Viola odorata), anemones (Anemone nemorosa),
hyacinths (Hyacinthus orientalis), and other flower species.
3. The tree in the medieval and Arab garden
In the Middle Ages, the garden called Hortus conclusus became a place of meditation
and spiritual retreat. Among the most useful literary sources for the comprehension of the
medieval garden, fundamental is the treatise of agriculture De Ruralium Commodorum,
written in 1305 by Pietro De Crescenzi, a jurist of Bologna, close to the Angevin court of
Naples. In this work one can understand how the garden, divided geometrically by beds
separated by alleys covered with pergolas, was often marked by the presence of the
Pomarium, composed of fruit trees set in rows. In the Hortus conclusus there was place
for flowers and fruits full of symbolic meanings, such as the rose, the Virgins flower, the lily,
symbol of purity and poverty; the pomegranate (P. granatum), a metaphor of the unity of
the church, and, among the trees, the palm (P. dactylifera and Chamaerops humilis),
symbol of justice, the fig tree (F. carica), a metaphor of sweetness, the olive tree (O.
europaea), symbol of mercy, and even clover (Trifolium spp.), a direct recall of the dogma
13
of trinity. In the Arab garden, water represented the main element of its composition, as it
was present in fountains, pools and canals. Among the trees, above all the cypresses (C.
sempervirens) were grown in large numbers, as they were mentioned in the Koran as
symbols of eternity and female beauty. Among the most beautiful creations of Arab gardens,
there are the Hispano-Arabic ones of Alhambra in Granada. Generalife and Alhambra are
connected by a very valuable avenue of cypresses.
4. The tree in Renaissance, Baroque, and English gardens.
In order to fully understand the different elements characterizing the garden of the
Renaissance and, consequently, the peculiar use of trees in the architectonic design, a
great importance is held by the work entitled Hypnerotomachia Poliphili, by the Dominican
Francesco Colonna (Tagliolini, 1991). It describes the love dream of Polyphilus and Polia,
transported to the island of Citera. The arrangement of the island and the setting of the
plants, strictly managed by perfect harmonical and geometrical rules and relations, constitute
the example of the garden during Humanism. The amphitheatre of Venus, placed in the
middle of the island astonishes Polyphilus, since on the top of the steps, instead of a
colonnade, like in the classical theatre, there are trees geometrized by the topiary art and
cypresses that create interlaced arches of a vague islamic taste.
The perfection of Renaissance gardens and their strong character of permanence derived
from a recurring use of evergreen trees and shrubs, such as cypresses, holm oaks, pines,
boxes, and citrus trees grown mostly in vase with an ornamental aim. A great fame was
acquired by the Garden of Hesperides where the golden pomes and the fruits bestowing
eternal youth and immortality were kept. A contribution to the cultivation of new tree and
shrub species arrived during the XVIth century from the development of botanical sciences
that led to the birth of tree and shrub collections inside botanical gardens, among which the
Garden of Pisa, founded in 1543, and that of Padua and Florence created in 1545 and 1550,
respectively. The studies of agronomy permitted to improve new short growth habits for
fruit trees, such as apple, pear and apricot trees (Pozzana, 1990). A precious witness of the
fashion prevailing at that time to prune the fruit trees in a dwarf shape is contained in the
work by the scholar Agostino del Riccio entitled Del giardino di un Re: Now I have in front
the garden of dwarf fruit trees, and one may say unmistakably that it is the pleasure of the
ladies and their young daughters, who often go into a small garden with dwarf trees for
their retreat and amusement, and they enjoy themselves indeed, especially when the small
fruit trees are full of their pomes of different kinds, and sometimes with great taste they
take them with their soft hands white like snow and pleasantly offer one to the other. None
the less pleasure has the King, when also he enters such a garden for his recreation and
walk. But in order to make these dwarf fruit trees be more desired by everyone and to
enable them to make them, I will describe them lovingly and nobody will overcome me,
unless with a good description in excellent style.
Also during the XVIIth century the scientific literature on botanical themes acquired a
remarkable importance thanks to several Authors who gave a precious contribution to the
knowledge of tree species, as in the case of the scholar Francesco Pona. The XVIIth century
garden did not abandon the axial composition ruled by geometric and mathematic principles,
but it widened, almost assuming the feature of a parkwood, joining ideally with the
surrounding land also because of the lack of a precise definition of its perimeter. The great
season of the Baroque garden had its major bloom in France after the first half of the XVIIth
century. Parterres, orchard theatres, plants reduced to geometrical shapes, and large
arboreous masses, with an evocative chromatic effect, composed the typical scenery of the
French garden (Mosser and Teyssot, 1990). Compared with the Italian one, there was a
greater presence of woods and thickets, made of medium and tall trees, with principal and
secondary avenues having a simple or double set of planting. Plant architecture achieved, in
the design of the XVIIIth century garden, a kind of micro-urbanistic complex, characterized
by a dedalus of walks and spaces, next to wide walls of green obtained with yews, cypresses
and laurels (Vercelloni, 1990). Besides such evergreen species, typical of the topiary tradition,
the French garden employed also a considerable variety of wide canopy deciduous trees,
such as hornbeams (Carpinus betulus), elms (Ulmus campestris), beeches (Fagus sylvatica),
maples (Acer campestre), lindens (Tilia cordata), plane trees (Platanus x acerifolia) and
horse chestnut trees (Aesculus hippocastanum). The palisades were created mostly with
beeches and maples, while the thickets were made mainly by oaks (Q. robur), beeches and
lindens. Box remained the shrub species preferred for the parterres.
During the XVIIIth century, the transition took place from the garden of strictness and
discipline of geometrical shapes, pertaining to the classical typology, to more various and
14
free settings, that led to the birth of the landscape garden. The trend towards an always
more romantic and open expansion of the natural element reached its highest expression in
the work of two famous landscapists, Lancelot Brown (1715-1783) and Humphrey Repton
(1752-1818). Compared with the rigid planning of arbored avenues and of symmetry axes
and with the neat definition of the garden limits, the use of tree and shrub species in more
disengaged shapes and groupings was promoted, as well as meandering and irregular walks
and the abolition of the garden margin with the aim of a total integration of it with the
surrounding landscape. In Italy, at the beginning of the XIXth century, Count Ercole Silva, an
expert botanist, revisited the Italian tradition according to the general lines of the English
school and published his renowned treatise Dellarte dei giardini inglesi: a work that influenced
considerably Italian designers during the whole century. In the course of the XIXth century
the interest towards exotic species grew remarkably; many of them were trees, that enriched
European and English gardens, in particular, with shapes and colours, thanks to the collecting
work in all explored continents by the famous plant hunters, who were active above all in
the United Kingdom.
5. The tree in town avenues and parks
After the appearance of new requests linked to the phenomenon of urban expansion
during the XIXth century, the concept of urban green established itself gradually. In the
Viennese reality, thanks to the demolishment of the walls, the rings could be built: arbored
avenues that could recreate the continuity between the historical centre and the town in
expansion. Also the city of Lucca, following the cultural models of the time, effected the
transformation of town walls from a defensive purpose to a place of walks with the vast
realization of arbored avenues. In France, thanks to Napoleon IIIrd, a broad establishment of
parks and green public areas in the towns had begun. In Paris, in particular, through the
demolition of the historical city, the great boulevards were created: arbored avenues able to
connect the greatest celebrative points of the city, planned for walking. They were composed
of two rows of trees, mostly plane trees (Platanus x acerifolia), next to a zone for pedestrians
in the middle (with kiosks and areas for music) and the route for carriages.
The realization of great parks received, furthermore, a meaningful impetus from beyond
the ocean, the most famous example of which is represented by Central Park in New York
designed by Frederick Law Olmsted, following the principle of naturalization of the city,
thanks to broad plantings of trees, aiming at a recreating a kind of urban wood. Such a
project criterion, conceived for the urban green, assumed the dignity of a real scientific
discipline in Anglosaxon countries, known as urban forestry, so to indicate that some green
areas can be proposed like oases of rurality inside urban habitats.
6. The tree in Piedmontese parks
In Piedmont the most important realizations until the middle of the XIXth century were
represented by the gardens of the royal palaces, followed by far, by size and care, by those
pertaining to villas and palaces of the nobility, influenced by court gardens and often made
by the same creators. The long season of the garden in Piedmont found an important
reference point in the two famous figures of André Le Nôtre and Michel Benard. Le Nôtre, the
celebrated designer of Vaux-le-Vicomte, Versailles, and Chantilly, was called in 1669 and
then in 1697 to give a new shape to the Savoyard gardens. The first plan, designed after a
visit to the site, was required by Savoia Carignano for the park of the castle of Racconigi
(Roggero Bardelli et al., 1990). The project drawn by Le Nôtre was characterized by a green
setting according to geometric modules in which, on a slightly degrading plain around the
castle, flower beds, grassy parterres, and water pools are displayed. At the end of the
median axis of the park, Le Nôtre placed a wide circular basin and behind it a continuous row
of trees, so to underline an arrangement of the space to infinity. Still today several of the
entrances of Piedmontese noble villas are characterized by the presence of great shady
alleys of poplars (P. nigra L.), elms or hornbeams, creating high green side walls (Accati and
Devecchi, 1996). In the middle of the XVIIIth century the French taste had settled down and
Charles Emanuel IIIrd entrusted Michel Benard with the management of the crowns gardens;
he was immediately engaged with the realization of the park of Stupinigi, inside the perimeter
already defined by Juvarra. The great axis of the entrance, as a major axis, with a strong
value in the design of the territory, permitted to join firmly the Palace to Turin. A great
importance was, In particular, the use of Lombardy poplars (Populus nigra var. Italica) was of
great importance to underline the design on the land thanks to the roads around the Palace
complex. A precious testimony of this is provided by the drawing by Ludovico Bo Pianta
15
della fabbrica da costruersi in contorno delle albere pine [] of 1779 (Mondini et al.,
2003).The diffusion of the landscaping style in Piedmont was due to Giacomo Pregliasco, a
scene painter and urbanist who started the first transformations of Racconigi since 1787,
with interesting insertions in a picturesque style. The complete transformations according to
the romantic taste of the age was accomplished by the famous German landscapist Xavier
Kurten, the author of the renewal of taste in the great number of Piedmontese gardens of
the first half of the XIXth century (Devecchi, 1999). Kurtens work had as main points the
isolated tree, shrub masses and thickets, groups of trees in circle, the lake with irregular
sides and a small island, the big lawn, the small hill, and sometimes a small temple. In his
several gardens the perspectives can be easily identified and represent the fundamental
elements of the theory of the landscape garden and of the picturesque garden fashionable
at the beginning of 1800 in Italy and in Europe. At Racconigi, thanks to Kurtens work, the
park received a remarkable enrichment of vegetation, also of trees, so to comprehend many
specimens of plane trees, maples, horse chestnut trees, birches, hornbeams, next to elms of
the Caucasus, Judas tree, liriodendron, etc. The perspective of arbored avenues and long
extents of lawns was a common feature also in Kurtens projects for the gardens of the
numerous Piedmontese noble residences, such as those of San Martino Alfieri (Accati and
Devecchi,1994; Accati et al., 1999), Sambuy, Monticello, Pralormo, Santena, Villa Il Torrione,
Sommariva Perno, Sansalvà, Castagneto Po (Salina Camerana,1994). At Pralormo, in particular,
he took the starting point from the natural scenery of the Alpine chain to propose wise cuts
between the trees so to enjoy some preferential views during the walks in the park.
The ideal route among the most representative figures who worked in Piedmont cannot
exclude the most renowned Italian landscapist of the past century: Pietro Porcinai (19101986). The modernity of Porcinais project solutions had a point of force in the attention
towards themes of ecology, in the research of a privileged relation with nature, through a
constant use of vegetation, but also of natural materials, such as wood, stone, and water
to mask the artificiality of architectonic manufacts. The simple and linear design of Porcinais
gardens found a cue also in the choice of the plant species with a preference for evergreens,
such as olive trees O. europaea, cypresses (C. sempervirens) and holm oaks (Quercus ilex).
Rhus typhina was a beloved species much used by Porcinai, who exploited the sculptorial
and sinuous aspect of its trunk and the particular projection of the canopy that always
hides possible constructive elements. In a writing by Porcinai of the 50s, starting from
correct considerations of a phytosociological kind, he confirmed the concept of harmonic
exaltation of shapes and colours of the trees: It has been discovered that when the plants
live together in full associative harmony (botanical harmony) also their habitus and their
shape express a harmonic perfection: and such a harmony involves of course also their
colour. The most perfect chromatic relations are attained, therefore, with plants that are
botanically in harmony. Porcinai understood the importance to propose gardens, not only
as places of aesthetical enjoyment of nature, but as realities where to prove the pleasure of
the knowledge of plants and the meaning of the different agronomic practices. Interesting
examples to this regard are the orchards rich of decorative elements and full of a thousand
year old agronomic culture, that were proposed on several occasions by Porcinai, such as
Villa Maggia on the hills of Turin. The fruition of gardens was encouraged by Porcinai also
thanks to decoration elements, such as a pool, a gazebo, a barbecue, and tennis and bowls
courts, included tactfully in the gardens structure, often screened with hedges of cypresses
C. sempervirens, hollies Ilex aquifolium, laurels L. nobilis, oleasters Elaeagnus pungens,
hawthorns Crataegus spp., etc., and groups of shrubs, among which, for instance,
butterbushes Pittosporum tobira, and boxes B. sempervirens (Accati e Devecchi, 2000). A
further remarkable example is represented by the garden of Cà Gianin at Trivero in the
province of Biella, that assumed, according to Porcinais and the owners idea, the meaning
of a botanical collection, where interesting tree species are required, having pleasant shapes,
colours and seasonality of blossomings. For example, besides the specimens of local or
naturalized species of that area, such as beech, sweet chestnut, and birch, a broad use of
evergreen species was made, such as Chamecyparis lawsoniana, together with different
species, sometimes poorly known, of the genera Picea, Abies, Juniperus, and Thuja. These
were planted with a great number of shrubs, above all acidophilous species, such as azaleas,
rhododendrons, Pieris, and hydrangeas, that Porcinai requested expressly, probably after
having seen them in full vigour in the Burcina Park.
7. Conclusions
Since ancient times the tree has held multiple meanings, also ritual and religious ones. Its
presence in a garden has always represented an element of capital importance for the
16
arrangement of a green area design, even if having diverse shapes and purposes. Therefore,
both plant architectures and monumental trees of a park and a garden, as they are in the
landscape, must be considered a precious historical and cultural heritage. So an always
greater attention and sensibilization of people is more and more needed as far as the
importance of safeguarding trees and defining correct management terms are concerned,
above all referring to the specimens of monumental interest, with the aim to prevent the
loss of a patrimony of exceptional value and not only naturalistic value.
References
AA.VV. (1990) Gli alberi monumentali dItalia. Edizioni Abete. Roma, 303 pagg.
Accati E., Bordone R., Devecchi M. (1999) Il giardino storico nellAstigiano e nel Monferrato. Libro,
Amministrazione Provinciale di Asti, 230 pagg.
Accati E., Devecchi M. (1994) - Alcuni giardini storici del Piemonte centro-meridionale: aspetti
vegetazionali e problematiche legate al restauro. Annali Accademia di Agricoltura di Torino, Vol.CXXXVI,
107-123.
Accati E., Devecchi M. (1996) - Evoluzione dei criteri di scelta delle specie vegetali nel giardino storico
piemontese dal XVI al XIX secolo. Atti del Convegno Vegetazione e giardino storico, Ace International,
pagg. 39 55
Accati E., Devecchi M. (2000) - ll significato e luso della vegetazione nel giardino di Porcinai. Atti del
Convegno La continuità e contiguità floristica e paesaggistica nella progettazione dei giardini.
Grugliasco, 25 maggio, 2000, pagg. 14 20.
Devecchi M. (1999) Il giardino storico nel Cuneese. Un patrimonio sconosciuto di arte e di cultura.
Provincia di Cuneo Ed., 145 pagg.
Fariello F. (1967) Architettura dei Giardini. Edizioni LAteneo, Roma, 230 pag.
Grimal P. (1990) - I giardini di Roma antica. Garzanti Ed., Milano, 518 pagg.
Mosser M. - Teyssot G. (1990) - Larchitettura dei giardini dOccidente. Dal Rinascimento al Novecento,
Electa, Milano.
Mondini G., Defabiani V., Re L., Nicolotti G., Odone P. (2003) Studio di fattibilità per la ristrutturazione
delle alberate circostanti la Palazzina di caccia di Stupinigi. Atti del Convegno Giardini storici. metodologie
per la conoscenza, strumenti operativi per la conservazione e il restauro, a cura di M. Devecchi e F.
Mazzino Roma, Consiglio Nazionale delle Ricerche, 6-7 dicembre 2000, 154 pagg.
Pozzana M. C. (1990) Il giardino dei frutti. Frutteti, orti, pomari nel giardino e nel paesaggio
toscano. Ponte alle grazie Ed., Firenze, 205 pagg.
Roggero Bardelli C., Vinardi M. G., Defabiani V. (1990) Ville Sabaude. Rusconi, Milano, 529 pagg.
Salina Camerana A. (1994) - Xavier Kurten: direttore del parco e giardini di Racconigi dal 1820. Atti
del Convegno I giardini del Principe, Racconigi,Ministero per i Beni culturali e Ambientali, 705713.
Tagliolini A. (1991) Storia del giardino italiano. Gli artisti, linvenzione, le forme dallantichità al XIX
secolo. La casa Usher, Firenze, 407 pagg.
Vercelloni V. (1990) Atlante storico dellidea del giardino europeo. Jaca Book, Milano, 207 pagg.
Fig. 1 An interesting example of the use of trees for creating avenues orienting the
views on the most valuable architectonic elements of the garden
[Sans Souci Palace Potsdam]
17
2b
2a
2c
2c
Fig.2 - The use of garden trees in an architectonic shape constitutes an element
of great value and recurrent interest in the history of garden art
[(2a) SchÖnbrunn Castle - Vienna; (2b) Het Loo Castle Apeldoorn;
(2c) Sans Souci Palace Potsdam; (2d) Hidcote Manor garden Gloucestershire]
Fig. 3 View of a XIXth century print depicting a monumental oak in the park of the Castle
of Villastellone, the monumentality of which represented at that time one of the most
important attractions of the park
4a
4b
Fig. 4 Trees represent a precious opportunity of putting colours inside a park and a
garden, coming from the foliage and, even if more transient, from the blooming
[(4a) Prunus pissardii; (4b) Liquidambar stiracyflua]
5a
5b
Fig. 5 The very wide range of shapes and architectures of tree canopies has always
been exploited by park and garden designers to evoke different and particular sensations
and moods in the observer [(5a) Fagus sylvatica cv Pendula; (5b) Salix babylonica]
18
THE TREES OF THE BOTANICAL GARDEN OF PADUA UNIVERSITY
P. Giulini
National Committee for the Historical Garden of the Ministry of Arts and Cultural Property
Introduction
The Botanical Garden of Padua (till 1591 was called Hortus Medicinalis) can boast of
being the most ancient university botanical garden in the world. It is still in the same place
and has the same functions: didactic, of research and of acclimatization of the plants, the
latter ordered by the University, just for the commercial advantages which the Republic
could derive from the botanical knowledge guaranteed by the garden.
To understand the importance of its foundation, preceded chronologically only by Matteo
Selvaticos medicinal garden of the Medical School of Salerno (Giulini, 1992) and by the one
of Pisa, we need to immerse ourselves in medieval knowledge when the Church catechized
that just God, during the creation, had granted to natural matters the capacities of treating
the body diseases, induced by those of the soul: sins. As a consequence of the Confession,
therefore, the sinners body was healed thanks to the medicinal herbs received from the
priest and had, only then, the certainty of having been absolved even in Heaven from the
sins committed.
From the threshold of the second millennium the treatment of the body and that of the
soul were progressively separated. The Padua School gravitated under the strong and
attentive leadership of the Venetian Republic and under the flag of Saint Mark, while the
power of the Church was definitely limited. As a result the Scholars, only in a very small part
Venetians, streamed into the Padua Athenaeum especially from Central Europe and from the
Balkans where for many years that contention the Church called heresy, and elsewhere
was called Reformation, had been spreading more intensely.
Next to the Tacuina sanitatis from the end of the fourteenth century the herbarium
manuscripts made by the amanuensis became more and more frequent as did the treatises
of the preparation of medicinal herbs not only in Latin after the invention of the printing
movable types. The same iconography had a strong evolution leaving more and more the
fantastic and superstitious aspects of the plants to look for, instead, the real and salient
details, to promote their identification. Thus, the time was ripe to deal with the teaching of
the simples (Lectura simplicium), that is medicaments of natural origin (prevalently vegetals)
and so called because from the union of the properties of each one, the compound was
extracted. Padua had its first professorship in 1533 with Francesco Bonafede from Padua.
He gave his lessons ex cathedra in Latin, so all the Scholars understood, despite the
different languages of provenance. However he realized how difficult it was to be able to
understand each other about the plants because already in Latin it was difficult to identify
every species with a unique European name and, above all, know what it interfered in the
absence of a sample. Therefore he sent a request to the Venetian Republic on behalf of the
Professors and Scholars to grant permission to create a Horto Medicinale near which
lessons of Ostensio simplicium could be held, taking the Scholars directly to the heart of
the subject. After a three-year wait the government of the Venetian Republic adopted the
request on 29th July 1545. By 1546 the Garden was ready for its activity, rich in vegetals
that in those times according to tradition, had healing powers. Science, however, was
already ready for the interpretation, the verification and discussion of the ancient Authors
authority.
The space destined to the garden was loaded with history and traditions both Roman and
monastic; just outside the medieval ring of walls, it was for some years surrounded in the
bastioned ring of walls. Its creation was charged to the builder Andrea Moroni from Bergamo,
who in those times was completing the most important public and religious buildings of the
Renaissance town. The project, said to be conceived even before July 1545 by Daniele
Barbaro and Pietro from Noale (Guazzo, 1546), was a summa of architectonic perfection in
the spirit of the Hortus conclusus of the medieval tradition and whose size depended only
on the available shape and space. The collaboration between the rising Garden and the
adjacent Benedictine Monastery, former owner of the land, was at the beginning so strong
that the Head typesetter of Saint Giustina was free with his advice and information.
The ligneous plants
Recently studies have been carried out on some drawings dating back to the decades
following the foundation (Terwen-Dionisius, 1994); in them the names of the plants are
19
quoted in their first position. Thanks to these lists, brought up to date in the botanical
nomenclature by Andrea Ubrizsy Savoia (1995), we can assert for sure that, already some
years after the foundation, numerous shrubby and arboreal plants, nowadays considered
autochthonous, but prevalently coming from areas commercially influenced by the Venetian
Republic, had been placed inside the Hortus conclusus. Among these: the silver fire (Abies
alba Mill.), the Italian cypress (Cupressus sempervirens L.), the maritime pine (P. pinaster
Ait.), the savin and prickly juniper (Juniperus Sabina L., end J. oxycedrus L.), the true laurel
(Laurus nobilis L.), the mulberry (more probably Morus alba L.), some oleanders (Nerium
oleander L.), the cork oak (Quercus suber L.), the wild service tree [Sorbus torminalis(L.)
Crantz], the common spindle tree (Euonymus europaeus L.), the bladdernut (Staphylea
pinnata L.), the white poplar (Populus alba L.), the golden chain (Laburnum anagyroides
Med.), the lote tree (Celtis australis L.), the chinaberry (Melia azedarch L.), the date plam
(Diospyros lutus L.), and several fruit-bearing trees as pear and plam trees (Prunus L.
sp.pl.). Few plants are not mentioned and many others, even exotic, are added in the list of
those cultivated in 1591 (Cortuso), list commented and identified according to the present
nomenclature by Elsa M. Cappelletti(1995). For instance, among the arboreous trees there
are planted out numerous conifers [Juniperus communis L., Picea abies (L.) Karst., Larix
decidua Mill., Taxus baccata L., Pinus pinea L.), the oak-trees (Quercus ilex L., Q. robur L.,
Q. macrolepis Kotschy, Q. coccifera L., Q. petraea (Matuschka) Liebl.], other poplar-trees
(Populus nigra L., P. tremula L.), the ash-trees (Fraxinus ornus L., F. excelsior L.), the
maple-trees (Acer platanoides L., A. campestre L.), the European field elm (Ulmus carpinifolia
Rupp. ex Suckow.) and other fruit-bearing trees enrich the list.
To the two lists, mentioned as the most ancient, reporting the trees planted in the
Hortus cinctus, successively 13 more followed up to 1842. From that date until 1938, there
followed other 45 indices seminum (Gola, 1947) and later 21 more from 1947 to 2004
(Botanical Gardens Library Archives). These catalogues are the list of the species whose
seeds are proposed for exchange with other botanical Institutions. However the indices
dont represent the list of all the trees growing in the Garden at a certain date, but only of
those offered for seeds exchange. For more than ten years the indices also have included
the seeds of dying out species, not only those picked up in the Garden but also in the
surrounding areas. After four centuries no trace remains of the above-mentioned shrubby
and arboreal plants. However we cant leave out two worth mentioning plants which date
back to that time. Northward, outside, but close to the boundary wall, there lived till 1984
a white-flowered, well grown-up chaste-tree (Vitex agnus-castus L.) with large foliage and
vast bloom. After 1975, unfortunately, a fungus infection to the conductive vessels little by
little made it die. The documentation which names it in 1550, the anomalous position in
which it lived and the suspected aphrodisiac properties marking this species make many
scholars conclude that this tree pre-existed the Gardens foundation and it could possibly be
a trait-dunion with the medicinal Benedictine Garden. The rests of this chaste-tree are still
preserved in stores, expecting to be shown soon.
Nowadays in the Garden, the oldest living tree is a dwarf palm or European palm-tree
[Chamaerops humilis L. var. arborescens (Pers.) Steud.] which dates back to 1585. This
palm, already bicentenary, was seen and studied by Johan Wolfgang von Goethe, during his
journey in Italy on 27th September 1786. The hypotheses obtained from this research were
published later in 1790 in Die Pflanzen Methamorphose thanks to which our palm-tree was
celebrated through the following centuries by the visit of thousands of Germans, as if going
on a cultural pilgrimage, so much so that it was no longer the dwarf palm tree of the Botanic
Garden but Goethes palm tree.
For centuries, in winter, it was protected by the movable store wooden structures in
order to avoid that this specimen, which had much grown and become historical not only
because of its age, might succumb to an exceptionally severe winter. In 1874 it was protected
by a larch greenhouse built ad hoc and replaced between 1935 and 1936 by another structure
of reinforced concrete. As the palm tree has always lived in a a favourable climate, it is still
very luxuriant and is provided with many stems, some of which are eight metres high. The
tree doesnt suffer from any pathology. Relatively nearer to us in order of time, since 1680,
outside the round enclosure, there has been living a western huge trunked largely hollowed
plane tree (Platanus orientalis L.). On the basis of a XIX century water-colour we learn that,
at the date of the picture, the trunk was still healthy and solid but had a large scar crossing
it through from top to bottom. The wound cause can be traced back to a thunder-bolt,
however a rot [Ganoderma applanatum (Fries ex Persoon) Pat.] hollowed the trunk out
within a century. In spite of the impressive cavity, the tree, regularly pruned in order to
avoid an excessive growth of its foliage and to grant a better stability, is living quite well
20
and, thanks to the treatments dating back to about 40 years of carbolineum diluted in
petroleum paintings, its infection has receded so much as not to have produced any more
fruitful bodies for almost 15 years. Two more over centenarian trees live inside the enclosure.
A male maidenhair tree (Ginkgo biloba L.) planted out near the corner of the fourth part
North west (Spaldo as it was called in old times) now called Quarto del Ginkgo dates back
to 1750. It is therefore the oldest specimen of this species still living in Europe. Half century
ago in one of its low branches was grafted a female branch which every year produces quite
a lot of fertile semen. This fragile wooded living fossil has lost for over one hundred years its
straight bole owing to the crashes caused by violent rain storms, yet its scars are quite
healthy with a large healed callus. A bull bay (Magnolia grandiflora L.) is living near the
centre of the fourth part in the South west side. Some sources date it back to 1756 while
others to 1786. Anyhow we are dealing with one of the oldest plants in Europe which, owing
to its position, has never been able to develop itself properly and has shown recently
important foliage thinness and a less flower blooming.
The radical apparatus is superficial because the soil is very heavy and asphyctic. This
very situation must be the main cause of its limited growth. It is one of the first plants in the
Garden infected by the honey fungus (Armillaria sp.) two decades ago at least. Various
areas of ceased growth and of consequent decortications such as, on the other hand,
mushroom clusters are present, late in Summer, on the infected roots. On the margins of
decorticated areas the reaction callus is always very limited, in spite of that, the whole
plant is still alive. Up to now no drastic intervention has been made partly because it is justly
believed that inside the Hortus conclusus arboreal species are not to be planted out, partly
because to cure this plant all the arrangement of the Fourth part which is entitled to this
magnolia, should be entirely upset, and thirdly because the intervention has seemed to us
to be in extremis. Outside the surrounding wall a very tall black pine (Pinus nigra Arn.)
dating back to 1772 is still perfectly luxuriant. It is the only plant still living which surely was
part of the Arboretum, conceived, carried out and corrected by Giovanni Marsili (17271795, Prefect of the Garden from 1760 to 1794). This particular Arboretum, few years later,
was largely imitated by many other Botanic Gardens. The certainty about the age of the
plant doesnt come only from XVIII and XIX cartographic documents but also from a check
through a dendrochronological study (Zennaro, 1996-97) made on numerous healthy subjects
present in the site. Again in the Arboretum context there lives a holm hoak (Quercus ilex L.)
dating back to the first lay-out.
Unfortunately an old devastating caries has transformed it into an empty trunk united to
the ground through stilts which prevents us from ascertaining its age. As to Marsilis plan it
had a short life, both because the Holm hoak was planted a order of a fixed plantation and
also owing to a terrific hail storm on August 26th, 1834 which destroyed the whole Garden
and its greenhouses [de Visiani (in Paganelli, 1995) relates that Bonato, at that time already
very old, almost died of broken heart]. Only few more competitive and strong subjects
survived and little by little they were substituted by other Prefects who come later and who
planted out new trees according to the growth size of any single species following Marsilis
specific indications: especially Giuseppe Antonio Bonato 1753-1836, Prefect between 1794
and 1835 and Roberto de Visiani 1800-1878, Prefect from 1836 to 1878.
Just from the beginning of the XXth century the Arboretum around the walled Garden has
extended and renewed itself, but above all, it has filled with new arboreous trees whose
seeds came from the Far East and America. Some deciduous plants are important for the
date of their arrival: plants such as Magnolia L., various walnut-trees as Juglans L. & Carya
Nutt, two bull bays at the entrance of the Garden which date back to 1801 and have always
exercised a great effect on visitors. Even the landscape of this vast area changes according
to the fashion of the English Garden with no longer rectilinear tracks and with the raising at
the South east edge of the Garden of a panoramic hill overlooking the surrounding gardens,
kitchen-gardens and the orchards. In 1828, close to the panoramic hill, the first deadar
[Cedrus deodara (D. Don) G. Don] was planted from seed in Europe. This date, reported in
literature, is the true one attesting the arrival of this species in Europe (Maniero, 2000). On
the western Garden edge, along the bank of Alicorno canal, near the border, a row of bald
cypress (Taxodium distichum (L.) Rich.) was planted. They are still living but have been
brutally cut on two following occasions owing to wrong interventions of the neighbouring
Jesuits (from dendrochronological researches all the trees present very deep hart rots). In
the second half of the nineteenth century, also some species of Japanese cedar (Criptomeria
japonica D. Don) and California redwood [Sequoia sempervirens (D.Don) Endl.] were planted
out. Certainly they hadnt a good growth owing to the soil nature and climate, nevertheless
this plant is still alive and thriving notwithstanding its stability problems.
21
The preservation of historical species
The preservation of species of particularly historical importance create many problems of
maintenance, especially for large plants in such a narrow space (the Garden of Padua has
had till now an area of little more than 2,2 hectares). Moreover the urban, more and more
polluted climate and the building siege all around cause serious problems during the summer
down-pours.
The exemplars bent by the wind or by crashes of fallen trees are steadily anchored to
close plants or plinths on the ground. A similar thing executed on some branches of large
size. The anchoraging grants not only an elastic support to the protected subject but also
avoids that a sudden crash may cause damages to the people working there (technicians)
and visitors. Therefore besides curative pruning on crashes and disinfection of wounds,
necessary to grant the health of our plants, we must also operate on contraction pruning
carried out with the utmost care and attention so as to lengthen these specimens lives,
which are often in a natural phase of aging but above all in an ecologically anomalous
environment as to their original climate.
Tree climbing modern technique helps us greatly especially in our space where the
extensible jibbed cranes have an overwhelming impact on the ground owing to their weight
and the scarce manoeuvrability of the cab among the foliage. Dendrosurgery is rarely used
because constant checks allow us to-day to intervene promptly on the saprophyte attacks.
In the past the use of carbolineum solved many problems, yet the results have not
always been positive in fact we have lost quite a lot of specimens, exotic for the most part,
owing to a basal stem rot (the empty spaces are not noticed by visitors, but for those who
have always worked there and lived in and for the Garden for a long time, they are and will
always be open wounds). Over ten years ago the news that a residential building, bordering
the Garden, was being built against any legal orders and breaking the low, spread far and
wide throughout the world.
For four months the surface water-bearing stratum was dried up, upsetting, in so doing,
the whole site where an underground garage 10.000 m2 large was built.
The opinions on the real responsibility of this crime for the damages caused to the
Garden are still much debated and perhaps almost impossible to demonstrate owing to timely
interventions. I myself am a strenuous supporter of the intransigent wing and believe that
the root rot which was modestly present in the past, is now the consequence to the present
hydro-derangement.
The University Committee promptly built an irrigation plant-system at their own expense.
However the going up and going down of the water are two physiologic situations quite
different if referred to plants with a physiologic precarious balance.
Since 1996 University Botanic Pathologists have planned a research with a view to
limiting the root rot diseases by removing less valuable vegetable subjects, especially those
more struck down by this illness and taking away the most infected soil and treating the rest
with fumigations. The two bull bays which stand at the entrance have been firmly anchorated
by strong supports. Their main roots have been laid bare, the soil has been substituted with
expended clay and Trichoderma sp. has been inoculated as a powerful antagonistic to
Armillaria sp. drug (Zuccoli Bergoni 2002-2003).
Conclusions
From what has been said the importance of historic tree conservation is evident. Historic
trees are the witnesses of mans life and of his landscape. Saving them depends almost
always on few experts responsibility. Destroying them has always depended on many peoples
interests and profits.
For a Botanic Garden the choice lies on the engagement to protect all subjects to
postpone their death which is unavoidable anyhow.
As to Historic Gardens, besides fighting in favour of their preservation, we must accept
the conscious choice of a renewing life because priority utterly concerns the vegetable
world as a whole.
Bibliographyy
Cappelletti E. M., 1995 Le collezioni viventi nellOrto botanico ai tempi del Cortuso. In
LOrto botanico di Padova 1545-1995" a cura di A. Minelli. Marsilio. Venezia. pp. 197-242.
Cortuso G. A., 1591 LHorto dei semplici di Padova, ove si vede. G. Porro. Venezia.
Giulini P., 1992 Quale futuro per il ritrovato Orto botanico della Scuola Medica Salernitana,
primo nella storia europea. In Pensare il Giardino a cura di P. Capone, P. Lanzara, M.
Venturi Ferriolo. Guerini, Milano. pp. 185-189.
22
Gola G., 1947 LOrto Botanico. Quattro secoli di attività (1545-1945). Liviana. Padova.
Guazzo M., 1546 Historie di tutti i fatti degni di memoria nel mondo successi dallanno
MDXXIIII sino a questo presente con molte cose novamente giunte Venezia.
Paganelli A., 1995 Giuseppe Antonio Bonato. In LOrto botanico di Padova 1545-1995" a
cura di A. Minelli. Marsilio. Venezia. pp. 97-107.
Terwen-Dionisius E. M., 1994 Date and design of the Botanical Garden of Padua. Journ. of
Garden History XIV: 213-235.
Ubrizsy Savoia A., 1995 LOrto botanico di Padova allepoca del Guilandino. LOrto botanico
di Padova 1545-1995 a cura di A. Minelli. Marsilio. Venezia. pp. 173-195.
Zennaro A., 1996-97 Indagine dendrocronologica su alberi viventi presso lOrto botanico
di Padova. Tesi di Laurea in Scienze Naturali, relatore P. Giulini. Università di Padova.
23
AGING PROCESSES IN TREES AND THEIR RELATIONSHIPS WITH DECAY FUNGI
D. Lonsdale
33 Kings Road, Alton, Hampshire UK
formerly of Forest Research - Alice Holt Research Station
Abstract
The development of physiological dysfunction within the central wood of old trees is a
major feature of the aging process, together with a tendency to become unable to maintain
a complete outer shell of functional tissues. Species-related differences in the durability of
the dysfunctional wood are of key importance in the ability of trees to live to a great age.
Due to the differing abilities of various decay fungi to colonise functional and dysfunctional
wood and to cause its degradation, the longevity of a particular tree depends partly on the
particular fungal species which colonise it.
Introduction
The developmental characteristics of a particular species play a major role in determining
its aging processes. Most tree species have an indefinite pattern of growth, as they
produce new shoots, roots and radial increments of wood and bark throughout their lives.
On the other hand, organisms with a definite growth pattern (e.g. coelomate animals)
usually have a far more limited potential for growth after reaching maturity. Thereafter, their
growth usually involves only the repair and replacement of worn out or damaged cells,
although some species may gradually increase in size throughout life. The repair of existing
body parts cannot indefinitely maintain full function, so that aging and death eventually
occur. In contrast, the ability of most tree species to form a new living outer shell in each
growing season could in theory be regarded as allowing some potential for immortality. In
practice, however, a tree tends to have a life-span which, although less pre-determined
than that of a human being, falls within a range typical of its species.
Although trees are fundamentally different to organisms with a definite growth pattern,
they share some processes of aging with them. These involve the aging of cells that
normally survive for a number of growing seasons, and perhaps also the accumulation of
errors within the genome of meristematic cells. Despite some indications that such aging
may have physiological effects on the newly formed tissue of old trees of some species,
there is no reason to believe that it limits their longevity. Instead, the main processes that
limit longevity are related to the accumulation of old, dead tissues within the tree. In
particular, the older layers of sapwood lose their water-conductivity and their parenchyma
cells eventually die. They are then described as being physiologically dysfunctional (or just
dysfunctional for short) even though they remain structurally functional.
The reasons why an increasingly large core of dysfunctional wood tends to limit the
lifespan of a tree include the following:
1. the progressive thinning and attenuation of the radial increments of new wood and bark
around a core of increasingly large girth;
2. the development of decay within the increasingly large and decay-prone dysfunctional
core of the tree, with two possible consequences: (a) the physical break-up of the tree
and/or (b) the killing of sapwood and bark by decay fungal species with an ability to
overcome the defences of functional tissues;
3. the alteration of the trees growing conditions due to its continued growth, including (a)
the depletion of mineral nutrients locked up in its wood and (2) alterations in the moisture
content and aeration of the soil beneath an increasingly large and dense rootplate.
The above three factors will now be considered. Additionally, the maintenance of functional
tissue within the main stem will be considered in relation to the retention and growth of
branches.
Change in ring width with age
During its early life, a tree colonises the space available to it, both above and below
ground (Raimbault, 1995), as determined by the environmental conditions and the trees
inherent physiological characteristics and growth potential.
During this formative or
exploratory phase, the volume of successive radial increments tends to increase, because
the crown volume and hence the photosynthetic capacity of the tree is increasing (White,
1998). Eventually, however, the crown approaches its maximum size, at which stage the
tree is regarded as having reached maturity. On this basis, White (loc. cit.) recognises
three phases in the life of a tree: formative, mature and senescent, although it should be
24
noted that the term senescence is perhaps unsuitable to describe an organism that still has
considerable vitality and thus shows re-iterative growth in between episodes dieback
(Raimbault 1995). Also, it should be noted that Raimbault (loc. cit.) has recognised a
number of intermediate stages, according to changes in the crown architecture.
The increase in diameter of the woody cylinder during the mature phase causes the
increments of new wood to become progressively narrower. This happens because the
crown of a tree reaches a maximum size in maturity and for a long period thereafter tends to
produce the same average amount of photosynthate each year, albeit with fluctuations due
to weather and defoliation events. The radial increments of new wood and bark therefore
have about the same volume in successive growing seasons, but are spread out over an
increasing girth (White, 1998).
White (loc. cit.) suggested that radial increments can continue to form, despite becoming
progressively narrower, until as many as 20 xylem increments make up one centimetre of
radial growth; i.e. the average incremental width is 0.5 mm. On the basis of Whites model,
a specimen of Quercus robur or Q. petraea, growing under the most optimal conditions
available in Britain, could theoretically maintain a complete outer shell of new sapwood and
bark until beyond the age of 4000 years (Fig. 1), by which time its stem would be almost 8
m in diameter. On the same basis, a specimen within a woodland would reach this stage at
about 1100 years of age, when its diameter would be nearly 2 m.
Although radial increments could in theory continue to form for centuries or even millennia,
it can be postulated that this process will eventually be perturbed because the increments
will become so narrow and attenuated as to have insufficient conductive and storage
capacity to maintain a full crown. It can further be postulated that a process of negative
feedback will then ensue; in other words the dieback of the crown, due to insufficient
physiological support from the vascular and storage system, leads to a reduction in the
supply of photosynthate to the cambium, which in turn leads to an acceleration in the
narrowing of new radial increments; more than would be expected purely because of the
geometrical effect of increasing girth. When a tree enters such a state, it shows
characteristics (especially episodes of dieback) which are regarded as typical of the declining
phase of its life.
Loss of continuity in the outer shell of functional tissue
Observations of ancient and veteran trees show that discontinuities eventually tend to
develop within the outer shell of living sapwood and bark. These usually take the form of
dead strips of tissue, subtended by individual branches or roots which have died back or
broken. In some cases, such strips may occupy a greater proportion of the trees girth than
the adjacent living tissue (Fig. 2). It is well known that the death, breakage or severance of
branches or roots can lead to the dieback of strips of associated cambium within the main
stem, but it is also possible that dieback could be initiated within the cambium, leading to a
situation in which a branch or root becomes deprived of a connection with new sapwood and
phloem and then declines. Although the exposure of dead tissue at the surface may
increase the rate of decay, the restriction of cambial growth to discrete strips around the
circumference of the stem may be seen as a survival strategy for a tree that can no longer
maintain a complete functional shell of sapwood and bark.
Dysfunction induced by injury
A completely intact tree has a covering of bark over its entire woody cylinder and a
covering of epidermis or other protective layers over its non-woody extremities. In practice,
virtually all trees suffer some degree of injury, which exposes the underlying tissue to an
altered environment. In particular, exposed sapwood is often subjected to desiccation and
a consequent increase in gas exchange (Boddy and Rayner 1983). In many cases, there is
also a direct severance of conductive pathways. These changes lead to a loss of physiological
function in the affected tissues, often culminating in the death of tissue within discrete
anatomical compartments (Shigo and Marx 1977). In old trees, such changes are of course
accompanied by processes of aging which may lead to dysfunction in their own right. (The
term veteran tree is sometimes used to describe a tree of any age that has survived the
vicissitudes of life, irrespective of whether it is ancient or has merely undergone much injury
or stress.)
In extreme cases, trees can become entirely dysfunctional as a result of severe injury
and thus die. This is particularly likely to happen in the case of ancient trees which, have a
very narrow and attenuated layer of functional xylem and phloem, overlying a large mass of
older dysfunctional wood. It is even more likely to happen if the tree species is one that
25
lacks a durable heartwood, since rapid fungal colonisation of the exposed dysfunctional core
can often spread to the overlying sapwood. This will be considered below in relation to the
colonisation strategies of different fungi.
Even if the entire crown of a tree is removed, this does not immediately cause the death
of tree, but it does destroy all conductive function within the entire cross-sectional area of
wood in the stem. Also the removal of foliage deprives the tree of its photosynthetic
capacity, so that there is a severe drain on carbohydrate reserves and a consequent
impairment of active processes in the formation of defensive barriers (Shigo and Marx 1977).
Also, there is much observational evidence that sapwood tends to become dysfunctional if
becomes isolated from the continuous network of living cytoplasm (the symplast) which
normally exists throughout the root and shoot systems.
As mentioned above, a tree with large, exposed areas of dysfunctional tissue can survive,
provided that its main stem retains functional strips of wood and bark. Such strips represent
living channels between the foliage and the tips of the roots and they appear to be of key
importance in the survival of ancient trees (Lonsdale 1996). Such trees may need to be
managed so as lighten a load of heavy branches that would otherwise fail and cause the
break-up these trees. In doing such work, it is recognised that living connections should be
protected, which can be achieved by retaining some of the branches. Some past attempts
to manage neglected ancient trees in Britain led to excessive wounding and hence to the
severance of all the living channels and in many cases death of the trees concerned.
The risk of ancient trees dying after major branch breakage or severance appears to be
increased by drought stress, leading to severe moisture loss from the exposed wood. Direct
heating of the stem, and perhaps also of the ground surface in the rooting zone, due to the
removal of shade appears to have a similar effect (E. Green, personal communication). On
the other hand, excessive retention of shade can inhibit the development of healthy new
shoots. The extent to which shading needs to be reduced or retained depends partly on the
tree species concerned; i.e. whether it is shade-tolerant. The local climate, the time of year
and the soil conditions are important factors in this respect.
If a tree loses most of its crown, its continued survival depends very largely on its ability
to form new branches and foliage. It has been observed in Britain that many of the trees
that have lived long enough to be considered ancient have, as individuals, a strong tendency
to produce epicormic shoots, especially in the case of Quercus robur and Q. petraea (Fig,
3). If a branch breaks or is removed, such shoots can rapidly develop into new branches,
thus maintaining physiological function within their associated parts of the main stem. It has
also been observed that individual trees of a given species differ in their ability to produce
new shoots from dormant buds (Read et al. 1996; Read 2000). Branches that have grown
slowly have more nodes per metre and hence more dormant buds. Another observation is
that adventitious buds in some species (e.g. Fraxinus excelsior) form more readily along the
torn margins of a branch break-out injury than in the vicinity of a saw cut.
When new branches grow following injury, they can continue to survive and thus to
contribute to the vitality of the tree only if they become independent of the existing tissues
before these undergo inevitable dieback and microbial attack. Once the new aerial growth is
producing enough photosynthetic material to support both root regeneration and the production
of new wood in the main stem of the pollard, the survival of the new tree is usually assured.
In some cases, trees have survived long enough to produce new growth, but this has
subsequently died back (Fig 4), perhaps because it was not linked via channels of new
tissue to the root system. Such dieback may be associated with fungal colonisation, as
discussed below. In such cases, the entire tree can die very quickly. Sometimes, however,
further shoot formation may begin lower down and thus closer to surviving roots.
Although a pollarded tree can be killed by total re-cutting of the crown, there are some
species, such as Salix spp., Tilia spp. and Taxus baccata that often produce new shoots
readily after such treatment. There are others that can also respond well, but that are more
likely to survive if at least one or two branches are retained; these include Ilex aquifolium,
Carpinus betulus and Fraxinus excelsior. Some species of oak, including Q. robur and Q.
petraea, often respond well even if most of the upper foliage-bearing branches are removed.
Dysfunction in the central part of the root system
Decay initiated below ground appears to be a common feature of all ancient trees,
whether or not they also have decay developing extensively from above-ground wounds.
The apparent seat of decay below-ground is often the region immediately under the main
stem, where there were once roots that formed early in the life of the tree. It is not entirely
clear at which stage such roots typically become dysfunctional, but the presence of decay
26
in the stem base is often not externally apparent until the tree is in the post-mature phase
of its life. Such decay can occur in younger trees, sometimes when there is a history of root
injury or disturbance. Well known examples of fungi that colonise the central rooting zone of
trees include the basidiomycetes Armillaria spp., Ganoderma spp, Meripilus giganteus,
Phaeolus schweinitzii, Sparassis crispa and the ascomycete Ustulina deusta (Lonsdale 1999;
Schwarze et al. 2000a). Extensive decay can also be caused by Inonotus dryadeus and
Grifola frondosa , both of which are particularly common on Quercus spp., but these fungi
often appear to leave enough of the lateral roots intact to ensure good stability.
The significance of sapwood and of old central wood in the survival of ancient trees
The high moisture content of functional sapwood usually provides insufficient gas exchange
for significant decay to occur. This is a form of passive defence against most decay fungi
(Boddy and Rayner, 1983). Even if dysfunction develops in sapwood due to injury or disease,
the dysfunctional zone may remain very localised within pre-existing anatomical boundaries,
such as vessel endings, or the interfaces between annual increments. The anatomy of the
wood is, therefore, an additional passive defence (Shigo and Marx 1977).
It is possible for a dysfunctional zone to become larger, due to further drying of the
wood, but this is often prevented by an active response of the sapwood, which helps to seal
off the damaged tissue. In this response, the cell lumina and inter-cellular spaces become
impregnated with substances which are produced by the parenchyma cells. These
impregnating materials may include gums, resins and suberin, as well as phenolic compounds
which inhibit fungal growth. Also, as pointed out by Shigo and Marx (loc. cit.), the new
annual increments which are laid down after the exposure of the sapwood are especially well
protected against the spread of dysfunction and decay.
The ability of sapwood to respond actively to injury and fungal invasion declines with age
because the parenchyma cells have a limited life. In some tree species, such as beech
(Fagus sylvatica), the process of cell death occurs gradually over several decades so that
the wood becomes less able to respond to fungal invasion if it happens to be exposed by a
wound. The same is true of certain other species, such as Aesculus hippocastanum and
Fraxinus excelsior, in which the heartwood is distinct from sapwood but lacks the active
defence mechanisms of sapwood. In yet other species, such as Quercus robur and Q.
petraea, however, the xylem parenchyma is programmed to die after a number of years, so
that the sapwood is converted into a distinct heartwood which contains substances that
protect it against microbial colonisation and which represents a form of passive defence.
Tree species in which the central core of dysfunctional wood is readily colonised by
decay fungi tend to live less long than species with a durable heartwood. This difference in
average lifespan is probably due in part to the tendency for extensive decay to lead to
major mechanical failure, which leads to massive exposure of wood to the atmosphere, an
accelerated rate of fungal development and in many cases death of the tree soon afterwards.
Such a sequence of events is well recognised in species such as F. sylvatica. If, however,
the central wood is a relatively durable heartwood (as in the case of Q. robur, for example),
fungal decay is often so slow that major weakening and catastrophic mechanical failure do
not occur until a very late stage, perhaps after several centuries have passed. In many
such cases failure never occurs, because it becomes less likely as the small-scale failure of
individual branches leads to a reduction in the size of the crown. Also, the radial growth of
the tree may to some extent keep pace with the development of the decay.
The role of different fungi in the death or survival of ancient trees
Species of decay fungi differ considerably in their ability to colonise and to degrade the
wood of trees (Rayner and Boddy 1988; Schwarze et al. 2000a). These differences relate
to their tolerance to or preference for particular conditions. These conditions include
moisture content, gas exchange rate, nitrogen content, and various defensive substances
including some that form physical barriers and others that are fungitoxic or fungistatic
(Pearce, 1996). The ability of a particular fungus to cope with a particular set of conditions
determines its ability to colonise functional sapwood, or dysfunctional wood which may be of
high or durability.
Sapwood pathogens tend to have a rapid invasion strategy, by which they can colonise
sapwood rapidly and extensively, but without causing decay until the wood later dries out
partially. At this early stage, they exploit easily assimilated food sources, such as sugars,
while colonising the tissues so rapidly that there is not enough time for the active defences
of the tree to halt their attack. At least some of these fungi also suppress the active
defences of the tree by secreting toxins which damage or kill the xylem parenchyma cells.
27
Such fungi are often known as fresh wound parasites or wound rot fungi, as they are
specialised invaders of living sapwood and are usually not adapted to colonise old wounds.
The most aggressive fresh wound parasites, such as Chondrostereum purpureum, are
not usually associated much with ancient trees, but there are other fungi such as Stereum
species and Bjerkandera adusta, which can colonise sapwood rapidly when it has been
rendered partially dysfunctional by wounding or disease (Lonsdale and Wainhouse 1987),
especially under desiccating conditions. The dead specimen of Carpinus betulus in Fig. 4
was colonised and probably killed by B. adusta. Another fungus that can colonise trees
desiccated by sunscorch or fire damage is Schizophyllum commune (Butin 1995).
Another strategy by which some decay fungi colonise sapwood is by spreading out from
a column of colonisation well established within the central dysfunctional wood of the tree.
Such fungi are probably more likely to limit the longevity of trees than those that remain
confined to the dysfunctional core. For example, Schwarze and Ferner (2003) have shown
that species of Ganoderma differ in their ability to colonise sapwood. They found that G.
adspersum was able to penetrate the defensive barrier separating functional from dysfunctional
wood. On the other hand, G. applanatum did not have this ability, but had a greater
potential to degrade the wood.
Within durable heartwood, only fungi with tolerance to the relatively adverse conditions,
in particular a high concentration of anti-microbial substances, can cause extensive decay.
Such fungi, such as the brown rotter Laetiporus sulphureus, tend to develop slowly, so that
ancient trees can often co-exist with them for many decades or even centuries. In this
context, one of the most benign decay fungi is probably Fistulina hepatica, which degrades
the tannins in heartwood for a long period before starting to degrade the cell walls (Schwarze
et al. 2000b).
Another important colonisation strategy by certain decay involves a latent or endophytic
establishment phase, in which no overt change occurs within the wood (Lonsdale, 1983,
1997). These fungi commonly occur throughout most of the sapwood of a wide range of
broadleaved tree species. In some cases, a genetically uniform fungal individual is present
within a strip of wood that can be several metres long (Boddy and Rayner 1981). Usually,
these fungi enter into an active decay or pathogenic phase only if the host tissues are
damaged or altered in some way, especially by desiccation. In ancient trees, fungi such as
Vuilleminia comedens and Peniophora quercina (Boddy & Rayner, 1991; 1984) frequently
develop in individual branches that have declined in vitality They can play a part in natural
pruning (Butin and Kowalski 1983), sometimes to the benefit of the tree if its crown would
otherwise remain too large to withstand strong winds. Some of these fungi, however, such
as Eutypa spinosa (Hendry 1993; Hendry et al. 1998), seem able to kill trees that have been
stressed. The type of wood degradation caused by a particular fungal species is another
factor in the ability of ancient trees to survive, as some kinds of decay are more likely than
others to weaken the wood (Schwarze et al. 1997). The main distinction is between brittle
decay and non-brittle decay, but there are many types of decay with intermediate mechanical
properties. Brown rot fungi, such as Laetiporus sulphureus, produce a brittle decay because
they degrade the rope like cellulose component of the wood, leaving the cement like lignin
almost intact. In contrast, fungi that cause a selective white rot degrade the lignin
preferentially, so that the wood retains some of its tensile strength, but loses its stiffness.
In some extreme cases, species of Ganoderma leave so much of the cellulose unaltered that
the wood can be bent like a rope, without breaking.
A relatively brittle decay can be produced by other kinds of white rot (simultaneous
white rot), in which the cellulose and lignin are degraded at about the same rate. The decay
produced by Fomes fomentarius is of this type. Eventually, either a selective or a simultaneous
white rot sometimes progresses to the complete destruction of the wood, so that a cavity is
formed. A relatively brittle kind of decay can also result from a form of rot in which the
fungal hyphae tunnel within the cell walls, degrading the cellulose microfibrils as in a soft rot.
This mode of degradation, known mainly in timber, is now known to be induced by a wide
range of tree decay fungi, such as Inonotus hispidus, (Schwarze et al. 1995), a species
commonly found in old specimens of Fraxinus excelsior, which also cause white rots, and in
a few cases brown rots (Schwarze et al. 2000a).
Alteration of the trees growing conditions due to its continued growth
The idea that trees alter their own growing conditions as they grow larger is perhaps
based more on observation and on theoretical assumptions, rather than on rigorous data.
As far as soil moisture and aeration are concerned, one observation is that signs of anaerobic
conditions, shown by the presence of a bluish colouration, are sometimes found in the soil
28
underneath the central zones of the rootplates of uprooted trees. Such colouration underneath
rootplates can be expected to occur in waterlogged or compacted soils, but it is sometimes
found in light, open-textured soils. It seems possible that, through respiration of roots
themselves, or of organisms colonising them, oxygen can become locally depleted. Whether
this is a factor in the eventual death of roots directly beneath the stem of a large tree is
uncertain. As mentioned above, this pattern of death appears to be important in the
development of below-ground decay in ancient trees.
Mineral nutrients such as potassium are clearly sequestrated within the wood of a large
tree, but it is not clear whether this process commonly results in a deficiency for the tree
itself. The decay process releases nutrients and is therefore likely to be of nutritional
benefit to the tree. In many cases, a hollow tree develops adventitious roots within its own
cavity, so that it can directly re-absorb nutrients that were previously locked up within its
dysfunctional core.
Conclusions
The aging of trees is often compared to that of humans and other animals, and there are
indeed some analogies that can be recognised. However, there are fundamental differences
due to the manner in which trees can continue to grow and to the microbial exploitation of
their accumulated dead tissue.
References
Boddy, L. & Rayner, A.D.M. (1981). Fungal communities and formation of heartwood wings in
attached oak branches undergoing decay. Annals of Botany 47, 271 274.
Boddy L. & Rayner A.D.M. (1983). Origins of Decay in Living Deciduous Trees: The Role of Moisture
Content and Re Appraisal of the Expanded Concept of Tree Decay. New Phytologist 94, 623 641.
Boddy, L. and Rayner A.D.M., (1984). Internal spread of fungi inoculated into attached oak
branches. New Phytologist 98, 155-164.
Butin, H. (1995). Tree diseases and disorders. (D. Lonsdale, R.G. Strouts., eds.), Oxford University
Press, Oxford, UK, 252 pp.
Butin, H., and T. Kowalski 1983. Die natürliche Astreinigung und ihre biologischen Voraussetzungen
I. Die Pilzflora der Stieleiche (Quercus robur L.). European Journal of Forest Pathology 13, 428 439.
Hendry, S.J. (1993). Strip cankering in relation to the ecology of Xylariaceae and Diatrypaceae in
beech (Fagus sylvatica L.) PhD Thesis, University of Wales, Cardiff, UK.
Hendry, S.J., Lonsdale, D. & Boddy, L. (1998). Strip-cankering of beech (Fagus sylvatica): pathology
and distribution of symptomatic trees. New Phytologist 140, 549-565.
Lonsdale, D. (1983). Some aspects of the pathology of environmentally stressed trees.
International Dendrology Society Yearbook 1982, 90-97.
Lonsdale, D. (1996). Pollarding success or failure; some principles to consider. In: Pollard and
Veteran Tree Management II, ed. H. Read, City of London Corporation, 100-104.
Lonsdale, D. (1997). Das Zersetzungspotential verschiedener holzabbauender Pilze in Bäumen.
Proc., Osnabrücker Baumpflegetage, Germany, 2-3 Sept., 1997 XI 12-22.
Lonsdale, D. (1999). Principles of tree hazard assessment and management. Research for Amenity
Trees No. 7, The Stationery Office, London, 388 pp.
Lonsdale, D. & Wainhouse, D. (1987). Beech bark disease. Forestry Commission Bulletin 69, 15
pp.
Pearce, R.B. (1996) Antimicrobial defences in the wood of living trees. (Tansley Review No. 87)
New Phytologist 132, 203 233.
Raimbault, P. (1995). Physiological diagnosis. In: The tree in its various states: diagnosis and
architectural training. Proc. Second European Congress of Arboriculture, Versailles, Sept. 1995.
Rayner, A.D.M and Boddy, L. (1988). Fungal decomposition of wood; its biology and ecology. Wiley,
587 pp.
Read, H. (2000). Veteran Trees: A guide to good management. English Nature, Peterborough UK.
Read, H.J., Frater, M. & Turney, I.S. (1996). Pollarding in Burnham Beeches, Bucks.: a historical
review and notes on recent work. In: Pollard and veteran tree management, 2nd edn, H.J. Read
(ed)., Proc. meeting, Corporation of London, Burnham Beeches, Bucks, March 1991.
Schwarze, F.W.M.R. Lonsdale, D. & Fink, S. (1995). Soft rot and multiple T-branching by the
basidiomycete Inonotus hispidus in ash and London plane. Mycological Research 99, 813-820.
Schwarze, F.W.M.R., Lonsdale D. & Fink, S. (1997). An overview of wood degradation patterns
and their implications for tree hazard assessment. Journal of Arboriculture 21, 1-32.
Schwarze, F.W.M.R., Engels, J. and Mattheck, C. (2000a). Fungal strategies of wood decay in trees.
Springer, 185 pp.
Schwarze, F.W.M.R, Baum, S. and Fink, S. (2000b). Dual modes of degradation by Fistulina
hepatica in xylem cell walls of Quercus robur. Mycological Research 104, 846-852.
Schwarze, F.W.M.R and Ferner, D. (2003). Ganoderma on trees: differentiation of species and
studies of invasiveness. Arboricultural Journal 27,
Shigo, A.L. & Marx, H.G. (1977). Compartmentalization of decay in trees. Forest Service USDA
Agriculture Information Bulletin No. 405, 73pp.
White, J. (1998). Estimating the age of large and veteran trees in Britain. Forestry Practice
Information Note FCIN 12.
Fig. 1
Fig. 2 Veteran Castanea sativa with one strip of functional stem tissue
29
30
Fig. 3 Ancient Quercus robur with abundant epicormic growth
Fig. 4 Ancient pollard of Carpinus betulus with dieback of new twigs that formed
after severe cutting
31
NEW ENTOMOLOGICAL ASPECTS AND STRATEGIES OF LOW ENVIRONMENTAL IMPACT
A. Alma
Di.Va.P.R.A. Entomologia e Zoologia applicate allAmbiente Carlo Vidano, Università degli Studi di
Torino - Grugliasco (TO), Italy
Broadleaf and coniferous trees are often attacked by different pests, that cause direct
and indirect damage and, in the most serious cases, may compromise irreversibly the plants
functionality. The most common and dangerous infestations are due to leaf-eating moths,
beetles and wasps, to wood-eating moths and beetles, and to plant-sucking bugs.
Indigenous species
Among the plenty dangerous indigenous species, one can remember the processionary
moths Thaumetopoea processionea (L.) and Traumatocampa pityocampa (Denis &
Schiffermüller) and the bark beetles, in particular Scolytus multistriatus (Marsham).
Thaumetopoea processionea and Traumatocampa pityocampa. They have very hairy
larvae, characterized above all by the presence of a lot of stinging hairs. These hairs, very
thin and small, detach easily from the body of the larvae and spread on the plants and in the
surrounding area. Such hairs may cause skin irritations and serious damage to vertebrates,
including man; especially when they affect the eyes or the respiratory mucose.
The larvae, normally hide inside silk nests. As they are gregarious, when they get out of
their shelters in search of food or of a place where to pupate, they move in long rows. For
this peculiar behaviour they are called with the common name of processionary moths.
Th. processionea lives on different species of deciduous oaks. It overwinters as eggs laid
in groups of 200-300 elements, protected by abdominal hairs on the bark of trunks and
branches. The gregarious and nocturnal larvae attack at first the younger leaves and on the
higher part of the canopy, then they feed on the lower part. At the beginning of July the
larvae reach maturity and spin a silk cocoon mixed with hairs and pupate inside the nest or
at the base of the infested plants. The adults emerge in August and after some days
copulate and lay the overwintering eggs.
T. pityocampa commonly known as the pine processionary moth attacks different species
of the genera Pinus and Cedrus. The infested pines are more or less defoliated according to
the density of nests and are proner to the attacks of xilophagous insects. This moth
accomplishes one generation a year. The adults are on the wing in July; the female lays the
eggs around a couple of needles so to form a sleeve completely covered by abdominal
scales. The larvae hatch at mid August and begin to feed on the needles near the egg
cluster; then they erode the needles at the end of the branches after having covered them
with silk threads. At the beginning of autumn they build a compact nest suitable to contain
the overwintering larvae inside. In the following spring, as soon as they reach maturity, the
larvae move in a procession to the ground, where they reach a sunny and dry site and bury
themselves and then spin a cocoon in which they remain in diapause and afterwards they
complete their metamorphosis. When the environmental conditions are not favourable the
diapause lasts until the summer after.
The two defoliating moths must be controlled in the larval stage. The interventions are
necessary above all in sites visited by people, so to prevent the considerable trouble caused
by the larval stinging hairs. As an alternative to the use of synthetic insecticides, one may
employ commercial formulations based on Bacillus thuringiensis Berliner variety kurstaki. This
product is particularly efficacious against young larvae (1st and 2nd instars). In the case of
initial infestations and whenever the size of the trees enables it, one can carry out a manual
collection of the nests by cutting the branches bearing them. Against T. pityocampa, the
control is compulsory (DM 17-04-1998) if the presence of this insect menaces seriously the
production or the survival of the trees or represents a risk for human and animal health.
Scolytus multistriatus. This bark beetle is common and present in all Italy. It has
settled and spread in all North America. It lives almost exclusively on elms and is the most
important spreader of the fungus Ophiostoma ulmi (Schwarz) Nannfeld the agent of the
disease called Dutch elm disease. The spores of the fungus are transported by the adults
inside the feeding galleries dug at the base of gems and twigs of healthy elm trees. S.
multistriatus overwinters in the larval stage inside galleries dug in branches and trunk. In
spring the newly emerged adults dig feeding galleries and then the females lay the eggs in
galleries dug in the bark. The larvae dig individual galleries until they reach the bark and the
sapwood. At the end of summer the new adults are on the wing and give birth to a second
generation.
32
Presently there is no perspective to refrain the infestations of this insect and of the
disease caused by the fungus; until now no resistant strains of elms have appeared. The
only kind of control is prevention, trying to keep the plants in optimal vegetative conditions,
effecting, if necessary and possible, also recovery irrigations during the hottest period of
summer. Moreover, it is useful to avoid increasing the bark beetles populations by felling and
destroying the suffering and infested trees. The synthetic aggregating pheromone is more
useful for phenologic surveys than for efficient adult mass capture strategies.
New entomological problems
Besides the number of problems caused by the activity of the different local pests, with
a higher frequency, almost daily, new entomological emergencies have to be faced, due to
the incidental introduction of exotic species and in some cases to the sudden and unexpected
aggressivity of species that were before indifferent and poorly known. Of the different
species reported by several authors, here I consider those that cause the most relevant
problems or that are held as potentially dangerous and therefore need the establishment of
adequate defense strategies for the safeguard of the infested plants (tab. 1).
Table 1. List of the species causing new entomological problems in Italy.
Corythucha ciliata. This Northamerican bug has become the most common insect of
plane trees. It was found for the first time in Italy and spread to different countries of south
Europe, France and Spain; central Europe, Switzerland, Germany, and Austria; east Europe,
Hungary, Rumania, Czech Republic, Slovakia, and Bulgary. The adults that overwintered
beneath the bark of the trunk migrate in spring to the foliage and feed on young apical
leaves. Young and adults live on the lower leaf page and feed sucking the cytoplasmic
contents of the palisade and spongy layer cells. Along the year from two to three generations
are completed; at the beginning of autumn the adults move to the trunks for overwintering.
In summer the leaves appear completely depigmented and assume a yellowish colour. Much
more serious than the aesthetic effect is the physiological damage that is caused to the
plant; such problems affect the general vegetative state of the plant and in the most
serious cases may reduce the wood growth.
The defense from C. ciliata is very difficult. In spite of a great number of local predators
that adapted themselves to the exotic species, their action proved to be insufficient in
refraining efficiently the infestations. On big trees a control of the pest by chemical treatments
is badly effectable, keeping in consideration the volume of the canopy. Good results may be
obtained by trunk injections (endotherapic method) of formulations registered for this use.
Corythucha arcuata. This new species of the genus Corythucha was recorded for the
first time in Europe in 2000 during entomological samplings in a park in the outskirts of Milan.
C. arcuata is widespread in Northamerica and in particular in southeast Canada. In its area
of origin, this insect lives mostly on different species of the genus Quercus and on Castanea
americana; occasionally it was found also on apple and maple. In Italy it was observed
33
especially on Q. robur and less on Q. pubescens and Q. petrea. This insect overwinters in
the adult stage and in spring, towards the middle of the month of May, the females lay eggs
between the secondary veins of the leaves. The first adults appear towards the middle of
June; in one year C. arcuata accomplishes three generations. The trophic activity of young
and adults provokes the appearance of obvious depigmented areas on the leaves; in the
case of strong infestations there is an early leaf fall at end summer.
In USA, in particular on strongly infested ornamental oaks, chemical treatments were
carried out, above all to control the first generation of this pest. It is therefore possible to
infer that C. arcuata, as it already happened for the congeneric C. ciliata, monophagous on
plane, could rapidly spread and cause even strong infestations on oaks, not only in woods,
but also in reforestations and in urban green.
Illinoia liriodendri. This aphid, recorded until now in Northamerica and Japan, was found
for the first time in Europe in parks of north Italy on plants of Liriodendron tulipifera. This
species colonized exclusively L. tulipifera; the infested plants are easily identifiable by the
shiny leaves covered with abundant honeydew produced by the aphid. The infestation
begins with the colonization of the lower leaf page, but soon, as the colony grows, also the
upper page is used. The introduction into Europe of this new Nearctic aphid will cause
remarkable problems for the use of L. tulipifera, until now widely employed in the realization
of parks, gardens, and avenues, since it was without pests. In fact, the abundant honeydew
produced by the aphid dirties the underlying surfaces and makes them unenjoyable by the
public. The strongly infested plants go through a partial leaf fall.
A biological control could be effected by local natural enemies that gradually adapt
themselves to the new aphid, thus creating a new biocoenotic complex.
Cameraria ohridella. This moth was described for the first time in 1986 in the Republic
of Macedonia; in Italy it was recorded in 1992. This leaf miner spread with a surprising speed
and with so high population densities as to cause early leaf fall already at end July on
Aesculus hippocastanum trees. The white flowered horse chestnut proved to be more
susceptible to the infestations of this pest. C. ohridella overwinters in the pupal stage inside
the fallen leaves. In spring the females lay isolated eggs on the upper leaf page. The larva
digs a mine in which it pupates at maturity. This moth carries out four generations in one
year; the first damage to the plants can be observed with considerable populations in
correspondence with the development of the second generation. Besides the summer leaf
fall, in case of heavy infestations there can be a reshooting and reblooming in late summer.
The technique of collecting and eliminating the fallen leaves that host the overwintering
chrysalids in the mines, even if it represents a control measure by reducing the initial
population in spring of the new year, does not refrain this leaf miner in a sufficient way. The
same applies for the action of local parasitoids that, though they show a satisfying capacity
of adaptation, as well as it happened in other countries affected by this phytopathological
problem, at present they do not appear able to control efficiently this pest.
Currently, chemical defense with the use of registered phytosanitary products is the only
means available to try to control C. ohridella infestations. Foliar treatments have remarkable
execution difficulties, as the trees are of great size and often placed in towns. Therefore, in
order to avoid consequent sanitary problems connected with the dispersal of pesticides in
the environment, the attention was drawn on endotherapy. Endotherapic treatments can be
applied by means of natural absorption or with pressure. The regular translocation of the
insecticide, necessary to assure the efficacy of the treatment, is conditioned by abiotic
factors (temperature, RH) and above all by the sanitary state of the treated plant.
Hyphantria cunea. This moth of Northamerican origin was found in Italy in 1980. It is
polyphagous, living on broadleaf trees, preferring mulberry, maple and walnut. The larvae
feed on leaves that are enveloped in a silk canvas and eroded at first on the lower page,
then they are entirely skeletonized. Normally there are two generations a year, in years or
areas with a milder autumn, there can be the beginning of a third generation. Overwintering
is in the pupal stage, sheltered in cracks of the trunk and of main branches. When the moth
appears with heavy infestations the plants are completely covered with silk and defoliated.
In the zones that have been recently colonized, the control of infestations can be made
eliminating the first infestations, as much as possible, by cutting and destroying the branches
attacked by the larvae. Localized insecticide interventions or treatments on the whole
canopy must be carried out on the young larvae, employing preferably formulates based on
B. thuringiensis variety kurstaki.
Anoplophora malasiaca. This cerambycid of Oriental origin, spread in Japan, Korea, and
Taiwan, was reported for the first time in Europe in 2001 from plant material imported into
north Italy. It is xylophagous and polyphagous and feeds on 50 species of broadleaf trees. In
34
the area of origin its biological cycle lasts one or two years, according to when the eggs are
laid. The adults emerge in June; females feed on young leaves and twigs. Eggs are laid singly
under the bark at the base of the trunk. The larvae dig galleries and feed on phloem and
xylem tissues, weakening the plant and leading it to death. Among the many plants attacked
by this cerambycid in Italy, there are: Acer saccharinum, Aesculus hyppocastanum, Carpinus
betulus, Fagus sylvatica, Platanus acerifolia and Quercus robur.
Very probably, this new pest, favoured also by its high polyphagy, will represent a new
problem for broadleaf tree management. In the attempt to control A. malasiaca biologically,
research has begun to identify parasitoids and predators of this oriental cerambycid.
Dryocosmus kuriphilus. It is a gall wasp of Chinese origin living on Castanea spp.,
introduced into Japan in 1941, into South Korea in 1961, and into USA in 1974; it was
recorded in Italy in 2002. This species carries out one generation a year, at the beginning of
summer the females lay the eggs inside the gems. First instar larvae overwinter without
showing any obvious alterations on the gems. At vegetative recovery, galls grow at the
expense of the shoots and compromise the plants development with a consequent decrease
of fructification and vigour, in the case of repeated attacks the plant may die. This gall wasp
spreads by means of the trade of infested shoots or scions and the flight of females.
Pruning and destroying infested shoots may slow down the diffusion of this pest. Keeping
in mind the inefficacy of insecticide treatments, in Japan this wasp was controlled biologically
by introducing its specific parasitoid Torymus sinensis Kamijo from China. Considering the
good results obtained in Japan in 2003, at less than one year from the first record of the
exotic pest, a biologic control plan has been set up for the introduction of T. sinensis in
Italy. From parasitized D. kuriphilus galls coming from Japan a first nucleus of parasitoids was
reared in the laboratory in Italy. In the current year, after further studies on the parasitoids
population, the opportunity to spread T. sinensis in the field will be evaluated. The expected
results are a slow establishment of the parasitoid followed by a rapid decline of the gall wasp
populations until the reaching of a biological balance, as it happened in Japan during a period
of about five years.
As it can be seen, the new entomological emergences, almost always due to exotic
insects introduced incidentally, have been growing constantly and worryingly in the last
years. The continuous alarm points out on the one hand the difficulties encountered by the
institutions in charge of carrying out a punctual and serious check of the biological material
imported and on the other hand obliges the researchers to find out endlessly control strategies
able to refrain efficiently the new pests without causing repercussions on local biocoenoses
and on the environment as a whole. Therefore, whenever possible, it is convenient to
employ selective synthetic insecticides, natural insecticides, entomopathogenic microrganisms,
and biologic control projects by introducing exotic natural enemies, coming from the same
places considered originary of the pest to be controlled, so to reach, usually in a medium or
long term, a lasting containment of the pest.
Essential references
Bernardinelli I., Zandigiacomo P. (2000) - Prima segnalazione di Corythucha arcuata (Say)
(Heteroptera, Tingidae) in Europa. Inftore Fitopatol. 12, 47-49.
Brussino G., Bosio G., Baudino M., Giordano R., Ramello F., Melika G. (2002) Pericoloso insetto
esotico per il castagno europeo. LInformatore Agrario 37, 59-61.
Clabassi I., Tomè A. (2000) Tecniche endoterapiche su ippocastano contro Cameraria ohridella.
LInformatore Agrario 33, 88-91.
Colombo M., Limonta L. (2001) Anoplophora malasiaca Thomson (Coleoptera Cerambycidae
Lamiinae Lamiini) in Europe. Boll. Zool. agr. Bachic. Ser. II, 33 (1), 65-68.
Grabenweger G., Lethmayer C. (1999) Occurence and phenology of parasitic Chalcidoidea on
the horse chestnut leafminer, Cameraria ohridella Deschka & Dimic (Lep., Gracillariidae). J. Appl.
Ent. 123, 257-260.
Moriya S., Inoue K., Otake A., Shiga M., Mabuchi M. (1989) Decline of the chestnut gall wasp
population Dryocosmus kuriphilus Yatsumatsu (Hymenoptera: Cynipidae) after the establishment
of Torymus sinensis Kamijo (Hymenoptera: Torymidae). Applied Entomology and Zoology 24, 231233.
Limonta L. (2001) Una forte infestazione di Illinoia liriodendri (Monell) (Rhynchota Aphididae)
nei parchi del Nord Italia. Boll. Zool. agr. Bachic. Ser. II, 33 (2), 133-136.
Pollini A., Angelini R. (2001) I nemici delle piante ornamentali. Ed. LInformatore Agrario, Milano,
183 pp.
35
CAN VETERAN TREES BE STIMULATED BY MYCORRHIZAL FUNGI?
S. Egli
Swiss Federal Institute for Forest, Snow and Landscape Research WSL, CH-8903 Birmensdorf,
Switzerland
1. Introduction
What are mycorrhizal fungi and mycorrhizas
The roots of almost all vascular plant species are known to form mutualistic symbioses
with a certain group of fungi, so called mycorrhizal fungi. The colonized roots are termed
mycorrhizas (fungus roots, from the Greek: mykes = mushroom or fungus and rhiza =
root). Mycorrhizal fungi - members of the Basidiomycetes, Ascomycetes and Zygomycetes
- play a crucial role in plant health by enhancing nutrient acquisition, drought tolerance and
pathogen resistance of their hosts (Smith & Read, 1997). In return, the autotrophic plant
hosts provide their heterotrophic fungal partners with photosynthetically derived carbon
compounds (sugars). Based on morphology and the fungal and plant species involved,
several different mycorrhizal types are recognised. The most important are:
Vesicular-arbuscular mycorrhizas (VAM) are found on the vast majority of wild and crop
plants, and most tropical tree species. They are associations where Zygomycete fungi in
the Glomales produce arbuscules, hyphae and vesicles within root cells. Spores are formed
in soil or roots. These associations are defined by the presence of arbuscules. VAM fungi
are generalists, i.e. they can associate with thousands of different host plant species.
About 150 VAM forming species are known worldwide.
Ectomycorrhizas (EM) are characteristic of most forest tree species in the temperate
and boreal regions of the world - for example pines, spruces, firs, oaks, birches in the
Northern Hemisphere and eucalypts in Australia. However, some trees (e.g. willows) can
have both ectomycorrhizas and vesicular-arbuscular mycorrhizas. Ectomycorrhizas are
associations where Basidiomycetes and other fungi colonise short roots and form short
swollen lateral roots covered by a mantle of hyphae. These roots have Hartig net hyphae
around the cells in the epidermis or cortex.
EM fungi are predominantly host specific, i.e. they form associations with certain tree
species or a restricted number of them. About 5000 EM forming species have been described
to date. Orchid mycorrhizas consist of coils of hyphae within roots or stems of plants in the
family Orchidaceae. Ericoid mycorrhizas have hyphal coils in outer cells of the narrow hair
roots of plants in the plant order Ericales
Why mycorrhizal fungi are important
Mycorrhizal fungi increase plant nutrient supply by extending the volume of soil accessible
to plants and by acquiring nutrient forms that would not normally be available to plants.
Root colonisation by mycorrhizal fungi can provide protection from parasitic fungi and
nematodes.
Carbon transfer through EM fungus mycelia connecting different plant species has been
measured. Networks of hyphae supported by dominant trees may help seedlings become
established or contribute to the growth of shaded understorey plants.
Hyphae of VAM fungi are thought to contribute to soil structure by mechanical aggregation
of soil particles.
Epigeous and hypogeous sporocarps of EM fungi are important food sources for forest
inhabiting animals and some of them are economically important as human food resources.
How to detect mycorrhizal fungi in the soil
Most of the EM fungi produce conspicuous fruitbodies: forest mushrooms such as boletes,
amanitas, chanterelles or subterranean truffles. The presence of fruitbodies is evidence for
the presence of mycorrhizal mycelium in the soil. However, if there are no fruitbodies apparent,
it does not mean that there are no mycorrhizal fungi present in the soil, since EM fungi do
not form fruitbodies on a regular basis.
The detection of VAM fungi in the soil by the naked eye is entirely impossible, since they
do not form visible fruitbodies, but only microscopic spores.
Nowadays there are new, highly sophisticated methods of detecting and identifying
mycelium of VAM and EM fungi in the soil using molecular tools, such as the T-RFLP method
or the DGGE (sequencing of cloned PCR-products). The progress in methodology in this field
is very fast-paced. A much easier way is to look at plant roots. If there are mycorrhizal fungi
in the soil, they colonise plant roots and form mycorrhizas; this is imperative, for they would
36
not be able to survive without doing so. Mycorrhizas can be investigated morphologically
and anatomically (morphotyping) or by molecular identification of the fungus by comparing
genetic fingerprints of unknown mycorrhizas with a reference data base.
2. Artificial mycorrhizal inoculation
The need of tree species for mycorrhizal associations was discovered when attempts to
establish plantations of exotic pines failed until the essential mycorrhizal fungi were introduced
(Marx, 1980). Since the seventies attempts have been made to artificially colonise seedlings
in the nursery with mycelia of EM fungi. The aim was to improve early growth of forest
plantations. So-called controlled inoculation was regarded as an energy-saving and
environment-friendly alternative to chemical fertilizers and pesticides. Today the production
of ecto- and endomycorrhizal inoculants is at a commercial level and a wide variety of
products is available.
Techniques of artificial inoculation
There are three main methods of application of mycorrhizal inoculum with regard to the
age of the tree to be inoculated:
- seedling inoculation in the nursery
- inoculation of trees at time of transplanting
- inoculation of mature trees at the site
Inoculant types vary from simple forms (e.g. inoculation with forest soil) to highly
sophisticated aseptically produced inocula based on pure cultures or spores, incorporated
into carriers and supplemented with growth stimulating additives, such as hydrogels, natural
humates, yucca plant extracts, seaweed extracts, kelp, humus, vitamins, amino acids, or
other beneficial soil microorganisms like Trichoderma species or rhizosphere bacteria.
EM inoculum can be applied as spores or mycelium grown in pure culture. Mycelium
inoculum usually causes faster infection but is more sensitive to desiccation and other
environmental factors. VAM fungi can be applied only as spores or as infected roots, because
they cannot be grown in pure culture on nutrient media. The fungi are multiplied by infecting
roots of an intermediate host through the use of spores.
Table 1: types of inoculum products and application ranges (s = seedling inoculation;
t = inoculation at time of transplanting; o = inoculation of mature trees)
Can the success of an artificial inoculation be guaranteed?
Artificial mycorrhizal inoculation may be successful only when the following conditions
are fulfilled:
1. There is no natural or appropriate inoculum in the soil or the inoculum level is low
2. The species present are less efficient at aiding the plant host than those being introduced
3. The host tree produces enough carbohydrates to keep the symbiotic fungi alive
As a result of the fact that almost all vascular plants live in symbiosis with mycorrhizal
fungi, these fungi are widely distributed all over the regions of the world covered by vegetation.
There are some special situations where the natural mycorrhizal populations can be perturbed
or insufficient: on sterile soils, e.g. mine spoils, artificial substrates, or on degraded soils,
e.g. in urban environments
37
The success of artificial mycorrhizal inoculation can never be guaranteed for two main
reasons:
1. the competition between the introduced and the soilborne fungi. Most soils already
contain a complement of mycorrhizal fungi that can out-compete the newly introduced
species.
2. the soil conditions may not be adequate for the growth of mycorrhizal fungi.
Costs
According to the dosage instructions of the producers the application costs of commercial
inoculum range from Euro 0.5 to Euro 10 per thousand seedlings (nursery application) and
between Euro 0.25 and Euro 0.70 per tree at time of transplanting. For soil restoration the
costs range from Euro 0.1/m2 (surface application) up to Euro 60/m3 (full soil inoculation).
Inoculation of mature trees by injection of liquid inoculum into the soil may cost even more,
depending on the dimension of the tree and its root system.
Selection of fungi for artificial inoculation: economics versus ecology
The first and most important selection criteria is the behaviour of the symbiont in pure
culture and the possibilities of producing inoculum in abundant quantities.
For EM inoculum the choice is very restricted because only a limited number of species
are cultivatable, e.g. Laccaria, Hebeloma, Paxillus. The large and widespread families of
Cortinarius or Lactarius are very difficult to take into culture even though they are known
as late-stage species, i.e. they preferentally colonise mature trees. Seedling inoculation
requires early-stage fungi, such as Hebeloma, Laccaria and Paxillus, whereas mature trees
should be inoculated with late-stage fungi, such as Boletus or Cortinarius species.
Another major criteria for selecting fungal symbionts to be utilized for inoculation of
mature trees is their root-colonizing ability and competitiveness against wild symbionts
already present in the soil. Artificial ectomycorrhizal inoculation Pisolithus tinctorius spores
have been the main component of commercial EM inoculum since the beginning. Fruitbodies
of Pisolithus tinctorius fungus produce high quantities of spores, but it can be questioned
whether this fungus is a good choice from an ecological point of view. It is known from
various studies that this species gives good results on mine spoils, but there is no evidence
that this fungus is competitive enough on other soil types.
The most important problem is that soil conditions in the landscape may be too variable
to be able to make generalizations about the usefulness of artificial inoculation with the few
selected species available commercially. Mycorrhizal fungi are - as vascular plants - site and
host specific. And above all they are not identical in their effect to the host plant. Some
species may have a positive effect, a neutral effect or under certain circumstances even a
detrimental effect on the host plant (Klironomos, 2003).
Inoculation of mature trees in urban environments
Urban soils are very different to forest soils since they are influenced by human activities
and therefore the soils natural characteristics that benefit trees are often degraded. They
rarely have an organic layer and they may have disrupted soil profiles as the result of
organic top layers having been removed or turned into mineral subsoil horizons by construction
activities. Often these soils are compacted, have an altered drainage and an elevated pH.
Additionally, they are submitted to stresses such as de-icing salt in winter and air pollution
from exhaust fumes. All these factors may harm root growth and health of the trees growing
on these soils and they also disturb the mycorrhizal flora. Since urban trees have the same
biological needs as forest trees, the idea of improving the soil by artificial inoculation with
mycorrhizal fungi was born.
An important point which makes the inoculation of mature trees problematic compared to
seedling inoculation in the nursery, is that the roots of mature trees are normally already
colonised by mycorrhizal fungi. In theory, the introduction of an alien fungus into an
environment that already is fully occupied by indigenous fungi is less likely to be successful
than its use in a situation devoid of such fungi.
The inoculation method for mature trees is limited to the injection technique using liquid
inoculum, or eventually the application of solid inoculum combined with a mulching procedure.
On the other hand seedlings are much easier to inoculate compared to mature trees: the
inoculum can be allocated directly to the root system in the nursery by mixing the inoculum
into the planting substrate of the seedbed or into the planting pot. The inoculum gets in
direct contact with the fine roots and root colonisation can happen easily. The soil can be
38
sterilized before inoculation to eliminate competing resident symbionts or pathogenic
microorganisms. Such a treatment can not be performed on mature trees.
3. Experiences to date with artificial mycorrhizal inoculation
Inoculation of seedlings in the nursery
In nursery inoculation there is a large body of experience and hundreds of studies which
show the positive effect of artificial inoculation with mycorrhizal fungi on seedlings: they
grow faster with less fertilisers. But the key question is what happens with these fungi after
outplanting? The existing literature indicates that fungal associations often change when
the plants are transplanted into the field.
Inoculation of trees at time of transplanting
At present there is very limited unbiased scientific evidence that artificial mycorrhizal
inoculation of trees at time of transplanting makes plant establishment more successful or
that the inoculated plants grow better over time.
Garbaye & Churin (1996) inoculated 8-year-old silver limes (Tilia tomentosa) with three
ectomycorhizal fungi. In spite of irregular colonization of the roots by the introduced symbionts,
tree growth was significantly stimulated in the three fungal treatments and yellowing of
leaves in autumn was delayed. Negative results are reported from Alvarez & Trappe (1983):
dusting roots with Pisolithus tinctorius spores even reduced seedling survival in some cases.
Pilz and Znerold (1986) inoculated Douglas firs with a slurry of Pisolithus tinctorius spores
and concluded that the application of P.t. spores to a seedlings roots immediately preceeding
outplanting appears to be ineffective South and Skinner (1998) reported on a study where
no benefit was obtained by injecting freeze-dried Rhizopogon spores into the soil after
transplanting. Other negative results are published by Martin & Stutz (1994) and Gilman
(2001): Inoculation of Argentine mesquite (Prosopis alba) with the VAM fungus Glomus
intraradices and of Live oak (Quercus virginiana) with a commercial inoculum, respectively,
showed no effect on growth or survival. In contrast, nursery production methods and
irrigation had a large and significant impact on water stress, tree death and growth after
transplanting. However, adding soil to the planting hole at time of transplanting seems to be
more promising. Two studies report positive results in survival and growth of Douglas fir
seedlings (Amaranthus & Perry, 1989; Colinas et al., 1994) after adding forest soil to the
planting hole.
Inoculation of mature trees at the site
There have only been two studies up to now which present results of inoculation of
mature trees (Marx et al., 1997; Smiley et al., 1997). Both studies show positive effects of
inoculation and/or fertilisation on fine root biomass and mycorrhizal colonisation of up to
250-year-old live oaks (Quercus virginiana). As inoculant a spore suspension of Pisolithus
tinctorius was injected into the root system to a depth of 20 cm.
No other publications presenting results of inoculation of mature trees exist. This could
either be due to a lack of studies or a tendency of reviewers to reject papers that show no
significant positive treatment effect.
5. Conclusions
The inoculation of mature trees with mycorrhizal fungi is technically possible but the
decision of whether an application is advisable or not needs careful analysis of the
circumstances. This is not because an inoculation could be injurious to the tree but because
the effort and the expenses could be economised if the prospects of success are analysed
from a realistic and objective perspective.
First of all we have to look at possible reasons for a trees loss of vitality, keeping in mind
the statement of Buschena (2000): Remember that interactions between mycorrhizal fungi
and other components of the landscape ecosystem are very complex. The problems with
your trees may not be related to the lack of mycorrhizal fungi. They quite often may be
related to the presence of some other organism or condition that is harmful to the trees.
If the tree is simply too old, inoculation will not make it younger. In addition, if the living
conditions of a tree are bad due to unfavourable soil conditions or environmental impacts,
inoculation only makes sense if the mycorrhizal flora is suffering from these conditions. We
have to consider that the two partners of a mycorrhizal symbiosis are living together in a
mutualistic relationship. It is not a one-way-profit system from the fungus to the tree. If the
tree is no longer able to sufficiently assimilate carbohydrates, the mycorrhizal fungus will be
39
suffering itself and will no longer be able to fully fulfill its beneficial functions for the tree.
Furthermore, if the chemical or physical soil properties are completely unfavourable for the
existence of mycorrhizal fungi, it would not make sense to artificially introduce them.
Consequently, a reasonable approach of ameliorating growth conditions of trees in urban
landscape, or of veteran trees, is to improve the basic conditions for tree growth. Current
research suggests that organic soil amendment, particularly the addition of composted
mulches, greatly enhances the mycorrhizal status of landscape trees. Another possibility is
to protect the trees against unfavourable influences (e.g. de-icing salt), or to select tree
species which are more resistant against such factors.
If artificial mycorrhizal inoculation is to be evaluated at all, the following points should be
considered:
- Use only correctly labeled inoculum that clearly states the fungal species and number
of propagules.
- The inoculum should contain propagules that are alive and effective and that correspond
in number to the claims on the label.
- Inoculum and inoculation procedures should be lower in cost than possible alternatives
(fertilization, pest control, site/soil amelioration).
In assessing the prospects of success of artificial inoculation we have to be conscious of
the fact that about 99% of positive effects of mycorrhizal fungi on their host plant
demonstrated in literature are based on experimental designs under more or less controlled
conditions. Observations of the reactions of plants to an inoculation after outplanting to the
landscape are very rare. The lack of knowledge in this field is underlined by the existence of
only these two previously mentioned publications about artificial inoculation of mature trees
under field conditions. One of the authors involved in these two papers refers to this
problem in one of his earlier papers (Marx, 1980): The ultimate proof of the value of
inoculation of bare-root or container grown nursery seedlings with specific fungi is their
performance under diverse field conditions. Meaningful conclusions can only be obtained
from properly designed, installed, and maintained field experiments which include periodic
tree measurements and mycorrhizal assessments conducted over several years. Only limited
field data of this type is available in the literature. In regards to mycorrhizal inoculation at
outplanting or inoculation of mature trees, this statement is as true today as it was in 1980.
Literature
Amaranthus, M.P., Perry, D.A. 1989. Rapid root tip and mycorrhizal formation and increased survival
of Douglas fir seedlings after soil transfer. New Forests 3: 259-264.
Bonello, P.E. Mycorrhizas in the Urban Landscape. Extension Factsheet, Ohio State University.
http://ohioline.osu.edu/hyg-fact/3000/3305.html
Buschena, C. 2000. Will mycorrhizal inoculations save your ailing tree? Minnesota Shade Tree
Advocate 3(3): 3-4.
Colinas, C., Perry, D.A., Molina, R., Amaranthus, M. 1994. Survival and growth of Pseudotsuga
menziesii seedlings inoculated with biocid-treated soil at transplanting in a degraded clearcut.
Can. J. For. Res. 24: 1741-1749.
Garbaye, J., Churin, J.L. 1996. Effect of ectomycorrhizal inoculation at planting on growth and
foliage quality of Tilia tomentosa. Journal of Arboriculture 22: 29-34.
Garbaye, J., Lohou, C., Laurent, P., Churin, J.L. 1999. Ectomycorrhizal inoculation of avenue trees
in Paris. Acta Horticulturae 496: 445-449.
Gilman, E. 2001. Effect of nursery production method, irrigation, and inoculation with mycorrhizaeforming fungi on establishment of Quercus virginiana. Journal of Arboriculture 27/1: 30-39.
Klironomos, J.N. 2003. Variation in plant response to native and exotic arbuscular mycorrhizal
fungi. Ecology 84/9: 2292-2301.
Martin, C.A., Stutz, J.C. 1994. Growth of argentine mesquite inoculated with vesicular-arbuscular
mycorrhizal fungi. Journal of Arboriculture 20/2: 134-138.
Marx, D.H. 1980. Ectomycorrhizal fungus inoculations: a tool for improving forestation practices.
In: Mikola, P. (ed.) Tropical Mycorrhiza Research. Oxford University Press: 13-71.
Marx, D.H., Ruehle, J.L., Kenney, D.S., Cordell, C.,E, Riffle, J.W., Molina, R.,J., Pawuk, W.H., Navratil,
S., Tinus, R.W., Goodwin, O.C. 1982. Commercial Vegetative Inoculum of Pisolithus tinctorius and
Inoculation Techniques for Development of Ectomycorrhizae on Container-grown Tree Seedlings.
Forest. Sci. 28/2: 373-400.
Marx, D.H., Murphy, M., Parrish, T., Marx, S., Haigler, D., Eckhard, D. 1997. Root response of mature
live oaks in coastal South Carolina to root zone inoculations with ectomycorrhizal fungal inoculants.
Journal of Arboriculture 23(6): 257-263.
Smiley, E.T., Marx, D.H., Fraedrich, B.R. 1997. Ectomycorrhizal fungus inoculations of established
residential trees. Journal of Arboriculture 23(3): 113-115.
Smith, S. E., and Read, D. J. 1997. Mycorrhizal symbiosis. Academic press, London.
40
HOW TO PROMOTE AND ENHANCE THE ROOT VITALITY ON VETERAN TREES: RESPONSES
TO NATURAL AND CHEMICAL PRODUCTS
G. Watson
The Morton Arboretum, Lisle, IL - USA
The Key to Longevity
Veteran trees have been defined as Trees of interest biologically, aesthetically or culturally
because of their age, trees in the ancient state of their life, and trees that are old relative
to others of the same species (Helen Read, Veteran Trees a guide to good management.
English Nature 2000). In order to care for these trees properly,
and insure their survival for many more years, it is important to
try to understand why these trees have been able to live so long
already.
It has been estimated that Britain may be home to around
80% of Europes ancient trees (The Ancient Tree Forum). It
doesnt take the deductive reasoning powers of Sherlock Holmes
to realize that the nearly ideal, moist, cool summer/moderate
winter climate imposes minimal stress on trees in Britain. The
veteran trees seen in photographs are always in open spaces
with minimal restrictions above and below ground. The situation
is similar in the Pacific coast where most of the very large old
trees in the US can be found, and for the giant Kauri trees of
New Zealand. Under these conditions, demands on the root
system are moderate, and episodes of stress are infrequent and
not severe. In contrast,
trees planted in the center
of American cities in small
root spaces, where stress is
One of the largest Kauri
both frequent and severe,
trees in the forests of
have been estimated to have
Northern New Zealand
an average life span of only
seven years. The environment must play a major role in
longevity.
There are other situations where trees can live a
very long time. On dry windswept mountaintops of the
Great Basin in the western United States grow earths
oldest living inhabitants, the bristlecone pines (Pinus
longaeva, Pinus aristata). Many of the trees living today
were seedlings when the pyramids were being
constructed over 4,000 years ago, and mature in the
time of Christ. In this environment, the roots must find
moisture between the rocks, crowns are small, and the
Bristlecone pine over
trees never get more than 8.3m tall, and usually much
4,000 years old
less. These are very specific adaptations to survive in
this harsh environment.Though not normally classified as veteran trees, Bonsai trees do fit
the definition. These tiny trees can easily live in
pots for hundreds of years. What do all these old
trees have in common? They have a good balance
between the crown and root development. The
branches and roots of bonsai trees are pruned
regularly to keep them healthy, but small. Traditional
pollarding used for centuries on trees of Europe
has the same effect of keeping the crown small
and rejuvenated, extending the life of the tree almost
indefinitely. Once pollarding is discontinued, it is
only a matter of time until the tree dies of old age.
The crowns of the Bristlecone pine trees usually
have much evidence of dieback, and are often very
A bonsai tree over 400 years old
small with only a small strip of live cambium
supporting this partial crown. Even in the nearly
ideal climates of Britain and the US Pacific Northwest, many of these very old trees show a
41
history of dieback to rebalance the crown with the root system.
In all of these examples, the crown is manipulated by nature or
by man to reach a balance with the root system. Promoting
good root health is also important in helping veteran trees to
reach that optimum above- and below-ground balance.
Soils and Root Growth
Healthy soil is required for healthy, vigorous root growth. Roots
will naturally develop to the full extent that is possible in the
existing environment poor soils are associated with poor root
development. Root growth is influenced by numerous factors
supplied by the soil. Most of the fine absorbing roots will usually
be found in the upper soil layers regardless of tree size, because
conditions for root growth are most often optimum there.
Even during periods of drought, the natural forest soil
environment can remain moist. This points out the need for
The largest giant sequoia
tree in California. Note
maintaining even soil moisture in the root zone. Root growth
dieback in the crown
stops in most species when soil moisture is reduced to -500 mbar
soil moisture tension. Accelerated root suberization (the deposition of a waterproof layer in
the walls of cells near the root surface) restricts absorption and is accelerated in dry soil.
Roots do not regain their full capacity for water uptake until new root tips can be produced.
When plants are watered immediately after cessation of root elongation, roots may not
resume elongation for at least one week. Resumption of root growth takes up to five weeks
if water is withheld longer. If the soil becomes too dry, some of the smaller roots may die.
Veteran trees must be well adapted to the site where they have been growing for
centuries, but subtle changes imposed in recent decades, within the trees root zone or
surrounding areas, can impact the soil environment immediately surrounding the trees and
lead to problems. Soil wetness and related drainage conditions are controlled by a number
of factors including: 1) precipitation, 2) soil texture and structure, 3) permeability, 4)
infiltration characteristics, and 5) landscape position. Soils are poorly drained if water
accumulates on the ground surface, or in the subsoil, for several days or weeks during wet
periods. This is especially prevalent in topographically low or flat sites that receive runoff
from surrounding areas, even if the slopes are very gradual. Seasonal wetness causes
decline in plants not adapted to wet conditions.
The importance of soil aeration cannot be overemphasized. Plant roots require oxygen.
Roots are generally not sensitive to soil saturation itself, but excessive soil moisture reduces
soil aeration because the water replaces the air normally held in the pores of the soil.
Compaction reduces air space and compounds the problem. In most soils, 8 to 10 percent
oxygen in the soil atmosphere is considered the minimum for good root growth. Below this
level, growth is inhibited. With the exclusion of air, roots are killed and cannot take up
moisture causing desiccation of foliage. As a result, drowning plants often exhibit the same
leaf symptoms as those suffering from drought. Lack of adequate gas exchange in waterlogged
soils can also lead to an increase in carbon dioxide, which is toxic to roots in higher than
normal concentrations.
Several types of air injection equipment have been developed to reduce soil compaction
and increase aeration. The effectiveness of these is questionable. They may be most
effective in light soils where they are needed the least. There have been no confirmed
reports of successfully improving root development as a result of their use.
Even when soil conditions are excellent, root systems are normally quite shallow and
spread far beyond the branch tips, regardless of tree size and age. Root penetration into
deeper soils is limited by most soils. Subsoils often have little pore space and the pore
space that is available may be filled with water at certain times during the year. With little
oxygen available, roots cannot survive there. At the time of the year when these subsoils
begin to dry out, aeration is improved. As soils dry, they often shrink and cracks form up to
several meters deep. The cracks help to improve aeration, allowing roots to penetrate
deeply to access deep soil moisture when surface moisture may be scarce. Though the
amount of root biomass in deep soils is quite small, these roots can be very important for
tree survival during drought. These roots will likely die back toward the surface during the
next wet season. Though it has not been studied directly, one of the keys to veteran tree
survival may be that they are growing in soils that allow unusually deep root penetration
that helps them to get through extreme weather periods without stress.
42
Optimizing Root Growth
Mulching The critical aspects of the forest soil environment in which the roots of most tree species evolved must
be maintained for good root health. The natural litter and
humus covered environment of the forest floor provides an
even temperature and supply of moisture, oxygen and nutrients to roots near the surface. Mulching has the same
effect. A sustained mulch layer can reduce soil compaction,
increase soil organic matter, water holding capacity, and
biological activity. The result can be a dramatic increase in
the development of fine absorbing roots. Compared to bare
soil, or competition with lawn grasses, mulch can easily double
the fine root density in the soil beneath, and increase it by
as much as 15-fold in some circumstances. Roots also grow
in the mulch itself, increasing the total surface of the root
system even further.
Roots of trees normally grow in a symbiotic association
Mulching can increase root
with certain soil fungi to form mycorrhizae (means fungus
development substantially
root). These fungi have evolved along with the trees and
are favored by the same conditions that promote root growth.
Mulching has been shown to increase development of both fine roots and mycorrhizae,
which in turn increases a trees ability to absorb available water and nutrients from the soil.
Surface mulching is easy and effective in improving soil conditions beneath it over time,
but in some situations there has been a desire to actually replace the soil. Development of
air and water excavation methods and tools has made it possible to remove soil with minimal
damage to even the smallest roots. An early study of partial soil replacement in the root
zone of mature trees did show that root development can be improved and twig growth
increased. The replaced soil may also favorably affect the soil beneath it, just as mulch
does, but it has no effect laterally if a pattern of deep narrow holes is used. Wide shallow
areas would be better.
Fertilization Phosphorous has long been thought to promote root growth. There is no
strong evidence to support this contention. Studies have shown that there is no increase in
root growth associated with phosphorous or potassium fertilization where levels were already
adequate. In nutrient-rich zones of the soil, the growth of the main root is reduced while
branching of lateral roots is increased resulting in greater fine root development. Similarly,
localized applications of nitrogen fertilizer can increase root density in the immediate area.
Though the addition of nitrogen fertilizer increases root density near the point of application,
this may not represent an increase in the total root mass. Root development in other parts
of the root system may be reduced. Excess nitrogen fertilization may reduce overall fine
root formation.
Fertilization could force the crown to grow excessively, enlarging the crown without
enlarging the root system. Increased shoot growth of radiata pine (Pinus radiata) and red
maple (Acer ruburm) due to high soil fertility resulted in a lower root:shoot ratio.
It is sometimes contended that fertilization will lead to greener, larger leaves and increased
carbohydrate projection, which would then provide increased carbohydrate supply to the
roots and increase root growth. This reasoning assumes that carbohydrates are in short
supply in trees that are growing slowly or showing signs of decline. Large declining white
oaks (Quercus alba) with poor root development were shown to have very high levels of
stored carbohydrates. However, trees that had been in similar condition at one time, but
then subjected to an aggressive fertilization program to bring back the green color and
increase shoot growth, had no increased root development and had very low carbohydrate
reserves. Fertilization increased the imbalance between the crown and root system. In this
case, fertilization of veteran trees should be limited to correcting demonstrated nutrient
deficiencies.
Tree Growth Regulators The growth regulator paclobutrazol (PBZ), a gibberellin
biosynthesis inhibitor, has been shown to reduce the shoot growth of many species. In some
situations, PBZ is also known to increase certain aspects of root growth. As a result of
reduced shoot growth and/or root growth stimulation, the effect of PBZ can be to increase
root/shoot ratio. Photosynthesis is not reduced by PBZ treatments and increases in root
growth may be due partially to increased carbohydrate supply to roots. Higher levels of ABA
often associated with PBZ treatment have been shown to maintain growth of roots under
drought stress. An increase in fine root development implies a more favorable root/crown
43
balance and less stress in treated trees. Reduced water use and improved water status has
been reported after treatment with PBZ. Apparent improvements in vigor, color and drought
resistance may be related to a greater capacity of the root system to absorb moisture and
mineral nutrients from the soil.
White oak at time of paclobutrazol treatment (left) and 10 years later
Mature, declining white oaks (Quercus alba) were treated with PBZ. Root density nearly
doubled in 3 years. Signs of crown improvement began to show (slightly greener color) the
second year after treatment and continued for over a decade. New growth was deep green
and vigorous and the leaves were not noticeably smaller. The leaves were much less
scorched by mid-summer compared to leaves of an untreated tree nearby. This technique is
new and untested on large trees that are centuries old, but it may someday prove to be a
useful tool for caring for veteran trees.
Any tree that can maintain an even physiological balance between the demands of the
crown for water and nutrients, and the ability of the root system to supply them, can thrive
indefinitely. Veteran trees have been able to do this, or they would not have survived. This
same approach can be used to improve health and lengthen the life span of any tree, even
those growing on very difficult urban sites.
FOR FURTHER READING
Ashokan, P.K., W.R. Chaney, and G.S. Premachandra. 1995. Soil applied paclobutrazol affects
leaf water relations and growth of American elm (Ulmus americana L.) seedlings. Plant Growth
Reg. Soc. Amer. Quar. 23:1-12.
Bausher, M.C. and G. Yelenosky. 1986. Sensitivity of potted citrus plants to top sprays and soil
applications of paclobutrazol. HortSci. 21:141-143.
Coutts, M.P. and J.J. Philipson. 1976. The influence of mineral nutrition on the root development
of trees. I. The growth of Sitka spruce with divided root systems. J. Exp. Bot. 27: 1102-1111.
Davis, T.D., N. Sankhla, R.H. Walser and A. Upadhyaya. 1985. Promotion of adventitious root
formation on cuttings by paclobutrazol. HortSci. 20:883-884.
Hackett, C. 1972. A method of applying nutrients locally to roots under controlled condition, and
some morphological effects of locally applied nitrate on the branching of wheat roots. Austral. J.
Bioi. Sci. 25:1168-1180.
Harris, R. W. 1992. Arboriculture: Integrated Management of Landscape Trees, Shrubs and Vines.
Prentice Hall, Englewood Cliffs, NJ. 674pp.
Himelick, E.B. and G.W. Watson 1990. Reduction of oak chlorosis with wood chip mulch treatments.
J. Arboriculture 16:275-278
Kozlowski, T.T. and S.G. Pallardy. 1997. Growth control in woody plants. Academic Press, New
York. 641 pp.
Lyr, H. and G. Hoffman. 1967. Growth Rates and growth periodicity of tree roots. Intern. Rev. For.
Res. 2: 181-236.
Nambiar, E.K.S. 1980. Root configuration and root regeneration in Pinus radiata seedlings. N.Z. J.
For. Sci.10:249- 63.
Pham, C.H., H.G. Halverson and G.M. Heisler. 1978. Red maple (Acer rubrum L.) growth and foliar
nutrient responses to soil fertility level and water regime. Forest Service Research Paper NE-412.
Ruter, J.M. 1994. Growth and landscape establishment of Pyracantha and Juniperus after
application of paclobutrazol. HortSci. 29: 1318-1320.
Ruter, J.M. and C.A. Martin. 1994. Effects of contrasting climate and paclobutrazol on the growth
and water use of two container-grown landscape plants. J. Environ. Hort. 12:27-32.
Swietlik, D. and S.S. Miller. 1983. The effect of paclobutrazol on growth and response to water
stress of apple seedlings. J. Amer. Soc. Hort. Sci. 108:1076-1080.
44
Wang , S.Y. and M. Faust. 1986. Effect of growth retardants on root formation and polyamine
content in apple seedlings. J. Amer. Soc. Hort. Sci. 111:912-917.
Watson, G. W. 1994. Root growth response to fertilizers. J. Arboriculture 20:4-8.
Watson, G. W. 1988. Organic surface mulch and grass competition influence root development.
J. Arboriculture 14:200 203.
Watson, G.W. 1991. Attaining root:crown balance in landscape trees. J. Arboric. 17:211 216.
Watson, G.W. 1996. Tree root system enhancement with paclobutrazol. J. Arboric. 22:211-217.
Watson, G.W., P.K. Kelsey, and K. Woodtli. 1996. Replacing soil in the root zone of mature trees
for better growth. J. Arboriculture 22:167-173.
Watson, Gary W. 2002. Soil replacement: long-term results. J. Arboriculture 28:229-230
Yeager, T.H. and R.D. Wright. 1981. Influence of nitrogen and phosphorus on shoot:root ratio of
Ilex crenata Thumb. I Helleri. HortScience 16:564-565.
45
ASSESSING ENVIRONMENTAL FUNCTIONS AND VALUES OF VETERAN TREES
D.J. Nowak
USDA Forest Service, Northeastern Research Station 5 Moon Library, SUNY-ESF Syracuse, NY
13210
Introduction
Urban trees can provide many benefits to society. These benefits include improvements
in air and water quality, building energy conservation, cooler air temperatures, reductions in
ultraviolet (UV) radiation, enhanced property values, and many other environmental and
social benefits (Nowak and Dwyer, 2000). These multiple benefits combine to improve urban
environmental conditions and associated human health and well-being.
However, not all trees are equal in the benefits that they provide for society. Selection of
proper species and locations can enhance desired benefits. Another important factor is tree
size. Veteran trees trees that have lived a long time and are significant elements of the
landscape often contribute substantially more benefits to society relative to other (smaller)
trees in the landscape.
Not only do veteran trees contribute the most cumulative benefits due to their relatively
long life span, but if healthy, these trees will also typically contribute the greatest annual
benefits per tree. The purpose of this paper is to illustrate, based on field data and modeling
from various cities, how the environmental benefits and values of veteran trees differ from
smaller, more typical urban trees. The benefits discussed in this paper are:
· Air temperature cooling and UV radiation reduction
· Building energy conservation
· Carbon storage and sequestration
· Air pollution removal
Though the focus of this paper will be on the environmental benefits of veteran trees, it
must be recognized that these trees also often have significant social benefits relative to
smaller trees (Dwyer et al., 1991; Barro et al., 1997; Nowak and Dwyer, 2000).
Urban Forests
Urban forests include the assemblage of all trees and other vegetation within an urban
area. To understand the structure and functions of these forests, data were collected on
trees throughout all land uses in selected cities. In the late 1990s, approximately 200
randomly located 0.04 hectare field plots were measured in Atlanta, GA; Baltimore, MD;
Boston, MA; Jersey City, NJ; New York, NY; Philadelphia, PA; Syracuse, NY; and Toronto,
Ontario. These field data were combined with local hourly meteorological and pollution
concentration data within the Urban Forest Effects (UFORE) model (Nowak and Crane,
2000) to quantify urban tree structure, functions, and values in each city. Results from
these analyses were summarized by diameter class to illustrate the difference in benefits by
tree size. Detailed methods and field sampling techniques can be found in Nowak et al.
(1998, 2000, 2002), Nowak and Crane (2002) and www.fs.fed.us/ne/syracuse. For this
paper, veteran trees are defined as trees greater than 76.2 cm in diameter at breast height
(1.37 m) (dbh).
Results from the cities reveal that typically the majority of trees are less than 15.2 cm in
dbh, and less than 3% of the population is veteran trees greater than 76.2 cm in dbh (Table
1). Even though there are relative few veteran trees, these trees averaged between 35 to
65 times more leaf surface area than small trees less than 7.6 cm in dbh in the cities
analyzed.
Table 1. Percent of total tree population in selected dbh ranges
46
Temperature and UV Effects
Leaf area is a critical factor in determining many environmental benefits of trees. Typically
the more healthy functional leaf surface area on a tree, the greater the environmental
benefits. Assuming a tree has ample soil moisture and all other factors are equal, trees with
a greater leaf surface area will typically transpire more water, thereby leading to greater
evaporative cooling (e.g., University of California Cooperative Extension, 2000). Increased
canopy cover can help reduce air temperatures, with reported reductions of maximum midday air temperatures ranging from 0.04oC to 0.2oC per percent increase in canopy cover
(Simpson, 1998).
In 1995, a heat wave in Chicago caused 514 heat-related deaths, and a heat wave in
London caused a 15% increase in all-cause mortality. Excess mortality during heat waves is
greatest with the elderly and people with preexisting illness. Much of this excess mortality
from heat waves is related to cardiovascular, cerebrovascular, and respiratory disease (IPCC,
2001). Increased urban canopy cover and leaf area, and its consequent reduction in urban
area temperature can have a significant human health impact.
Increased leaf area and canopy size will also typically lead to greater shading effects,
which consequently can affect the amount of ultraviolet radiation (UV) received by humans.
Rates of skin cancer have increased greatly in recent years, and increased ultraviolet B
radiation caused by reductions in stratospheric ozone may be responsible for this increase.
Epidemiological considerations suggest that routine exposure to UV in urban areas can
produce adverse health effects (Heisler and Grant, 2000). As tree leaves typically absorb
greater than 90% of ultraviolet radiation reaching its surface, larger tree canopies can lead
to greater reductions in UV rays reaching urban inhabitants.
Building Energy Conservation
Trees affect local building heating and cooling energy needs by shading buildings and
reducing air temperatures in the summer, and by blocking winds in winter. However, trees
that shade buildings in winter also can increase heating needs. Energy conservation from
trees varies by regional climate, the size and amount of tree foliage, and the location of
trees around buildings. Tree arrangements that save energy provide shade primarily on east
and west walls and roofs, and wind protection from the direction of prevailing winter winds.
Energy use in a house with trees can be 20 to 25% lower per year than that for the same
house in an open area (Heisler, 1986).
Based on results of energy simulations for 11 different climate zones in the United States
(McPherson and Simpson, 1999), large (> 15 m tall) deciduous trees adjacent to buildings
have an average effect on building energy use 4 to 27 greater than small deciduous trees
(6-10 m tall) in the same position (median value = 9 fold difference between large and small
trees). This range is based on the average difference between large and small trees, with
one tree at each of the 8 cardinal directions around a post-1980 vintage building. Model
results of these trees revealed energy reductions in the cooling season and increased
energy use in the heating season in all climate zones analyzed.
Carbon Storage and Sequestration
Increasing levels of atmospheric carbon dioxide (CO2) and other greenhouse gases
(e.g., methane, chlorofluorocarbons, nitrous oxide) are thought by many to be contributing
to an increase in atmospheric temperatures by trapping certain wavelengths of heat in the
atmosphere. Globally averaged air temperature at the Earths surface has increased between
0.3 and 0.6oC since the late 1800s. A current estimate of the expected rise in average
surface air temperature globally is between 1 to 3.5oC by the year 2100 (Hamburg et al.,
1997). Global warming is implicated in the recent discovery that floating ice over the Arctic
Ocean has thinned from an average thickness of 10 feet in 1950 to less than 6 feet in the
late 1990s, and a large expanse of ice-free water that has opened up at the North Pole in
2000 (Appenzeller, 2000; BBC News, 2000).
By storing carbon through their growth process, trees act as a sink for atmospheric CO2,
a dominant greenhouse gas. Larger trees, due to their increased size, will store larger
amounts of carbon in their tissue as approximately half of the dry-weight of a tree is carbon.
In addition, large healthy trees will typically be able to sequester more carbon annually than
trees with smaller diameters. To estimate monetary value associated with urban tree carbon
storage and sequestration, carbon values were multiplied by $20.3/tC based on the estimated
marginal social costs of carbon dioxide emissions (Fankhauser, 1994).Based on data from
various cities, veteran trees store between 600 to 1,000 times more carbon within their
47
biomass than trees less than 7.6 cm dbh (Table 2). In addition, veteran trees continue to
store additional carbon and annually sequester between 30 to 80 times more carbon than
small trees less than 7.6 cm dbh (Table 3).
Table 2. Differences in estimated carbon storage and value between small (< 7.6 cm dbh)
and veteran (> 76.2 cm dbh) trees in various cities
Table 3. Differences in estimated annual carbon sequestration and value between small (<
7.6 cm dbh) and veteran (> 76.2 cm dbh) trees in various cities
Air Pollution Removal
Air pollution is a multibillion dollar problem that affects many major cities worldwide. Air
pollution is a significant human health concern as it can cause coughing, headaches, lung,
throat, and eye irritation, respiratory and heart disease, and cancer. It is estimated that
about 60,000 people die annually in the United States from the effects of particulate pollution
(Franchine 1991). In addition, air pollution damages vegetation and various anthropogenic
materials.
Major air pollutants in urban areas are carbon monoxide (CO), predominantly from
automobiles; nitrogen oxides (NOx), mainly from automobiles and stationary combustion
sources; ozone (O3), formed through chemical reactions involving the principal precursors of
NOx and volatile organic compounds; sulfur dioxide (SO2), emissions mostly from stationary
combustion sources and smelting of ores; and particulate matter. Small particulate matter
results from local soils, industrial processes, combustion products, and chemical reactions
involving gaseous pollutants.
Gaseous pollution removal by trees occurs predominantly through the leaf stomata,
though some deposition occurs on the plant surface (e.g., Smith 1990; Fowler 1985; Murphy
and Sigmon 1990). During daylight hours when plant leaves are transpiring water and taking
up CO2, other gases including pollutants are taken up into the leaf. Once inside the leaf,
these gases diffuse into intercellular spaces and can be absorbed by water films on innerleaf surfaces. Pollutant uptake by plants is highly variable as it is regulated by numerous
plant, pollutant, and environmental forces (e.g., plant water deficit, light intensity, windspeed,
gas solubility in water, leaf size and geometry, etc.) (Smith 1990).
48
Particles can be dry deposited on plant surfaces through sedimentation under the influence of gravity or through impaction resulting from wind. Particles hitting the tree may be
retained on the surface, rebound off it, or be retained temporarily and subsequently removed (resuspended into air or transported to soil or other surface) (Smith 1990). Thus,
vegetation generally is only a temporary retention site for atmospheric particles as particles
can be resuspended to the atmosphere, be washed off by rain, or drop to the ground
through leaf and twig fall.
Trees can also emit volatile organic compounds such as isoprene and monoterpenes into
the atmosphere. These compounds are natural chemicals that make up essential oils,
resins, and other plant products, and may be useful in attracting pollinators or repelling
predators (Kramer and Kozlowski 1979). These compounds can also contribute to ozone
formation (Brasseur and Chatfield, 1991). Even though trees may emit VOCs, other attributes of trees (air temperature reduction, pollution removal) can lead to reductions in
ozone. Comprehensive ozone studies are revealing that increased urban tree canopy cover
leads to reduced ozone concentrations (Cardelino and Chameides, 1990; Taha, 1996; Nowak
et al., 2000; Luley and Bond, 2002).
A significant factor affecting the influence of trees on air pollution is the amount of
functional leaf surface area. Veteran trees remove 30 to 65 times more air pollution annually
than small trees less than 7.6 cm in diameter in selected cities (Table 4).
Table 4. Differences in estimated annual average air pollution removal and value between
small (< 7.6 cm dbh) and veteran (> 76.2 cm dbh) trees in selected cities. Pollution
removal is the total for carbon monoxide, nitrogen dioxide, ozone, particulate matter less
than 10 microns, and sulfur dioxide. Values are based on median U.S. externality values for
each pollutant (Murray, 1994)
Conclusion
On a per tree basis, veteran trees typically contribute significantly more environmental
benefits and value to society than smaller trees. These beneficial functions provided by
veteran trees require that these trees be healthy, functioning elements in the urban landscape.
By being healthy, veteran trees offer significantly more leaf surface area to interact with the
surrounding environment. The gas exchange exhibited by large, functioning veteran trees
can provide significant environmental benefits such as air pollution removal, carbon
sequestration, and air temperature reduction. In addition, the relative large leaf surface
area of veteran trees often provides more shade than smaller trees, leading to increased
potential benefits from reduced building energy use (if trees are located in the proper
position around buildings) and reduced exposure to ultraviolet radiation. As veteran trees
produce some of the greatest environmental values, these trees can offer the greatest
single tree effects to improve human health and well-being in urban areas.
References
Appenzeller, T., 2000. Plying a fabled waterway. U.S. News Online. http://www.usnews.com/
usnews/issue/000828/passage.htm (last accessed June, 2001)
Barro, S.C., P.H. Gobster, H.W. Schroeder, and S.M. Bartram. 1997. What makes a big tree special?
Insights from the Chicagoland treemendous trees program. J. Arboric. 23(6): 239-249.
BBC News. 2000. North Pole ice turns to water. BBC News Online. News.bbc.co.uk/english/
world/americas/newsid_888000/888235.stm (last accessed June, 2001).
Brasseur, G.P. and R.B. Chatfield. 1991. The fate of biogenic trace gases in the atmosphere. In:
Sharkey, T.D.; Holland, E.A.; Mooney, H.A., eds. Trace gas emissions by plants: Academic Press,
New York. pp. 1-27.
49
Cardelino, C.A. and Chameides, W.L. 1990. Natural hydrocarbons, urbanization, and urban
ozone. J. Geophys. Res. 95(D9):13,971-13,979.
Dwyer, J.F., H.W. Schroeder, and P.H. Gobster. 1991. The significance of urban trees and forests:
Toward a deeper understanding of values. J. Arboric. 17(10): 276-284.
Fankhauser, S., 1994. The social costs of greenhouse gas emissions: an expected value approach.
The Energy Journal 15(2), 157-184.
Fowler, D. 1985. Deposition of SO2 onto plant canopies. In: Winner, W.E.; Mooney, H.A.; Goldstein,
R.A. eds. Sulfur dioxide and vegetation. Stanford, CA: Stanford University Press: 389-402.
Franchine, P. 1991. Soot kills 60,000 a year in U.S., survey shows. Chicago Sun-Times. June 30.
Hamburg, S.P., N. Harris, J. Jaeger, T.R. Karl, M. McFarland, J.F.B. Mitchell, M. Oppenheimer, S.
Santer, S. Schneider, K.E. Trenberth, and T.M.L. Wigley. c. 1997. Common questions about climate
change. United Nation Environment Programme, World Meteorology Organization.
Heisler, G.M. 1986. Energy savings with trees. J. Arboric. 12(5):113 125.
Heisler, G.M. and Grant, R.H. 2000. Ultraviolet radiation in urban ecosystems with consideration
of effects on human health. Urban Ecosystems 4: 193-229.
Intergovernmental Panel on Climate Change. 2001. Climate change 2001: Working group II:
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ipcc_tar/wg2/353.htm (last accessed February, 2004)
Kramer, P.J. and T.T. Kozlowski. 1979. Physiology of woody plants. Academic Press, New York.
Luley, C.J. and Bond, J. 2002. A plan to integrate management of urban trees into air quality
planning. Report to Northeast State Foresters Association. Davey Resource Group, Kent, OH. 73
p.
McPherson, E.G. and J.R. Simpson. 1999. Carbon dioxide reduction through urban forestry:
Guidelines for professional and volunteer tree planters. USDA Forest Service, Pacific Southwest
Research Station, Gen. Tech. Rep. 171. Berkeley, CA.
Murray, F.J., L. Marsh. and P.A. Bradford. 1994. New York State energy plan, vol. II: issue reports.
New York State Energy Office, Albany, NY.
Murphy, C. E. and J.T. Sigmon. 1990. Dry deposition of sulfur and nitrogen oxide gases to forest
vegetation. In: Lindberg, S. E.; Page, A. L.; Norton, S. A. eds. Acid precipitation. Volume 3: sources,
deposition, and canopy interactions. Springer-Verlag, New York. 217-240.
Nowak, D.J., K.L. Civerolo, S.T. Rao, G. Sistla, C.J. Luley, and D.E. Crane. 2000. A modeling study
of the impact of urban trees on ozone. Atmos. Environ. 34: 1601-1613.
Nowak, D.J., and D.E. Crane. 2000. The Urban Forest Effects (UFORE) Model: quantifying urban
forest structure and functions. In: Hansen, M. and T. Burk (Eds.) Integrated Tools for Natural
Resources Inventories in the 21st Century. Proc. of the IUFRO Conference. USDA Forest Service
General Technical Report NC-212. North Central Research Station, St. Paul, MN. pp. 714-720.
Nowak, D.J. and D.E. Crane. 2002. Carbon storage and sequestration by urban trees in the
United States. Environ. Poll. 116(3): 381-389.
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Service, Northeastern Research Station, Gen. Tech. Rep. 290. Newtown Square, PA.
Nowak, D.J., D.E. Crane, and J.F. Dwyer. 2002. Compensatory value of urban trees in the United
States. J. Arboric. 28(4): 194-199.
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ecosystems. In: Kuser, J. (ed.) Urban and Community Forestry in the Northeast. Plenum Publ. New
York. pp. 11-25.
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of urban vegetation on air pollution. In: Gryning, S.E. and N. Chaumerliac (eds.) Air Pollution
Modeling and Its Application XII. Plenum Press, New York. pp. 399-407.
Smith, W. H. 1990. Air pollution and forests. Springer-Verlag, New York.
Taha, H. 1996. Modeling impacts of increased urban vegetation on ozone air quality in the South
Coast Air Basin. Atmos. Environ. 30(20):3423-3430.
Simpson, J.R. 1998. Urban forest impacts on regional cooling and heating energy use: Sacramento
County case study. J. Arboric. 24(4):201-214.
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of landscape plantings in California. California Department of Water Resources, Sacramento, CA.
50
RESTORATION AND MANAGEMENT OF HISTORICAL PARKS
G. Bovo, G.M. Cirulli
Municipality of Turin Green Management Section
General
What does monumental tree mean? If we try to give a spontaneous and immediate
definition, we think of an important tree, a tree of remarkable age and size, worth of
particular care. If we want to give this mayby somewhat simplistic definition a more
authoritative and exhaustive outline, we find a number of prescriptive references which
widen the concept and meaning of monumental tree:
- Law 1089/39, absorbed into unified code 490/99, gives the definition of a cultural
asset and states that objects being of a historical and artistic interest (and therefore trees
too) must be at least 50 years old, states the principle of a public enjoyment of cultural
assets, stipulates about authorisations in the case of an intervention of any nature on the
cultural asset, imposes the principle of conservation also to private possessors of objects
being of a cultural interest, states sanctions in the case of a breach of said principles;
- Law 1497/39, Protection of the beauties of nature, also includes villas and parks
not protected by particular rules but distinguishing for their unusual beauty, provides for the
compilation of lists on provincial basis by a dedicated panel;
- Unified Code no. 490/99 that collected all environmental laws and rules into a sole
law instrument;
- Regional Law no. 50 of April 3rd, 1995, to protect and improve Piedmont monumental
trees having a high naturalistic and historical value. It is a specific law aimed at identifying
the monumental trees and rows, being of an interest from the landscape point of view, that
are present on the region and at promoting their protection and improvement. It defines, as
monumental trees and rows, being of an interest from the point view of history and culture,
as well as environment and landscape:
¨ trees either isolated or belonging to natural or artificial wood formation which can be
considered as rare examples of imposing and long-lived trees for their age or size;
¨ trees having a precise reference to events or memories rilevant from a historical or
cultural point of view;
¨ tree rows of particular value from the landscape point of view, as monumental trees, and
from a historical or cultural point of view, including rows inserted into urban centres.
The law is also aimed at producing a census the list of which is published on Piedmont
Region Official Bulletin (B.U.R.) and sets up a Technical Committee for the protection and
improvement of monumental trees and rows. It is a definitely important measure, specifically
focused on monumental trees subject. Besides involving particular regulations, monumental
trees have features, quite different from ordinary trees, requiring specific actions and
interventions:
· they are to a greater extent subjected to meteorological and climatic events (the action of
wind, changes in humidity, sudden changes in temperature, excessive solar radiations,.),
therefore resulting that it is important to regularly monitor their conditions, mainly after
particularly severe events;
· they are characterised in the so called terminal growth, i.e. crown developed mainly on
their terminal portion and very heavy branches accumulating strains and breakage risks,
which can be pruned for lightening by cutting out their dry parts, also with the purpose of
making light access easier and photosynthesising superface larger;
· felling neighbouring trees results in loosing the wood effect and making sudden crashes
more likely; this is an event which occurred in plenty of instances, both in private homes
and public green areas, sometimes with unpleasant consequences;
· frequent are problems at root level, which result in a lower growth, thinned out leaves,
chlorotic colour;
· cavities are more likely to be found where it is possible to intervene both by reducing the
crown and restoring its balance and by using dynamic tie rods. The latter is a technical
contrivance which is still unfrequently used but could where matched to a sound pruning
remarkably contribute to improve the safety coefficient of trees having problems related to
performance and steadiness.
It results from these short considerations that monumental trees may have health problems,
that they may be somehow delicate subjects and that also for these reasons, besides their
importance, a historic park and its trees must be considered a heritage to be protected and
at the same time shared and kept alive.
51
Cavour park at Santena
Benso of Cavour park lies at Santena settlement, a village close to Turin, and, although
developing over an area having a rather small size (about 16 hectares), it represents a very
interesting example of a historical Park with a public management and use owing to history
and tree heritage contaied (several specimens result to have been registered already in
1762). It started as a a private residence and, after a turbulent and articulate history rich in
ups and downs, it finally become a public park with characteristics that are atypical with
respect to ordinary standards.
Benso Family was rooted on Santena region and their presence in this small village is
proved by documents already since XII century: it results from this fact that the history and
events of the park and and buildings that are present there were closely connected to the
chequered fortune of the family. In the second half of XVIII century, a park could be already
identified, having a geometric design, made up of four parterres, a vineyard bounded by
borders and a stream (Old Santena) crossing the area splitting it into two portions and
flowing into Banna torrent; there were also regular curve tree lines bounding garden central
visual space. The parterres were then converted into a sole large regular meadow maybe fit
out for agricultural purposes.
Banna torrent control works go back to the period between XVIII and XIX century. This
torrent often overflew into Santena property and settlement. Back to this period goes a
project to modify the garden. This project can be attributed to architect Lorenzo Lombardi,
who had already devised 1797 Turin Napoleonic Land Use Plan. This was the first complete
project of the park, named Plan Geometrique des Jardines de Santena [Geometric Plan of
the Gardens of Santena], where the main role was assigned to the arrangement of vegetation
by using shrubs, hedges, borders. As a matter of fact, no reliable testimonies of this project
live on. Therefore, it was either left uncompleted or distroyed by one of Banna torrent
floods. Park present shape and size were reached in early XIX century thanks to the
arrangement of Abbot of Arvillars, commissioned by Benso Family. As a matter of fact, no
evidences proved by documents and reliable confirmations of his contribution exist about
this step too. Anyhow, the park results to have had at a romantic feature that time, with
vegetation elements arranged in groups and groves and winding paths, all this providing an
informal atmosphere.
Based on the example of main European courts, in Piedmont too the art of building
gardens became popular and Xavier Kurten, one of the best known landscapists of the time,
was in 1820 appointed Director of the gardens of the House of Savoy and of the park of the
residence of Racconigi. The influence of this great landscapist, thanks to his being backed
at Savoy court, spread out not only into royal residences but also into numerous residences
of nobles. The known landscapist was commissioned to intervene on the park of Santena,
also considering that the role of Benso Family wthin Royal Family had now become relevant
and that the residence needed to be transformed from an agricultural firm into a country
palace.
Kurten operated a number of botanical choices on a general plant which was already
defined at that time (1830). His botanical choices represent the park artitecture itself. From
the avenues, he chose the most significant and representative tree specimens, which were
kept isolated or clustered. Evident is the use of compositive categories that are typical of
this designer, such as the isolated tree, aligned tree, group and grove, although adapted to
park small size. Park area hydrogeological characteristics are one peculiar elements. Already
in XVIII century, there was a marshy area because of both neighbouring Banna torrent and
Old Santena torrent flowing splitting the property into two portions. Banna torrent control
by building a two-metre bank and burying Old Santena torrent allowed to recover the area,
even though the nature of the soil did not cange, so that Kurten decided to keep existing
ponds providing an aesthetic feature.
The so sketched park can be led back to three prevailing elements concerning the
landscape that are related to to the project:
- a circular path characterised by imposing present trees;
- a path, maybe prior to Kurtens intervention, connecting the Villa to the pond;
- a third path, connecting the two, with a more evident panoramic feature.
From the intervention by Kurten in the first half of XIX century to nowadays, the park
was not subjected to big modifications but for some planting on the celebration of the
centenary of the Unification of Italy (in the 60s) and for some maintenance interventions
needed after Banna torrente floods; the most significant floods occurred in 1901 and 1951.
In 1958, the City of Turin operated a number of interventions through Gardens and Trees
Lines Service in order to make the park more accessible to the public and, on this occasion,
52
a hundredth of veteran trees, which were considered to be unstable and dangerous, were
felled. A successive opening of the park to the public, joined to a defective conservation
management of the tree heritage, forced massive phytosanitary interventions in late 80s,
with felling of seriously impaired specimens.
In this period, there are both a complete inventory of the tree heritage by filing the
specimens from a phytopathological point of view integrating visual checks with instrumental
analises using a Presslers sampling borer (V.T.A. was not yet mentioned) and collaboration
with the University of Turin aimed at gaining scientific information and data useful for
improving park management. In early 90s, in the Park, there were made the first stability
investigations with V.T.A. (Visual Tree Assessment) method. This technique was at that time
innovative. It was used at a national level for the first time. In 1996, Park monitoring was
completed with V.T.A. This method has since then been a consolidated practice contributing
to define trees health state on a yearly basis. Trees health state is a data that is fundamental
in setting maintenance interventions.
Between 1994 and 1997, the City of Turin commisioned the University to make a study
aimed at trying to investigate on the crash of monumental specimens appearing to be
healthy but in retrospect showing limited root development. The study results did not
include particularly serious pathological situations and the study identified following
contributory factors among possible causes:
- abundant water present in surface profiles with resulting root aparatus in surface horizons;
- consequent development unbalanced between hypogeous and epigeous portions;
- numerous trees slanted as first bed out in clusters, then led into rows;
- soil chemical and physical characteristics not contributing to cohesivenss between soil
and root.
Just to give an idea about figures and connected maintenance needs (in economic
terms, without being limited by them), consider that the Park at present includes about 800
tree specimens (580 of them are taller than 10 metres) often having an extraordinary size in
crown both height and diameter, the species most abundantly present being the plane
(going back to XVIII century for numerous specimens, which are taller than 30 metres), oak
(common oak and durmast), hornbeam, cypress.
Benso of Cavour park is a particular instance also from property point of view. After
chequered fortunes and numerous conveyances of propriety, in 1947, Marquis Visconti Venosta
donated the Palace and the buildings of Cavour Museum and Archive to the City of Turin.
Since 1988, a covenant, now expiring, has been in force governing the relations among
the City of Turin, the City of Santena and the Camillo Cavour Foundation (set up in 1955)
and has established the technical and legal terms that are relating to the managemt of
assets. The Foundation is managing the buildings (the Palace, Cavour Museum and Archive)
and a park portion relevant to them, while park remaining portion is up to Santena Municipality,
the two being superseded by the City of Turin to which the management of all area tree
property is up in consideration of the specificity of specimens present.
Such an articulate and artificial splitting of competence and duties into three bodies is
not responsive to functionality criterions and further generates plenty of logistics and
management troubles; most of all, considering that two of these bodies (the Foundation and
Santena Municipality) are rather unwilling to schedule funds for managing the asset, also
because of their actual difficulty in finding dedicated resources, an area overall situation
results not being adequate to the importance and history of the park itself. In last months,
the paperwork to roll over the already expired covenant has been in progress. The priciple
the paperwork is based on is a revival of this historical residence on the whole (Palace,
Library and Park) and its innovative element is the identification of a body which will be
entrusted with the management of the whole asset and obviously will have to meet regulation
constraints and jontly agree upon and operate with both proprietor (the City of Turin) and
Public Green in all management choices and actions.
The drafting of a park avorall restoration program has been recently (1994) commissioned
to achitects skilled in historical residences and gardens. The estate use and management
program guide lines have also been identified and defined in this drafting.
The project provides to maintain and recover the arrangement, proposed by Kurten,
through the analysis of architectural, botanic, landscape and phytosanitary components. It
highlights as a negative element the splitting of management competence into more bodies
and reckons that the implementation of the restoration program is closely depending on a
more functional and organic arrangement, with a lightening of use load through the realisation
of a riverine park in the portion now subjected to agricultural use and with an improvement
of the distincion among areas uses.
53
About arboreal part, the project provides to: maintain the most abundantly present and
most representative species (plates, oaks, limes and hornbeams) as single, twinned or
clustered trees; reintroduce clustered minute texture species, and only use coniferous trees
for extending sight (thanks to dark leaves) and creating groves within a limited space and
time. It proposes to reintroduce either native species or species that became acclimatised
thanks to leaf chromatic alterations (copper beech, white popler, catalpa), to be used at
points of particular interest.
It is desirable that the future manager of the area applies the line guides that have been
identified in this restoration program in preparing a new covenant, with the purpose to give
back the park and residence the status and role deserved by them.
Monumental trees management and the instance of Santena
The subject of managing aged tree specimens is quite involving and there are often
clashing postions. Recently, in some contexts, it seems that a critical line is prevailing with
respect to management choices, which are aimed at keeping alive not perfect specimens,
because of economic costs considered unsustainable, perhaps thinking to apply firm and
industrial principles where all is depending on economic rules.
Urban tree lines and also trees in historical gardens and parks often are not in optimal
healthy conditions indeed; in some cases, they are affected by age and hard life together
with man, the city and connected needs, with a management which did not prove to be
adequate at a both technical and cultural level. Replacing partially impaired specimens by
new specimens can make some sense in determined circumstances, but it is not a care for
all problems. Monumental trees are to be considered as an integral part of cultural heritage
and, therefore, must be treated from the point of view of conservative management, avoiding
to compare historical green to conventional urban green, working on terms of maintenance,
conservation and restoration. A frequent question made by people or by ourselves is till
when have I to keep (alive) trees?
A reply could be: till they are sure, and longer, if I can. Arboricolture technologies and
know-how make it possible to best manage aged tree lines preserving the specimen considered
to be valuable and undertaking to reintroduce new ones in valid stational conditions rather
than just to step into a breach and show that something is being made, either using
specimens and trying to keep the original design or through a smooth replacement or an
integral reconstruction of arboreal. population
Ordinary and extraordinary maintenance interventions in a histotical context must be an
integral part of a management plan resulting from the analysis of original project, vegetation
component, landscape and architecture knowledhe/significance, aspectations, user safety,
and its interactions.
Tree management must be based on criterions, that are objective, and not only linked to
technical know-how, as well as on the identification of intervention priority levels. This is
also to avoid that, within a context characterised in a constant lack of funds, choices are
forcedly conditioned by a subjective (or, more correctly, emotional) component.
In the City of Turin, there has for some 10 years been developing a cultural transformation
process in tree management with the aim of introducing a model which, starting from (technical
and territory) knowledge and based on objective criterions, is aimed at optimising the choices
and substantially includes three main stepss:
- knowledge
- planning
- action
One of main points in this new management model is introducing a planning tool to
identify intervention priorities named Arrangement Plan (P.d.A.).
It is a tool based on the identification of technical and scientific parametars making a
snapshot of analysed object (the tree line, in this case), where each pareameter is given a
fixed, not weighed out weight (score); the addition of the various scores defines the tree
line potential risk level. Used parameters include dimensional, physiological data, linked to
trees health state and context where trees are located. By adding the data relating to
maintenance history, the urgency level is obtaiend, so a grid is generated, which simply and
objectively defines, for each tree line or homogeneous unit, both a score that is linked to
the potential risk level and an intervention urgency level index.
This tool is used to manage pruning and stability checks and is provided with verification
and self-checking mechanisms allowing for analysing and possibly justfying in retrospect the
choices that were made. This is a fundamental value, in a sector where management results
in responsibilities at civil and penal level. It is a tool which, coupled to the knowledge of the
54
region and the experience of cultivation/tree technique, also enables to plan and schedule
the interventions. Turin experience showed that, while maintaing the first position to the
role of the technician, with his/her know-how and experience, it is useful to use management
systems which somehow aseptically and objectively identify risks and priorities. In a linear
and somehow homogeneous context, such as the one of a tree line, it is simpler to adopt
this management guide line, also because the health state of trees, the presence of anthropic
activities force somehow the need of regularly intervening with more or less regular shifts
(provided that economic availability allows it).
In a reality characterised in differing features, such as the one of a historical park with
monumental trees, the point of view is changed, because the identification of a risk index
not necessarily must correspond to a concrete action, which could irreversibly damage the
specimen, although, on the other hand, a normal event like a dry branch fall can produce
serious consequences on oversized trees. Having to manage plenty of historical parks used
by the public, it can be useful to transfer this objective and functional management model
fitting it to the peculiarity of the arboreal populations of these sites, with the aim of creating
a data frame allowing to somehow standardise the approach, being aware that there are
faced specimens that are in some way sole specimen, where the priority is to know, not to
plan. Tecnichal and operational choices such as stability check, the application of more or
less regular pruning shifts on monumental trees can become meaningless and be insufficient
to assure asset good management and even obtaining a priority index could be unsuitable
to the context. Using urban tree lines pda, modifications were made and parameters were
introduced being more suitable to the reality of the historical park which were grouped into
homogeneous sub-groups, obtaining a set of categories taking into account:
- stability analysis with relating risk class;
- potential risk from the tree objactively occurring, for its position (target of and exposition
to wind), this being an element which can be managed but not modified;
- potential risk linked to tree size (hight, diameter, crown) and faults present (rot, stringy
branches, slanted trunk, etc..), this being a data which acan be modified and managed
with cultivation operations;
- morphological and geological peculiarities linked to context, in the case of Santena the
presence of the surfice layer which conditions root apparatus growth and tree stability.
In this way, there are not obtained any overall final scores, which wuold have been
rather useless, but a set of distinct values, which define aframe repreenting the peculiarities
of monumental trees in a historical park and identifies risk areas, attention thresholds
where interventions are to be focused to a greater extent.
The different data can be used either disaggregated or together in order to decide
maintenance interventions also considering the point where trees are located and personalising
choices depending on cases; as an example, on trees with stability problems having a high
target, crown reduction operations shall be performed, while isolated trees can just be kept
under observation limiting interventions to dry portions removal and periodic stability
verification. This data can be trasferred to plans in order to map risk areas and obtain a
region deep knowledge visual frame. So a transition is made from the management of a
typical urban environment, where, owing to large figures and management needs, the
judgement about the tree unit is uniformed and where we are somehow forced to manage
trees in the logic of compulsory rated interventions, to a management which, although
adopting an objective methodology, takes into account both context and particolarities odf
specimen which are sole specimens. It is an operation requiring a remarkable expenditure of
energy in the preliminary step, but the result achieved is a an easy-to-use tool which does
not pervert the technical role and is anyhow the evidence of adequate involvment and care,
as well as a summary of what is provided by arboricolture techique and technology as
applied to an atypical context.
In a reality of this kind taken in account can also be management improvement choices
such as elevation check, root inspections, which, in urban contexts, can involve huge
difficulties in application and a risk of creating a precedent.
Considerations
Tree management probably needs a cold blood or perhaps sound madness, as well as a
serenity in facing living being which, by dying, may unfortunately create even serous problems
to users and environment.Looking at past texts, you find out that wood rot was considered
in XVIII and XIX centuries by our collegues as a natural event, a sign of the age, especially
for very old trees, while serenely accepting the cours of nature and time. Perhaps such
serenity came from missing legal implications on users safety, but also from a more aware
55
relationship between man and nature, where the decay and death of a tree were correctly
considered as all natural events.
In tree management in last decades a transition occurred from choices borrowed from
other fields (namely agriculture), to panic linked to bad events, running after a remedy to
dispose of / release from problems, responsibilities, risks. As soon as a serious event occurs
linked to the fall of a tree, there is a temptation to react trying to remove the problem,
maybe even before understanding what happened and why, without caring about whether
making like this it is nullified a heritage of knowledge, experience and results buit up over
years. If the point is removing any responsibility, there is a sole reply: not being involved in
managing trees or convincing the one who holds the reins that in front of any doubt the
problem must be suppressed at the root (fitting, isnt it?.).
In my opinion, it can now be tried to approach again to a serene but aware management
concerning the treatment of monumental trees marked by time and man. Research, technique
and technology, and current practice have extended the range of choices and management
capabilities, while keeping steady the strong points, which are the respect of the dignity of
the tree and what is represented by it whlile guaranteeing users safety.
Literature
AA.VV. The gardens of the Prince IV International Meeting on Hisorical Parks and Gardens.
22-23-24.09.1994
AA. VV. Vegetation and the historical garden Proficiency Course in Parks , gardens and green
areas University of Turin, Faculty of Agriculture Day of study 22.04.1996
La MARCA O., BOVIO G., BOVO G., SANESI G. - Methodological aspects in the management plan of
the Park of Maddalena Arboretum Taurinense of Turin Abstract from Yearly Review by Italian
Acadamy of Forestal Sciences 1996
NICOLOTTI G., BOVO G. Crasshes in monumental trees subjected to uprooting. Acer 1997.
AA. VV. The Hisorical Garden: representation, reading and ornamenta species National
Council of Researches School of Specialisation in Parks and Gardens University of Turin, Faculty
of Agriculture. Torin May 8th 1998.
C. Bertolotto, G. M. Cirulli, P. Odone Urban tree lines: diagnostic systems, management of
know-how and interventions Proceedings of the National Conference on Urban Green Accademy
of the Georgofili Florence. October 9th-10th, 2002
56
MANAGEMENT OF MONUMENTAL TREES: REVIEW ON THE EFFECTS ON PHYSIOLOGICAL
BALANCE AND ON TREE BIOMECHANICS
F. Ferrini
Dipartimento di Produzione Vegetale - Università di Milano
Introduction
It is known that as a tree ages its growth markedly changes and that several physiological changes are associated with plant aging. Unfortunately, while aging of cells and organs
(i.e. leaves) has been deeply studied, only limited information can be found on woody plants
considered as a whole. As a matter of fact, though woody plants show significant and
predictable patterns of changes in morphology and physiology as they age, the study of the
possible mechanisms controlling these changes is quite difficult because of the large biomass interested and the complexity of the processes involved which have also arisen some
controversies among the different authors.
Understanding the growth and the physiological behavior of old trees is important both
for ecological studies of natural stands (Ishii et al., 2000) and, as in our case, to know what
are the effects on tree physiology and on tree biomechanics of some technical practices
which are commonly applied in mature to veteran tree management.
Aspect of aging
It is quite difficult to situate exactly the beginning of the aging (senile period) in woody
plants, because the processes that regulate aging are not fully understood in these kind of
plants like they are in animals and annual plants, which aging and senescence are genetically regulated (Bond, 2000). We may consider that it happens at the moment when both
vegetative growth and differentiation phenomena reach their maximum expression. Senility
then can be defined as the phase of life that begins when the individual is at the last stage
of adultness and it is characterized by erosive processes which conduct toward death.
Similarly to what happen in the change from juvenile to mature phase (Greenwood, 1995),
there are probably a number of switches, either in series or parallel, both endogenous and
exogenous that must be activated for the senescence phase to occur.
It is evident that at least in some woody plants the absolute quantity of organic matter
does not increase during the senile period; on the contrary it diminishes. The changes that
take place during this period are mostly endogenous and of physiological and biochemical
nature, circumstances that make the bibliographical search not easy. In addition ontogenetic aging (maturation) in trees has received less attention compared to other research
topics because, as already stated, the study of woody plants becomes more difficult with
aging and tree size.
In spite of some studies published on this subject, it is not easy to distinguish between
the effect of age, size or environmental changes connected to aging, much less the interactions among these factors. However, new techniques (i.e. analysis of stable isotopes, improved approaches for measuring sap flow) and better field equipment are helping to make
studies of tree aging more feasible, though we are far from a comprehensive understanding
(Bond, 2000). Furthermore there is no full agreements about what the word aging really
means, because terms related to plants can have a similar or different meaning (Fontanier
and Jonkers, 1976; Nooden and Leopold, 1988). As underlined by Trippi (1963) many authors
refers to aging when they talk about the transition from juvenile phase to adult or senile
phase; also when they talk of vegetative and reproductive state (in this case the term
maturation seems to be more appropriate). Others state that the senescent phase begins
when the trees start to deteriorate as a results of damage or disease (Del Tredici, 2000).
Paraphrases such as decreasing vitality and other definitions have been used for it
(Bernatsky, 1978).
According to other authors we can describe three different types of aging in plants
(Fontanier and Jonkers, 1976; Clark, 1983; Del Tredici, 2000; Fay, 2002).
- chronological aging, which is the time that has elapsed in the course of the lifespan of
the entire plant or some part of it.
- Ontogenetical aging, related to the process of a plant passing through different phases
of development (i.e from seedling to senescent phase). The ontogenetical aging process,
called maturation or phase change by some authors (Ritchie and Keeley, 1994), is controlled
by the meristematic tissues of the tree and its not uncommon for different parts of the tree
to be in different growth phases at any point in time, as when juvenile suckers originate from
57
fully mature trunk tissues. According to Fontanier and Jonkers (1976), ontogenetical aging is
genetically programmed, localized in the meristems, not related to exhaustion, and cannot
easily be reversed.
- Physiological aging (senescence), referring to the general condition of the whole plant,
describes the development as well as the deterioration of the life-support systems of the
tree. It represents the negative aspects of aging such as loss of growth vigor, the increased
susceptibility to adverse conditions (stresses), etc. These negative aspects gave origin to a
new branch of science called phytogerontology which, however, hasnt developed like others. Del Tredici (2000) states that physiological aging specifically covers the loss of vigor in
the root or shoot system that results from environmental stresses or from the damage
caused by wind, fire, ice and snow. In general, the physiological aging process is controlled
by the differentiated tissues of the tree. Physiological aging is correlatively influenced and
caused by an increase disorganization and exhaustion, and it is not localized in the meristems. When not advanced, a reversal is possible (Fontaniers and Jonkers, 1976).
This paper will be mainly focused on reviewing the present knowledge with regard to the
changes that happen during physiological aging.
The major symptoms of this phenomenon are a decrease of the metabolism, decrease in
both photosynthesis and respiration, changes in enzymes activity, reduced growth of vegetative and reproductive tissues, different hydraulic and mechanical properties of woody
tissue, increase in dead branches, heartwood formation. Slow wound healing, and changes
in resistance to invasion by certain insects and pathogens are other typical features of
woody plant senility (Kozlowski, 1971; Fontanier and Jonkers, 1976).
Some of the mentioned aspects are the object of other presentation in this Congress so
I will focus, according to the title, on the physiological aspects of woody plant aging and on
the effect of some management techniques on tree physiology and biomechanics.
Physiological and anatomical changes
The phase of aging is characterized by a slowing down of metabolism activity. Some
studies have shown that while leaf area of aging trees remains practically constant, its total
photosynthetic output slightly declines while respiratory consumption of food increases (due
to the increased amount of non-photosynthetic tissue increase), so that the leaves are not
able to provide adequate photosynthates for the requirements of the old tree (Kozlowski,
1971; Day et al., 2001). The results obtained from research carried out on conifer trees
have shown an age-related trends in both morphology and physiology, an increased competition for nutrients between the various parts of the plant (Moorby and Wareing, 1963) a
decrease in photosynthetic rates contributing to declining productivity in old trees (Bond,
2000; Day et al., 2001). Several studies attribute this lower photosynthetic rates in older
trees to a reduction in stomatal (or crown) conductance with increasing tree age which, in
turn, is caused by a lower hydraulic conductivity in their longer or more complex hydraulic
pathways. Based on this some authors have proposed the hydraulic limitation hypothesis
(Ryan and Yoder, 1997), which states that with increasing tree height growth and productivity decline because of stomatal limitation induced by greater tortuosity (i.e. branch juncture), increased hydraulic pathway length resistance and gravity and reduced allocation to
roots (Ryan and Yoder, 1997; Bond, 2000; Phillips et al., 2002). Increases in hydraulic
resistance could reduce the supply of water for transportation, which in turn could limit
stomatal conductance and photosynthesis (Bond, 2000; Coder, 2002). This hypothesis is
supported by recent data obtained on Quercus robur mature trees (Rust and Roloff, 2002).
In addition to the lower conductivity of xylem in old trees, structural changes in shoot and
crown architecture need to be considered when analyzing water relations and photosynthesis in mature and declining trees (Rust and Roloff, 2002). However, some contrasting results
do exist and it seems that hydraulic limitation, though may be a significant factor determining growth reduction (Battaglia, 2001), does not act on photosynthesis in a simple mechanistic way or that other factors play a key role in age-related decline in some species (Day
et al., 2001). Actually, as shown by West et al. (1999) conducting tubes must taper and,
consequently, the resistance to fluid flow per tube are independent of the total path length
and plant size. Becker et al. (2000) state that leaf area:sapwood area ratio rather than path
length, may dominate in determining whole plant conductance. These authors also state
that the structure of the xylem cells might change as tree grow older to make the wood less
resistant to water flow. As a consequence the sapwood area per unit area might increase
and the sapwood of large trees might store large amounts of water, thus buffering the
effect of hydraulic resistance (Bond, 2000; McDowell et al., 2002).
58
According to Coder (2002), several physiological causes are involved in tree aging responses. He reports that 25% of these responses are due to photosynthesis reduction, 10%
to sapwood respiration, 20% to soil resource availability, 39% to transport path length and
complexity, 5% to detrimental mutations in genetic materials and 1% to reduced defense
ability. Grulke et al. (2001) also found a different allocation, with young plants having the
highest allocation in roots and foliage and older plant in woody tissues, though their work
was limited to mature and not senescence trees.
Among the other physiological factors it is known that hormones play a dynamic causal
role in endogenous regulation and control of plant senescence (Noodén and Leopold, 1988).
While this concept is generally accepted, much is yet to be learnt about their effect on
mature tree physiology. Actually, even if research on the classical plant hormones continues
to uncover fascinating interactions among these crucial regulatory compounds and how
these interactions can affect signal transduction or hormone biosynthesis (Fontanier and
Jonkers, 1976; Ross and ONeill, 2001), the results are mainly related to herbaceous plants
and, as such, not always can be directly applied to explain some physiological traits of
woody plants.
Vegetative growth
Even perfectly healthy and undamaged trees slow down in growth as they reach an
advanced age. This lack of vigor may also cause an increase in susceptibility to insect pests
and to pathogens. With aging shoots become shorter and weaker, the amount of food
absorbed being insufficient to support the whole crown, and as time goes on they gradually
die downwards towards the trunk. Clark (1983), referring to other authors works, states
that as the tree grows larger, the ability to respond to environmental stimuli or timing of that
response increases. This can explain why older trees in landscape situations are much more
sensitive to site disturbances. Kozlowski (Kozlowski, 1971) affirms that loss of apical dominance usually accompanies reduction of shoot growth in aging trees. The same author,
referring to a previous research on conifers, states that as the branches became older, they
changed their growth angle to a more horizontal, so that the structure of the crown can be
strongly modified. This has to be taken into account when managing monumental trees.
Changes in wood characteristics
In the old trees the wood is not uniform throughout the trunk: there is a definite pattern
in its development which reflects the changing activities of the vascular cambium and
changes in cellular differentiation at different periods in the life of a tree (Jane, 1970).
In fact, several important anatomical changes occur during the aging of trees which
influence wood quality. Kozlowski (1971), reviewing other Authors papers, states that with
increasing age the percentage of latewood (wood formed later in the season) increases for
a number of years and this change is accompanied by increase in specific gravity and
strength. In over-mature trees, however, the specific gravity of wood often declines and
little or no latewood is produced. Also the over-mature wood can have a higher lignin and
lower α-cellulose content than wood formed when the tree is younger.
Another change of paramount importance regarding wood anatomical and mechanical
characteristics is the heartwood formation. As known the wood of young trees is entirely
made of sapwood which is physiologically active (it contains from 5 up to 40% of living cells)
because it serves as an avenue for translocation of water and minerals (Kozlowski, 1971).
The changes in wood associated with aging are a result of a genetically controlled process
(Shigo, 1984) and are primarily functional, for, after a time, the parenchyma in any zone of
wood in a tree loose their its living protoplasts and the vessels and tracheids cease their
conductive function (Jane, 1970). It is generally believed that after these changes have
taken place, the only functions of the wood are those of support and as a repository for
waste materials and is considered physiologically inactive, although it has been suggested
that the wood may still serve as water reservoir.
As sapwood passes into heartwood, some changes in physiology and anatomy happen.
These include altered metabolic rates, changes in enzymatic activity (i.e. increased peroxidase activity), starch and food reserves depletion, darkening of xylem associated with
deposition of extractives, gums, resinous and phenolic components, tannins, coloring matters, changes in wood density, anatomical changes such as increase pit aspiration in gymnosperms and formation of tyloses in angiosperms, and changes (decrease) in moisture
content (Jane, 1970; Kozlowski, 1971; Gjerdrum, 2003). These changes can have a direct
influence on wood disease resistance, because heartwood is less prone to be attacked by
59
fungi and insect due to its higher content in preservatives substances, though this statement has been disputed by old and recent studies because there is a sufficient air in the
heartwood for fungal growth, while the wetter sapwood does not contain enough air to
make it suitable substrate for wood-rotting fungi (Jane, 1970; Read, 2000). Decay of the
inner wood can be actually positive because the hollowing are part of a nutrient recycling
process and as stated by some authors (Read, 2000), tree can make use of the products of
wood decay inside the trunk by producing aerial roots form its above ground parts, which
grow into the rotting stem.
Management techniques of veteran trees
The problem which quite frequently arises is whether it is worth spending money on very
old trees in order to lengthen their existence, or whether they should be left alone and a
young tree planted somewhere in the vicinity. No one would spend money in a obvious
wreck, but any tree worth keeping is worth some sort of attention. It needs very little, as a
rule to keep a tree wind- and water tight (Le Seur, 1934).
According to Read (2000) the first thing to be considered is to distinguish two types of
veteran trees: those that have been actively managed in the past and those which are not,
though in practice, the techniques may not be so diverse. In addition we should bear in mind
the location of the tree. Veteran trees located in the urban environment are subjected,
compared to those located in the open country, to several stresses which can strongly
affect their health and shorten their lifespan; this must be considered when managing these
trees. There are numerous management techniques that must reflect the changing and the
function and that must consider the long-term consequences of environmental changes
(Clark and Matheny, 1991). Some of them (tree securing, use of biostimulants, growth
retardants and mycorrhizal fungi) have been extensively reviewed by other speakers in this
Congress; therefore they will not be considered in this paper that will try to provide an
outline of the literature pertaining to the effects of pruning and, in general, of some cultural
techniques on tree function and structure. However, according to Clark and Matheny (1991)
we can state that the maintenance of a balance between growth and the environment is a
basic requirement for continue development and longevity.Arborists must strive to maintain stable growing condition through long-term programs of care and facilitate the restoration of balance within a tree whose environment has been disturbed. The same authors
arise a practical question that is: what management techniques can be applied to a tree to
avert or postpone the development of the mortality spiral?1.
Pruning
The first answer to the question is to help the plant to develop a stable structure. Crown
structure has a fundamental importance for tree physiological behaviour determining substantially the spatial distribution of the photosynthetic surface, the water loss (evaporation
and transpiration) and, as a consequence, directly influencing the mechanisms of water and
nutrient uptake and transport. Crown structure also affects the mechanical resistance of
the tree though a notable variability exists in the geometric structure due to a great
phenotypic plasticity, that makes the schematizations difficult but, on the other hand,
allows great manipulation possibility of tree form.
In this scenario we can easily guess how pruning techniques can affect tree physiology
and have strong effects on tree health. Actually, pruning determines a different partitioning
of the total dry weight, with a greater production of new shoots and a smaller development
of the structure (branches, trunk and roots). However the growth of such new shoots is
proportional to pruning intensity only to a certain extent, over which it decreases.
Fontanier and Jonkers (1976) state that a severe pruning of the branches or stems is
effective in delaying the time of aging. It shortens the internal transport system and improves the supply of the periphery with water and nutrients. This can be regarded as a
physiological rejuvenation. Pruning also induces younger buds or tissue to form normal or
adventitious shoots, those being more juvenile than those removed. This can be seen as a
kind of semi-ontogenetical rejuvenation. Though severe pruning and crown restructure can
be required for safety reason, such a rejuvenation cannot be continued indefinitely, because
each pruning activates the present meristems, involved the commitment of significant resources; the typical response to this kind of pruning is profuse sprouting that can result in
energy depletion, dieback, increased susceptibility to secondary pests or decline, thus
inflict an additional stress to old (or declining trees), and stimulating their ontogenetical
aging (Clark and Matheny, 1991). Furthermore the elevated production of new vegetation
60
strongly reduces nutrients reserves, in particular of carbohydrates, stored in the unpruned
part of the tree. In fact plants subjected to pruning show alterations in carbohydrates
metabolism in comparison with the unpruned plants, in particular at the beginning of the
vegetative season, when, in the shoots in active growth, a presence of an elevated level of
soluble carbohydrates, above all with regard to the contained in starch, can be detected,
while the reserve accumulation phase begins more lately. According to Evans (2004) this
kind of pruning has deleterious repercussions on the relative allocations and prioritisation of
a trees carbohydrates budget.
A review on this subject was made by Clair-Maczulajtys et al. (1999). Based on the
assumption that reserves are not homogeneously distributed in the tree, but are stored in
special areas or compartments, in relation to the species, stage of development, environmental conditions, and cultural techniques like pruning, they showed how tree pruning
(especially when heavy pruning is applied) can induce a decrease in the quantity of reserves
(crown volume reduction, foliage removal, new sinks) and determine important changes in
their partitioning. They underlined how abrupt changes in tree care, can have deleterious
effects on tree health, causing a general decrease of reserves and, as a consequence,
reduce the resistance to pathogens and predators and to the environmental factors. Thus,
to avoid radical pruning effects on tree structural stability and on pest problems, pollarding
can be considered as a real alternative (Coder, 1996). A tree responds to pollarding by
building a dense mass of woody fibres around the cutting points. This bulky mass resists
decay and effectively divides the vigorous juvenile growth from the aging stem (Harris et al.,
1999). Hence, the defensive and structural integrity of the tree is maximized using this
pruning system, because pruning cuts are made when biological reactivity of the trees is
quite high and living cells quickly react to wounds and environmental changes and can
develop a strong defensive reaction (Coder, 1996). Also pollarded trees develop a constantly rejuvenated, energy-creating young canopy, on top of an increasingly ancient trunk.
This slows the trees normal aging processes. However, while some species can positively
react to pollarding (Quercus, Platanus, Tilia), some others (Fagus and Acer species) do not
always tolerate pruning (Mattheck and Bethge, 1998). According to Raimbault (1995) we
can state that pollarded trees anticipate the natural, uninfluenced behaviour of at least
some species.
Even the hormonal frame of pruned plants can be deeply altered because of the removal
and activation of numerous meristems that are, at the same time, hormone producers and
users. In particular an increase in the activity of cytochinins, auxins and gibberellins has
been found, with some fluctuations according to the phenological phase of the plant.
Cytochinins content and activity is very high in the growing shoots of pruned plants, while
gibberellins content is relatively low in the bud break phase to significantly increase only
later in the season, showing substantial differences among pruned and unpruned plants. The
auxins seem to increase above all in the branches following the stimulus induced by cytochinins,
even if a strong activity of synthesis of the root system, due to the altered crown/root ratio
cannot be excluded. The increase in the auxins and gibberellins synthesis promotes the
development of the vascular system and activates nutrient transport, thus intensifying the
growth of the new vegetation.
Bearing in mind this knowledge about how pruning can influence the physiological balance
of a tree it is easy to guess how difficult is to manage veteran trees in order to improve their
stability without negatively affecting their physiological balance which, in the long term, can
push them ahead into a mortality spiral (Clark and Matheny, 1991).
Older trees, due to their health and stage of life, require more attention before pruning.
They cannot withstand pruning as easily as younger, vigorously growing trees, because they
have limited energy reserves to fight invading diseases and insects, especially at the pruning wounds (NAA, 2004), and when they have been subjected for years to irregular pruning
which creates zones impoverished in carbohydrates (Clair-Maczulajtys et al.,1999). As a
consequence old trees should be pruned only as needed. Pruning should be limited to remove
dead, suppressed, structurally weak, diseased and insect damaged branches or to lighten
heavy horizontal branches. In general, it is better to remove less than 25% (other authors
recommend less than 10%) of the total tree leaf area (or branches) per year (Gilman, 1997;
Elmendorf, 1998), or even better, limit the cuts to crown cleaning without removing living
tissue (do as little as possible in the way of cutting, Read, 2000).
It is fundamental to keep in mind that the destabilisation of thinning operations increases
exponentially with increasing tree age and height. Niklas (2002) underlined that when
stems are exposed by the removal of neighbouring portion of a tree, parts that were shel-
61
tered and strong might deform or break even under normal wind conditions. Pruning also
shifts the self-loading conditions of branches or roots. This can have negative effect on
tree biomechanics by decreasing the safety factor (the quotient of the load capability and
the actual load of a structure or the ratio of the breaking stress of a structure to the
estimated maximum stress in ordinary use)(Niklas, 1999; 2002). Further, when trees are
topped, overpruned, or stressed, they produce epicormic shoots which are weakly attached
and prone to mechanical failure (Hayes, 2002). The modelisation of tree mechanical characteristics has been subjected to some critics by some researchers who state that also
morphological, histological, and physiological aspects must be considered (Fournier-Djimbi
and Chanson, 1999). Recently a new failure criterion for non decayed wood has been
proposed by Mattheck et al. (2002) based on the Height/Diameter (H/D) ratio that relates a
higher mechanical safety and a better biological supply with water and assimilates to tree
with a lower H/D ratio. Management techniques (first of all planting not too dense) should be
aimed to decrease or maintain a lower H/D ratio.
In conclusion, according to Davis (2002) we can state that there is no hard-and-fast
rule as to how much an individual trees growth can be cut back. Different species can
differently react to heavy pruning and disagreement in the literature is not surprising given
that different species where studied, and that in many cases the environmental conditions
and the historical background differed. Also, as previously stated the negative effects of
improper pruning should be taken into greater consideration when dealing with veteran tree
in the urban environment and different management techniques might be needed.
Root Pruning
Trees in the urban environment are often subjected to heavy root loss due to soil
excavation near trunks. This is not obviously a management technique and its long-term
effect on tree health and structural stability is really negative (Harris et al., 1999). As a
matter of fact, there is a direct relationship between root loss and growth reduction which
triggers a negative-feedback loop, alters the root-shoot ratio, stimulate decay and internal
defects, and pushes a tree in the mortality spiral. In fact, beside nutritional interactions,
there is also evidence that hormones play a role in mediating root-shoot interactions. Auxins
produced by the leaves flow downward to the roots and stimulate new root formation and
cytochinins, probably the major antisenescence hormone (Noodén and Leopold, 1988), produced by the roots go upward to the leaves, stimulating shoot growth. Altering this balance
can have a direct on plant health.
As a consequence, we have to be very careful when cutting roots, because, besides
increasing uprooting potential (short-term effect), due to the fact that root not adequately
anchor the tree against wind and weight, we deeply alter the physiology of the tree (longterm effect). Heavy crown pruning in this case, it is probably not the best way to restore
the balance between the root system and the canopy, but we have to consider to stabilize
the tree or to reduce the force of the wind against the tree by crown thinning, which,
however should not be considered a long-term solution to root loss and deformities (Gilman,
1997; Elmendorf, 1998).
Other cultural techniques
As described, pruning is by far the technique that most affects tree growth and physiology, but there are other treatments that can be done for old trees. All the techniques
should be aimed to reduce the stresses of various type both intrinsic to the site (soil
physical and chemical characteristics) and extrinsic (severe chilling, heat, drought, diseases), that are able to induce or accelerate many changes related to plant senescence.
Some of them are directly applied to the plants, some others are aimed to the improvement
of soil fertility and to prevent conditions which are known to be the trigger for any kind of
disease. However, as stated by Clark and Matheny (1991), each of the treatments may
have good and bad consequences on tree health because they can both positively and
negatively interact with the development of a stable environment.
Coder (2002) indicates several treatments that can be applied to old trees that can be
summarized in keeping the tree healthy by establishing good and stable soil and environment
conditions. Among them improving soil fertility seems to have a certain effect, although
controversy exists about the effect of fertilization on veteran tree physiological health and
on the interaction between fertilization and other management technique like pruning.
When fertilizing it should be underlined that N efficient uptake occurs during period of
active growth and depends on active photosynthesis. If we reduce the photosynthetic
62
area, we can negatively affect N uptake. Also high N applications reduce the concentration
of defensive compounds increasing the trees susceptibility to certain pests (Struve, 2002).
Fertilizers should be applied lightly for mature and old trees in late summer or early fall to
promote nutrient storage. Mulching can reduce environmental stresses by providing trees
with a stable root environment that is cooler and contains more moisture than the surrounding soil. Mulch can also prevent mechanical damage by keeping machines such as lawnmowers
and weedwhips away from the trees base. Further, mulch reduce competition from surrounding weeds and turf (ISA, 2004).
Conclusion
In spite of the progresses made in the different topics related to plant physiology our
present knowledge about the process of aging is not fully adequate to enable us to fully
explain it. Understanding aging process is important for setting up management techniques
to operate on mature or veteran trees. Such information would be also useful in determining
how biotic and abiotic stresses contribute to the loss of vigor and eventually lead to
mortality in old trees and how these individuals will respond to the different treatments.
We believe that it is necessary to point out the need for special studies, in order to
elucidate the real ontogenetical significance from the morphological and physiological changes
associated with the different phases of life juvenile, adult and senile.
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(Footnotes)
1
A mortality spiral describes the sequenze of the events as a tree
s condition changes from healthy to stresses to declining to death (Harris et al., 1999)
64
SURVEY METHODS & DEVELOPMENT OF INNOVATIVE ARBORICULTURAL TECHNIQUES
IN KEY UK VETERAN TREE SITES
N. Fay
Arboricultural Consultant: Treework Environmental Practice, Chairman of the Ancient Tree Forum
Summary
The quality and condition of Britains old tree heritage is reflected in the great number of
ancient tree sites found in the British Isles, reputed to be among the finest in Northern
Europe. Environmental arboriculture and veteran tree conservation methods have been
influenced by a multidisciplinary approach that considers the tree in co-evolutionary terms,
inherently linked to its ecological context. This approach considers the importance of the
ageing process and the use of terminology relating to the developmental stages a tree
passes through. The interactions between trees, fungi and other dependent organisms are
considered, particularly in the light of the need for arboriculture to take account of how tree
management can work to maintain or re-establish conditions suitable for a functioning treeecosystem. Understanding the rates of decline in old tree populations has been improved
considerably in the UK since the development and use of the Specialist Survey Method.
Studies of important veteran tree sites indicate that the rate of tree loss may be unsustainable.
This in turn threatens the continuity of dependent saproxylic communities. Innovation in
arboricultural management techniques has been influenced by observations of natural
processes. The recent emergence of environmental arboriculture provides a framework for
considering such issues and for developing appropriate practices to manage trees to enhance
longevity and biodiversity. Principal among these is the development of Individual Tree
Management Plans for veteran trees, which set planned treatments programmes for 30 to
100 years. Environmental arboriculture, while responding to all current conventional
arboricultural considerations and practices (including tree hazard management and amenity
tree care), offers scope for an interdisciplinary synthesis of perspectives between all those
involved in the appreciation of veteran and ancient trees.
Terminology: Veteran & Ancient
In the UK the term veteran is used to describe both the age and condition of a tree. A
veteran tree has the anthropomorphic, cultural connotations of a battle-scarred survivor:
a valued, old comrade that has been through the tribulations of life. Veteran has come to
describe the quality of dead wood habitat in trees. The term is widely used, being both
accessible to the specialist and to the public imagination. In recent years an increasing
appreciation that decay in trees is important for wildlife. As a result, arboricultural techniques
have evolved that inflict deliberate damage or wounding on trees to induce conditions
suitable for the progression of rot or other niche habitats. This has caused the need to
invent and convey unusual concepts, such as to veteranise and veteranisation. These
express effects or actions (deliberate or inadvertent) that impact upon trees, causing the
development of dead wood habitat features.
The terms veteran, old and ancient are all used to describe trees that are of interest,
biologically, aesthetically or culturally (Sissitka 1996) as a product of age or condition
(Read 2000). Moreover, veteran is used to describe an old and valued specimen, which
may have survived beyond the typical age range for the species (Lonsdale 1999). These
terms are often used interchangeably. This paper will explore the conceptual difference
between the factors of age and condition and why it is important to clarify these concepts
for the purposes of developing appropriate criteria for recording the biodiversity value of
such trees and for the formulation of appropriate methods for their conservation. In broad
terms, old and ancient refer to age class, while veteran refers to habitat condition (Fay
2002).
The term ancient tree may be understood as an age classification to describe the stage
when, after the loss of apical dominance a tree passes beyond full maturity and the crown
begins to shed redundant parts and accumulate dead wood. The crown begins to reduce in
size (crown retrenchment) and the annual increment (CAI) eventually reduces, compared to
earlier developmental stages in the trees growth (White 1998). This is the final stage in the
life of the tree (Read 2000) and, where conditions are favourable, can be the longest.
While all ancient trees will have habitat features sufficient to qualify them as veteran
trees, all veteran trees will not necessarily have entered into the ancient age-class.
Mature trees that show a moderate to high level of veteran features are now termed early
veterans. Until recently, the terms veteran and ancient had been used interchangeably,
65
however it is useful to clarify this distinction. For survey purposes, when required to quantify
veteran trees to assess the quality of tree habitat, all ancient and early veteran trees will
typically be included. When surveying to evaluate the age structure of the tree population,
the inventory of the ancient age class will include only those trees past full maturity.
Therefore, as there is scope for misinterpretation, it is important that, when using the terms
ancient and veteran, the above contextual distinctions are understood and explicit.
As the ageing process progresses, dead and dysfunctional woody tissue is colonised by
fungi, which change the nature and condition of wood material. Natural damage and shedding
of tree parts can lead to trunk hollowing, branch cavities, live stubs, shattered branch ends,
loose bark, sap runs and a range of rot types. The organs of the saproxylic fungi (fruiting
body, mycelia etc) may in turn be colonised, for example, by specialised invertebrates. This
complex saproxylic substrate, held within a living sapwood envelope of the tree, provides
specialised niches for different organisms with diverse life-styles. A recognised exemplary
system, developed in the UK, provides an index of conservation value for woody habitats.
This is known as the Saproxylic Quality Index, which compares the site-specific species
richness of saproxylic Coleoptera (dead wood beetles) against a standard list, for which
rarity scores have been assigned (Fowles, Alexander & Key 1999). Colonising saproxylic
invertebrates may have very limited powers of dispersal and certain species may only colonise
rot sites once circumstances are favourable. The greater the length of time a group of trees
exists on a site, the greater the possibility for particular specialised and rare species to
colonise dead wood habitat. Alexander notes that six percent of British invertebrate fauna
depend on other species that, in turn, depend upon decaying wood. He estimates that as
many as 1,700 invertebrate species are dependent on ancient trees (Butler, Alexander &
Green 2002). Continuity is therefore a major factor in biodiversity associated with old trees
(Alexander 1996 & 1999).
UK Context
History of Tree Cover: wood-pasture and parkland
In the UK, wood-pastures are the natural inheritance of medieval hunting forests, historic
parks and wooded commons. Records indicate that there has been continuous grazing in
wooded landscapes throughout lowland Britain, dating from the Norman Conquest. These
show that large areas of wood-pasture existed both in private ownership and on common
land in the eleventh century (Rackham 1993). Recently, the significance of grazing animals
in the development of wooded landscapes has been examined with the conclusion that
grazers are effectively a natural agent of landscape management. Taking the oak as a focus
of study, Vera examines the natural processes involved in wood-pasture mosaic habitats,
and concludes that the relationship between herbivores and trees is co-evolutionary (Vera
2000).
Grazing history has been a major factor in the formation of the British landscape. Britain
has a history of emparkment dating from medieval times. Our ancestors used wooden staves,
hedging and walling to enclose deer, and the relics of these boundary features can still be
found in many parks. After the Norman Conquest, fallow deer (Dama dama) were introduced
and the practice of establishing new parks spread. By the fourteenth century, it is claimed
that 3,200 parks were recorded in England, estimated to cover 2% of the country (Rackham
1980).
While many original parklands still exist, the Romantic Movement that flourished in the
seventeenth and eighteenth century inspired the construction of naturalistic, designed
landscapes with formal gardens and features. These parks were associated with the conscious
planting of trees of great character, often intended to provide pleasure gardens and framed
views. Tree plantings were often superimposed on an existing matrix of old trees (Fay 2001).
Parklands today typically contain examples of tree populations dating from the earliest
period of recorded emparkment to modern times, including a great number of pollard trees,
cut to prevent deer from browsing regrowth.
Pollards were cut and managed as working trees (Green 1996) for a wide range of
produce. The size and frequency of cutting depended on local and regional economic
requirements (Read 2000). Principal traditional pollard species include oak (Quercus robur
and Q. petraea), hornbeam (Carpinus betulus), beech (Fagus sylvaticus), common lime
(Tilia cordata), willow (Salix fragilis et al), ash (Fraxinus excelsior, holly (Ilex aquifolium) and
sweet chestnut (Castanea sativa).
In the UK, old trees are abundantly found in old growth woods, parklands and woodpastures, and to a lesser extent in hedgerows, river and boundary banks, commons and
churchyards, (Read 2000). In woodlands, their long-term presence is often the result of
66
coppice history, where it was periodically necessary to manage and restrict grazing animals
to prevent browsing of new growth.
The cultural tradition of pollarding exists throughout the European wooded landscape.
Old pollards may be seen from the wooded meadows and pastures of Sweden and Finland
(Hæggström 1998; Ranius 2000; Slotte 2000) to the silvopastoral La Dehesa systems of
southern Spain (Montero, San Miguel & Canellas, 1998). They are found in wood-pastures in
upland Scotland (Quelch 2000) and in the grazed olive groves of Crete (Rackham & Moody
1996). Their continued presence today owes much to methods of husbandry. The practice
of cutting tree crowns above grazing level for produce, while varied by region, culture and
species, has ensured the endurance of pollards in the landscape as open grown trees (Green
1996).
Pollard wood-use included fodder, firewood and charcoal, fencing, furniture, tannin, wickerwork, and house and boat building, and it is interesting that a very large population of old
pollards still exists within a twenty-mile radius of the London conurbation. An example is
Epping Forest, with an estimated population of 50,000 veteran trees over 400 years in age,
the majority of which are pollards. This forest, like many wood-pasture sites, is characterised
by areas of open space, roads, housing and extensive areas of pollards set in grassland and
shrub. It historically formed part of the medieval Royal Forest of Waltham, subject to Forest
law according to which commoners enjoyed rights of pasture and woodcutting. Many woodpasture sites passed through different ownerships while retaining their open wooded character,
despite periodic attempts to enclose portions and suppress commoners rights of use. Since
the late eighteenth century, throughout most of Britain, pollard management practices have
progressively fallen into disuse. At Royal hunting forests such as Epping Forest, dwindling
deer populations coincided with declining Crown interest, illicit enclosure and urban exploitation.
Wood-pasture systems are richly present in the UK and widely distributed. Many contain
a significant population of pollard trees with a mosaic of habitats, showing continuity and
structure remaining unchanged for many centuries. Hatfield Forest is one such example that
has been extensively documented. Recorded originally in the Doomsday Book in 1086, it has
remained virtually unaltered for over one thousand years, still containing all the elements of
a medieval forest (Rackham 1998). The ancient trees at this site have been surveyed and
monitored, the results of which have been used to inform management prescriptions for
environmental arboriculture restoration treatment (Fay & Fay 2000), as will be discussed
later in this paper.
Initiatives to Record & Conserve Veteran Trees: Habitat Action Plans
The UK Biodiversity Group (1998) refers to lowland wood-pastures and parkland as the
product of historic land management systems and represent a vegetation structure rather
than being a particular plant community. Typically, this structure consists of large opengrown or high forest trees (often pollards) at various densities, in a matrix of grazed grassland,
heathland and/or woodland floras. Much of the nature conservation effort in Britain is
currently directed through Habitat Action Plans (HAPs). One of these is the Lowland Parkland
and Wood-Pasture HAP. It recognises that various factors are necessary for the biodiversity
of old tree habitat, and in particular, that the high levels of light and warmth afforded by
open-grown trees favour special colonising communities.
The loss of old trees is identified as a major cause of the decline and poor condition of
dead wood habitat and dependent communities. The Common Agricultural Policy (CAP) has
caused considerable harm to veteran trees in arable and pasture land. Deep ploughing, the
use of herbicides, inorganic fertilisers, wormicides and other veterinary pharmaceutical
products, have damaged soil structure, mycorrhizae and other parts of the root ecosystems.
In the UK veteran tree populations have suffered from the effects of poor tree and land
management. Isolation and fragmentation of wood-pasture habitats are a threat to dependant
communities. Where there are large populations of veteran trees with officially recognised
nature conservation value, such sites usually have a survey history. However, survey methods
are typically inconsistent with respect to veteran tree data collection. While the value of
many UK veteran tree sites is acknowledged, the habitat quality and tree condition is poorly
documented and understood. This situation is slowly changing. One of the factors influencing
the momentum for improvement has been the involvement of arboriculturists with
conservationists.
During the early 1990s, there was a growing interest in the necessity to compare
information gathered about veteran trees. Until that time, no standardised system had been
developed. English Nature (UK government agency for implementing nature conservation
policy) identified a broad strategy for improving survey data quality and methodology. The
67
Ancient Tree Forum (ATF) is the lead UK NGO for the conservation of ancient trees and their
habitat. It is a collaborative group of conservation professionals, specialists and managers.
The ATF identified the need for a standardised recording system to collect tree habitat
information. This was considered essential to the understanding of the national status of
veteran trees through recording and monitoring key factors influencing population dynamics.
(Fay & de Berker 2003).
A multidisciplinary approach, led by arboriculturists, resulted in the publication of the
Specialist Survey Method (SSM). This is the current national standard for veteran tree
surveying. It operates on three levels. Level 1 is the introductory standard for non-specialists;
Level 2 is the first level technical standard (typically for arborists, foresters, etc.); Level 3 is
used by conservation specialists. The SSM records basic tree data (position, species, form,
dimensions), dead wood habitat (tears, scars, stubs, hollowing, rot, dead wood), tree
associates (flora and fauna) and growing context (damage, shade, management) (Fay & de
Berker 1997).
Conservation experts claim that Britain contains the greatest number and the best
concentrations of old trees in Europe (Alexander, Green & Key 1996). This claim has both
raised awareness and stimulated study in attempts to quantify the population. Recent
research has shown that surveys using the SSM have recorded over 45,000 veteran trees
at key UK sites (Fay & de Berker 2003). Assuming that 1 in 200 trees have been recorded, as
a conservative estimate, this would indicate that there are more than 9 million veteran trees
in the UK. To date, the traceable investment in nature conservation surveying of old tree
habitat using the SSM is an estimated £291,000.
While veteran trees may be present in great numbers in the UK, there are disturbing
trends. Studies show that many veteran trees are under threat and there is evidence that
the future of veteran trees at these UK sites is not promising. Data collected from a number
of populations indicates that, even at protected sites, and those that are considered to be
in the best condition (Cox & Sanderson 2001), populations are susceptible to unsustainable
rates of tree loss, posing a direct threat to the dead wood (saproxylic) communities.
Fig 1:The Bowthorpe wood-pasture oak: Britains
largest Quercus robur, (Girth at 1.5m height is
12.79m) Shed a major part of pollard crown in
2003.This tree is said to be over 1000years old
Fig 2: Ancient tree wood-pasture at Brockworth,
Gloucestershire. The fate of many veteran trees in
the UK. Lapsed pollards with crown limbs prone to
mechanical failure. Often crown limb loss threatens
the viability of the entire tree
Population Dynamics
One of the major ancient tree sites in the UK is Burnham Beeches, occupying 220
hectares of wooded common. In the seventeenth century, there were 3,000 pollard trees.
By 1957, this number was reduced to approximately 1,300. In 1990, when survey methods
became more detailed, the population numbered 555. By the year 2000, the total had fallen
to 463. The rate of population decline in recent decades is typical for many ancient tree
sites. At Burnham Beeches, the rate of loss represents 16.6%, which is an average of 1.6
trees per annum (Read 2000). Attrition rates of between 0.9% and 1.8% are common. The
main cause is loss from collapse from mechanical failure (as a result of the cessation of
pollard practice) (see Fig 1) and rapid decline from environmental impacts (Fay & Rose
2003).
68
Fig 3: Survey of ancient pollards
at Ashton Court, Bristol and Lords
Bushes, Epping Forest. Data
derived from surveys at two key
sites of 444 trees and 155 trees
respectively, with neglected,
lapsed pollards, shows trunk
hollowing to be significantly higher
at the top of the bole, whereas
hollowing is common at the base
of maiden veteran trees. Failure
trends are the result of heavy
pollard branches breaking at
mechanically weakened pollard
points or tipping the entire tree
due to excessive end loading
(error bars ± one standard error).
(Fay & Rose 2003)
Recognition of current rates of loss in old tree populations has resulted arboricultural
intervention to mitigate the risks posed to trees.
Modelling a Sustainable Population
The key to a sustainable population capable of supporting a functioning ecosystem
requires that first an existing ancient tree population is consolidated. Secondly sufficient
numbers of trees must remain in the vicinity of the current population to be capable of
becoming veteran and then reaching the ancient stage. This may require the recruitment of
non-veteran mature trees and veteranising these (to prematurely create bridge saproxylic
habitats). This treatment involves implementing techniques that mimic natural damage.
Tree population dynamics have conventionally been used to model populations based on
utility. In this context, full maturity is regarded to be the optimum target age class. Utility
considerations of trees places value on the sound wood condition of the main trunk prior to
the development of decay. Techniques of tree population management have yet to be
developed that favour post-mature age classes. Such an approach requires the assessment
of numbers and mortality rates in each age class. It is then necessary to ascertain whether
sufficient numbers are present to ensure successors for older age classes to produce a
sustainable population structure. Typically this involves considering arboricultural intervention
to reduce mortality rates in the older pre-ancient generations. Site management techniques
also need to be targeted to enhance tree longevity for all age classes.
Management for a sustainable tree population, targeted to maintaining functioning tree
ecosystems, must be based on knowledge of tree mortality. This needs to take account of
loss in each age class within the overall population. By responding to these factors, the
required rate of recruitment into the veteran population can be estimated. This form of
modelling can identify expected change in the veteran population over time and is vital to
understanding the actual vulnerability of the ecosystem at a particular locality. This method
has been applied to a number of sites to identify the safeguard-requirement of younger ageclass trees. The need for tree planting is widely recognised. However, the reasons for
conserving mature and fully-mature age classes are now better understood.
Tree life expectancy in the UK may be progressively being eroded due to human influences
on the environment. If the future ancient tree populations are insufficient in size or integrity,
local populations of dependant species may collapse. If this takes place then current
investment in the conservation of wood-decay ecosystems will fail. It is therefore a priority
that resources are targeted to evaluating ancient tree populations, requirements for succession
and sustainable management.
Management: concepts of environmental arboricultural
Compared with the animal kingdom, ageing in trees is not necessarily unidirectional.
Trees and fungi may both be described as indeterminate systems (Rayner 1993), equipped
with the ability to alter developmental patterns in response to environmental stimuli. The
meristematic (embryonic) system provides the tree with the potential for rejuvenation so
that at any stage different parts of the tree may be in a different growth phases. Del Tredici
refers to the various rejuvenation processes that occur in trees (ontogenetic, natural and
physiological) reflecting the way the ageing clock is influenced by genetic or environmental
factors (del Tredici 2000). Protracted serial rejuvenation in some species of tree is so
effective that there is a tendency to near immortality (Pinus longaeva, Tillia cordata, Taxus
baccata).
69
Fig 4: Phoenix Crataegus monogyna at Hatfield Forest, Essex
Natural vegetative regeneration in old trees may be considered as a survival strategy.
When this occurrence is successful, the re-generated tree is termed a phoenix tree (Fay &
de Berker 1997). A number of phoenix strategies have been noted in UK fieldwork. Examples
include cases where following tree collapse, the specimen layers, establishes roots and
second-order laterals become first-order trunks of a successive generation. Similarly, when
the adventitious roots become established within a hollow trunk, the roots may eventually
change their mode and develop structural functions (and become independent). Hollow
ancient trunks have been observed to rot ands break up to form two or more columns, each
becoming independent and capable of breaking free from the original system. These processes
are significant in the context of continuity of habitat, when considering that the woody
substrate of the tree acts as a Noahs ark for the dependent colonising fauna and flora.
These observations are significant, as they have influenced arboricultural management
practices intended to support strategies for tree longevity.
The convergence between arboriculture and other disciplines, particularly with ecology
has led to a transformation in the understanding and appreciation of ancient trees, especially
when considering the tree as a co-evolutionary partner that has developed in association
with colonising species. Significantly, there has been a reconsideration of the interactions
between fungi and tree. Much of the arboricultural terminology typically used to describe
the presence of fungi in trees, presumes or implies a pathogenic relationship. Ingress is a
basic presumption and the presence of fungi in or on trees is generally described in terms of
invasion, with modes of attack and degrees of aggression; implying that the tree has
evolved a primarily and comprehensively defensive relationship with respect to fungi.
During the 1990s, new insights were gained from investigations into the range of colonising
strategies of different fungal species. Mycological research began to surface in the field of
arboriculture, introducing notions of complexity not previously recognised. This described
the presence of endophytic (dormant or latent) fungi that operate territorially and become
visible after bark wounding and dysfunction have occurred. This complexity is evident where
natural processes may be observed in sites such as old growth forests and low-intervention
wood pasture. Arrays of different fungal modes operate including wood decomposition,
recycling, nutrient foraging and pathogenic processes, all potentially organised through
mycelial interconnection (Rayner 1993). The perception of the tree-fungi-system as complex,
multifunctional and interactive is a vital concept in environmental arboriculture. It is
fundamental to comprehending the co-evolution process as a factor of tree longevity and to
informing tree health and pathology diagnosis.
New Arboricultural Techniques for Veteran Tree Management
In the eyes of environmental arborists, chainsaw cuts result in an unnatural flat planesurface (i.e. such surfaces are literally not found in nature) and apart from the concern to
replicate naturalness of form, there are further ecological considerations that have promoted
work to develop natural fracture pruning methods. Branch breakage (from mechanical weakness
and storm damage to trunk and limbs) results in a variety of effects on wood tissue at the
70
point of breakage, leading to fibre separation (along the grain) and splintering in various
planes (linear, radial and circumferential). This occurrence creates microhabitats that are
colonised by microorganisms and succession species.
Fig 5: Viability assessments of veteran oak populations at four key UK ancient tree sites. The
Specialist Survey Method has been further developed to enable an arboricultural assessment of
tree stability and vitality to be carried out. This is used to inform an assessment of tree viability
to allow comparisons between sites and inform30-year individual tree management plans
Interactions between trees and the species that live on them may have developed over
exceptionally long periods of time, and as some trees may be several thousand years old,
speculation therefore may extend to the relationships between tree longevity and the
continuity of the organisms living on and inside the tree, and those living underground that
are associated with the rhyzosphere. Over recent decades there has been a prejudice
against dead wood in arboriculture, forestry and agriculture. This is now being redressed.
There is an emerging trend to value biodiversity and to promote arboricultural practices for
the benefit of wildlife, leading to the development of techniques designed to retain (and
even create dead wood habitat) in crown management.
Fig 6: Natural and artificial breakage in an oak tree:
both show high levels of growth response at Melbury Park, Dorset
Natural Fracture: Techniques that Mimic Natural Processes
Coronet cuts - Dead wood management
Natural fracture techniques involve pruning methods that are used to mimic the way that
tears and fractured ends naturally occur on trunks and branches. A coronet cut is a type of
natural fracture technique that is particularly intended to mimic jagged edges characteristically
seen on broken branches following storm damage or static limb failure. It is carried out as
a pruning treatment to a stub or reduced limb to mimic natural breakage. The form of the
coronet cut is designed to shape the branch or trunk end-surface to resemble the fracture
that might be imagined following a storm, (such as Beaufort storm force 9/10) and is cut to
71
resemble a broken or shattered appearance. Early experimental work exploring methods of
cutting dead branches to mimic natural breakage was carried out at Ashtead Common
National Nature Reserve, Surrey. This led to further developments and the current use of
coronet cuts in both living and dead limbs. It was first trialed following a catastrophic fire,
which seriously scorched, damaged or killed several hundred veteran trees on the Ashtead
Common, affecting a significant proportion (10%) of the population of over 2000 veteran
oaks at that site (Adam Curtis, James Green and Bob Warnock. 2000). The presence of so
many dead trees in an area frequented by the public initially prompted a requirement to
remove the trees for public safety. After consideration of the conservation values of the
dead wood habitat, it was decided to retain as many standing dead trees as possible, while
carrying out varying degrees of reduction to reduce risk of crown or trunk breakage to an
acceptable level. Dead wood (over 150mm) was deemed potentially suitable for carrying
out this exploratory coronet-cutting work.
Earlier attempts at replicating what was observed in nature had varying results. Trials at
Stowe Park, Buckinghamshire, were carried out in the early nineties using explosives on dead
trees to see what type of fragmented ends would result (Finch 1996). The use of explosives
is not now advocated in the UK for both the obvious reason of safety and that outcomes are
uncontrollable. The author witnessed similar attempts during a visit to Sweden in 1992,
where the Swedish army had been recruited at a nature reserve to use explosives on live
trees attempting to recreate habitat-types suitable for rare invertebrates.
Other experiments carried out at Windsor Great Park, involved winching off partially cut
branches to produce rip or tear-cuts on dead trees. This was in some measure successful,
but it proved impossible to predict the appropriate winch-tension necessary to effect breakage.
Many trees failed at their roots before the attached branch broke off. As a result such
practice has for the most part been stopped as it is deemed to be harmful to the root
system.
Where trees are scheduled for felling coronet cutting is typically carried out as an
alternative in order that a part of the trunk may be safely retained, in reduced-scale as
dead wood habitat, following the removal of the scaffold branches. It is also carried out
following branch reduction (usually of second or third-order limbs).
Trials took place between 1997 and 1999 to retain as much of dead oak as standing hulks
with a reduced branch framework. Many of the truncated trees were experimented upon to
promote a natural breakage effect through skilful chainsaw use. This resulted in the first
studied attempts at coronet cutting (The practice was so called because of the crown-like
appearance of the branch ends). It is noteworthy that this was well received by the public.
Retained standing trunks have been termed Monoliths (Alexander, Green & Key 1993)
and are defined as those trees where tree removal would normally be required but are
retained as standing trunks in reduced and stabilised form (usually at some 4m to 6m height)
as dead wood habitat. It is necessary to re-inspect monoliths to assess and address tree
stability and the risks posed, as with any standing tree.
As aerial deadwood is valuable habitat, its removal is only specified where its presence
about the tree is considered a threat to tree stability or public safety. In such cases, the
removal of dead wood should apply only to the material that is considered unstable and
prone to failure. Where dead wood removal is proposed it should be restricted to those
aspects of the crown where dead wood failure may cause damage or harm. Elsewhere, dead
wood may be retained and reduced in extent to stable proportions (Davis, Fay & Mynors
2000).
It is noted that with oak, hardened dead aerial branches can often be retained without
undue risk, however where risks may be present from dead wood breakage, it is essential
that this is assessed and managed as with any part of the tree. As a result of these
developments in environmental arboriculture, current guidelines for risk management of aerial
dead wood now frequently stipulates that aerial dead wood can be preserved, subject to an
assessment of its condition so that it may be retained in stable form (with reduced lever arm
and end-loading).
Coronet cuts-Live wood management
Currently the techniques involved in dead wood management are now also considered in
the pruning of live amenity trees. Since the work at Ashtead, some pioneering work has
been carried out by arboricultural practices in the UK. Treework Environmental Practice and
others involved in environmental arboriculture have extended this form of dead wood
management to the management of living trees to promote dead wood habitat (Fay 2002).
This practice is termed veteranisation (Cowan 2003).
72
Fig 7: Coronet cut on live Quercus robur stub at Richmond Park, Surrey
The general guideline for this technique requires the selection of potentially suitable
stubs for retention. These are cut at a minimum distance that is approximately five times
the diameter of the branch when measured at the point of attachment to the stem or higher
order branch. Suitable branches will have a diameter greater than 150mm in diameter. The
stub length is estimated from the point of attachment with the parent higher order member.
Stubs are cut into a coronet appearance through skilful chainsaw use. Live branches may
be selected for this treatment where crown reduction (see retrenchment pruning) is being
carried out. A proportion of suitable live limbs (up to 15%) are typically selected for coronet
cutting. This type of natural fracture pruning is applied to non-crucial structural members
only. Cutting is carried out to give the appearance of deep uneven, shattered ends;
optimally with an acute angle. Where occasional major stems require heavy reduction
truncation, the final cuts are varied to promote a jagged finish.
Retrenchment pruning
Retrenchment pruning is a term coined by Paul Muir of Treework Environmental Practice
to describe the technique. It is a refinement of the concept of restoration pruning referred
to in the European Treeworker Handbook (EAC 2000) and has been developed to imitate the
natural process of crown ageing, often referred to as the stage beyond full maturity when
the tree grows downwards (Green 1996).
The term crown retrenchment is used to
describe the way in which peripheral dieback occurs as the tree redirects energy and growth
to the formation of a consolidated lower region of the crown. Crown retrenchment pruning
is used to extend tree viability, (both in relation to vitality and stability), whilst retaining
habitat features associated with ageing.
Retrenchment pruning is a technique that can be used to reduce the potential for a fully
mature, late-mature or ancient tree to collapse or disintegrate under its own weight, as a
result of excessive end-loading associated with long or weakly attached limbs. It is carried
out according to a long term programme - typically termed Individual Tree Management
Plan (the ITMP). The ITMP may typically extend up to thirty years.
The technique is also used in trees where incipient decline appears to result from excessive
transportation distances from the root system to the crown periphery. While this technique
may have a general value, it is especially useful for managing lapsed old pollards and mature
maiden trees that show signs of dieback, physiological stress or a tendency to long-term
limb breakage (i.e., not where there is an urgent need to reduce crown limbs to avoid
breakage).
The practice of retrenchment pruning follows a detailed inspection, which assesses the
viability of the tree in terms of current vitality, the probability of tree loss as a result of
73
expected decline in vitality or from structural collapse. This assessment informs decisions
as to whether retrenchment pruning is appropriate. If the tree is an important specimen
prone to imminent mechanical failure, threatening its viability, then gradual retrenchment
treatment would not be appropriate. In such cases an alternative method is suggested
involving significant reduction to selected failure-prone limbs (see Read 2000, pp 42-43).
If the tree shows a moderate level of vitality and mechanical stability appears vulnerable
in the long term, while being sufficient to support a moderately reduced crown structure in
the short term, then retrenchment pruning may be carried out to restructure the framework.
The Individual Tree Management Plan will follow from the assessment of tree viability,
and will specify the first stage of treatment (possibly involving as little as 10% or less than
a metre reduction). The Plan sets an ultimate height above the bolling or from ground level
(Target Height) to which the crown will eventually be reduced at the time of Plan completion.
In addition this will specify the return period (Retrenchment Cycle) for future retrenchment
pruning visits, typically 3 to 5 years. Lastly the Plan Duration is set. This is overall duration
for the programme of treatments up to completion (usually between 12 to 30 years, but
sometimes up to 100 years).
Retrenchment pruning is carried out in stages and involves the reduction of the tree
height and the extent of crown growth over a protracted period of time. It is carried out to
4th or 5th order branching, often within the constraints of using a turbo saw and secateurs,
and usually involves at least three return treatments involving periodic monitoring and allowing
re-growth to occur in the interim.
The process is intended to promote early crown stabilisation and reduce the risk of
traumatic structural failure by reducing the lever arm, while at the same time increasing light
penetration to inner aspects of the scaffold limbs. Epicormic growth arising from these lower
and internal crown areas have the potential of becoming the scaffold limbs of a future
reduced crown framework. The method is intended to stimulate internal and lower crown
growth (rejuvenation) through reducing apical dominance to redirect hormonal growth
regulation capable of re-iterative stimulation. Eventually retrenchment pruning will create a
reduced crown framework over the Plan Duration.
For trees with moderate to high vitality, the first stage of retrenchment pruning should
avoid overall reduction by more than 20%. For trees with low vitality the first stage of
retrenchment pruning is typically less than 10%. Where tree stability is already heavily
compromised reduction levels should be sufficient to reduce the lever arm to an acceptable
level.
Conclusion
In the UK, governmental and non-governmental conservation agencies have recognised
the value of old trees for wildlife. Through the work of a number of pioneering conservationists,
drawn mainly from the ranks of the Ancient Tree Forum and the Woodland Trust (lead
voluntary agencies with interest in old tree conservation), understanding of the biological
and cultural values has been improved. A wide consultation between owners, managers,
conservationists and professionals, involved in the study and care of old trees, has led to a
number of publications to guide survey methodology and management. The publication of
the Specialist Survey Method as the UK national standard for surveying veteran trees has
provided the framework for consistent recording and data collection. While the British Isles
is recognised to contain a very high proportion of Northern Europes ancient trees, population
studies at key UK wood-pasture sites have shown that there is an unacceptable rate of tree
failure. This recognition and the convergence between arboriculture and ecology has resulted
in an improved understanding of the ageing process in trees. Fungi are now understood to
have a principally benign interactive relationship in the tree-fungi-system, creating conditions
for colonisation by dependent species, many of which have poor powers of dispersal. The UK
arboricultural profession is beginning to recognise that it is necessary to develop appropriate
tree management techniques to foster optimum conditions suitable for the continuity and
diversity of saproxylic species-rich communities. As the ancient tree is the ark that carries
these species through time, it is necessary that the features of value to dependent organisms
are a focus for management practice. This approach has led to arboricultural innovations,
such as the development of natural fracture techniques, coronet cutting and retrenchment
pruning, and particularly the need to manage old trees in terms of appropriate space and
time. When determining work programmes for old trees, management processes need to
consider the whole environment of the trees root-space and soil ecosystem. The conceptual
framework for management prescriptions should consider the tree-time (not human economictime) necessary to implement a long-term Individual Tree Management Plan.
74
Acknowledgement
I am grateful to Ted Green and Ben Rose for their help, comments and suggestions.
I am immensely grateful to Ellen Fay for her help in typing this paper.
Treework Environmental Practice can be contacted on its website: www.treeworks.co.uk
The Ancient Tree Forum may be contacted on their website: www.woodland-trust.org.uk/
ancient-tree-forum
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Read, H.J. (2000). Burnham Beeches Pollard Work Programme, 2000 - 2006, Corporation of London
(Unpublished).
Cox, J. & Sanderson, N. (2001). Livestock grazing in National Trust Parklands its impacts on tree
health and habitat. The National Trust Estates Department, Cirencester.
Sisitka, L (1996) Guide to the care of ancient tree. Veteran Tree Initiative, English Nature)
Slotte, H. (2000). Lovtatlet I Swerige och pa Aland Meoder och Paverkan pa landskapet. Doctoral
Thesis, Swedish University of Agricultural Sciences, Dep. Of Landscape Planning. Uppsala.
UK Biodiversity Group (1998). UK Biodiversity Group Tranche 2 Action Plans Volume II: Terrestrial
and freshwater habitats. Species and habitat action plans. English Nature.
Vera, F.W.M. (2000). Grazing Ecology and Forest History. Oxford: CABI.
White, J. (1998) Estimating the Age of Large and Veteran Trees in Britain. Information Note,
Forestry Commission, Edinburgh.
76
SECURING OF BREAK-ENDANGERED TREE CROWNS
Klaus Schröder
Urban Forestry Service - Osnabrück
Abstract
Breaking-off of crown parts, forks and large branches are the most common types of
failure of urban trees (WILDE, 1996), resulting in substantial damage to objects and persons.
Additionally, the trees are also often irreversibly damaged. Reasons for this type of failure
usually include bark in forks, decay or fractures in branches. As an alternative to lop crowns
or felling hazardous trees, systems for securing of break-endangered tree crowns were
developed. One of the first of these systems was the double belt System Osnabrück,
conceived by the green-department of the City of Osnabrück, Germany (SCHRÖDER, 1990).
Introduction
Creatures of nature are normally adapted to withstand weather because regular recurrent
situations have resulted in optimising processes of permanent adaption and selection over a
long period of time. As an example of such creations of nature, trees are often exposed to
extreme weather and they must resist storm, rain, snow and ice. Forces with an impact of
some tons must be withstood. The experience of arborists shows, that straight grown trees,
as well as certain types of branches best resist the rigours of the weather, whereas other
shapes fail in this respect under the same conditions. Rugged tree crowns can be achieved
with simple methods such as planting correctly grown trees and proper breeding pruning
adapted to the actual development of the trees. Consequently, the implementation of crown
securing systems would not become necessary.
However, in case of the old tree population with problematic crowns preventive measures
cannot help and it is for these old trees that crown securing systems have been developed.
In Germany, the law requires that the breaking-off of parts of trees must be prevented,
according to the decision of the Federal Court from 21. January 1965 concerning the legal
duty to maintain safety. It states amongst other things, that the responsible party must
remove trees and parts thereof which endanger traffic, particularly in those cases when
these are no longer steadfast or parts thereof are in danger of breaking off (BRELOER 1996).
Securing break-endangered crowns is therefore an alternative to felling or lop crowns
and offers an acceptable implementation of the law which requires the removal of above
mentioned dangers.
Left illustration: So called pressure forks are optimised for withstanding pressure in the forking area.
Nonetheless, the narrowest point between the stems is exposed to great tension in the contact zone when
the stems are bent by weather. The cross section shows, that there is bark enclosed in the contact area of
the fork and only the outer annual rings have grown together. This type of fork breaks relatively often under
traction power. Therefore, securing is important in most cases.
Central illustration: So called tension forks are normally naturally well-formed. These are not at risk of
breaking any more often than other healthy parts of trees.
Right illustration: The installation of a crown securing system (break-securing) works like the pivot of a
seesaw. The swing of the stems away from each other is transformed and results in pressure on the forking,
for which this area is optimally shaped. Consequently, the break can be avoided. (Illustration by / comments
according to MATTHECK)
77
Illustration of Crown Securing Systems
(Figures and parts of the text in support of the German rules and regulations for tree
care methods - volume 2001 ZTV-Baumpflege- Ausgabe 2001-)
Crown Anchoring System: Made of threaded bolts, steel cable, and fastening material.
NONE-injury free installation.
The extent of injury caused by the installation of crown anchoring systems is so
great that this system should not be used in the future
Hollow Rope Securing Systems: Made of braided synthetic fibre. The rope is spliced
back through the hollow rope and is fixed by tension. Therefore, no additional fastening
elements are necessary (Single Component Securing System). Injury free installation.
(VETTER & WESSOLLY, 1994)
Band Securing System (Gurtbandsicherung): Made of woven synthetic fibres, and
slung around those parts of the tree crown which are to be secured. The belt is locked with
a buckle (Single Component Securing System). Injury free installation. (SINN, 1989)
Multi Component Securing System (Double Belt Securing System): Made of separate
belts, with a loop on each end. Most of these products consist of a strong, outer holding
belt and a second inner fastening belt, which includes a stretch element in some cases. The
connecting elements (e.g. synthetic hollow ropes, steel cable) are pulled through the end
loops. Injury free installation. (SCHRÖDER, 1993)
78
Multi component securing system - double belt System Osnabrück: broad belts, tightly fixed around the
trunks (or the trunk and the branch), absorb the power occurring in mobile parts of the crown and divert it
into stable tree parts. Elasticity and high breaking force are the best requirements for using synthetic fibres
in crown securing systems. In this case (left ill.) all components are made of polyester fibres. The connecting
element is a hollow rope, but every other suitable connecting element can be considered. Therefore the
double belt securing systems provide a variety of possibilities. The stretching element in the fastening belt
(right ill.) prevents the secured tree parts from growing over the belt (Ill.: KREKELAAR)
In 1997 beech trees were examined in an urban forest in Osnabrück. In these trees double belt securing
systems had been installed six years ago. Results of the wood-biological investigations prove that It can be
stated that even after six years, no damage to the trees resulted from the installation of the crown securing
system. (STOBBE, DUJESIEFKEN & SCHRÖDER, 2000)
Break-securing / Fall-securing
Methods of crown securing should be functionally differentiated according to whether
these prohibit breakage or prevent parts of trees from falling down. (SCHRÖDER, 2002; SPATZ,
2003). While break-securing aims at preventing parts of the crown in the first place whereas
fall-securing is designed to prevent a part of the crown from falling down after it has come
to a break, despite the attachment of a break-securing system. Fall-securing thus aims at
keeping the branch up in the tree.
Installation
Before installing a crown securing system one should be examined, whether pruning of
the tree crown is necessary or possible.
Break-securing systems should be installed at a height of 2/3 of the secured part of the
crown, if possible in a triangular connection. When a single break-protection is applied, an
additional ring connection should also be used in order to lessen the risk of a twisting
break. Install at right angles from the axes of the parts of the tree crown. The natural
mobility of the secured parts of the tree crowns should be taken into consideration, in order
to further encouraged the adaptive growth in the now mechanically burdened parts of the
tree.
Calculation
The calculation of break protection systems shown below is founded upon the following
securing philosophies: Crown securing systems (break protection systems are meant here,
the author) be dimensioned tree equitable if the earliest point at which they fail is the point
at which the secured crown part in mechanically healthy condition would fail under the same
stress (BETHGE, MATTHECK & SCHRÖDER, 1993). Accordingly, where a branch- or forking
defect is assumed, a crown securing system (break protection system authors note) must
withstand as much stress as the corresponding structure in a mechanically healthy condition
could hold (SPATZ, 2003).
Break protections should be calculated in according with the following calculation formula:
(BETHGE, MATTHECK & SCHRÖDER, 1993)
79
Illustration: GEMEIN
sB indicates the medium bending strength (Biegebruch) of green woods. These values
originate from the American and English literature (LAVERS, 1983; US FOREST PRODUCTS
LABORATORY, 1987). They are presented in Mpa, for use in the above formula they should be
converted into kp/cm² (and therefore multiplied by 10,2) in order to reach the bearing
capacity tonnage (t) of crown securing systems common in arboriculture. R equals the
radius of the secured part at its base (or the potential point of fracture) and h (2/3 of the
total length) represents the distance between the break-securing to be applied and the
base of the tree part to be secured.
The following table, based on the above mentioned formula, has been developed in
order to help practitioners with actual set-ups on location, with consultation and with
financial estimates. It allows to rapidly and exactly working out the dimension of necessary
break-securing systems (SCHRÖDER 2004). The relatively common H/D-ratio values of 20,
30 and 40 (Height [total length] / Diameter) were applied to the crown parts. As an
example the table is shown with the H/D-ratio of 40. All tables can be downloaded from
internet under www.demetra.net .
80
Table for the Dimension of Break-Protections
Example: H/D-Ratio:40
Precautionary advice
Conditions for the application of the tables must be a generally right angle binding of the
break-securing to the tree part to be secured and its securing in 2/3 of the total length.
Because not all conditions of a tree or the influence of weather at the particular location
can be taken into account, it is recommended to estimate the factors of dimension generously.
This means that if in doubt select a higher collapse load than necessary! With regard to the
tables, this would result in choosing a lower H/D-ratio. The calculated collapse load must
still be sufficient towards the end of a crown securing system s working life.
Should a truncation of the particular crown part be carried out parallel to installing a
break securing system, the estimation of the necessary size of the break-securing can
occur according to the H/D-ratio calculated before the pruning took place.
The tables may only be used if the crown parts are unable to plunge in free fall after an
eventual break. Therefore, no crucial dynamical loads are expected and the calculated H/Dratio in the actual case is available.
The breaking out of heavy crown parts and the resulting acceleration of gravity is only
controllable, when supplementary fall-securing systems are installed. Thus, these must be
used in order to prevent fall movements of broken crown parts immediately after breaking
out.
However, even in this case when the height of fall merely equals the rope stretching, the
securing components experience at least double the weight load of the branch which is held.
A tree part which weighs 1 tonne therefore exerts a dynamic load upon the fall-securing
system which corresponds to a weight of at least 2 tonnes. The dynamic load increases
over proportionally through increasing the height of fall. If, for instance, this branch should
fall one meter, the superlative factor may increase manifold (TESARI, MUNZINGER & MATTHECK,
2003).
81
Components from material with a high collapse load are especially suitable for fall-securing
systems. In Germany different single- and multi component systems are available from
various suppliers, whereby the load-bearing capacity differs greatly. Details and figures are
available from the following addresses:
Fabritz GmbH ([email protected]/www.gefa-fabritz.de)
GEFA- Schlaufenband multi component securing system.
Connecting elements = hollow ropes and steel cable
GEFA-Gurtband mit Schnalle single component securing system:
Libre Power sails ([email protected]/www.libre.de)
Libre-Baumhalteschlaufen - multi component securing system
Connecting elements = hollow ropes and steel cable
Meyerdiercks ([email protected]/www.meyerdiercks.de)
CrownTex multi component securing system (double belt System Osnabrück).
Connecting elements = hollow ropes, steel cable and any other connecting element with a
sufficient load-bearing capacity.
pbs-GmbH ([email protected]/www.cobranet.de)
cobra single component securing system
ZENITH ([email protected]/www.zenith24.de)
Crown Keeper - single component securing system
Shock absorption
When break-securing systems slow down crown movements, this should happen in a
gentle manner without a sudden stop of the secured tree parts. Otherwise this could
cause injuries. However, even the securing system itself should be spared from strong
dynamic loads, because strains by sudden stops can much reduce the durability of synthetic
woven fabrics and roping, a phenomenon we know from seat belts.
All known types of crown securing systems can be equipped with shock absorption at low
extra costs, whether it is a single or multi component securing system or a connection to
the tree parts through roping, band or steel cable. The shock absorption occurs simply
trough the integration of elements also known in boating sport (SCHRÖDER, 2002).
However, it has to be kept in mind, that shock absorbers may under certain circumstances
cause a reduction of the load-bearing capacity, e. g. when these are fed into hollow ropes
(TESARI, MUNZINGER & MATTHECK, 2003).
If a rope of artificial fibres is used as a connecting element, an additional installation of a
shock absorber might indeed not even be necessary. Due to their construction- and materialstretchability, these materials are often elastic enough to already function shock-absorbingly.
An elasticity rate of 10 % is not unusual.
For this reason, the usage of this type of rope, in certain cases, meets the need for a
retarding and soft braking of swinging crown parts. Control
Control
Materials used for the crown-securing systems age due to the influence of various
factors. In the crown, the materials have to endure exposure to sunshine, frost, rain,
soiling, perhaps also microorganisms, as well as mechanical strain such as the braking of
vibrations, amongst other things, all affecting the efficiency of the installed crown securing
system.
The chemical and physical influences do not pass without leaving trace. Metals begin to
corrode, synthetic fibres become brittle, splices and knots might loosen. Therefore, the
efficiency of crown-securing systems must be checked regularly, according to the instructions
of the manufacturer. The following checklist can be helpful when doing so (SCHRÖDER, 2002).
The check-up of the securing system should be documented. For this purpose, forms
have been designed which cannot be printed here, due to lack of space. However, they can
be downloaded from internet under www.demetra.net .
82
Checklist for the visual control of crown securings
1.
General
1.1. Is/are the installed crown securing system/s still suitable for the current safety
requirements?
1.2. Is the crown securing installed expertly?
1.3. Is, as far as individually relevant, the material suitable for the bearing of continual
loads?
1.4. Has the crown securing system changed position?
1.5. Is the position of the securing system situated at 2/3 of the total length of the tree
part to be secured (above the base)?
1.6 Are the components ingrow-endangered?
1.7 Are the connecting elements secure?
1.8 Is the installation of further securing systems (e. g. fall securing systems) or securing
levels necessary?
1.9 When was the crown securing system installed, is a replacement necessary, according
to the manufacturer?
1.10 Other
2.
2.1.
2.2.
2.3.
2.4.
2.5.
2.6.
Checking the components
Corrosion or brittleness of metal components?
Torn ropework fibres / belts?
Other visual recognizable signs of a diminishing ability of load-bearing?
Fixed screw connection of wire-rope clips when using steel cable?
Correct condition of splices or knots when using rope work?
Other
3.
3.1.
3.2.
3.3.
3.4.
3.5.
3.6.
Checking the tree
Ingrown parts of crown securing systems?
Chafing caused by girdled components?
Chafing caused by connecting elements?
Rot?
Breaksafety of supporting tree parts guaranteed?
Other
4.
4.1.
4.2.
4.3.
4.4.
4.5.
4.6.
Removal of deficiencies
Renewing the complete crown securing system
Adapting the crown securing system to the current situation
(Loosening) widening the securing belt, band securing or hollow rope
Installing supplementary crown securing systems e. g. fall-securing systems
Replacement of damaged parts / systems
Other
5.
5.1.
5.2.
5.3.
5.4.
Tree care measures
Realisation of relieving pruning measures
Removal of ingrown components
Wound treatment
Other
Exemption from liability
The tables were designed to our best knowledge their use from the original version is
permitted for everyone. The writer expressively emphasises, that the control and dimensioning
of crown securing systems must happen according of the judgement and specialized knowledge
of the individual expert. Conditions for each individual case have to be carefully considered.
Therefore, the writer is exempt from any liability for damage to persons, objects or property
resulting from the use of these tables.
The writer reserves the right for additions and alterations for the purpose of optimizing.
Suggestions and advice are welcome.
Zusammenfassung
Der Ausbruch von Kronenteilen, Zwiesel und langen Ästen, stellt die häufigste Versagensart
bei Stadtbäumen dar (W ILDE , 1996). Hieraus können schwerwiegende Sach- und
83
Personenschäden resultieren. Aber auch die betroffenen Bäume werden durch einen Ausbruch
häufig irreversibel geschädigt. Ursache für dieses Versagen sind üblicherweise eingeschlossene
Rinde in Zwieseln sowie Fäule und Risse in Ästen. Als Alternative zur Kappung oder Fällung
solcher als bruchgefährdet erkannter Bäume wurden Kronensicherungssysteme entwickelt.
Eines der ersten dieser Kronensicherungssysteme war das Doppelgurtsystem Osnabrück,
erdacht im Grünflächenamt der Stadt Osnabrück (SCHRÖDER 1990).
Many thanks to ELENA SCHMITZ & KARIM MC LEOD for translation and SVEN DÜYFFCKE & THOMAS MAAG for assistance!
References
BETHGE, K., MATTHECK, C. & SCHRÖDER, K. (1994): Dimensionierung von Kronensicherungen ohne
Windlastabschätzung. Das Gartenamt 4/1994. Patzer Verlag, Berlin Hannover.
BRELOER, H. (1996): Verkehrssicherungspflicht für Bäume aus rechtlicher und fachlicher Sicht.
Bernhard Thalacker Verlag, Braunschweig, 1996
FORSCHUNGSGESELLSCHAFT LANDSCHAFTSENTWICKLUNG LANDSCHAFTSBAU E. V., BONN: ZTV-Baumpflege, Zusätzliche
Technische Vertragsbedingungen und Richtlinien für Baumpflege, Ausgabe 2001
LAVERS, G. (1983): The strength properties of timber. Building Research Establishment Report, 3.
edition, HMSO, London.
SCHRÖDER, K. (1990): Doppelgurt für Bäume. Deutscher Gartenbau 31/1990. Verlag Eugen Ulmer,
Stuttgart.
SCHRÖDER, K. (1993): The double Belt System For Tree Crown Stabilization. Arboricultural Journal,
volume 17, Number 4, November 1993.
SCHRÖDER, K. (2002): Zur Ruckdämpfung von Kronensicherungen. LA Landschaftsarchitektur, März
2002, Thalacker Medien, Braunschweig
SCHRÖDER, K. (2002): Zur Kontrolle von Kronensicherungen. LA Landschaftsarchitektur Mai 2002,
Thalacker Medien, Braunschweig
SCHRÖDER, K. (2002): Die Auffangsicherung, integrales Element der Kronensicherung. GrünForum.LA,
September 2002, Thalacker Medien, Braunschweig.
SCHRÖDER, K. (2004): Zur Dimensionierung von Kronensicherungen. GrünForum.LA, Februar 2004,
Thalacker Medien, Braunschweig.
SINN, G. (1989): Ein neues Kronensicherungssystem zur Verkehrssicherheit von Bäumen. Neue
Landschaft 84/1989, Patzer Verlag, Hannover, Berlin
SPATZ, H.- C.(2003): Kronensicherung und Auffangsicherung. Ein Kommentar zur ZTV-Baumpflege
2001, Tabelle 1 des Anhangs. Stadt und Grün 67/2003. Patzer Verlag, Berlin- Hannover.
STOBBE, H., DUJESIEFKEN, D. & SCHRÖDER, K. (2000): Tree Crown Stabilization with the Double-Belt
System Osnabrück; Journal of Arboriculture, Vol. 26, No.5, Sept. 2000, pp. 270-274
TESARI, I., MUNZINGER, M & MATTHECK, C. (2003): Untersuchungen zu Kronensicherungssystemen. 9.
VTA - Spezialseminar Messen und Beurteilen am Baum 1. 2. April 2003, Forschungszentrum
Karlsruhe.
US FOREST PRODUCTS LABORATORY (1987): Wood Handbook. Wood as an engeneering material. Agricultural
Handbook 72. US Department of Agriculture.
VETTER, H. & WESSOLLY, L. (1994): Ein neuartiges Seilsystem zur Sicherung von Baumkronen. Neue
Landschaft 1/94. Patzer Verlag, Berlin Hannover.
WILDEM. (1996): Baumkontrollen im Rahmen der Verkehrssicherungspflicht als Aufgabe kommunaler
Verwaltungen. Schriftenreihe des Fachbereichs Landschaftsarchitektur, Heft 13, Fachhochschule
Osnabrück, 1996
84
COMPRESSED AIR DIGGING DEVICE AS A TOOL FOR THE INVESTIGATION OF ROOT
SYSTEMS. A CASE HISTORY
A. Pestalozza, G. Passola, F. Ferrari
1. Introduction
When considering trees in built environments, as cities or roadways, the interactions
among trees building and utilities are critical. Trees are strongly affected by development;
construction influences the space available above and below ground as well the surrounding
microclimate. In the other hand trees may also directly impact constructions an infrastructures
built near them. Trees may develop against utility lines or against buildings or grow into
sewers and other drainage pipes. Tree roots are often damaged during building maintenance
operation or construction projects, particularly
during trenches excavation for underground
installation as pipelines, phone, electrical cables
etc.
Conventional soil scrapers are heavy
machinery, such as excavators or backhoes,
which heavily impacted the root systems during
the soil removal and the trench creation. Soil
excavation should be necessary during the
above mentioned situations or in addition for
tree root inspection as well as for soil
decompactation.
The root inspection performed by soil
excavation is a very useful practice, basically
for city trees, when it is necessary to evaluate
Figure 1 Roots attacking a wall
the root system conditions in order to have
information about tree stability. As we know it
is very difficult to assess root damages by means traditional VTA techniques even if
supported by instrumental analysis.
2. How to inspect and manage root system
Different alternative soil excavation methods exist that preserve tree roots. These methods
include manual, hydraulic and pneumatic systems. The manual soil excavation system is
performed by hand tools such as shovels, weeding hoe, small rakes and brushes, to remove
soil from the root zone. The benefit of this method is that the tool cost is very low and the
workers training too. In the other hand, from the financial point of view, the working time is
maximize and from the qualitative point of view only the large roots are preserved while
smaller diameter roots are often broken. The hydraulic soil excavation system has been
recently refined (Gross, 1995) by using water to remove soil from the root surface. This
technique is the most powerful and therefore the fastest of the alternative soil excavation
methods. There are several drawbacks in that method as high water consumption, slurry
production (to be drained) and fertile soil substitution. The pneumatic system produce a
series of small explosions away from non porous objects, such as underground utilities or
plant roots, the air flow impact is quite soft
against these bodies because the excavated
soil is transformed into scrapes or small
fragments so this technique protects tree
roots, including small diameter and fine roots.
Additional benefits of the pneumatic soil
excavation method is the unlimited air supply,
relatively minimal clean up and reusability of
the excavate. The pneumatic soil excavation
system can also be used in combination along
with conventional machinery. First the soil
among the roots is excavated pneumatically
then a conventional excavator can be used
below the root level to increase the trench
depth and the production rate, avoiding root
Figure 2 - Two person crew do about 70 m2/day
damages.
for about 0.2-0.25 m depht
85
3. Case history
3.1 VTA in Caserta Botanical Garden: Un example of root inspection by AS system
In April 2003 has been made a root inspection of a great Cupressus macrocarpa situated
inside the Caserta Botanical Garden. This tree was affected by a large internal cavity in the
stem, detected by Resistograph system, but no other defect was found.
The inspection was made by Air-Spade tools, using a big compressor with 4500 l/h air
flow and pressure about 7 bar. This tool was chosen in order to avoid damage at the root
system, and for his easy use and efficacy. The various step of the intervention have been:
- To cut very short the grass, in order to simplify the excavation.
- Preparation of the yard. Is very important to bound the yard with special tissue, to avoid
accidental damage to person or things, caused by chips or flying gravel.
- Digging. Depending of the soil density, moisture and compactness, is possible to remove
different quantity of material.
The inspection of the Cupressus roots showed us
something unexpected, in fact there was a large
injury and cavity in the main and secondary roots.
All the wounds was situated about 1,5 meter from
the stem, and they was probably caused by a deep
ploughing made during the park maintenance after a
long time of disuse. The biggest hurt in the root
showed in the picture has probably advanced in the
wood till the stem, causing the big hollow detected
before. Inspection allows us to understand the cause
of the internal defect, and show how is dangerous
to plough or excavate next the tree. Besides this
work will help the tree in the future growing, because
the soil has been improved adding lapillus and a lot of
Figure 3 - Serious damages under
nutritive elements.
soil level
3.2 Yard operation around root system: how to dig, how to find, deviate and
properly cut root branches
The air excavation is a hand held tool that produces a laser-like jet of air moving at
approximately 2000 km/h, i.e. twice the speed of sound. The tool consists of a manually
operated, spring return, on / off valve, a rigid barrel, and a supersonic nozzle. It is to be
connected to a standard industrial air compressor capable of producing the above stated
flow at the above stated pressure. Air excavation system is really easy and efficacious
digging system, and in order to operate is enough to follow some simple rules. Is basic to use
the right compressor, in order to have the necessary powerful. For the standard nozzle, it is
recommended that this tool would be used with a
compressor rated at a minimum 4.6 m3/min, and 6.4
bar . If alternate nozzles are purchased, the
compressor must be of sufficient pressure capacity,
6.4 bar, and have a flow at least equivalent to 110%
of the nozzles m3/min rating. During the digging
operation, the operator have always to wear
appropriate protective work clothing and equipment.
Cut and puncture resistant gloves, approved safely
eye glasses with side shields and / or face protection,
and approved hearing protective earplugs or earmuffs
are recommended. In extremely dusty conditions,
operator should wear approved respiratory
protection.
Figure 4 Transplanting operation
For normal excavation, the best performance is
(G. Passola)
achieved by holding the nozzle roughly perpendicular
to the ground Depending on the soil type, the air-system is best moved along the surface to
be excavated at a rate on the order of one to two foot per second (0.3 to 0.6 m/sec).
Except in very hard and compacted clays, dwelling on the same spot tends to reduce the
rate at which material is excavated and can increase the amount of material blown away
from the excavation site. When boring a narrow hole in the soil, the tendency to expose the
operator to material blown back directly out of the hole is increased. The air system for
general excavation is supplied with an auxiliary dirt shield that serves to confine any excavated
86
material that may become airborne from leaving the general area of the nozzle. If soil is
encountered that is difficult to dig, try adding some water to soften. Repeat until the
desired results are obtained. The air excavation is essential in every kind of work side by
side the tree. Is particularly indicated in root collar excavation, radial trenching bare rooting,
transplanting, and moving large tree, work root structure analysis, new construction and
landscape architecture, installing irrigation lines and locating utilities. A correct digging
permits to follow all the main root, and deviate it, in order to avoid all the possible cut. The
root bending, have to be made for little angle, because the roots are not too flexible and
risk to have internal crack. If the cuts are inevitable we can choose where and how to cut,
reducing the impact in the big tree. During the root pruning is essential make little and
careful cut, using un apposite saw. If the analysis, and the digging are made in a hot and
sunny days, we have to cover all the roots using a wet jute o tissue, to preserve vitality
condition.
3.3 Inspection and un-compaction
Inspection activity, quite often has a good feedback for the tree
Air excavation permits to have complete view over the roots system, showing all the hide
defects. For this reason is considered a very good way to assess the root system conditions.
Air digging has the double purpose to analyze roots and to improve the soil features. First of
all, excavation reduce the soil compacting, and increase the underground oxygen next the
roots. The soil could be improved too with the addition of nutritive elements, humus, micro
elements, mycorrhiza, lapis, acc The choice of the elements depending of the health
status of the tree, and the soil condition. Our experience show that trees enjoy the soil
improvement, and the effect are manifested already the first year after application. Would
be better to repeat the treatment the following years, in order to increase the success
likelihood.
4. Conclusions
4.1 Air excavation and removal soil system is essential for the tree assessment
requiring a root inspection
Air excavation, and every kind of removal soil
system solve just the inspection problems. Is
necessary in fact to have the necessary experience
to evaluate the soil and the root conditions, in order
to advance advice about tree and root stability. Right
wood inspection device, as Resistograph or sonic
instrument are always essential to evaluate wood
condition and defect detection. But roots strength
could be detected only with dynamic system, that
check the tree behavior submitted to natural o
artificial stress.
4.2 It gives a good contribute to clarify root geometry and conservation
Air excavation as we have demonstrated permits to have a complete view of the roots
geometry and conservation. The health wood condition and the smallest root twigs vigour
could be checked. The complete or partial absence of root twigs indicate a poorness of
nutritive elements or oxygen in the soil, that is possible to improve thanks good soil and
nutritive elements add. The air excavation overwork the soil macro porosity, destroying all
the compact earth. For that reason the roots and the pipes lacking of macro porosity are
not destroyed.
4.3 It is very handily efficient and financially cheap
Air excavation for its efficiency and easy use is considered really advantageous. This
system need just un adequate compressor and the air tools indeed. No long experience or
complex instrument are request. In other world doesnt exist, at the moment, other way to
excavate so cheap, complete and suitable for this work.
87
Bibliography
The landscape below ground (D. Neely, G. Watson)
Trees & building sites (D. Neely, G. Watson)
Supersonic Air Jets Preserve Tree Roots in Underground Pipeline Installation (R. Gross, M. Julene)
Vita da alberi a Milano (ACER 4/2001 A. Pestalozza; A. Pellegatta)
Air Excavation to improve Tree Health (T. Smiley Tree care Industry)
Posters
90
International Congress on the Trees of History
91
MONUMENT TREES AS WITNESSES OF LOCAL POTENTIAL VEGETATION AND LANDSCAPE
EVOLUTION
G. Barbera1, S. Pasta2 and T. La Mantia1
1
2
Dipartimento di Colture Arboree, Facoltà di Agraria - Palermo
Palermo
Introduction
During the last years several researches have been carried out on the Italian monumental
trees; more recently, more attention has been paid on Sicilian ones (Schicchi and Raimondo,
1999). Monument trees are getting more and more important for the key role they play as
witnesses of both local natural history and human activity. Besides, through modern tools,
such as Pressler increment borer, monument tress can be exploited also to obtain accurate
data on climate and atmosphere evolution during the last centuries.
The study case of the monument trees of the Favorita Park is here discussed. This Park,
between Monte Pellegrino and the city of Palermo, is about 300 Ha wide and belongs to the
B zone of Monte Pellegrino Nature Preserve, instituted by Sicilian Autonomous Regional
Government in 1995. This Park gives hospitality to some scattered relics of semi-natural
vegetation, while other surfaces are still occupied by .crops and formal gardens deriving
from the first decades of the XIXth century.
Study area
Some information on the environmental characteristics, the history and the land use
evolution of the Favorita Park are useful for a better understanding of the value of the
monumental trees which live in it. Palermo Plane is characterized by a typical Mediterranean
climate and a very good soil quality; thus, no surprise that the area was known as ü êÞðïò
(= the Garden) by Greeks (Rocci, 1980), was called Geonard (= the Paradise on Earth) by
Arabs (Pirrone et al., 1990), and, since the XVIth century, was named Conca dOro (= the
Golden Valley). The local original climax probably was a mixed forest dominated by the
evergreen holm oak (Quercus ilex L.) and some deciduous thermophilous oaks such as
Quercus virgiliana (Ten.) Ten. and Q. amplifolia Guss (Fig.1). Centuries of frequent and
intense human impact (cutting, wildfires, grazing, cultivation and, more recently, pollution,
urbanisation, afforestation and alien plants introduction) totally erased the primary vegetation
in the whole territory. Favorita Park is someway an exception within this sad picture.
The Park history is strictly linked to the Christmas day of 1798, when King Ferdinand IV of
Bourbon escaped from Naples to Palermo. Already in the first months of the following year,
through a royal edit, he bought the goods of many local noble families (Airoldi, Salerno,
Pietratagliata, Niscemi, Vannucci, Malvagna, Lombardo, etc.). In a few months, the Real
tenuta della Favorita was ready, so that the king could enjoy his favourite hobbies: hunting
and agriculture. Little woods, dominated by plants typical to the Mediterranean evergreen
maquis, were planted; they were interrupted by numerous hunting lanes, alle statues and
doric columns: A certe determinate distanze sincontrano delle deliziose colline che incantano
lo sguardo colle mirabili e variate scene della natura Si osserva in una di queste un
ombroso e solitario boschetto, nel di cui centro sorge la statua di marmo bianco della
cacciatrice Diana. (Palermo, 1816). At the same time, some experimental fields were realized,
such as orchards and vineyards, whose irrigation system are easy to recognize still nowadays:
Si sono da S.[ua] M.[aestà] tentate in questi terreni diverse speculazioni ed esperimenti al
miglioramento dellagricoltura, applicandovi le teorie dei moderni e più accreditati autori, i
quali su queste agrarie materie hanno dottamente scritto e la vegetazione delle piante,
delle frutta, e di altre produzioni, ne ha riportato un utile e felice successo. (Palermo,
1816). Pasca (1868) writes that dalla Real Favorita venne larancio-mandarino di cui la
pianta madre primitiva esiste tuttora sin dal 1810, e oggi se ne fa commercio.
As well documented (La Mantia, in press), the local crops were the same of the Piana dei
Colli (localized between the ancient city and the northern villages of Mondello and
Sferracavallo). Olive groves were the most widespread culture, together with almond
(Amygdalus communis), sumac (Rhus coriaria) and prickle pear (Opuntia ficus-indica)
cultivations, while mulberries (Morus alba and M. nigra), carobs (Ceratonia siliqua), wallnuts
(Juglans regia), figs (Ficus carica) Mediterranean hackberry (Celtis australis) and annual
crops were rare. Between 1856 and 1922 the area experienced some relevant changes in
land use patterns: Arundo donax, Rhus coriaria and Fraxinus ornus cultivation and of most
part of the annual crops, once characterising the local agricultural landscape, totally
disappeared, while a powerful spreading of Citrus orchards (from 12 to 31 Ha), led in the
following years to a local triumph of citrus cultivation (Fig.2).
92
Investigation methodology
Our field survey, carried out within the Favorita Park, aimed to individuate the most
noteworthy trees. This census was achieved by using a schedule already available in literature
but modified. These schedules (see annexes 1-2) contain the following data: Identity (binomial
classification, family and vernacular name); Localization (municipality, name of the locality,
way of access); Ownership (public or private); Environmental characteristics of the stand
(altitude, exposition, inclination and substrate); Major morphological (general description,
maximum circumference at 1,30 m, overall plant height, crown width, estimated age) and
biological characteristics (vegetative and phytosanitary state); Threats; Proposed
interventions. A particular attention was payed to verify both the vegetative and phytosanitary
state and the proposed interventions. In case of lack of dendrochronological relieves, the
age of the plants has been estimated.
Results
Notwithstanding the lack of a standard definition of what monument trees actually are,
there is no doubt that within the Favorita Park grow several noteworthy plants.Most of them
derive from the XVIII century shaping and designing of the park itself, while only in some
cases they seem to be native plants survived to man impact and, thus, they are localized in
the most undisturbed areas. During this preliminary field survey 29 monument trees have
been encountered: 13 Quercus, 6 Cupressus, 3 Pinus, 2 Schinus, 2 Celtis, 1 Olea, 1 Ceratonia,
1 Morus. These trees grow within the wood, hedges, or as relics within the cultivated areas.
Monument trees play a major role in defining the local potential vegetation. For example, the
huge individual of Quercus virgiliana was probably already there before Bourbons interventions,
as its estimated age is of about 300 years. Up to the middle of the XXth century, another
large white oak grew not far from this one, and its acorns were toasted by local farmers to
make a surrogate of coffee. The presence of this white oak confirms the current hypotheses
on the potential vegetation of the Park and of the whole Conca dOro (Brullo & Marcenò,
1985; AA.VV., 1996; Gianguzzi et al., 1996). Besides, this plant probably is the last - and the
only - native deciduous oak detected in the whole Conca dOro since when Gussone (18421845), more than 150 years ago, noticed Q. virgiliana elsewhere in the Plane, near Roccazzo.
Still nowadays Favorita Park maintains many evidences of the transformations it underwent
due to the intervention planned by King Ferdinand IV: on Monte Pellegrino foots still survive
the last examples of dry orchards, with olive and almond groves. Within these orchards, it is
still possible to find some very old olive trees (Olea europaea), carobs (Ceratonia siliqua)
and white mulberries (Morus alba). Most part of the censed monument trees (12 holm oaks,
6 cypresses, 3 stone pine, 3 Peruvian peppertree and 2 Mediterranean hackberry) grow
within the little Quercus ilex-dominated woods realized by Bourbons or along the hedges
(Fig.3). The artificial origin of the little holm-oak woods is revealed by the geometric patterns
of their design and shape; nevertheless, in those scattered areas of artificial forest, which
could be classified as old coppices, it is still possible to glimpse the primary vegetation of
the Park and, more generally, that of the whole Conca dOro. In particular, the biggest holm
oak trees give an image of high wilderness.
Conclusions
Favorita Parks monumental trees shall be considered as witnesses of all the different
land use typologies once present in the area and allow us to make some hypotheses on the
local potential vegetation and on the landscape evolution as well. This census shall be
considered as a starting point for a more accurate investigation on the tree heritage of the
Favorita Park. The active safeguard of these plants (e.g. through germplasm gathering,
conservation and diffusion) is very important; besides, many of these plants need a periodic
monitoring and some dendrochirurgical cares, as they are weakened due to their age .Future
investigations should offer further surprises. For example, the huge Quercus virgiliana (Ten.)
Ten. was never noticed before, although if careful investigations have been recently carried
out on the flora (Raimondo, 1992), the vegetation (Gianguzzi et al., 1996) and the land use
of the Favorita Park (La Mantia, in press).Another point to clarify is what monument trees
really rare: this concept seems particularly ambiguous if we consider the fruit orchards.
Some mandarin, for example, deriving from the orchard realized at the beginning of XXth
century shall be considered as monuments, indeed, as they were explanted from Citrus
orchards of Palermo city when they were already adults, between 1950 and 1965.
Finally, Favorita Park gives hospitality to several fruit trees, such as a very old apple tree
(similar to limoncella, a very rare local cultivar). Thus, the project to transform the actual
93
agricultural landscape of the Favorita Park to restore the XVIII century design worths a
careful re-consideration.
References
AA.VV., 1996 - Carta della vegetazione potenziale, f.-t.- In: Regione Siciliana, Assessorato Beni
Culturali e Ambientali e Pubblica Istruzione (a cura di), Linee-Guida del Piano Territoriale Paesistico
Regionale.
Brullo S., Marcenò C., 1985 - Contributo alla conoscenza della classe Quercetea ilicis in Sicilia.Not. Fitosoc., 19 (1) [1984]: 183-229.
Gianguzzi L., Ilardi V., Raimondo F.M., 1996 - La vegetazione del promontorio di Monte Pellegrino
(Palermo).- Quad. Bot. ambientale appl., 4 [1993]: 79-137.
Gussone G., 1842-1845 - Florae Siculae Synopsis exhibens plantas vasculares in Sicilia insulisque
adjacentibus hucusque detectas secundum systema Linnaeanum dispositas. Neapoli, Typ. Tramater,
3 voll.
La Mantia T., In press Ecologia e agricoltura nel parco della Favorita. Comune di Palermo
Palermo G., 1816 - Guida Istruttiva - giro della mura, delle porte e delle loro adiacenze- Palermo.
Pirrone G., Buffa M., Mauro E., Sessa E., 1990 - Palermo, detto Paradiso di Sicilia (Ville e Giardini,
XII-XX secolo).- Centro Studi di Storia e Arte dei Giardini, Palermo, 285 + i pp.
Rackham O., 1992 - Trees and woodland in the history and archaeology of the landscape: 249263. In: Bernardi M. (Ed.), Archeologia del paesaggio, IV Ciclo di lezioni sulla ricerca applicata in
Archeologia (Certosa di Pontignano, Siena, 14-26 gennaio 1991), C.N.R. - Univ. Siena. Ed. Allinsegna
del Giglio, Firenze.
Raimondo F.M. (ed.), 1992 - Studio e catalogazione della flora, della vegetazione e delle emergenze
botaniche ed ambientali del Monte Pellegrino (Palermo).- Comune di Palermo, Palermo, Assessorato
Parchi, Verde ed Arredo Urbano, 222 pp. + carta (scala 1:8.000).
Rocci L., 1980 - Vocabolario Greco-Italiano. Soc. Ed. Dante Alighieri, Firenze.
Schicchi R., Raimondo F.M., 1999 - Contributo alla conoscenza degli alberi monumentali delle
Madonie (Sicilia centro-settentrionale).- Naturalista sicil., s. IV, XXIII (1-2): 229-314.
Tabb. 1-2 Schedules examples (Fig.3)
94
Fig.1 The monumental Quercus virgiliana living at Parco della Favorita
Fig.2 The last examples of dry orchard in Conca dOro are found at Parco della Favorita.
Monumental olive trees still live in the area (right plate); in many cases some individuals
pre-existing to citrus orchard plantation survive (left plate)
Fig.3 Hercules column surronded by monumental cypresses in 1930 and present-day pictures
95
96
MOLECULAR TOOLS FOR IDENTIFICATION OF DECAY FUNGI DIRECTLY FROM WOOD
**S. Bergemann, *C. Billi, **M. Garbelotto, *P. Gonthier, *F. Guglielmo, *G. Nicolotti,
**J. Tse
* DI.VA.P.R.A. Plant Pathology University of Torino, Grugliasco (TO), Italy
** Dept. ESPM - University of California at Berkeley California , USA
Summary
A PCR-based technique for the identification directly from wood of some of the most
important decay fungi of standing trees is developed in this study. Taxon-specific Polymerase
Chain Reaction (PCR) primers were designed in the 25S region of the ribosomal DNA for
several taxa of Basidiomycetes belonging to the following genera: Armillaria, Ganoderma,
Hericium, Inonotus, Laetiporus, Omphalotus, Phellinus, Pleurotus, and Stereum. When tested
on colonized wood blocks primers selectively amplified the target species. No cross-reaction
occurred against DNA of closely related genus or species. This procedure serves to be a
promising tool for the rapid diagnosis and identification of decay fungi.
Introduction
Wood decay of trees represents a distinct problem not only for horticulturists and arborists,
but also for veteran tree managers. Problems related to decay in trees range from unappealing
aesthetics to hazardous situations. While only a few decay fungi are directly responsible for
tree mortality, the loss of mechanical strength caused by these organisms is inherently
linked to tree windthrows or limb failures. The detection of hazardous trees is currently
based on Visual Tree Assessment (VTA) (Mattheck and Breloer, 1994), or on related
approaches such as Static Integrated Assessment (SIA) and Static Integrated Methods
(SIM) (Wessolly, 1995).
The basis of VTA is a visual scoring of obvious symptoms (e.g. emerging wood decay,
branch flagging, reduced vigor, etc.) and signs (e.g. ring bulge, cracks, ribs, etc.) known to
be connected to significant decay within the tree. In order for signs and symptoms of decay
to be visible, the decay process must be in a relatively advanced stage. Although good
training and VTA standardization efforts have partially overcome the problems due to the
subjectivity of the observer, VTA still allows for a large error in the evaluation process.
Various and different technologies have been developed to assess extent of decay within
a tree both in invasive (e.g. resistograph, portable drill), and in non-invasive ways (Nicolotti
et al., 2003). Some of them (e.g. resistograph) are already included in VTA protocols to
analyze suspected trees. These approaches are constantly being improved, but they are in
general unable to effectively identify the decay agent in its first stages. This drawback,
while significant for all types of decay, becomes more problematic when the decay agent
may be extremely active and decay may progress extremely rapidly from an undetectable
stage to an hazard stage. Alternatively, this limitation may become serious for types of
white rot decay in which loss of mechanical strength is progressive but extended over
relatively long periods of time. In the case of monumental trees, veteran trees, or trees with
historical importance, this drawback prevents a timely employment of treatments such as
extensive pruning, harnessing, or filling and sealing of the decay cavity.
Fruit bodies differentiation frequently occurs late, when decay is already at an advanced
stage, or often it does not occur at all. That represents a serious problem because, unless
fruiting bodies are visible, it is extremely difficult to diagnose the fungal species responsible
for the decay. Knowledge of the organism(s) involved is pivotal in understanding how fast
the decay process is going to develop, which part of the trees are likely to be involved, and
what is the potential of spread from one tree to neighboring trees. These information may be
of help for prognosis.
Diagnostic methods based upon the detection and the analyses of fungal DNAs, particularly
by Polymerase Chain Reaction (PCR) have been successfully employed in several fields of
plant pathology. However, methods allowing for the distinction of the most important decay
fungi directly from wood are not available yet. The success of these methods is largely
dependent on whether sufficient pure fungal DNA is extracted from wood or not (Jasalavich
et al., 2000; Gonthier et al., 2003; Sicoli et al., 2003). Several technical problems connected
with the complex chemistry of the wood may affect DNA extraction.
The goals of the present study were: i) to develop and test a protocol allowing for
successful fungal DNA extraction and PCR amplification from wood, and ii) to design and test
molecular markers to distinguish some of the most dangerous and widespread decay agents.
97
Material and Methods
Samples used for fungal DNA extraction from wood
Attempts of fungal DNA extraction were carried out on thirty Quercus agrifolia and Q.
kellogii wood samples putatively colonized by fungi. Samples, of about 6x4x2 cm, originated
from different locations in California (USA). To test the extraction of fungal DNA also from
coniferous wood, 10 putatively colonized Pinus cembra samples, originated from Aosta Valley
(Italy), were included in the experiment. Wood samples were stored at 80°C.
DNA extraction from wood for fungal Internal Transcribed Spacer (ITS)
amplification
Slivers, of about 1x1x2 mm, obtained from the wood samples were lyophilized for 36
hours in 2 ml Eppendorf tubes. Three sterile glass beads were added to each tube. The
tubes were precooled in liquid nitrogen and then the material was pulverized in an amalgamator
at 6.5 m/sec for 25 sec. The frozen powder was immediately transferred at 80°C before
DNA extraction. The fungal DNA was extracted directly from pulverized wood using the
QIAamp DNA Stool Mini KitTM(Qiagen) according to the manufacturers instructions. A 1:100
dilution of extracted DNA in PCR water was used for amplifications.
The success of fungal DNA extraction from wood was verified using ITS primers specifically
designed for fungi, named ITS-1F (5'-CTTGGTCATTTAGAGGAAGTAA-3') and ITS-4 (5'TCCTCCGCTTATTGCTATGC-3'). Amplifications were carried in 25 ìl volume containing 50mM
MgCl2 (Invitrogen), 10X PCR buffer (Invitrogen), 20mM dNTPs (Invitrogen), 5U/ µl Platinum®
Taq DNA Polymerase (Invitrogen). Reactions were conducted in a Thermal cycler programmed
for an initial 2 min. denaturation at 94°C followed by 32 cycles of denaturation (1 min. at
94°C), annealing (1 min. at 55°C), and extension (1 min. at 72°C). A final extension of 10
min. at 72°C followed the 32 cycles. Amplification products were analyzed by electrophoresis
on agarose gel (1.5%) in 0.5X TBE (Tris-Borate-EDTA) for 1 h and 20 min. at 70 volts.
Products were stained in ethidium bromide and visualized under ultraviolet lamp.
Isolates and DNA sequences used for taxon-specific primer design
Isolates belonging to 36 species included in 9 genera of wood decay basidiomycetes
were used to develop taxon-specific primers. Isolates belonged to Armillaria, Ganoderma,
Hericium, Inonotus, Laetiporus, Omphalotus, Phellinus, Pleurotus, and Stereum. The
identification of fungi was performed on the basis of the macroscopic and microscopic
features of their fruiting bodies, and pure cultures were obtained from the context of
basidiocarps. In addition to the isolates, all the sequences published on National Center for
Biotechnology Information (NCBI) Genbank and referring to each taxon of interest were also
used for taxon-specific primer design. The number of isolates for each species and the
closely related species used as outgroups are shown in Table 1.
Table 1. Number of isolates for each species and corresponding outgroup taxa used
for taxon-specific primer design
98
Design of taxon-specific primers
The 25S region of the nuclear Large subunit RNA (nLSU) was selected for the purpose of
designing generic-specific primers, and species-specific primers for Phellinus gilvus. Speciesspecific primers were developed for Inonotus andersonii and I. dryadeus both on 25 S and
ITS. Few hyphaes from aerial mycelium were collected by pipette tips from three day-old
pure cultures grown on Malt Extract Agar (MEA; 20 g agar, 20 g glucose, 20 g malt extract,
2 g peptone, 1 l deionized water), and placed into 100µl of sterile water in Eppendorf tubes.
The tubes were freezed on dry ice and then thawed quickly by placing them at 75°C in a dry
heat block. After thawing, the tubes were vortexed for 1 min. and spinned in a micro
centrifuge at top speed for 5 sec. Cycles of freezing and thawing were repeated for three
times. The tubes were then placed in a 75°C dry heat block for 15 min., and finally spinned
for 5 min. at maximum speed. Direct PCR was performed on the hyphal suspension without
any dilutions. Fungal DNA was also extracted from the entire culture using CTAB and phenol/
chloroform protocol, as described by Gardes and Bruns (1993). A 1:1000 dilution of extracted
DNA in PCR water was used for amplifications. The 25S region of the nuclear ribosomal DNA
was amplified using the universal primers CTB6 (5-GCATATCAATAAGCGGAGG-3) and TW13
(5-GGTCCGTGTTTCAAGACG-3).
PCR-amplified products were electrophoresed on a 1.5% agarose gel as described above.
Amplicons were sequenced using an ABI 3100 (Applied Biosystems, California) automatic
sequencer. Sequences assembly and manual refinement of alignments were carried out using
the Sequencer 4.1 program. The sequences from each taxon were aligned with sequences of
closely related groups (outgroups) in order to ensure the specificity for the target organism.
A highly conserved sequence in the 25S DNAwas used to design a forward (5→3) primer,
that we named 25S-F. Taxon-specific primers were designed as reverse (3→5). The same
approach was used to design species-specific primers for Phellinus and Inonotus. The
amplification of ITS was performed using the primer combination ITS-1F and ITS-4. The PCR
conditions were as described above, except for the annealing temperature of the reaction
that was lowered to 53°C. The ITS3 primer (5-GCATCGATGAAGAACGCAGC-3) was selected
as forward primer. Primer design was performed with PRIMER 3 software in order to maximize
its efficiency.
Taxon-specific primer testing
The specificity of primer pairs was tested on DNA extracted from pure fungal cultures.
Primers were finally tested on fungal DNA extracted from 60 wood samples (1x1x2 mm) of
Quercus agrifolia and Q. kellogii colonized by known wood decay agents. Fungal DNA was
extracted directly from wood as described above. PCR conditions were separately optimized
for each primer combination. Amplified DNA was visualized and its size determined by standard
DNA electrophoresis on agarose gel. In order to confirm the specificity of the primers a
subsample of 25% of PCR products were also sequenced. The ABI 3100 genetic analyzer
was used for an accurate fragment size analysis to verify the specificity (GeneScan technique)
of primers (not shown).
Results
The DNA extraction using the QIAamp DNA Stool Mini KitTM allowed the amplification of
putative fungal DNA from all samples included in the experiment. The ITS amplified region of
unknown fungi resulted in PCR products of various length (from 750 bp to 800 bp,
approximately) (Fig.1). The CTAB phenol/chloroform extraction generated good amplifications
from pure cultures.
Fig. 1 ITS amplification of fungal DNA extracted from 10 wood samples.
ITS was amplified with the primer combination ITS 4-ITS 1F
99
Sequence alignment showed a region in common for all taxa within the 25S. Such DNA
region is about 30 bp long, and its location within the nLSU is shown in Fig 2.
Fig 2 The black box indicates the region (about 30 bp long) in common for all taxa within the Ctb6-Tw13
region of the nLSU. This 30 nucleotide (nt) sequence was used to design the the 25S-F primer
The 25S-F primer is 18 nt long. The sizes of taxon specific amplicons generated through
PCR are listed in Table 2.
Table 2 Length of the amplicons (base pairs) originated through PCR in the nLSU and ITS
All taxon specific primers designed on nLSU allowed selective amplification of pure cultures
with no cross-reactivity with other taxa (Fig. 3)
Fig 3. Amplification product obtained with the taxon-specif primers 25S-F
and Phellinus gilvus reverse: lanes 1 to 14
Species-specific primers designed in the ITS region showed cross-reactivity with other
species while tested on pure cultures (Fig. 4). This was particularly true for Inonotus
andersonii and I. dryadeus with Ganoderma, Stereum, and several Phellinus species.
100
Fig 4 Amplification product obtained with the specific primer set ITS 3 (forward) and Inonotus dryadeus
reverse on pure cultures of different species. The bands show unspecific amplification. I. dryadeus
reverse primers cross-reacted with: Ganoderma (lane 1), Stereum (lane 2) and several Phellinus species
(lanes 3 to 5). Lane 6 shows the amplification of Inonotus dryadeus DNA
While tested on the 60 wood block samples, taxon specific primers allowed the detection
of 47 fungi. Taxon specific primers allowed the amplification of expected fungal taxa in the
77% of cases (Table 3). In 5 samples (8%), expected fungi were not detected with taxon
specific primers. In 9 wood samples (15%), more taxa than the only one species expected
were detected. Phellinus was the most frequently observed genera.
Table 3. Extract from observed versus expected taxa in primer testing on 60 wood samples
The basidiomycetes considered in this study are responsible for most of tree failures
reported in the temperate areas of the world. Although some of the above listed genera
include more than one species, the biology of congeneric species is quite similar, and differences
are often in host specificity.
The QIAamp DNA Stool Mini KitTM is a method that simplifies isolation of DNA from stool
with a fast spin-column procedure, no phenol and chloroform are required. This procedure
allows for the amplification both from Quercus and from Pinus. These two hosts are known
to be reach in polysaccharides, proteins and phenols, inhibitors of the PCR reaction (Khanuja
et al.1999). Furthermore field samples may often contain contaminants, or compounds causing
DNA degradation. The kit offers a fast and easy purification of the total DNA recovered from
field samples, even from recalcitrant wood.
Specific reverse primers for genera and for species were successfully developed in the
25S region of the ribosomal DNA for Armillaria, Ganoderma, Hericium, Laetiporus, Omphalotus,
101
Pleurotus, Stereum, Phellius gilvus, Inonotus andersonii, Inonotus dryadeus. Use of nuclear
ribosomal regions is recommended as they are present in many copies within the genome,
and allow for detection of a minute amounts of the target DNA. This is a region that is
frequently conserved within genera and variable between genera. Species specific primers
designed in the ITS showed cross-reactivity while used on pure cultures and did not work
when tested on wood samples. The ITS generally shows an high level of both interspecific
and intraspecific polymorphism (Wagner and Fischer, 2002), and it does not appear suitable
the goals of this research. The results reported here indicate that it is possible to identify
the pathogens directly from wood without the step of culturing the fungus. Fruiting bodies
of the fungus can provide material for its identification; however they are very ephemeral
and do not necessarily occur at the first stage of the wood colonization. Other molecular
techniques for the detection of targeted organisms, as RFLP, need longer procedure, restriction
profiles are often difficult to read and they do not allow for a secure identifications (Fischer,
1996; Jasalavich et al., 2000). We developed a rapid, reliable and sensitive method to
detect specific fungi in the wood. One of the main advantages of this approach is that the
diagnostic approach can be highly specific, meaning that it can be designed to target all
known organisms deemed responsible for important decay effects on trees of relevance to
the urban landscape and to ornamental arboriculture.
Although at present the identification of fungi with the technique described in this paper
still requires 2 days, the optimization of reactions with multiplex PCR approaches will allow
faster detections, providing a reliable tool for routine inspections of suspected trees.
References
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Gonthier P., Garbelotto M., Nicolotti G. 2003. Swiss stone pine trees and spruce stumps represent
an important habitat for Heterobasidion spp. in subalpine forests. Forest Pathology 33, 191-203.
Jasalavich C.A., Ostrofsky A., Jellison J, 2000. Detection and identification of decay fungi in spruce
wood by restriction fragment length polymorphism analysis of amplified genes encoding rRNA.
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Khanuja S. P. S., Shasany A. K., Darokar M. P., Kumar S.1999 Rapid Isolation of DNA from Dry and
Fresh Samples of Plants Producing Large Amounts of Secondary Metabolites and Essential Oils.
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102
THE HISTORIC CYPRESSES OF BOLGHERI: RESTORATION AND ENHANCEMENT OF A
HERITAGE OF EUROPE
R. Danti1, P. Raddi1, A. Panconesi1, R. Serra2, M. Tognotti2
CNR, Istituto per la Protezione delle Piante, Area della Ricerca, Sesto Fiorentino - Italy
Provincial Administration of Livorno - Italy
1
2
The symbolic role of cypress at Bolgheri and in Tuscany
The five kilometre Viale di Bolgheri runs across the coastal plain straight from the SS1
Aurelia, which it crosses at the village of San Guido, and leads up to the ancient village
situated on the lower slopes of the hills overlooking the sea (Fig. 1). The two straight rows
of cypresses of the Viale form a harmonious composition and an architectural planting which
forms a vista with tree-like wings set, as it were, between two
stages: the hillside village of Bolgheri and the land stretching
towards the sea. The avenue is set in an area where the beauty
of the surrounding countryside has remained largely unspoilt by
indiscriminate urban and tourist development and where agricultural
management enhances it further (Bezzini 1990). The cypresslined road rises from the plain forming a spectacular, stately
geometric line intersecting the flat land and the undulating hills.
Visitors travelling along it are struck by the perspective before
them and by the charming, enchanting atmosphere (Fig. 2). The
poems that Carducci wrote about his childhood haunts in the
Maremma, including the famous Davanti San Guido dedicated to
this very cypress avenue, have helped to create the myth and
fame that still surrounds Bolgheri and its Viale today.
Overall, the Viale forms a landscape design which, placed
harmoniously in the hilly countryside of Bolgheri, has acquired
considerable cultural and environmental value. The Ministerial Order
Fig. 1 Panoramic view of of 21 August 1995 declared the Viale di Bolgheri to be part of the
the village of Bolgheri and artistic and cultural heritage and, as such, subject to protection
the Viale which runs across
as provided for by Law nr. 1089 concerning the architectural heritage.
the coastal plain straight
The Viale represents one of the best known and, probably, the
most famous examples of the symbolic, expressive role of cypress in Tuscany. In this region,
cypress is no longer bound to the role of a funerary plant that was always ascribed to this
tree in popular tradition, and instead takes on an auspicious, positive function. The cypress
thus appears to be an intrinsic element of the Tuscan landscape, the result of a such a
sensitive mixture of respect for the environment and the work and traditions of man as to be
regarded as a quintessential symbol of the cultural identity of Tuscany. At Bolgheri the
ornamental, cultural and historical value linked to this plant blend to create one of the most
typical and charming effects.
The common cypress (Cupressus
sempervirens L.), that grows wild in Asia Minor
and in the Eastern Mediterranean (Gellini and
Grossoni, 1979), was brought to Italy by the
Etruscans and the Romans, the latter using it
mainly as a ornamental tree, for plantings around
villas, monuments and sacred places. During
the Renaissance the cypress enjoyed a revival
in Tuscany when it began to be used once
more to decorate the homes of the aristocracy,
but also on account of its valuable timber and
for use in agricultural work, so that over time it
Fig. 2 - A perspective view of the Viale
became a plant associated with rural life and
labour. Planted singly or in small stands, near
villas, churches, inns or crossroads, the cypress was used as a landmark by wayfarers and
its timber was used to make shutters and frames, doors and furniture (Giannelli 2002). The
outlines of this conifer are such a well-known sight today throughout Tuscany, from coastal
areas to inland hillsides, that it is an essential, familiar element of a landscape that has now
become famous all over the world.
103
The difficulty in the control of cypress canker disease
Since ancient times, the common cypress has been considered a healthy, strong and
disease resistant tree. Since the 1950s, however, it has been facing a serious health
problem: the Seiridium cardinale canker (Panconesi and Raddi, 1991). The gradual deterioration
of an extremely important landscape and forest feature prompted
investigation of a range of direct and indirect methods to control
the spread of the disease and put a stop to this deplorable stream
of losses (Fig. 3).
So far the instruments that have proved most effective in
controlling the disease have been sanitation (in terms of elimination
of infected trees or portions of trees), to protect affected stands
and ornamental plantations (Parrini 2003; Panconesi and Danti, 2003),
chemical prevention in the nursery (Panconesi and Parrini, 1979)
and genetic improvement of cypress as a deterrent for the spread
of the canker and to restore affected formations (Raddi and
Panconesi, 1998). The relevant Regional, Provincial and Local Councils
have always been sensitive to the problem and have supported
projects for the control of the disease. At EU level as well the
cypress problem has been given attention since the seventies through
the financing of four international research programmes that have Fig. 3 A cypress of the
attacked
led to important results of practical value, such as the selection of Vialebyseverely
S. cardinale
a set of canker resistant cypress clones.
Today, however, 50 years on from its first recording, as a result of the endemic nature
assumed by the disease and the impossibility of dealing with the entire region in a brief
space of time, S. cardinale canker continues to severely affect cypress, to the extent that,
according to recent surveys, areas where the total of infected plants is nearly 50% are still
common. Because of the symbolic value of this tree in Tuscany and central Italy, cypresses
damaged by canker give tourists the impression that the area is carelessness and neglected.
The Protocol of Agreement for the conservation and restoration of
theViale di Bolgheri
The first serious symptoms of bark canker in the trees in the Viale occurred between the
1960s and 1970s, when bark canker reached epidemic level in many areas of Tuscany
(Parrini, 1991). The planting of the trees in rows and mild, damp climatic conditions typical
of the coastal area encouraged the development and reproduction of S. cardinale, favouring
its spread throughout plantations. Consequently the Bolgheri cypresses have repeatedly
suffered from various outbreaks of the disease, with severe damage and many losses being
recorded over the years. For years they have been the subject of attention by the Regional
Council, the Livorno Council, the Forestry Commission of and scientific institutions, alerted
by the continual, inexorable, rapid deterioration affecting this monument.
Interventions to protect the Bolgheri cypresses, started in 1979 and repeated during the
1980s and 1990s, have unfortunately been isolated and sporadic and, for this reason, have
not controlled the disease effectively. Plant health surveys carried out in 1995 and 1999
continued to highlight the recurrence of serious attacks, both on trees that had previously
been cured and on trees that had previously been free from the disease. While in 1995
surveys showed the need to fell 42 cypresses and to sanitise 400, in 1999, four years after
the performed sanitation, it was once again necessary to fell 94 plants and treat 421.
Towards the end of 1999 the continuous, unstoppable occurrence of damage and losses
of the Bolgheri cypresses united governments and authorities responsible for the protection
of the Viale in the need to carry out an urgent, organic, synergic programme of work to save
the monument from deterioration and to go ahead with its improvement. Therefore the
Provincial Council of Livorno, the Regional Council of Tuscany, the Local Council of Castagneto
Carducci, the Superintendency of the Historical, Artistic, Architectural and Environmental
Heritage of Pisa, ARSIA1, ARPAT2, ISZA3, the private owners of the historic cypresses and
the CNR IPAF4 signed an agreement in December 99 for the creation of a 10-year project
for the restoration and enhancement of the historic avenue.
The ten-year programme was co-ordinated by the Provincial Council in a series of important,
inter-related activities. Investigations based on tree health status and topographical surveys
were followed by work aimed at treatment, restoration and maintenance, together with
research work for the selection of canker resistant genotypes among the trees in the
historic avenue.
104
Major programme operations and current status of the activities
Planning and Intervention
Two sanitation programmes, drawn up by the Provincial Administration and by the CNR,
approved by the Superintendency, were completed in 2000 and 2002 respectively, with the
aim of gradually reducing the incidence of cypress canker disease in the two rows along the
Viale and in immediately surrounding areas. The drafting of the projects required the
implementation of health surveys reporting on fungal and insect attacks, the recording of
data in a specially created database, the preparation of descriptive printout and photographic
testimony. Landscape experts were entrusted with a design study aimed at controlling and
enhancing the presence of the undergrowth located intermittently along the two rows of
the avenue, mainly consisting of shrubs typical of the Mediterranean area. Special attention
was paid to Cercis siliquastrum, which is a spring flowering species that creates a wonderful
colour contrast against the dark green of the cypresses.
Training
Before sanitation works started, theoretical and practical courses were organised to
train the workforce, aimed at increasing knowledge of the most important cypress diseases
and their respective methods of control. Special attention was given to symptomatology,
identification and spread of S. cardinale canker as well as methods of control the disease on
infected plants, illustrating the basic criteria for correct implementation cuttings. Technicians
from the Livorno Provincial Council, ARPAT and the Comunità Montane took part, together
with operators from firms specialised in urban landscaping.
Restoration
In the spring of 2002, 102 7-9 metre tall specimens of C.
sempervirens var. pyramidalis were planted to replace previously
felled trees. The planted trees, divided into 60 different canker
resistant genotypes, were taken directly from CNR research fields
(Fig. 4).
Fig. 4 - Specimens of cypress
clones selected for resistance
to S. cardinale infections,
which were planted along the
Viale to replace previously
felled trees
Maintenance
Tests were carried out periodically throughout the year by
the IPP-CNR and ISZA to assess the presence of problems due
to fungal and insect attacks. In addition to S. cardinale infections,
populations of Cinara cupressi aphids and Scolytids of the genus
Phloeosinus require constant monitoring (Panconesi et al., 2003).
In favourable years the former can cause extensive desiccation
of the cypress crowns. Prompt treatments were carried out on
some stretches of the avenue planting to prevent serious aphid
infestations. The latter, by feeding on the shoots, may transmit
infections of S. cardinale from diseased trees to healthy ones.
Research (genetic improvement)
Work aimed at selecting resistant genotypes of the cypresses in the historic avenue took
place in stages. To date, 250 particularly vigorous and aesthetically valuable subjects have
been propagated by grafting. The young saplings obtained from subjects propagated in 2000
and 2001 have already been planted in research fields where their ability to resist S. cardinale
will be tested, and in a conservation field near the Viale. The plot of land for conservation is
near San Guido and has been granted to the Provincial Council of Livorno under a free
contract for twenty years by the owner, Marchese Nicolò Incisa della Rocchetta. The land
has been suitably fenced off; planting, cultivation of the soil, weed-control and regular
maintenance work are carried out by Livorno Provincial Council employees.
Computerization
Zerobyte Sistemi is a firm in Florence which, under contract to, and in collaboration with
the Local Council, IPP-CNR and ISZA, have set up a specially designed computer system to
create a historical archive and to plan the work on the trees in the avenue. The system is
based on the use of transponders (microchips) that issue a signal in code form so that once
the sensor is inserted in the trees, it allows them to be immediately identified. Using specially
designed software, it is possible to view and update reports and therefore organise a
105
database where the history of each tree is registered. The software has also been designed
to assist the planning of work performed on the plants and to manage the accountancy
aspects.
The European importance of the Bolgheri Avenue: the Interreg III B Medocc
Cypmed project
The Cypmed5 project, officially approved by Feder and by the Ministry for Transport and
Infrastructures on 1.1.2002, aims to demonstrate the utility of the cypress as a multipurpose plant for the improvement of the environment and the Mediterranean landscape, in
the light of results obtained with genetic improvement during previous Community research
programmes on cypress (Agrimed 1, Agrimed 2, Camar, Air). Thirteen Italian, French,
Portuguese and Greek operative units are taking part in the project, which is headed by IPP
CNR. They are deeply involved in the ecological, economic and decorative-historical role of
the cypress.
As a result of a shrewd conservation policy put into operation by the Livorno District
Council for the Viale di Bolgheri cypresses, an inter-disciplinary work group has been formed
and asked to take part in the Cypmed project as a unique example of cooperation between
public authorities and research institutions in a ten-year work project.
The combined efforts of the CypMed members ensure both a range of urgent, correct
interventions and European-level visibility of the problem Ornamental Cypress canker
caused by Seiridium cardinale. In addition, it promotes training of technical staff and the
wide-scale dissemination of methods used for sanitation and recovery of cypress trees. The
results obtained on the sanitation, replanting and management of the Bolgheri Avenue
cypresses may be of great interest for the restoration of historical cypress plantations in
Italy and in other Medocc (Western Mediterranean) countries. The inclusion of the Bolgheri
Cypresses in the Cypmed project is recognition of an operation in which scientific progress is
highlighted, confirming the international fame of the avenue that is visited every year by
hundreds of foreign visitors who are captivated by such a wealth of natural beauty.
Bibliography
Bezzini L., 1990 - Bolgheri. Bandecchi e Vivaldi Ed., Pontedera.
Gellini R., Grossoni P., 1979 - Aspetti botanici del genere Cupressus. In Il Cipresso: malattie e
difesa. V. Grasso, P. Raddi Ed.,Comunità Economica Europea, 27-43.
Giannelli L., 2002 - Il cipresso. Storie e miti di terre toscane. Scramasax, Rep. San Marino, 151 pp.
Panconesi A., Parrini C., 1979 - Nuove esperienze di lotta chimica contro il Seiridium (Coryneum)
cardinale. Inf.tore Fitopatol., 29 (5), 13-17.
Panconesi A., Raddi P., 1991 - Cancro del cipresso. Aspetti biologici ed epidemiologici. In Il
cipresso, CNR, Regione Toscana, 49-60.
Panconesi A., Danti R., 2003 - Quando risanare, quando abbattere. In La bonifica fitosanitaria
a tutela del cipresso. ARSIA, Regione Toscana, 67-78.
Panconesi A., Danti R., Binazzi A., Roversi P.F., Pennacchio F., 2003 - Le avversità più ricorrenti del
cipresso. In La bonifica fitosanitaria a tutela del cipresso. ARSIA, Regione Toscana, 15-35.
Parrini C., 2003 - Presupposti teorici e risultati attesi dalla bonifica. In La bonifica fitosanitaria a
tutela del cipresso. ARSIA, Regione Toscana, 59-66.
Parrini C., Panconesi A., 1991 - I metodi di lotta contro il cancro corticale del cipresso. In Il
cipresso. CNR, Regione Toscana, 94-109.
Raddi P., Panconesi A., 1998 - Valorizzazione del patrimonio genetico per la resistenza al cancro
del cipresso. Ann. Acc. It. Sci. For., XLVII: 45-53.
1
2
3
4
5
Agenzia Regionale per lo Sviluppo e linnovazione in Agricoltura
Agenzia Regionale per la Protezione Ambientale della Toscana
Istituto Sperimentale per la Zoologia Agraria
Consiglio Nazionale delle Ricerche Istituto per la Patologia degli Alberi Forestali (now IPP
Istituto per la protezione delle Piante)
www.cypmed.cupressus.org
106
MONUMENTAL TREES INVENTORY OF THE PROVINCE PISTOIA, ITALY
R. Ferretti*, M. Giachini, D. Giorgi**, M, Vannuccini ***
* Executive of Territorial Resources Planning Service, Pistoia Province
** Independent professional
*** Independent professional, Studio Tecnico Eureco
1. Introduction
Monumental trees are a multifunctional resource, due to their naturalistic and historical
relevance and to the important impact on landscape. In Tuscany, the value of monumental
trees heritage has been recognized by the local law L.R. 60/1998. This law identifies the
status of monumental tree, defines the rules for trees protection and valorisation and
establishes a regional catalogue of monumental trees.
The Territorial Resources Planning Service of the Province Pistoia, back in 1989, set up
an inventory by which forty-one trees were identified, that according to their extraordinary
age or size could be considered as monumental. Most of them are located in the mountain
area of the province. The inventory was although not exhaustive, since it only took into
account a part of the provincial territory: the lack of data and information about the wide
district of municipalities of Pistoia, Montale, Pescia, Montecatini etc., leads to think that a
consistent monumental trees heritage is still to be identified, also by taking in consideration
the local dense historical villas system. In accordance with law 60/98 the opportunity to
program protection and valorisation measurers is also given. These measures can although
be only implemented on the basis of updated and consistent information on quantitative
(morphometrical and dendrological data) and qualitative (physiological and sanitary conditions)
characteristics of the trees and also about the changes of the area in which trees are
located (SHIGO, 1993). In the frame of the new Co-ordinate Territorial Plan (P.T.C.), which
considers monumental trees within the list of environmental resources of the provinces
territory, a new initiative was taken in order to extend the inventory on the whole province
and herewith establishes an exhaustive data base in relation to the trees consistency and
health conditions, which will be integrated in provincial administrations Geographical Information
System. Particular attention will be given to geo-referencing trees locations, as a necessary
premise to their correct identification on site.
2. Available information
The available knowledge on the amount and conditions of monumental trees of the
province Pistoia arise from four different sources which, at different times and with different
criteria, attempted to assess the situation of the provinces green patriarchs.
The first inventory, promoted by the National Forest Service (C.F.S.) in 1982, concerned
the whole national territory. As far as the province Pistoia is concerned, thirteen monumental
trees were singled out. Out of the twenty-two municipalities of the province Pistoia, only
eight were represented, within the inventory, by at least one tree of extraordinary historical
or monumental value. Municipalities such as Pistoia, Pescia and Quarrata, which represent a
remarkable portion of provincial territory, contributed with no tree, whereas six monumental
trees were identified in the territory of San Marcello Pistoiese. In 1989 the Provincial
Administration of Pistoia performed an inventory by which forty-one monumental trees were
identified, mainly located in the mountain area of the province and, in specific, in the
territories of San Marcello Pistoiese, Sambuca Pistoiese and Abetone.
In spite of the knowledge that was acquired through these census initiatives, only one
tree of the province Pistoia (located in the municipality Lamporecchio), is actually inscribed
in the Monumental Trees Regional List ex L.R. 60/98, out of a total of forty-nine trees
setting up the list itself. In order to update and enrich the Regional List, the Regional
Administration of Tuscany, in co-operation with the W.W.F., promoted the Monumental
trees in Tuscany school contest in the school-year 2002-2003, addressed to the students
of Tuscanys schools. Thanks to this initiative, one-hundred and twenty-five trees were
identified, eleven of which in the province Pistoia.These inventories, for several reasons,
failed to give a global and exhaustive picture of the real situation of the monumental trees
heritage on the wide territory of province Pistoia. If a comparative evaluation of all actions
undertaken till now is performed, a basic incommunicability between different lists comes up.
In other words, the regional list seems not to completely take into account the results of
previous inventories. As a consequence, the Provincial Administration of Pistoia called out
for an overall inventory which foresees the detailed analysis of the provincial territory, while
updating and harmonising the information from previous initiatives. In particular, the lack of
107
knowledge about municipalities as Pistoia, Montecatini, Pescia and Quarrata, having a high
incidence of remarkable villas and historical gardens, leads to think that a substantial
monumental trees heritage is still to be identified.
3. Monumental tree inventory
With reference to intervention measures foreseen by the regional regulations, which are
put into effect by a specific action in the regional Rural Development Plan (P.S.R., Reg.
2057/99 EU), the present research and inventory initiative was set up according to some
fundamental requirements:
- Accurate trees geo-referencing, in order to obtain a certain tree identification on site,
both for management and for eco-tourism activities.
- Exhaustive description of sanitary and physiologic tree conditions, necessary to plan care
and management measures.
- Collecting exhaustive information about naturalistic, historical, traditional and landscape
aspects related to each tree, in order to give to the regional Scientific Commission ex
L.R.49/1995 (competent for evaluation of proposals for the admission to the regional list)
as much information as possible, supporting the tree-candidates that will arise through the
inventory.
- Create an integrated management tool in accordance with the provincial Geographical
Information System.
The complete information collected throughout the inventory will be filed into a dedicated
data base, developed in a Ms Access environment, linked to a point theme in shape format
which stores spatial information (i.e. geographic location of each tree).
4. Research and documentation
A preliminary documentation and research phase is essential for singling out monumental
trees. Analysis of individual mentions, archive research, etc, will be collected and evaluated
with the aim to obtain a wide range of preliminary knowledge.
The primary information source is of course the provincial inventory of 1989, which will
be eventually integrated with the results of the C.F.S. national inventory, and furthermore
updated by recent acquisitions from the school contest organised by the regional administration
and the W.W.F. Taking into account that a large portion of the provinces territory was not
involved in the mentioned initiatives, it is of utmost importance to investigate documentary
sources, which may lead to obtain remarkable information on monumental trees. For instance,
the wide bibliography on historical villas and gardens is supposed to give suitable information,
while also performing an analysis on local places names: quite often these names are
originated by trees that were considered remarkable under a certain point of view.
In order to collect direct mentions, a dedicated form was prepared, through which
anyone can bring remarkable trees to notice. The form, which is accompanied by a short
guide containing the requirements to which a monumental tree must be conforming, foresees
that the user reports useful information for localisation of the tree and for a first screening
of the received forms. The call for mentions will follow both institutional channels (municipalities,
mountain communities, C.F.S. stations, etc.) and preferential channels in co-operation with
environmental or cultural associations or any other institution having a direct interest on the
territory. The inventory will also be promoted on Internet, by means of a web page linked to
the web sites of the province, municipalities, and any involved association.
5. Monumental tree database
In order to collect and file both field information and geographic data, a dedicated
Geographical Information System was set up. Alphanumeric information, which means all
quantitative and qualitative information, is managed by a data base developed in Access
environment; spatial data (which means a point vector theme in shape format) is linked to
the database via Windows ODBC protocol, and therefore the information can be managed
directly in a GIS environment.
The database is provided of proper forms for data input and visualisation, which allows a
prompt data recall and change by the user. Data is recalled through several pages of
access, each containing following information:
- Tree identification, containing dendrological data and all useful information for the tree
characterisation and localisation;
- Tree conditions, containing morphometric data and a general description of physiological
and biomechanical aspects;
108
- Sanitary conditions: the form contains specific information about a possible stress situation
caused by biotic and/or non biotic factors and about identified pathologies, where applicable;
- Management: the form contains a short report that summarises threats against the trees
conservation, and technical and operative notes, in order to achieve a correct tree
management and protection;
- Monumental value: the form collects all available information about the historical, naturalistic,
cultural and landscape values of the tree.
Available data concerning the trees overall conditions (health and physiological status,
biomechanical information) are also summarised on an analytical form, containing standard
information, which is used both to obtain descriptive statistics about tree populations and
also as a summary report that allows the field technician to keep the information during any
future periodic inventory up to date.
6. Database contents
In order to obtain information in the most standardised way as possible, a proper inventory
form was prepared for field data collection, in which actual tree conditions are recorded.
The inventory form is made up of keys recalling the tree characterisation and check, as well
as indicators concerning tree location, structure, morphology and sanitary conditions.
Tree identification
The form concerning the tree identification (Figure 1) reports some general information
(identification code, species, date of first inventory) and the related photographic
documentation. Furthermore, particular care is given to the tree localisation; as a matter of
fact, geo-referencing the tree is of utmost importance in regards to the objectives of this
work; therefore, an instrument assuring a high precision level in determining point location
was chosen.
The geographic location of each tree is therefore acquired by a Global Positioning System,
transferred to a GIS software and finally reported in the regional technical cartography
(CTR).
The form contains:
- Municipality, locality and eventually (for trees located in a garden or near a house) the
street and the number of the house;
- Gauss Boaga coordinates of the tree location;
- Section of the regional technical map (CTR 1:10.000);
- Land-registry references (sheet and parcel number): these references are requested
within the authorisation procedures for different kinds of human activities, having an impact
on the territory; therefore they represent an important control tool to check for possible
modifications of the site.
Finally, the property is identified (public or private) and references on the owner or the
manager are recorded.
Figure 1. Tree identification form
109
Tree conditions
The tree conditions form (Figure 2) reports, first of all, dendrological and dendrometrical
main parameters, as circumference, diameter at breast height (this is actually a redundant
data, but on the other hand the diameter allows to better assess the trunk size), height,
height at which the green crown base starts (i.e. height of first living branch) and crown
width (this is defined by the radius in the four directions, perpendicular one to each other).
Some general information concerning the specimen to be preserved is also recorded: this
can be an individual tree or a bio-group, which intended as a group of individuals originated
by a single mother-plant and which cannot be classified as a single tree. The trees overall
conditions are assessed through short descriptive reports concerning the location in which
the tree lives (planting site), each of the trees main apparatuses (root system and collar,
trunk, crown) and eventually recent management interventions.
The soil and planting site aspects are of utmost importance for the evaluation of the
roots water supply and the possibility to exchange gases. Therefore, some related aspects
are put into evidence, as the kind of ground coverage, the soil compactness, eventual
limitations to the root systems development, morphological root anomalies, root decay
symptoms, damaged roots, basal cavities etc. In reference to the trunk, some information
about the morphology is registered and, eventually, damages and structural anomalies. In
regards to the morphological aspects, the trunk inclination from the vertical axis is taken
into account, as also any peculiar aspect such as V-shaped crotches, crooks, etc. Damages
and anomalies due to factors having either a biotic and/or a non biotic origin are recorded,
as indicators of pathologies or symptoms of reduced vigour or loss of mechanical wood
stability.
For instance, the following data is recorded:
- Wounds on both bark or wood;
- Emergence holes made by bark and wood miners;
- loose bark or bark necrosis;
- Cavities, of different depths and healing stadiums, due to pruning, wounds, wood decay
and mechanical damages;
- Wood decay fungi fruiting bodies, as symptoms of decaying wood, or visible wood decay;
- Foreign body inclusions.
Figure 2. Tree condition form
In regards to the crown, all remarkable aspects are recorded, in order to describe trees
physiological conditions and to make a precocious diagnosis of suffering conditions:
- Presence of cavities, decaying wood and fungi fruiting bodies on branches;
- Presence of dead or compromised branches;
- Presence of pruning scars and wounds on main branches;
- Presence of epicormic branches;
- Stress symptoms due to pathologies of biotic or non-biotic origin, as leaves chlorosis and
colour loss, leaves necrosis, cancers, microphyllia, crown dieback etc.
Finally, some conclusive consideration on physiological and sanitary conditions are reported
(in the section vegetative state) as a synthetic description of actual tree state.
110
All collected information by means of descriptive reports, can be viewed in a synthetic
way through the analytical form (Figure 3), which allows to export data in an Excel file for
statistical analysis or in order to produce final reports about the whole tree population. The
analytical form consists of standard voices which allow to define the trees overall conditions.
Figure 3 Analytical form
Health condition
This section contains a report about trees sanitary conditions, with a particular look at
pathogens. The form contains photographic documentation related to present pathogens
(insects, fungi, bacteria, etc.) and also any possible non biotic damage. The contents of
this section can be viewed in the analytical form, too.
Management
The section related to tree management contains the guidelines about the proposed
future tree management interventions, while also putting in evidence any need to go into
further depth on specific aspects. The reported interventions can be determined either by
an immediate need for safety assurance or by a long-term planning, which, for instance,
might be a site environmental improvement. Here below the possible intervention measures
are reported:
- Hazard tree assessment, which may be applicable for all trees located in areas with a high
frequency of visitors and whenever symptoms of reduced carrying capacity are present
(MATHENY & CLARK, 1994). The mentioned assessment is therefore strictly restricted to risk
situations which require extraordinary management measures (BRELOER & MATTHECK, 1998);
- Pruning is foreseen either as an extraordinary measure where a risk condition is given, or in
case a clear negligence on planned intervention measures is assessed. Pruning prescriptions
go always together with detailed operative technical notes and also specific photographic
documentation;
- Consolidations: these arboricultural tools are intended to prevent branch collapse through
the use of moorings and supports, while also preventing from branch injuries occurring
during branch fall, which is obtained by establishing predetermined falling directions;
- Site improvement management measures; for instance, waterproof paving removal, soil
improvement through agronomic interventions, etc.
- Preventive or corrective sanitary treatments.
This section also reports the main biomechanical parameters taken into account by the
S.I.A. (Static Integrated Assessment) method. S.I.A. allows the assessment of some tree
static characteristics by simply surveying dendrometrical parameters, as, for instance, tree
height, dbh and crown shape. Once this data is assessed, through statistical models which
were identified for each tree species, the base carrying capacity can be determined (a
parameter that concerns the tree structural dimensioning), as well as residual wall thickness
which is required in order to have a trunk with a 100% base carrying capacity (below this
value the tree is under-dimensioned towards the crown loading).
S.I.A. parameters were addressed within this work in order to obtain a first evaluation
about the tree static characteristics and also to have a base reference for any future
deepening needs on the hazard tree assessment. Up to present, S.I.A. models are available
only for certain tree species, while static-morphologic mathematical relationships for many
Mediterranean species (helm, cypress, etc.) are still to be investigated.
111
Figure 4. Management guidelines form
Monumental value
In the last section all information related to naturalistic, historical, architectonic and
landscape aspects or reference to local use and traditions linked to the trees is collected.
According to Regional Law 60/98 a monumental tree is not only a tree of extraordinary size
or age, but also a tree having a precisely defined reference to historical events or to local
traditions. The documentation related to these specific aspects is therefore necessary to
sustain trees candidates for the insertion in the regional list. This is moreover useful information
for the tree valorisation (by means of informative activities) and for promoting the provinces
natural heritage in the frame of environmental tourism.
7. Conclusions
The described research and inventory programme on monumental trees in the province
Pistoia is, at present, the most complete and exhaustive experience in the Tuscany region.
This inventory, which is based on a solid arboricoltural basis, does not only allow to
identify and register monumental trees, but it permits also to obtain a wide knowledge base,
which is a useful tool for any management, protection and valorisation activity.
Under a technical point of view, the collected information will provide a useful basis to
develop a management disciplinary tailored on each tree, which can then be put into practice
thanks to financial measures that are foreseen by regional laws, but which are also taken
into account very seldom. Taking into consideration that monumental trees can be considered
as a rural landscape promoting tool, the set of information that was collected can be used
to promote environmental tourism and educational initiatives. The available digital archive,
would in any case find in the web its natural divulgation mean.
References
WESSOLLY L., 1995. Fracture diagnosis of trees. Part:2 Static Integrated Methods Statically
Integrated Assessment (SIA). The practitioners method of diagnosis. Stadt und Grun, 8: 570573.
AA.VV., 1989. Censimento delle piante monumentali (L.R. 82/82). Provincia di Pistoia, 92 pp.
BRELOER H., MATTHECK C., 1998. La stabilità degli alberi. Fenomeni meccanici e implicazioni legali dei
cedimenti degli alberi. Il verde editoriale, Milano, 281 pp.
SHIGO A.L., 1993. A new tree biology. Shigo and Trees Associates, Durham, New Hampshire.
MATHENY N.P., CLARK J.R., 1994. A photographic guide to the evaluation of hazard trees in urban
areas. Ed. International Society of Arboricolture (U.S.A), 85 pp.
112
CURES OF MONUMENTAL TREES: A METHODOLOGICAL APPROACH
F. Grisoni, E. Viotto, M. Palenzona
IPLA S.p.A. - Torino
Abstract
In application of a regional law (n°50, 3.04.1995), Protection and Evaluation of
Piedmontese Monumental trees with high naturalistic and historical importance, Piedmont
Region has started a series of activities: catalogue and protection of monumental trees.
Since Spring 2000 until today, IPLA, in collaboration with the Department for Evaluation
and Protection of Agroforestry Resources (Turin University) and with the Italian Forestry
Corps, has realized activities of planning, management and cures. By indications of a special
Regional Commission, each subject or group has been accurately described, according to its
morphological characteristics, and then cured. During three years of work, treatments were
applied to 39 arboreal groups mainly belonging to native species and chosen homogeneously
in the Piedmont Region. On the base of the tree health, a different kind of cure has been
selected: dry branches elimination, pruning, recovery.
Today it can be stated that the treated plants appear such vigorous as to assure a
majestic future presence. Therefore, constant monitoring and on-time-treating is of primary
importance, in case of new health problems.
Introduction
By a Regional Law (n°50, 3.04.1995), Protection and Evaluation of Piedmontese
Monumental trees with high naturalistic and historical importance, attention is addressed to
these living monuments, because their presence can contribute to improve the regional
landscape, and its environmental and cultural evaluation.
The law provides for a catalogue of the Piedmont monumental trees (single trees, groups
or monumental tree rows); their protection, by Regional financing of ordinary and extraordinary
cures; the promotion of actions to evaluate and know monumental trees and understand the
importance of their protection. Since many years, IPLA (Istituto per le Piante da Legno e
lAmbiente, Turin, Italy) has been working with the DI.VA.P.R.A. (Department for Evaluation
and Protection of Agroforestry Resources Turin University) and with the Italian Forestry
Corps, in order to apply the 50/95 Regional Law. Because of its technical practical
competences, IPLA has been involved in pilot activities of cures planning and realisation,
since the beginning of this project. The aim was to cure and recover particularly interesting
trees from the monumental point of view. Later on, IPLA was involved in the monumental
trees catalogue and in spreading this kind of activity, also because of its contacts with
many Piedmont Municipalities.
Since Spring 2000 until today, IPLA was charged by the Region with the task to carry out
an annual activity of works planning and management, realisation of cures and evaluation,
on monumental trees according to the Regional 50/95 Law. The main objective of these
activities is to provide a methodological example by treating a chosen group of trees. On the
trees marked by a special Regional Technical Commission, IPLA has supervised the provided
activities and finally produced technical and explicative cards to be spread out.
Materials and methods
The first step of the project is to choose trees to be treated. IPLA technicians, in
collaboration with the Turin University researchers, made preliminary field surveys to estimate
characteristics of each tree indicated by the regional Technical Commission.
During this first inspection, the location has been verified and a preliminary picture of the
tree has been described, including a summary of the main health problems.
Later on, the following activities have been developed on each chosen tree:
I) Primary visual inspection
An accurate description was performed, with particular attention to the phyto - sanitary
and static conditions. In details, the following aspects were analysed:
apparent energy (new foliage development, presence and diffusion of dry leaves, crown
colour);
root anchorage and potential dangerous situations depending on rooting specific sites
(asphalted or transit areas, slopes, presence of manufactures or stagnant waters, ecc.);
crown form (regular, eccentric, unbalanced);
branch ramification characteristics: protrusion from main axis, insertion angle into the
113
trunk, inner and external injures (wounds, breakages, damages from lightning, tense wood,
torsion effects, cavities, malformations, ecc);
injuries in the trunk or at the tree foot;
presence, shape and health of roots (development, emergence, phyto - sanitary conditions,
ecc.);
presence of all types of phyto pathologies, in particular of butt rot fungi.
II) Treatment programme
After a preliminary tree analysis, the plan for the main treatments has been defined. The
following kind of cures were provided:
pruning for foliage reduction and safety measures, to lower the sail effect of apex parts
(especially the lateral branches exposed to winds and far from the main axis), by lightening
malformed branches;
pruning dry branches to avoid the danger of unexpected falls;
disinfection of superficial wounds on healthy wood by cupric oxychloride solutions, in
order to improve plant reactions against wood fungi attacks and to preserve mechanical
resistance of trees;
in case of open large wounds, operations of dendro-surgery by removing decayed and
injured wood parts, to eliminate infection sources (recovery), and subsequent treatments
on wood by cupric oxychloride;
wound dressing: application of seals (usually thin lead slabs) over open-up wounds more
subject to wood decay because of rainwater infiltration;
wound dressing: application of protection nets, to preserve cavities from storage of
vegetal detritus (leaves, ecc.) and/ other materials;
rod bracing to consolidate the unbalanced ramifications by anchoring branches, with
opposite barycentre, tied each other to compensate tensions, or by anchoring the most
divaricated and dangerous branches to the trunk;
realisation of specific and special supports to fix great and too much unbalanced
branches, if rod bracing is not possible;
indication of integrated works to improve landscape and monumental values and the tree
protection (for example, pruning on contiguous trees, realisation of flower beds with
protection curb, ecc).
IPLA has consulted Turin University specialists to choose the specific cures to the most
difficult cases of stability and vegetative decay. During this phase, also site accessibility
has been studied and the most suitable tools to operate on tree crowns has been chosen.
A specific field card (fig. 1) has been utilised to describe trees and observe the main
characters (point I and II). Denomination and location of the analysed monumental tree, site
accessibility, tree description and suggested cures, final evaluation and list of photos are
reported on this card.
Figure 1. Field card
114
III) Works management
Cures have been usually performed by Airgreen of Fratelli Airaudi, Robassomero (TO),
that has realized the jobs according to indications and supervision of the IPLA technicians.
Different models of hoists have been utilised. They are suitable to catch up the higher and
majestic tree tops and can get in and work in the less accessible crown parts.
In some cases, difficult access to the site tree has imposed the use of special tools:
self-moving hoists mounted on crawlers (fig. 2), able to drive off the roads, on mountain
tracks, and to reach out of the way sites, as, for example, the Strobe Pine of Chiusa Pesio
(CN) and the Ilex of Rigoroso Arquata Scrivia (AL).
Figure 2. A particular type of hoist
mounted on a caterpillar tractor.
Chiusa Pesio (CN)
Figure 3. Tree climbing technique is used to
prune trees unreachable by mechanical
means. Pietraporzio (CN)
In other cases, operations were carried out by the aid of stairs and tree climbers,
pruners that climb the plant and work using ropes and hooks (fig.3). Two example are the
Chestnut tree of Crodo (VB) and the Larch of Pietraporzio (CN).
Results
During the three years (2001-2003) of work, cures were performed on 39 trees or
arboreal groups (fig. 4). The chosen plants, placed in homogenous patterns in the Piedmont
region (fig. 5), belong mainly to native species; only in some cases they are exotic, like, as
an example, the Sequoias of Burcina Park (BI) and Roccavione (CN) or the Gingko of
Casalbeltrame (NO). Faced problems were very heterogeneous: in some cases treated trees
presented only dry branches (for example the Ilex of Rigoroso, AL, and the Larix of Rima,
VB); in other cases the crown was so poorly balanced and badly conformed that specific rebalancing and crown reduction tinning was necessary (for example, the Yew-tree of
Cavandone, VB, and the Horse-chestnut of Casorzo, AT). Sometime many wood decays
were detected so recovery techniques were to be used (for example, the Cedrus of
Montalenghe, TO, the Chestnut of Bioglio, BI, the Ash of Moncenisio, TO); finally, some
trees were so injured and presented so complex problems that a specific recovery project
was necessary; it usually included not only the common cures but also the realisation of
particular supports (for example, the Lime of Macugnaga, VB, the Planes of Savigliano, CN).
Described and treated plants appear sufficiently such vigorous as to assure a majestic
presence along time. Obviously, the necessary conditions are their constant monitoring and
on-time execution of the necessary cures in order to avoid serious damages to the tree in
the future.
115
Figure 4. List of treated trees
Figure 5. Distribution of the Trees
in the Piedmont Region
In the first enclosure, some pictures of some types of cures, executed during the project,
are reported.
Acknowledgements
The authors thank very much Federica Spaziani and Annamaria Ferrara who helped to
write this work and Fabio Petrella who helped to translate it into English 116
First enclosure
Pictures of the main types of carried out cures
117
118
119
120
121
THE PRODIGIOUS CYPRESS OF SAN BENEDETTO IL MORO
D.S. La Mela Veca*, M. Ala*, F. Terranova** and G. Barbera*
* Dipartimento di Colture Arboree, Università di Palermo
** Centro Regionale per la Progettazione e il Restauro, e per le Scienze Naturali ed Applicate ai Beni
Culturali, Assessorato dei Beni Culturali ed Ambientali e della P.I., Regione Siciliana
1. Introduction
In the Mediterranean culture, the cypress is traditionally a sacred tree, often with
funeral meaning. The Etruschi, the Greek and the Romans used to represent it on the funeral
urns. The cypress was devoted to Plutone and was planted in front of the doors as mourning,
the funereal crowns had been woven with leafy branches of myrtle and cypress. As funeral
trees, the cypress is remembered by Plinio and sung by Ovidio and Virgilio (CHIUSOLI, 1979).
The sacredness of the cypress is confirmed by an old imposing exemplar, considered as the
oldest tree in Palermo (PINTAGRO, 1992). It is located next to the fifteenth-century convent
of Santa Maria di Gesù in the outskirts of the city. According to the tradition, cypress is
sprouted miraculously from a fixed baton in the ground by S. Benedetto il Moro, born of
Ethiopian slaves in 1524. He lived for a long time like a hermit and therefore, since 1562,
lived in the convent, with the exception of a brief permanence in the convent of SantAnna
in Giuliana, up to 1589. He was considered a holy thaumaturge man, he was patron of
Palermo and he was known through the Franciscan Order and the Spanish Court also in
Spain and in Latin America. He was canonized by Pio VII in 1807. His body is conserved in
the Church of Santa Maria di Gesù and it is still today an attraction of pilgrimage (DELLAIRA,
2003; FIUME, 2000).
Figure 1 - The cypress of San Benedetto il Moro with the Conca dOro in a press of 1840
(drawn from Pictures from Sicily, London)
According to the legend about the veneration of the Saint, the thriving cypress - next to
the chapel where Benedetto stopped for praying, located not very far from the convent
along a path of the slopes of Mount Grifone which is used for celebrating of the via crucis had been grown through a baton used by him. The exceptionality of the cypress is testified
also by a habitus considered unusual for the disposition of the principal branches on the
stem that is derived from the fact written in 1612 by the great Spanish dramatist Lope de
Vega, il frate nero piantò (il bastone, ndr) capovolto nel terreno prima di morire. I suoi
rami non spiovono intorno come quelli degli abeti comuni. Si allargano verso il cielo, alla
rovescia (DELLAIRA, 1995). The cypress is either important for its great historical and
religious meaning, or for its presence connected to the cult of a very popular and revered
Saint. It is surely a monumental tree for its age, dimensions, visibility in the landscape,
history and religious values (PAVOLINI, 1999). The dating and the analysis Visual Tree
Assessment (VTA) of the cypress, further to have a religious value, (the necessity of the
miracle would be denied by a non compatible age with the years of the permanence of the
Saint in the convent), constitutes an important contribution to the knowledge of the richest
vegetable patrimony of a city, whose suburban territory (the Conca dOro) is known to the
historians of the environment and the agriculture as di antico e quasi mitico predominio
dellalbero (B EVILACQUA , 1996). For the dating of the tree has been carried out a
dendrochronological analysis. Through the dendrochronological approach with the simple
determination of the number of rings of growth in the stem is, in fact, possible to determine
the age of the tree investigated and to quantify, potentially, the relationships between plant
and environment (CORONA, 1980).
122
2. Location, environmental and botanical aspects of the study area
The cypress of San Benedetto is located in the park of pertinence of the convent and
the monumental cemetery of Santa Maria di Gesù at an altitude of 190 m a.s.l. and at slopes
of Grifone Mount, in the southern part of the city of Palermo (Fig. 2).
Figure 2. View of the Convent and of the monumental Cemetery of Santa Maria di Gesù
The area represents a roughed morphology with superior inclinations over 40% and with
exposure N-NW. The climate is characterized by mild temperatures and precipitations like
those regional. According to the Rivas-Martinez bioclimate classification the climate is upper
Thermo-mediterranean-subhumid. The local primary vegetation probably was a mixed
Mediterranean oak forest dominated by Quercus virgiliana and Quercus ilex, while the areas
characterized by shallow soil and a warmer climate were probably characterized by an
evergreen sclerophyllous maquis. Despite the strong human impact on the territory, on the
NW slopes of Grifone Mount grow different species of the Rhamno alaterni-Quercetum ilicis,
an evergreen plant community typical on limestone slopes of the coastal area of Palermo
Mounts (BRULLO and MARCENÒ, 1985; GIANGUZZI et al., 1996) (Fig. 3).
Figure 3. Shrub community near the cypress of San Benedetto il Moro
On the slopes along the path which from the sanctuary takes to the cypress, it is
possible to notice some pre-forest vegetation fragments belonging to Oleo-Ceratonion siliquae
alliance, grassland features belonging to Hyparrhenion hirtae alliance, as well as rocky cliffs
communities referable to Dianthion rupicolae alliance.
The actual landscape is characterized by rock outcrops and by xeric and poor grasslands,
dominated by Hyparrhenia hirta. Elsewhere are present several species quite common in
open maquis (Oleo sylvestris-Euphorbietum dendrolidis), such as Olea europaea var. sylvestris,
Euphorbia dendroides, Ceratonia siliqua, Prasium majus, Asparagus albus, Calicotome infesta,
Ruta chalepensis, Teucrium fruticans, and many species of the more mature maquis
communities (Rhamno alaterni-Quercetum ilicis), such as Fraxinus ornus, Pistacia terebinthus,
Rhamnus alaternus, Asparagus acutifolius, Rosa sempervirens, Rubia peregrina, etc.
In the recent past these semi-natural and subnatural communities have been overlapped
with Pinus halepensis, Pinus pinea, Cupressus sempervirens and Acacia saligna plantations.
Despite their high density, within them it is possible to observe quite remarkable processes
of early naturalization stages. Near the convent and inside the cemetery there are different
monumental individuals of cypress (Cupressus sempervirens). The most imposing one is
actually the cypress of San Benedetto (C. sempervirens var. horizontalis), which grows
isolated on the slopes of Grifone Mount near the chapel dedicated to the Saint (Fig. 4): its
circumference is 3.50 m (at 2 m above ground) and its height is 23 m.
123
Figure 4. The cypress of San Benedetto il Moro today. The background which remains of Conca dOro
The crown shows some empty spaces because of the desiccation of different branches,
especially in the basal part. The stem also is damaged probably caused by fires and buttresses
typical of old trees.
3. Dating and stability of the cypress of San Benedetto il Moro
3.1 Methodology
For the dating has been taken out a tree core with the incremental borer of Pressler in a
height of around 25 cm from the ground. In laboratory the tree core has been pasted on a
wood support with a central groove. In order to examine the transversal section, there has
been performed the pasting of the core taking care of that the woody fibres which were put
in orthogonal way on the plan of support. The tree core has, finally, been smoothed with a
thin abrasive paper (100, 250 and 400), in order to underline the growth rings and to make
easier their reading and measurement (Fig. 5).
The preliminary phase of analysis of the sample was the cross-dating (FRITTS, 1976)
which means giving the exact forming year of every single ring. This operation has been
performed with a stereoscope dating the series beginning from the last ring that is formed
under the bark. The dating has been performed comparing the series with another of a near
cypress of inferior age.
Figure 5. Pasted and smoothed tree core, ready to be analyzed
The comparison has been effected considering the total thickness of the rings
(characteristic rings), the thickness of the zone with the spring and summer wood, the
mean vase dimension and the presence of possible scars (SCHWEINGRUBER et al., 1978). The
individualization of characteristic rings has a fundamental importance to resolve doubtful
cases and to individualize absent or double (false) rings. The dating has been very difficult
because of the irregular rhythm of growth of the species that often determines the formation
of false rings. The cypress, for such reason is considered by dendrochronologists a trouble making species. For these reasons the cypress is a low studied species, although in Italy
have been done some short chronologies and well cross - dating on trees located in the
southern Appennino (Salerno and Potenza) by CORONA (1970).
The individualization of false rings has been, in our case, difficult because was examined
only a small section of the plant (only one tree core, not being able to withdraw others for
the presence of an adjacent wall on the base of the stem) so it hasnt been possible to
verify if there were vanished false rings which are absent in the whole circumference. In
124
order to recognize the absent rings it has been necessary to start from the consideration
that they differ from those true. The true ones showed an early thick and a late thread-like
zone. Furthermore, in the true rings, the limit between the late and early zone is marked but
that one between the early and late zone is a little vanished. In the conifers generally the
false rings are separate from those true because of their external part which is less intensely
coloured (UZIELLI E NARDI BERTI, 1979; GIORDANO, 1981) (Fig. 5).
The thickness of rings has been measured with the dendrochronograph LINTAB 3. The
measures have been performed with a precision of 1/100 mm beginning from the first ring at
the centre of the tree. Considering that the cypress of San Benedetto is a monumental tree,
we have also effected, in sight of possible protective interventions, an analysis of the
stability according to the criterions of evaluation established by the methodology VTA (MATTHECK
E BRELOER, 1998) and according to the suggestions by the Protocol ISA on the Evaluation of
the Stability of Trees © that provide a visual and instrumental examination. The data
sampled has been transcribed on a special card, which will constitute a general updating of
informative base for the following instrumental analyses e/o for the evaluation of the level of
stability in order to define the possible necessary interventions and the periodicity
recommended for the following controls.
The instrumental examination has been performed using the Resistograph (model F400 S)
and the fractometer. The research has been assembled at the base of the stem, and from a
first visual investigation, has been underlined a light camber, a possible symptom of inside
degradation. There have been effected 5 tests in order to investigate the whole circumference
of the stem. The tests with the fractometer (3 measurements) have been performed on a
tree core, withdrawn in correspondence of the resistograph survey n. 1, with the purpose to
determine its moment of breaking.
3.2 Results
The Cypress of San Benedetto is 426 years old and, therefore, it is born in 1577. In the
figure 6 are represented the elementary chronology of the tree. Being formed from a single
ring series, it can be suffered from errors due to the individuation of false rings.
Its annual mean growth has been of 87,88 cents of mm; after a first short period of slow
growing, and then about two hundred years of sustained growth followed by a slowdown.
However there is large variability in tree-ring width probably due to exceptional climatic
events e/o troubles of human origin, mainly fires. The progress of the broken one is sufficiently
homogeneous and typical of isolated tree.
&XSUHVVXVVHPSHUYLUHQV
/
800
700
600
P
P
500
H 400
UR
VV
HS 300
6
200
100
0
1574
1599
1624
1649
1674
1699
1724
1749
1774
1799
1824
1849
1874
1899
1924
1949
1974
1999
2024
$QQR
Figure 6 - Elementary chronology of the cypress of San Benedetto il Moro
The resistograph profiles dont clearly underline the growth intervals because the transition
between early and late zone is gradual. However it has not been possible to compare the
profiles with the graph derived by the dendrochronological study of a tree core withdrawn
immediately on the resistograph profile n. 1 (Fig. 7). For the analysis of the stability, the
graphs got with the Resistograph showed, along their length, a regular progress. The increasing
progress of the graph from the outside of the stem toward the inside is caused by a greater
content of extracted. This helps to increase the density of the heartwood in comparison to
the sapwood. The investigations with the resistograph and with the fractometer have not
underlined wood degradation.
The fractometer tests performed on the tree core have underlined values of the parameters
125
(moment of fracture and angle of fracture) comparable with the safety limits drawn by field
studies on trees of the same species.
Visual analysis has, in fact, pointed out light defects of form and small anomalies. The
risks of the crashing down are referable to those of the class A. The light morphological
anomalies can get worse in the time. From the visual analysis have not been found, however,
symptoms of degradation in the stem and in the principal branches. A light torsion of fibres
noticed on a branch, as light lines on the stem, take part of the morphological characteristics
of the species and they are common in old trees.
Figure 7 - Profile n. 1 of resistograph analysis
4. Conclusions
Dating performed using dendrochronology analysis has allowed to certify that the tree is
about 426 year old. Going back for an equivalent period of time, we reach 1577 that is
almost in the mean of the period of permanence of the Saint in the convent (1567-1589).
Beyond every fideistic approach it is possible that San Benedetto has transplanted in that
place, less probable - for the difficulty of the cypresses to take root by cutling - that
originates from the Saints baton! Its crown shape (Fig. 4) considered strange and its old
age, in fact, are perfectly compatible with the fact that the tree belongs to the variety of
horizontalis. In fact, the historical image goes back to 1840 and shows a typical cypress of
this variety; following alterations which could have been caused by winds, lightnings and
fires. The research has surely confirmed the elevated historical-religious value of the
monumental tree which in the future merits to mostly be protected and respected. The
analysis of stability has also allowed to give useful indications to its safeguard. On the stem
has been observed, died fragments caused by precedents badly cuts susceptible of
degradation. It is advisable, therefore, the trimming of the same to avoid that the agents of
degradation can pass to the healthy portions of the wood inside the stem. Furthermore, on
the internal part of crown there are different died ramifications of first and second order
that makes opportune pruning practice. Besides, the pruning is important to decrease the
resistance of the crown against the wind.
Dealing with a subject of the crashing down risk belonging to the class A, it is necessary
a biennial visual analysis and an instrumental verification after three years. The results
encourage to keep on studying the dendrochronology of the cypress in order to draw
information on the climatic history and on the quality of the air of Palermo.
Acknowledgements
A particular thanks to Salvo Pasta for his contribution for the floristic analysis and to
Carlo Di Leo for the stability analysis.
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FRITTS H.C, 1976 - Tree Rings and Climate. Accademic Press, New York.
GIANGUZZI L., ILARDI V., RAIMONDO F.M. (1996) - La vegetazione del promontorio di Monte Pellegrino.- Quad.
Bot. Ambientale Appl., 4 (1993): 79-137.
GIORDANO G.¸ 1981 Tecnologia del legno. Volume 1. La materia prima. UTET, 100-109 e 232-234
pp.
MATTHECK C. E BRELOER H., 1998 - La Stabilità degli Alberi. Il Verde Editoriale.
NARDI BERTI R., 1993 La struttura anatomica del legno ed il riconoscimento dei legnami italiani di più
corretto impiego. Contributi scientifico-pratici, XXIV: 892-893.
PAVOLINI M., 1999 - Alberi monumentali e territorio. Evoluzione geostorica, considerazioni fitogeografiche
e valenza dei grandi patriarchi italiani. Rivista di Storia dellAgricoltura, Anno XXXIX, n°1: 4-32.
PINTAGRO M., 1992 Arborea. La storia di Palermo in cento alberi illustrati. Helix Media Editore, Palermo.
SCHWEINGRUBER F.H., FRITTS H.C., BRAKER O.U., SCHAR E., 1978 - Dendroclimatic studies on conifers from
central Europe and Great Britain. Boreas, 8: 427-452.
UZIELLI U., NARDI BERTI R., 1979 Aspetti tecnologici del legno di Cipresso (Cupressus sempervirens
L.). In: Grasso V. e Raddi P., Atti del seminario Il cipresso. Malattie e difese, Firenze, 23/24
Novembre, pp.95-109.
127
INVENTORY OF THE VETERAN TREES DESERVING PROTECTION IN THE PROVINCE OF
FERRARA
E. Mantovani1, G. Morelli2, L. Raspanti3, The Committee for the Safeguard of Trees in the
Ferrara Province4
Provincial Administrator in Ferrara; 2 Professional, Ferrara; 3 Professional, Bologna; 4 The
Committee for the safeguard of trees in the Ferrara Province comprises the representatives of the
following associations: Friends of the Ferrarese Museums and Monuments, AREA, Unione circle,
Deputazione di Storia Patria, the Biology Department of Ferrara University, the Faculty of
Architecture of Ferrara University, FAI, Ferrariae Decus, Ferrara Garden Club, the UNESCO-Ferrara
group, ITALIA NOSTRA, Legambiente, LIPU, the Roll of Forest Agronomists of the Ferrara Province,
the Ferrara Naturalists Society, WWF
1
Introduction
In 1977 the Emilia-Romagna Region established, according to the Regional Law n. 2 of
the selfsame year, the preservation and safeguard of arboreal specimens, single or grouped,
in copses, in rows, of outstanding scientific or monumental interest. The basis for this
legislative norm was a summary inventory, carried out on the principle of the unprompted
notice on the part of local administrations of the trees, both privately and publicly owned,
that seemed deserving protection. In the context of the Emilia-Romagna Region, the Province
of Ferrara appeared to be the least endowed with trees having a monumental character,
with a total of 20 protected single trees or groups of trees, i.e. only 3.12% of the overall
patrimony of the Emilia-Romagna Region. Next to these trees another 60 trees were mentioned,
identified as remarkable, whose botanical and environmental importance was recognized,
but no specific control was provided for them. As from 2003 the Province of Ferrara has
decided to see to the updating of the information relative to the protected specimens,
entrusting the survey relative to the Ferrarese territory to the Studio Progetto Verde,
together with Ms. L. Raspanti, agronomist. At the same time, the Province of Ferrara has
started a program for the identification and the valorization of the environmental pity points
that, starting off from known and verified data, would then merge all the available data, and
then proceed to a rational management of the whole of the provincial patrimony. In practice,
this is an inventory that requires a careful and thorough survey, as of now still in progress,
on the presence in the territory, of vegetation emergencies of the arboreal and shrub type
linked to the landscape, with particular attention to the arboreal specimens possessing
monumental importance. The present study illustrates the methods by which this survey
will be carried out, anticipating some of the results already achieved.
Materials and methods
The elements of the landscape with which the Ferrara Provincial Administration is concerned
are: single trees, copses, rows of trees avenues, hedges, traditionally planted orchards of
typical trees, rows trees planted for vine-bearing. Limiting the treatment to single trees
only, the information to be gathered are the following dendrometric, morphologic and
architectonic data, conditions of visibility and accessibility to the site, and the perception of
the tree in the landscape, that is its relevance to the landscape. The survey operations
have been organized according to a feed-back principle and can be schematically described
in the following way:
128
The first process entails making the local authorities, in particular municipals, aware of
the need to signal the elements worthy of entering the inventory, using as a prop a summary
survey card called Individuation file-card (Attachment n.1 Individual file-card for single
tree) The whole corpus of these reports, together with those produced by the Committee
for the Safeguard of Trees is received by the Province through the second process. The
evaluation of the incoming data allows the identification of the elements in the landscape
actually deserving protection. For these, through the third process, an actual inventory is
activated, which requests a detailed survey chart, called Complete specialist file-card
(Attachment n.2) filled in by the professionals. This stage is also accompanied by the
topographical identification of the tree, by means of G.P.S. technology, ad by its position on
specific thematic maps. In the detailed survey, particular importance is given to photographic
data, which must significantly illustrate the data described in the file-card. All gathered
information, organized on computer, is given back to the Province though the fourth process,
so as to be reorganized and used for management, planning and information aims.
Results
As already said, the work is still in progress, and it is thus impossible, at the moment, to
produce data on the scope of heritage of monumental trees of the Province of Ferrara, or on
its intrinsic features. Nevertheless, a first summary of the surveys carried out for the
updating of information relative to the trees protected under regional law n. 2, 1977, allows
us some fundamental considerations. The data gathered in the past on the basis of
spontaneous information without successive verification are approximate and often incorrect.
A simple spontaneous indication does not permit an exhaustive picture of the veteran trees
that are actually present in a given area which, in the case of the Province of Ferrara,
seems to be much richer in valuable arboreal elements than the historical data in possession
of the Province indicated. The lack of updating available information, lasting more than two
decades, supplies a much more optimistic view of the arboreal monumental heritage than
hitherto supposed.
Lastly, it can be observed that the mere safeguard of an arboreal specimen, detached
from a monitoring and enhancing program on its behalf does not guarantee it effective
safeguard. These initial considerations confirm the validity of the choice of several different
figureheads (volunteer associations, local administrators and professionals) concurring together
to the inventory of remarkable trees. Furthermore, they underline the need of coordinating
the work and of safeguarding at a more limited level than the regional one, that is at
provincial level.
Conclusions
The work so far carried out, on the basis of previous experiences, strongly supports the
idea of creating a data-bank that would transcend being a simple cognitive reference, but
which might become a tool in the valorization of the territory. To achieve this result, it is
expedient to link all gathered information with the dynamics of the area they refer to,
shifting from a merely impositive view of protection to a propositive one, thanks to which
the identification and the filing of a monumental tree be translated in an undertaking of
responsibility towards it, whereby any desire of safeguarding it be translated in an actual
act of management and valorization.
Bibliography
Assessorato allAmbiente, Istituto Beni Culturali, Regione Emilia-Romagna (1991). Alberi
monumentali dellEmilia-Romagna. Censimenti e tutela. Bologna.
Lonsdale D. (1999). Principles of Tree Hazard Assessment and Management. The Stationery Office,
Norwich England.
Morelli G. (1999). Il Censimento del verde del Comune di Ferrara. Estimo e Territorio, 9: 54-56.
Nicolotti G., Della Beffa G., Mondino G. P., Palenzona M. (2003). Alberi monumentali in Piemonte.
Presenze e avversità. Priuli & Verlucca editori, Ivrea (To).
Read H. (2000). Veteran Trees: a guide to good management. English Nature, Peterborough
Inghilterra.
Tosetti T., Tovoli C. (ed.) (2002). Istituto per i beni artistici culturali e naturali della Regione Emilia
Romagna. Giganti protetti gli alberi monumentali in Emilia Romagna. Editrici Compositori, Bologna.
129
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131
OBSERVATIONS ON THE EPIDEMIOLOGY OF CERATOCYSTIS FIMBRIATA F.SP. PLATANI
ON PLANES IN A HISTORICAL LINE AND ATTEMPTS OF DISEASE CONTROL
R. Martinis, P. Gonthier, F. Guglielmo, G. Nicolotti, A.M. Ferrara°, F. Tagliaferro°, E. Viotto°
University of Torino, Di.Va.P.R.A. Plant Pathology, Grugliasco (TO) - Italy
°Forest and Environment Institute I.P.L.A. S.p.A. Istituto per le Piante da Legno e lAmbiente,
Torino - Italy
Summary
Four Platanus hybrida trees suddenly died in summer 2001 in a historical line at Serralunga
di Crea (Al), North Western Italy. The death was due to the canker-stain disease caused by
Ceratocystis fimbriata f.sp. platani. This paper describes the patterns of epidemics of
Ceratocystis within the line. Since summer 2001, seven trees have been dying, and 12 trees
were found to be infected by the pathogen in the xylem vessels either of the stem or of the
roots. The role of root contacts, root anastomoses, and vectors for the spread of the
disease within the line is discussed in the paper. Attempts to stem the epidemics by physical
barriers were also made, and preliminary results are given.
Introduction
Among the tree species growing in urban environments or parks, the planes (Platanus
spp.) are commonly considered as good candidates to became monumental trees. Their
relatively rapid growth, allowing to attain great dimensions, the shape of their crown, the
morphology and colour of their bark, all accounts for such position. According to a recent
census of trees in Piemont (North Western Italy), about ten percent of candidates to
become monumental trees are planes (unpublished data). Planes are susceptible to wood
decay fungi, root rot and leaf disease agents that may affect their vitality and integrity
(Nicolotti et al. 2001; Marchetti, 2003; Nicolotti et al., 2004). Planes are also susceptible to
a lethal fungal disease named canker-stain, and caused by Ceratocystis fimbriata f.sp.
platani. Ceratocystis infects planes by spores or mycelial fragments on contaminated pruning
tools, or through terracing machinery which causes damage to the roots (Vigouroux and
Stojadinovic, 1990). It has also been shown that the fungus may spread from one tree to
another via root grafts (Accordi, 1986). Despite these findings, the epidemiology of cankerstain disease still need investigations.
Since the disease is extremely serious, protocols for the quarantine or the control are
prescribed by the law in several European Countries. In Italy, according to the D.M. 17/04/
1998, infected trees and any surrounding trees must be felled, and their wood must be
incinerated or, alternatively, buried. Stumps should be extracted from the soil or killed by
chemicals. The Italian protocol prescribes that all operations (i.e. felling, transport of infected
wood) must be carried out avoiding sawdust dispersion in order to minimize the risk of new
infections. As these approaches are quite onerous, any alternative strategies for disease
control would be appreciable. The goals of this paper were: i) to describe the patterns of
epidemics of canker-stain in a historical line, where no pruning (i.e. infection courts) has
been occurring for decades, ii) to calculate the number of root contacts and anastomoses
between neighboring trees, in order to assess the potential for tree to tree fungal spread,
and iii) to check for the presence of C. fimbriata in roots of different diameter classes.
Attempts to stem the epidemics by physical barriers within the line were also made, and
preliminary results are given in the text.
Materials and method
The present study was carried out in a historical line (Fig. 1) comprising 36 Platanus
hybrida Brot., located at Serralunga di Crea (Al) (Tenuta Guazzaura), in the North Western
Italy. Planes were about 160 years old, 30 m high, and their diameter at breast height (DBH)
ranged between 70 to 160 cm. In summer 2001 four trees suddenly died. Diagnosis revealed
the presence of C. fimbriata f.sp. platani inside the xylem vessels of dead trees. Such
finding was interesting because i) the line was far away from any other plane formations,
and ii) no pruning has been occurring for decades, so no apparent infection courts may
explain how the fungus established there.
Patterns of epidemics of C. fimbriata f.sp. platani
All trees were carefully mapped, and their general health conditions were monitored
monthly since summer 2001. Trees displaying withering on crown, or simply sparse chlorotic
132
foliage, were sampled, after bark removal, by extracting wood pieces of about 4 x 4x 3 cm
by a sterilized scalpel from the edge of areas of xylem discoloration or at 1.3 m above
ground. Wounds were treated with methyl thiophanate (Enovit Metil, Sipcam).
The presence of C. fimbriata f.sp. platani was detected from collected samples either by
incubating them in a moist chamber at 22° C in order to induce fruit bodies differentiation, or
by extracting wood slivers (5-6 x 2-3 mm) and incubating them for 5 days onto 5 cm Petri
dishes filled with Potato Dextrose Agar (PDA) (PDA 39g, streptomycine sufphate 0.150 mg, 1
l distilled water). The identification of fungal colonies was performed on the base of their
macro- and microscopic features. All Ceratocystis isolates were subsequently subcultured
and stored at 5° C on MEA (20 g glucose, 20 g malt extract, 2 g peptone, 20 g agar, 1 l
distilled water).
Fig. 1- Historical line of Platanus hybrida at Serralunga di Crea (Al) (Tenuta Guazzaura)
Investigations on root contacts and anastomoses between neighbouring trees
To study the potential for fungal spread via root contact or anastomoses, the root
system was excavated between two neighbouring planes (Fig. 2) to check for the occurrence
of root contacts or anastomoses between them. The two trees were 4,2 m far from each
other. The excavation was about 60 cm depth. All roots, down to 0.5 cm diameter, were
labelled and their diameter was measured each 10 cm.
Fig. 2- Excavation of the root system between two planes at Serralunga di Crea (Al) (Tenuta Guazzaura)
The following parameters related to the root system architecture were considered: i)
mean diameter and number of roots at 70, 140, 210, 280, 350, 420 cm from the collar of
trees, and ii) the total number of root contacts or root anastomoses between trees. Regression
analysis was used to explore the relationships between the diameter of roots and their
distance from the collar of the tree. To investigate for the relative importance of contacts
vs anastomoses, the surface of root contacts and root anastomoses between trees was
measured and compared.
Presence of C. fimbriata f.sp. platani in the roots
The presence of C. fimbriata f.sp. platani was checked in roots of three planes. Excavations
about 70 x 450 cm, and 160 cm depth, were made at about 3 m from the collar of trees. The
133
relative X Y coordinates of all roots visible on the profile were taken. A total of eighty roots
were sampled by excising transversal disks. The presence of the pathogen on the collected
samples was assessed as described above, or by checking for the presence of the typical
clamydospores of C. fimbriata f.sp. platani inside xylem vessels. Transversal sections 30 mm
thick were obtained by a microtome, and observations were performed under a light microscope
at 400 x magnification.
Attempts to control the epidemics within the line
Attempts to control the epidemics within the line were made by isolating uninfected from
infected trees. For this purpose, a total of 40 m of trenches, each about 170 cm depth,
were excavated in summer 2003. Broken roots on the walls of trenches were treated with
methyl thiophanate. Root barriers (RootcontrolÒ) were buried into the trenches in order to
prevent the negative effects of root growth (Fig. 3). The location of trenches is shown in
Fig. 4.
Fig. 3- Trenches were made in order to separate asymptomatic from infected trees.
Root barriers were buried into the trenches
Results
Patterns of epidemics of C. fimbriata f.sp. platani
Since summer 2001, 8 planes died (22%) in the line. C. fimbriata f.sp. platani has also
been isolated from four additional planes, displaying withering on crown, or sparse chlorotic
foliage. The location of trees within the line and their health conditions are shown in Fig. 4.
Fig. 4- Location of Platanus hybrida trees in the Tenuta Guazzaura line. The health conditions of trees, as
specified in the legend, is up dated to October 2003. Numbers in bold characters are ID numbers of trees.
For each tree, remaining numbers refer to the number of months, calculated from July 2001, when first
symptoms of canker-stain and death occurred, respectively. The figure also shows the location of trenches
and root barriers
134
Starting for the first infection center, comprising the four trees died in July 2001 (ID 12,
13, 14, 15), the disease spread to tree number 16, 17, and 11. A second infection center
appeared at least one year later at about 50 m far, and comprises trees number 4, 1, 3, and
6. Tree number 24 displayed canker-stain symptoms starting from March 2003, and it died in
July 2003. Trees have been dying four to ten months after showing first canker-stain
symptoms.
Investigations on root contacts and anastomoses between neighboring trees
The number of roots increased with the increasing of distance from the collar of trees.
On the other hand, regression analysis showed a negative relationship between mean diameter
of roots and distance from the collar (Fig. 5). The regression line indicates that at 5.37 m
from the collar the diameter of roots equals 0.
Fig. 5- Regression analysis between mean diameter of plane roots
and theirdistanc from the collar of trees
Three root anastomoses, and 1 root contact between the two trees were noticed. Total
surface was 590 cm2 and 80 cm2 for anastomoses and contacts, respectively.
Presence of C. fimbriata f.sp. platani in roots
Clamydospores of C. fimbriata f.sp. platani were found on roots laying from 10 cm to 170
cm depth (Fig. 6), and the fungus was successfully isolated from three roots.
Fig. 6- Clamydospores of Ceratocystis fimbriata f.sp. platani inside xylem vessels of plane trees
Roots of 2 out of 3 of the investigated trees were infected. The percentage of infected
roots from these trees was 14% and 28%. Evaluating the percentage of infected roots for
roots included in three diameter classes (0-1, 1-2, and 2-3 cm) (Fig. 7), the maximum
percentage of infected roots resulted in the highest diameter class (50%).
135
fig. 7- Percentage of infected roots for each of three root diameter classes
Attempts to control the epidemics within the line
A total of 64 m2 of RootcontrolÒ barriers were unrolled. Since the moment when such
barriers were placed into trenches, no further death has been occurring. The time last since
that moment is however not sufficient to assess the effectiveness of such control measure,
and thus the monitoring is ongoing.
Discussion
The Tenuta Guazzaura at Serralunga di Crea represents a good site to study the
epidemiology of Ceratocystis fimbriata f.sp. platani for three reasons: 1- canker-stain has
never been reported previously in the area, 2- the historical line is at least 3 km far from the
nearest plane trees, and 3-, as mentioned above, no pruning has been occurring for decades
there.
Two different, but not mutually exclusive, hypothesis may be formulated in order to
explain how the fungus came, presumably in 2001, into the line: by infected wood traveling
on the Asti-Mortara railway, and by long-distance animal vectors. Both insects and rodents
are potential agents of spread for Ceratocystis species (Crone and Bachelder, 1961; Panconesi
and Nembi, 1978). Woodpecker drilling holes rather than galleries of insects were noticed
through surveys performed with an elevator in the plane trunks and branches at Serralunga.
The role of woodpeckers as vectors for Ceratocystis should thus be taken into account for
future studies.
Three Ceratocystis infection centers are recognizable in the Guazzaura historical line,
comprising four trees, three trees, and one tree, respectively. Root contact and anastomoses
are likely to have played, as they can do (Accordi, 1986), an important role in the shortdistance spread of the disease within the infection centers. It has been shown that both
root contacts and root anastomoses are frequent between neighboring trees at Serralunga.
Moreover, the fungus was present into the xylem vessels of roots.
The spread of the disease between infection centers cannot be explained in terms of
tree to tree spread of the fungus via root grafts. According to the regression curve presented
in this study, the probability of root system overlapping would be negligible if two trees are
at 12 m or more far from each other, while infected trees comprised into different infection
centers are at least 40 m far from one another. Animals might have playied an important role
also in short and medium distance transmission of the disease.
Although further investigations are needed, we propose that animals living in the soil (i.e.
rodents, insects) rather than birds or flying insects may account for short and medium
distance fungal spread at Serralunga. The greater importance of soilborne vs airborne infection
in the line is supported by the following observations: i) infected trees died suddenly (4 to
10 months after first symptoms display), ii) xylem discoloration and cankers rarely developed
on branches and, on the contrary, were commonly associated with basal portions of stems,
and iii) in trees that became infected even though they were growing far away from any
previously infected trees (i.e. tree n. 24), the fungus was isolated from the collar and not
from the upper portions of the trees.
Root barriers we used in the line, should be, at least in the theory, useful to prevent new
infections in such a complex scenario, where the spread of the disease is likely originated
either by root grafs / root contacts or by vectors living in the soil. We are now assessing the
effectiveness of root barriers both in the laboratory and in the field, trough a periodic
monitoring of the health status of trees. The Tenuta Guazzaura also represents a good site
to test different methods to control unwanted spread of the fungus. For instance, we are
136
now testing the effectiveness of the wood solarization and chemical treatments as possible
methods to kill the pathogen into felled infected wood.
Acknowlegements
This research has been supported by a grant of the Regione Piemonte Assessorato
Politiche per la Montagna, Foreste e Beni Ambientali. The authors are grateful to Dr Mario
Palenzona for revising the text. We also thank Miss Ilenia Marafante, and the Servizio
Fitosanitario Regionale for their help in performing field surveys.
Refefences
Accordi M. S., 1986. Spread of Ceratocystis fimbriata f. platani through root anastomoses.
Informatore Fitopatologico 36, 53-58.
Crone L.J., Bachelder S., 1961. Insect transmission of canker stain fungus, Ceratocystis fimbriata
f.sp. platani. Phytopathology 51, 576.
Marchetti L., 2004. La difesa fitosanitaria delle piante ornamentali e forestali. Informatore Agrario
59, 89.
Nicolotti G., Gonthier P., Cellerino G. P, 2001. Malattie delle principali specie arboree ornamentali.
Informatore Fitopatologico 51, 21-26.
Nicolotti G., Gonthier P., Pecollo D., 2004. Ecologia e grado di preferenza dospite dei funghi
agenti di carie / I parte. Acer 1, 47-51.
Panconesi A., Nembi V., 1978. La Ceratocystis fimbriata del platano: aspetti biologici e possibilità
di lotta. Informatore Fitopatologico 28, 17-27.
Vigouroux P.A., Stojadinovic B., 1990. Possibilités dinfection du platane par Ceratocystis fimbriata
f. platani après contamination de leau où se développent des racines blessées. European Journal
of Forest Pathology 20, 118-121.
137
DEFENSE OF THE MONUMENTAL TREES IN SPAIN
B. Moya Sanchez
Director of the Department of Conservation of Monumental Trees, Deputation de Valencia IMELSA
Spain
The juridical protection of the Natural, Historic, Cultural, Social patrimony such as the
monumental trees and its outskirts, is the solution to guarantee their continuity and survival.
Now the Spanish State has trasfered his Environment competence to the AutonomyCommunities; for this reason only they are responsable of this patrimony.
But only few of the Autonomy-Communities have specific and efficienty giuridical protection
on this matter so that ours monumental trees are threaten and subject to:
- drastic pruning
- innatural transplantation
- urbanistic and industrial interest
- agriculture trasformation of uncertain reason
- arson
- defect to phytosanitary control and conservation technique
With this desolating situation is our opinion that all Autonomy-communities should encrease
their monumental trees protection by introducing the figure of the Local interested tree.
In this way is more easy to protect end encrease the number of the monumental trees in
local reality, and near to the people who lives in contat day by day, because they are ables
to understand the social, cultural, historical importance of those trees as testimonial of their
history and life. Most of our countries, for their environment and historical characteristic,
has support the existence of large bio-diversity of autochthonous and allochthonous trees,
that forms some parts of the woods, agricoltural cultivation and the ornamental vegetation
of our cities.
For this reason in the natural and urban ambient exist groups and botanic exemplaries
with historical, cultural, social, scientific exceptional characteristics and with great value
and local interest. This exemplary-list represent a irreplaceable trees patrimony that should
be protected. Also they are point of interest with cultural, social, economics and educational
function and point of start for diffuse the ambiental- sensibility , educational and the rispect
of natural resorse with the promotion of sustainable development.
The law 7/1985 Reguardora de las Bases de Règimen Local art. 25.2, par. d), e), f) e
m) stated the rules for the protection of parks, gardens, historical and artistic patrimony, in
order to declare directly protection to the trees, shurbs, palms or natural areas of Local
interest that they consider important, without any others supervision or authorization.
Based on this law, the Dipartiment of Monumental trees, Deputation of Valencia, has
elaborate a specific Municipal Order for the Local Interest Trees Protection . This Order is
a list of rules where are defined, in a legal context: - the subject - the application - the
validity - the interpretation - the system of catalogation - the rules for the trees and
environment management - the specific techique for the conservation - the financing the right and duty for the people and trees - the infraction and the sanction, according to
the statal rules.
This Municipal Order, adaptable to all Municipality, has been studied and adopted by a lot
of Municipality of the comunity of Valencia, Andalusia, Castillia La Mancha, Castilla Leon,
Madrid, Extremandura, Andalusia.
In this occasion we have a objective to diffuse this metodology of conservation with the
aim of protection of the monumental trees with the partecipation of the people.
The Dipartiment of Monumental Trees, Deputation of Valencia, is the only one recognized
Dipartiment in Spain from more than ten years . During this time his has become a center of
reference for the protection, management, recovery, promotion and valorization of the
monumental trees in Spain. This experience has allowed us to understand and to face all the
problems arised around the trees and their relation with the people.
Recently, in last December, we have showed the first book that by a well defined and
integral Spain cartography, describe our great biodiversity, his value and his state of
preservation (J. Plumed, J. Moya and B. Moya, 2003)
138
MONUMENTAL TREES OF LIGURIA (NORTH-WESTERN ITALY)
F. Russo(1), P. Du Jardin(1), G. Paola
(2)
(1) Regione Liguria, Dipartimento Agricoltura e Turismo, Servizio Politiche per lEntroterra
(2) Università di Genova, Dipartimento per lo Studio del Territorio e delle sue Risorse (DIPTERIS)
Introduction
The Liguria Regional Council has issued a regional list of Monumental Trees (Liguria Regional
Council Official Bulletin N° 15 of 10/04/2002, part II) according to Article 12 of Regional Law
n° 4 of 22nd January 1999, Norme in materia di foreste e di assetto idrogeologico (Forestry
and Geo-hydrological Regulations). The law regulates, for the first time in Liguria, the protection
and recognition of the value of the regions monumental trees, entering in a specific list
tree specimens, wherever rooted, that are of special naturalistic, environmental or historical
and cultural interest for the Region. It is important to point out that the protection afforded
by this regional law covers not only particular forest trees but also agrarian and ornamental
specimens. This is especially significant above all considering the history of Ligurian flora in
general and in particular the urban flora. In this region, due to the morphology of the terrain
and its specific climate, there is an unusual altitude-related distribution of forest species
due to the extreme closeness of the mountains to the sea and to the ease with which plants
originating from far-off countries become acclimatised.
Creation of the list of monumental trees of the liguria region
The Regional Council has issued specific instructions for approving, keeping and updating the list of Monumental Trees of the Liguria Region.
The work of searching for, conducting the census and describing the specimens started,
in the first place, with the acquisition of existing material from Public Bodies, because both
the Forestry Authorities and other public administrative bodies already kept lists of trees of
special interest. A form was then prepared for reporting specimens, for use by local authorities
(Provincial Councils, Mountain Communities, Municipal Councils, Park Authorities), associations
of various types (environmental, cultural and so on), schools and scientific organisations
and individuals. These forms can be used to provide information concerning either an isolated
specimen or groups of plans believed to be of special interest. The survey methodology was
then formulated, defining the assessment criteria and the parameters to be used. The task
of identifying the specimens and collecting the data were entrusted to the Provincial
Coordination Centres of the Forestry Corps.
The first list of Monumental Trees of Liguria was approved on 26th February 2002, and
subsequently up-dated (Official Bulletin part II n° 15 of 10/4/2002 and N° 20 of 14/5/2003).
It contains 108 single specimens plus 11 rows or groups of plants.
Monumental trees of liguria
The list of Monumental Trees includes very diverse plant typologies, bearing witness to
the heterogeneous composition of the vegetation of Liguria. Alongside the commonest species,
typical of the Ligurian woods, such as downy oaks, holm-oaks, beech trees and so on, and
plants proper to the regions rural heritage such as chestnut and olive trees, there are also
ornamental and exotic species, situated mainly in urban environments, such as several
species of palms.
The most widespread indigenous monumental trees were found to be Quercus ilex L.
(with 12 specimens listed), Quercus pubescens Willd. and Fagus sylvatica L. (11 specimens
each). Other species of evergreen and deciduous oaks are also listed ( Quercus suber L.,
Quercus crenata Lam., Quercus petraea Matt.), although the number of specimens is
decidedly lower, while there is no specimen of Quercus cerris, well represented nowadays
above all in the eastern part of the region and mentioned extensively in Medieval and later
documents also referred to central and western Liguria. These presences fit in well with the
vegetation cover of the region and are, after all, the living memory of the vegetation of past
centuries. The holm-oak is dominant along the Tyrrhenian coastal strip, thermophilous and
mesophilous oak woods higher up on the slopes facing both the coast and towards the Po
valley, and beech woods at yet higher altitudes on the Ligurian Apennines. The Alpine part
of the mountains of western Liguria features the presence on the list of Larix decidua Mill.
and Abies Alba Mill. The list also indicates indigenous species not frequently encountered
nowadays in our woods, such as Taxus baccata L. (3 specimens in the central part of the
region) and Tilia platyphyllos Scop. Two species proper to the regions rural heritage occupy
a special place: Olea europaea L. and Castanea sativa Miller. Only a few specimens of these
139
species are listed (4 and 5 respectively), in spite of the fact that they are both extremely
widespread in Liguria and well-known for their longevity. With reference to the olive-tree, it
is possible that the current scarcity of majestic specimens is due to the way in which it is
managed on the terraced slopes of the Mediterranean coastal strip of Liguria paying the
main attention to the best yield. As far as concerns the chestnut, the scarcity of veteran
specimens can be attributed to the changes introduced in the management of chestnut
woods following the arrival of chestnut ink and bark diseases.
Exotic species play a considerable part in the overview of monumental trees in Liguria: all
of 22 species indicated on the list do not belong to our own flora. Pinus pinea L. has also
been included in this list, since it is not spontaneous in this region. As many as 10 pine-nut
producing pines have been considered monumental, and almost all of these have an important
role in the landscape. The only other pine on the list is a specimen of Pinus canariensis
Smith, while there is no mention at all of either Pinus pinaster or Pinus halepensis, both
extremely widespread nowadays in Ligurian woods.
Although the highest trees in Liguria are above all exotic species, some indigenous
species such as the beech find conditions enabling optimum development on our Apennines:
Liriodendron tulipifera L. reaches 40 metres, Eucaliptus globulus Labill. 37 m, Fagus sylvatica
L. 37 m, Pinus canariensis Smith 36 m, Cedrus atlantica Endl. 35 m, Picea excelsa Link. 34 m,
Abies nordmanniana Spach. 32 m, Platanus orientalis L. 32 m, Cedrus libani A. Richard 30 m,
Cupressus sempervirens L. 30 m, Populus nigra L. 30 m, Sequoia sempervirens Endl 30 m,
Tilia platyphyllos Scop. 30 m.
Some exotic species have become typical of the Ligurian landscape, in particular along
the coast, such as the araucarias of Bordighera (Araucaria excelsa R.BR.) and palm trees.
There are three species of palm on the list: Jubaea chilensis H.B.K., Phoenix reclinata Jacq.,
and Washingtonia filifera Wendl., the first two being rare and the last extremely common.
The species of palms most common along the coast, Phoenix dactylifera and Phoenix
canariensis, are not listed at all.
Special links have developed over the centuries between trees and religious buildings.
Indeed, many monumental trees grow near chapels, churches, abbeys or shrines. In these
cases it can be said that the aesthetic and landscape value of the architectural complex is
enhanced also by the presence of these living monuments of nature. The species most
commonly found close to religious buildings are the cypress, found near the shrine of the
Madonna di Reggio in Vernazza (La Spezia) or that of the Madonna di Soviore in Monterosso
(La Spezia) and again near Borzone Abbey in Borzonasca (Genoa). Some of these trees are
several centuries old, this being a peculiar feature of cypresses, which at times are of the
same age as the nearby religious buildings.
Another species often found near churches is the holm-oak, of which there are handsome
specimens near the shrine of Our Lady of Lampedusa in the municipality of Castellaro (Imperia),
near the churches of Santa Giulia in Lavagna (Genoa), of Santa Maria del Campo in Rapallo
(Genoa), at the Montallegro shrine in Rapallo and again near the shrines of the Madonna di
Reggio in Vernazza (La Spezia) and of the Madonna di Soviore in Monterosso (La Spezia).
There are, however, also some less common species, such as the horse chestnut in front
of the churches of Sant Agostino and of San Bernardino in Triora (Imperia), or the nettletree in Piazza San Michele in Diano Borello (IM).
The maintenance and survival of these trees, now admired by us as monumental, may
have been facilitated by various different situations. Specimens growing in anthropic
environments, near religious buildings, in the gardens of stately homes, in public places and
on squares, as well as those close to houses in rural environments enjoy the constant
attention of people, who generally develop a special bond, often of affection, with them. As
far as concerns large old trees growing in woods or fields, it can be supposed that they were
very often maintained as signs for marking borders between estates, communities and
sometimes even between states.
This list of monumental trees of the Liguria Region is not exhaustive. It is intended,
rather, as a starting point for improving knowledge of the vegetable wealth of the region and
as a stimulus to encourage its careful management.
Bibliography
PAOLA G., CICILIOT F., 1998 - Woodland management and timber supply for ship masts in
eigtheenth century western Liguria (Italy), in Watkins C., European Woods and Forests: Studies
in Cultural History, pp. 157-163. CAB International, Oxon - New York.
PAOLA G., MINUTO L., 1994 - Indagine floristica sulle specie ornamentali nel verde pubblico della
fascia costiera franco ligure. Giorn. Bot. Ital. 128: 381.
140
PAOLA G., MINUTO L., 1998 Prime note sulle Palmae della Liguria. Medemia 1: 15-21, 1997.
RUSSO F., DU JARDIN P., BELTRAMI F., RUZZEDDU G., PAOLA G., 2003 Alberi di Liguria, monumenti
viventi della natura. Regione Liguria, Assessorato alle Politiche per lAgricoltura e lEntroterra,
Servizio Politiche per lEntroterra, Assessorato al Territorio e Ambiente, Ufficio Parchi e Aree Protette,
Corpo Forestale dello Stato Liguria, catalogo dei beni naturali n. 4, Erga Edizioni, Genova
Appendix
141
142
143
144
ON THE HEALTH OF A MONUMENTAL TREE OF FICUS MACROPHYLLA DESF. EX PERS. SUBSP.
COLUMNARIS (C. MOORE) P. S. GREEN (SIN. = FICUS MAGNOLIOIDES BORZÌ VAR. MAGNOLIOIDES)
IN PALERMO
L. Torta, G. Zoida, S. Burruano
Dipartimento S.En.Fi.Mi.Zo., Sezione di Patologia vegetale e Microbiologia agraria, Università degli
Studi - Palermo
Introduction
Some monumental trees of Ficus macrophylla Desf. ex Pers. subsp. columnaris (C. Moore)
P. S. Green (sin. = Ficus magnolioides Borzì var. magnolioides; Fici and Raimondo, 1996) are
present in many parks and gardens of Palermo; the species, belonging to the family of the
Moraceae, originating from Australia, has been introduced into Europe in the early 19th, via
Palermo (Botanical Garden), where they become estabilished. Currently, some secular
monumental exemplars of stately dimensions (over 30 m of height and 40 of diameter of
leafage), and good health conditions characterize the parks of Giardino Garibaldi (Fig. 1a, b),
Villa Malfitano (Fig. 2), and Botanical Garden; nevertheless, since over one decade, on both
young and old neighboring trees to the aforesaid exemplars, a slow but progressive decay
was noted. Particularly, the plants initially show a slight apical defoliation with chlorosis and
leaves small, evolving in an apical drying that can affect one or more branches, or the whole
crown. Moreover, wood rot (white and brown, as well) in the trunk and in the principal
branches are evident, and, at the same time, more or less widespread cancerous lesions,
often with lactiferous flow, are present too. The first research on the etiology of such
alteration and on the possible contamination from the damaged plants to the healthy ones,
didnt give any definite results, inducing to hypothesize the physiological origin of the decaying
(Torta and Mondello, 1997). Recently, the decaying has also been noted in some ficus in the
park of Villa Malfitano where is present one of the most interesting monumental specimen,
together with secular and young trees. Therefore, a preliminary study has been started on
three different trees: the first, the monumental specimen, showing occasionally in some
branches an initial chlorosis, apical defoliation, and slight transparence in parts of the
crown; the second tree, showing apical drying widespread to more branches (Fig.3a), and
typical cancers; the last one, very damaged, with evident drying on branches and on the
whole crown (Fig.3b), showing defoliation, frequent cancerous lesions (Fig. 4a) with redbrownish underlying tissues (Fig. 4b), and abundant lactiferous flow. Furthermore, in the
first and third trees there were, both on the trunk and along the principal branches, evident
white or brown wood rot. In this first step, our observations were aimed to determine the
fungal community associated to the altered organs, pointing out the species that could be
correlated to the lesions.
The Park of Villa Malfitano
The Park of Villa Malfitano (belonging today to the Foundation Whitaker), was founded in
1886, for Giuseppe Whitakers will. Following the canons of the Romantic Garden, a rare
collection of exotic plants, which most of them are still living, has been planted inside the
park. The park, that occupies an area of over 4 Ha, today hosts about 250 species, most
tropical and sub-tropical and some Mediterranean taxa such as leccio (Quercus ilex), tino
(Fliburnum tinus) and colonies of dwarf palm (Chamaerops humilis). The peculiarity of the
park, however, is the monumental specimen of F. macrophylla subsp. columnaris, planted in
late 19th and today take an area of about 1.000 m2 (Raimondo, 1995)
Material and methods
A branch showing different symptomatologies (wood rot, cancerous lesions, lactiferous
flows, desiccation of branches, defoliation, leaves small and chlorosis) has been chosen and
cut in several portions, for each tree. From each of these portions, some samples were
taken, bagged in polyethylene sacks, and brought to the laboratory. The samples, after
preliminary washing by tap water, were used for preparation of moist chambers and techniques
of isolation. In this last case, the surface of samples have been previously sterilized, by
immersion in aqueous solution of sodium hypochlorite at 5% for 5 minutes or by rapid flaming.
Fragments of woody tissues in the marginal zone of the lesions, have been taken in sterile
way, and put in Petri dishes containing universal medium (PDA); both these, and the moist
chambers, were incubated at 21 °C. The pure cultures were identified on the base of their
macro- and microscopic features, using taxonomic keys and atlas of identification (Barnett,
1965; Hawksworth et al., 1995).
145
Results and discussions
The laboratory analysis showed a certain biodiversity inside the fungal community related
to the different symptomatologies, as reported in TAB 1. Particularly, colonies of Rhizoctonia
spp., Gliocladium spp., Alternaria spp., Trichoderma spp., Stemphylium spp., etc, ubiquitary
saprotrophyc microorganisms or weak pathogens, grown both in moist chambers and on
PDA. Colonies belonging to genus Cytosporella (Fig. 5) were the most frequently isolated:
numerous strains, in fact, were constantly connected to the apical drying and, on the
second tree, to all the different symptomatologies.
Since some species of Cytosporella are known like primary or secondary agents of dryings
of the branches on different forest trees, like pine (C. damnosa; Goidanich, 1964) and
poplar (C. populi; Stefanov et al., 1961), it is possible to consider such fungus implicated in
manifestation of the alteration. Relatively to the most declining specimen sample inside
fungal community of the cancerous lesions of the xylematic necrosis and wood rot, have
recurrently revealed the presence of strains of Verticillium spp. and Fusarium spp., fungal
genera well-known as tracheomycotic agents.
Further pathogenecity tests on healthy plants will allow to define the possible role of
Cytosporella spp. on the manifestation of the apical drying of F. magnioloides subsp.
columnaris and, in particular, of the monumental tree.
The observations on the fungal community associated to the different symptomatologies,
compared to results obtained from the most declining specimens, could give useful indications
on the interaction between the most recurrent taxa and the development of the decline.
Tab.1: Fungal genera associated to the lesions of the three specimens of Ficus macrophylla
subsp. columnaris (Villa Malfitano, PA)
a
b
Fig. 1 - An asymptomatic monumental tree of F. macrophylla
ssp. columnaris in Giardino Garibaldi in Palermo:
a) crown; b)trunk with columnar and tabular roots
146
Fig. 2 - The monumental tree of F. macrophylla ssp. columnaris
in Villa Malfitano (specimen 1), showing a slight transparence in the crown.
a
b
Fig. 3 - Different stages of the decline of F. macrophylla ssp. columnaris:
a) apical drying widespread in some branches; b)evident drying of the whole crown
a
b
Fig. 4 - Xylematic alterations detected during the observations:
a)cancers; b) reddish, brownish, and necrosis of the tissues
147
Fig. 5 - Pure colony of Cytosporella sp., isolated from apical drying of F. macrophylla ssp. columnaris;
in the frame, section of a pycnidia formed in black, irregular stroma (bar = 50 µm)
References
Barnett, 1965: Illustrated Genera of Imperfect Fungi. Burgess Publishing Company, Minneapolis;
Fici S., Raimondo F.M., 1996: On the real identity of Ficus magniolioides. Curtiss Botanical Magazine,
13, 105-107;
Hawksworth D.L., Kirk P.M., Sutton B.C., Pegler D.N., 1995: Ainsworth & Bisbys Dictionary of the
fungi, 8th ed. International Mycological Institute, CAB International, University Press, Wallingford,
UK;
Goidanich G., 1964: Manuale di Patologia vegetale, Vol. II. Edagricole, Bologna, 928;
Raimondo F.M., 1995: The Garden of Villa Malfitano, Giuseppe Witakers Foundation, Palermo;
Stefanov D., Zashev B., Tsanova Mme P. 1961: Brown sap-flow and some fungi on stems and
branches of Poplars in the Peoples Repubblic of Bulgaria. Nauch. Trud. vissh. Lesotekh. Inst.,
Sofiya, 9, 143-156. In R.A.M. 1963, 42, 577;
Torta L., Mondello V., 1997: Osservazioni sullo stato fitosanitario di Ficus magnolioides Borzì var.
magnolioides nella città di Palermo. Atti III Congresso Europeo di Arboricoltura; II Giornate Meranesi
dellAlbero. Merano, 14-16/05/1997.
148
THE IMPACT OF RESISTOGRAPH ON TREE DECAY
A. Toussaint, JP. Baudoin, B. Campanella, Pr. R. Paul
Unit of Tropical crop husbandry and Horticulture, FUSAGx
Laboratory for environmental Toxicology, FUSAGx
Acknowledgements
This work was founded by the Ministry of the Walloon Region (Belgium), G.D. for Natural
Resources and Environment and G.D. for Employment and Training. We also thank F.N.R.S.
for its financial contribution
Summary
People in charge of green heritage are even more frequently asked for objective information
about future of street or park trees showing signs of decay. Generally, these are needed for
insurance or security reasons. Resistograph is one of the most commonly used tools in
establishing rapid diagnostic. It is easy to use, affordable for most of public authorities and
resistogram is a visual proof of the analyses.
Nevertheless, in some cases, this tool may induce side effects that are not negligible.
This study on Tilia sp. shows a four fold increased spread of heart rot in the wood crossed
by the resistograph needle. If lignolytic fungi attack trees, one can fear a faster disease
spread inside trunk and/or branches but also a possible transport from tree to tree if needles
are not properly disinfected. As a consequence, this invasive technique has to be used only
when necessary, and not systematically.
Introduction
In 1992, 280 roadside trees (Tilia cordata and T. europea) were drastically pruned.
During the next ten years, numerous sprouts were produced (Toussaint et al. 2002). New
intervention was necessary to avoid that natural selection led to branch fall. In 2002,
experimentation was started to test the efficiency of several soil treatments in increasing
vitality, but also to assess the problems of wounds and cavities. Numerous 10 years old
wounds are now presenting rots and cavities. Another important problem is the infection of
old injuries by decay fungi (Ganoderma sp. and Ustulina sp.).
In the frame of stability diagnostic, resistograph was used to precisely measure the
extension of decay. People in charge of green heritage are even more frequently asked for
objective information about future of street or park trees showing signs of decay. Generally,
these are needed for insurance or security reasons. Resistograph is one of the most commonly
used tools in establishing rapid diagnostic. In our study, diagnostic was realized for urban
authorities and it was recommended to cut 3 trees down for security reasons. After this,
trees were divided in sections and the extent of decay was observed to confirm diagnostic.
Results
Decaying tree was firstly pointed out following the VTA method (Betghe and Mattheck
1993). Three clear symptoms were:
The crown heterogeneity. In addition to the severe crown disorganization due to over
pruning, this tree showed one half of dying branches (strongly reduced foliage, small and
chlorotic leaves when present).
The progressive decay of bark at trunk base.
The presence of heart rot fruit body (Ganoderma sp) at trunk base and 120 cm. At this
level, an old bark wound (15 x 25 cm) has not been overlaid by wound wood.
Six measurements were realized with Resistograph IML-Resi F-400 at trunk base and 120
cm. Data were processed according to a method described previously (Campanella et al.
2003). Following the localization of weakened zones in the 6 directions, an estimation of
fungus extension in the trunk was presented to local authorities to traduce the risk associated
with this tree (figure 1). After tree cutting down, two major observations were made:
Extension of the discolored zone and the fungus is more important than postulated after
resistograph measurements. It is particularly true in the direction of measurements 1,2 and
3. This could be partly due to heart rot progress during 4 months. Data processing could
also be improved. Particularly, it would be important to better distinguish weakened wood
limits. Moreover, fungus activity is not directly traduced by a decrease in wood density.
149
Impact of measurements 2 and 3 are visible. Locally, where new injuries occurred, the
discolored zone is more extended (figure 2).
Figure 1: scheme of 6 measurements with resistograph
at trunk base (%: correct density; ---: weakened or
amorphous wood). Fungi fruit bodies are shown in
black, estimated decaying zone in pale gray and the
observed decaying zone in dark gray
Figure 2: discolored zone following
resistograph measurement in
transversal (above)
and longitudinal (below) section
Two wood samples were taken to describe the extension of reaction zone in the 3
dimensions. Polyphenol accumulation was also visible under microscope. This accumulation
occurs in vessels as well as parenchymatic rays. Wood chips were taken, discolored with
oxygen peroxide and treated with acidic fushine to stain fungal hyphae. No trace of fungus
was identified in the discolored zone.
Table 1 : dimensions of reaction zones
in the two samples
Dimensions of the neo-formed reaction zone are slightly different between the two
samples (table 1). Compartmentalization is more efficient in the tangential direction (e) than
in the longitudinal one (a, c), which is consistent with CODIT model (Shigo, 1989). In this
particular case, the extent of reaction zone is 4 fold increased after drilling. It must also be
mentioned that wall 4 of the CODIT model has been broken by the fungus. No wall was
detected by resistograph measurements.
Conclusion
In this particular case, resistograph was useful to complete diagnostic and demonstrate
the importance of decay. Nevertheless, intrusive measurement will have consequences on
fungus development. After 4 months, reaction zone has normally developed around the hole.
Even if fungus has not been detected in the hole, its radial growth will certainly be easier. It
is then important to know that the use of resistograph could accelerate the process of wood
decay. Moreover, the even more common practice of systematic resistograph use should be
avoided as some trees showing cavities could be remained in place if the decay was efficiently
contained. Systematic measurements realized in cities could accelerate the decay of street
150
trees. These observations confirm suspected phenomenon, but it is, as far as we know, the
first time that it is quantified in lime tree. Another well-recognized risk is the fungus transport
from trees to trees if needles arent disinfected.
Current experimentations are designed to measure the progressive development of fungi
in the hole and tree reaction after drilling (evolution of reaction zone with time and kinetic of
wound cover). These observations are realized mainly on lime trees infected by various rots.
References
Betghe, K. and C. Mattheck (1993). VTA - Visual Tree defect Assessment and related testing
methods. 9th Int. Meet. Non-Destructive Testing., Madison, USA.
Campanella, B., A. Toussaint, et al. (2003). Amélioration de linterprétation des données fournies
par le résistographe pour la gestion darbres dalignement. 1 : le cas du tilleul. Arbres et Sciences 9.
Shigo, A. (1989). Tree pruning: a worldwide photo guide for the proper pruning of trees. Durham,
A. Shigo, ed., 187p.
Toussaint, A., V. Kervyn, et al. (2002). Analyse de limpact physiologique et économique de
lélagage des arbres dalignement en port libre. Biotechnol. Agron. Soc. Environ. 6(2): 99-107.
Regioni
152
153
IL VALORE STORICO, CULTURALE E PAESAGGISTICO DEGLI ALBERI
GLI ALBERI MONUMENTALI
B. Sara
Dovendo intervenire in un convegno che tratta in modo approfondito e scientifico i temi e
le problematiche degli alberi, alla presenza di molti ed illustri competenti in materia, credo sia
necessario, innanzi tutto, confessare di non sentirmi e non essere un addetto ai lavori
nonostante gli uffici del Settore di cui sono responsabile si occupino anche di Alberi
Monumentali.
Avrei delle grosse difficoltà a parlare scientificamente o quantomeno come esperto di
alberi. Io mi ritengo, innanzitutto, un utente degli alberi, uno dei tanti che dagli alberi
traggono sensazioni, emozioni, stati danimo, direi, in ultima analisi, giovamento.
Chi, daltro canto, oltre a usufruire dei benefici effetti prodotti dagli alberi, sulle qualità
fisiche dellambiente in cui vive, non prova, anche se molte volte a livello inconscio, piacevoli
sensazioni di pace, di tranquillità, di antica maestosità a seconda che si soffermi sotto un
gruppo di alberi o si trovi in un bosco ? Chi non si stupisce della loro forza vitale quando gli
capita di vedere alberi che tentano di svilupparsi e di crescere nelle situazioni più ostili, tra le
crepe di un muro o annegati in lastricati di cemento ?
Esiste poi un aspetto degli alberi che mi affascina particolarmente, probabilmente per
deformazione professionale: la loro architettura. Suscita sempre un grande stupore soffermarsi
ad ammirare larchitettura degli alberi ovviamente, a maggior ragione, se si tratta di alberi di
più antico impianto e di più rilevanti dimensioni, architettura a volte imponente, severa, a
volte leggera, elegante, che pur avendo ragioni assolutamente scientifiche raggiunge, in
molti casi perfezioni e ritmi che sembrano rigorosamente studiati per ottenere, con ricercate
simmetrie o volute casualità, risultati estetici di grande effetto. Sempre per una deformazione
professionale, dovuta ai miei trascorsi di urbanista, vorrei ricordare anche limportanza degli
alberi e delle alberate nel disegno della città.
Basti pensare a quello che rappresentano nel contesto cittadino i viali, soprattutto i viali
storici, monumentali (come spesso si trovano nelle città europee, non ultima Torino che è
caratterizzata da numerosi viali monumentali le cui alberature, per altro, sono già vincolate)
sia che essi attraversino il centro urbano o che lo perimetrino. Ben difficilmente il viale è solo
un luogo di transito veicolare.
In genere il viale è anche un luogo di passeggio, di sosta, di incontro, di socializzazione.
Un luogo di cui hanno usufruito intere generazioni, che appartiene alla memoria collettiva,
che entra a far parte della storia della città, un luogo che non solo evoca ricordi negli
abitanti ma che caratterizza la città nella memoria dei visitatori.
A questo proposito mi pare di poter affermare, dopo aver esaminato numerosi Piani
Regolatori di città di ogni dimensione, che oggi, troppo spesso ci si dimentica della insostituibile
funzione degli alberi. Al di là di insignificanti giardinetti, nati più dalla necessità di assolvere
obblighi legislativi che non da un preciso disegno urbano, ben difficilmente nei contesti urbani
di nuova edificazione o di nuovo impianto sono stati previsti o vengono previsti spazi verdi
con significative masse arboree o, tanto meno, viali che, potendosi chiamare tali e per
lunghezza e per caratteristiche, ne connotino, oggi e negli anni futuri, limmagine.
Tralasciando altre possibili riflessioni, credo che molte volte la presenza degli alberi, quali
elementi del paesaggio non solo agricolo ma anche urbano, e, in ultima analisi, la loro
insostituibile funzione per migliorare la qualità della vita sia decisamente sottovalutata;
anche perché la fretta e labitudine sovente ci impediscono di percepirne appieno e di
valorizzarne la silenziosa presenza.
È quindi necessario che si parli di alberi. Ed è in questo senso che mi sembrano
particolarmente utili le azioni che ha inteso portare avanti la Regione Piemonte ed in particolare
lAssessorato alle Politiche per la Montagna, Foreste e Beni Ambientali: sia promuovendo il
dibattito scientifico e lo scambio di esperienze, soprattutto sul tema della conservazione e
della cura del patrimonio arboreo esistente, sia producendo e distribuendo materiale divulgativo
di più immediata e generale comprensione al fine di richiamare lattenzione degli abitanti del
Piemonte ed in particolare dei ragazzi (vedasi il CD Alberi Monumentali del Piemonte) sulle
tematiche degli alberi e sugli aspetti storici e sociali che ad essi possono essere collegati.
Infatti ritengo importante, da un lato, suscitare linteresse ed educare i cittadini a
riconoscere limportanza degli alberi, incominciando proprio da quelli che, dal punto di vista
storico e/o paesaggistico, costituiscono, per così dire, gli episodi più significativi presenti sul
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territorio regionale e, daltro lato, adottare strumenti per la loro tutela affinché questultima
non venga interpretata come unimposizione calata dellalto ma divenga invece unesigenza
condivisa, frutto di un pensiero comune che identifica loggetto della tutela come un patrimonio
dellintera collettività.
In questo senso è stata emanata ed è gestita la Legge Regionale n° 50 del 3 aprile 1995
che promuove il censimento, la tutela e la valorizzazione di alberi, filari e alberate di alto
pregio naturalistico e storico del Piemonte ovvero la Legge sui, così detti, Alberi Monumentali.,
Volendo illustrare, per sommi capi, i contenuti e le azioni che la Legge in questione
intende attuare è necessario, innanzi tutto, chiarire cosa si intenda per Alberi Monumentali:
· gli alberi che per età o dimensioni possono essere considerati come esempi unici di maestosità
o longevità;
· gli alberi che hanno un preciso riferimento ad eventi o memorie rilevanti dal punto di vista
storico o culturale;
· filari e alberate di particolare pregio paesaggistico, monumentale, storico-culturale, comprese
quelle inserite nei centri urbani.
Partendo dalla giusta considerazione che uneffettiva tutela, quindi una tutela mirata e
non generica, debba necessariamente basarsi su di una puntuale conoscenza dei beni da
salvaguardare, la Legge 50/95 promuove, innanzi tutto, il censimento degli Alberi Monumentali,
invitando, in unottica di massima partecipazione, i Cittadini, gli Organi e gli Enti Pubblici o le
Associazioni a segnalare lesistenza di tutti quegli esemplari che per le loro peculiarità potrebbero
essere definiti tali.
Tale censimento è stato di fatto avviato nel settembre 1999 con linvio, a tutti i Comuni,
alle Associazioni interessate e agli Enti preposti alla tutela, di una circolare con la quale li si
invitava ad attivarsi per effettuare le segnalazioni e nello stesso tempo li si informava della
avvenuta costituzione della Commissione Tecnica per la tutela e la valorizzazione degli
alberi, filari ed alberate monumentali prevista dalla Legge in questione.
La Commissione è presieduta dallAssessore ai Beni Ambientali e Paesaggistici (attualmente
è quindi presieduta dallAssessore Roberto Vaglio) e di essa fanno parte lAssessore ai Beni
Culturali o un suo rappresentante, un rappresentante dellIPLA (Istituto per le Piante da
Legno e lAmbiente), un rappresentante della Soprintendenza ai Beni Ambientali ed Archeologici
del Piemonte, un rappresentante del Corpo Forestale dello Stato e un Rappresentante della
Facoltà di Scienze Forestali dellUniversità di Torino.
Successivamente, la Giunta Regionale ha ancora adottato la metodologia di rilevazione e
la Scheda di identificazione necessarie per predisporre il censimento, elaborate dalla
Commissione. Su tali schede vengono riportati, non solo la descrizione dellalbero o degli
alberi segnalati, le loro caratteristiche fisiche, il loro stato di salute, ma anche notizie sulla
loro storia, sul loro rapporto con lambiente e con la cultura locale.
Vorrei aprire una parentesi per sottolineare ancora questaspetto che mi pare
particolarmente significativo ovvero la volontà del legislatore e quindi dellAssessorato di
tutelare l oggetto albero non solo per il suo interesse botanico, ma anche perché parte
integrante di quel patrimonio delementi che caratterizzano un luogo dal punto di vista
paesaggistico e che ne costituiscono le radici storiche e culturali.
Le proposte di vincolo vengono quindi trasmesse alla Commissione Alberi Monumentali che
le valuta e decide con parere obbligatorio e vincolante quali, tra gli alberi segnalati, abbiano
le caratteristiche per essere inclusi nellelenco degli alberi monumentali e, come tali, essere
oggetto di vincolo.
A questo punto inizia liter procedurale che vede impegnati gli Uffici del Settore Beni
Ambientali (convocazione dei Sindaci dei comuni interessati, atti di deposito, pubblicazione e
pubblicizzazione, raccolta osservazioni, ecc) che si concludono con la formalizzazione del
vincolo da parte della Giunta Regionale, iter procedurale che come tutte quelli preordinati
allimposizione di vincoli, non è né breve né facile e che si conclude con le notifiche ai
possessori e laffissione del provvedimento allAlbo Pretorio.
Altra particolarità importante della Legge è che prevede che vengano erogati contributi
per la cura ordinaria e straordinaria degli alberi considerati monumentali e che la Giunta
Regionale possa promuovere iniziative per la loro valorizzazione. A tal fine la Giunta Regionale,
in ogni esercizio finanziario, dispone lassegnazione al Settore Beni Ambientali di un budget di
spesa per la promozione, il finanziamento degli interventi sostitutivi e per la valorizzazione
dei siti arborei. Questo Budget si aggira mediamente, su base annua e a seconda delle
effettive disponibilità , intorno ai 250/500.000 Euro.
A questo proposito ritengo utile segnalare che la Regione Piemonte ha ritenuto di intervenire
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direttamente e con propri mezzi economici e professionali nellesecuzione degli interventi di
cura delle alberature sollevando quindi i comuni o i privati da qualsiasi tipo di defatigante
procedura burocratica nellassegnazione degli incarichi e di responsabilità nella fase operativa
potendo la Regione stessa garantire lalta professionalità degli operatori tramite laffidamento
degli incarichi allIstituto per le Piante da Legno e lAmbiente e allUniversità sulla base di un
programma annuale dintervento.
Il 30.12.2002 si è finalmente giunti allapprovazione del primo elenco degli alberi monumentali
costituito da cinque esemplari. Attualmente sono in fase di completamento le procedure per
il riconoscimento di altri diciotto alberi monumentali mentre per cinque alberi è stato affidato
un incarico al corpo Forestale dello Stato per lacquisizione della documentazione tecnica
necessaria per iniziare le procedure di vincolo. Vorrei citarne almeno alcuni per dare unidea
di come tali alberi siano esemplari che suscitano stupore per le loro caratteristiche, siano di
antica o antichissima origine e abbiano, come si diceva prima, attraversato intere generazioni
entrando, a pieno titolo, nella storia e nelle leggende dei paesi in cui sono collocati:
- il Frassino di Moncenisio, posto sulla Piazza Parrocchiale del paese, la cui età è valutata
in circa 500 anni, simbolo della montagna e dalla sua storia;.
- il Tiglio di Macugnaga che potrebbe avere addirittura dai 685 ai 887 anni se, come vuole
la tradizione, è coevo della vicina chiesa. Sotto la sua chioma si dice si radunasse un tempo
il consiglio comunale;
- il Platano di Napoleone posto lungo la strada che da Alessandria portava a Marengo e
sotto il quale, si dice, si sia soffermato Napoleone nel giugno del 1800 dopo la famosa
battaglia di Marengo;
- limponente Cedro di Montalenghe, di circa 13 mt. di circonferenza e 36 mt. di altezza, la
cui età si aggira intorno ai 350 anni e che risulta essere uno dei più grandi e vecchi cedri
dItalia.(vincolo in itinere)
- il bellissimo Tasso di Cavandonesituato nellomonima frazione di Pallanza, di 3,6 mt. di
circonferenza e 26 mt. di altezza, che con i suoi 450 anni e il tronco contorto e possente è
una vera opera darte della natura.
Da questi pochi esempi, è evidente quindi linteresse scientifico, storico e culturale che
gli alberi monumentali suscitano. Ma occorre dire che a questi interessi se ne possa aggiungere
un altro: quello turistico. Questultimo, se opportunamente incentivato e sfruttato potrebbe
costituire per alcuni dei Comuni interessati un valore aggiunto non trascurabile, sullesempio,
per altro, di quanto accade in altre nazioni a noi vicine nelle quali episodi anche meno
significativi vengono regolarmente segnalati ed enfatizzati su tutte le guide turistiche.
Ritornando un attimo al tema più generale dellutilizzo degli alberi e delle alberature, mi sia
concesso concludere con una brevissima annotazione connessa al mio attuale incarico nel
Settore Gestione Beni Ambientali, Settore che si occupa di verificare il corretto inserimento
ambientale degli interventi che ricadono in ambiti vincolati e nei cui uffici quindi transitano
quotidianamente progetti di ogni genere.
Gli alberi, in molti casi, possono avere unimportanza assolutamente non trascurabile nella
progettazione; gli alberi, se attentamente progettati sia per posizionamento che per tipo,
si integrano nel progetto stesso, lo completano, lo valorizzano e, per così dire, lo arredano.
Purtroppo, questa grossa potenzialità non sempre è percepita correttamente dai progettisti.
Non ultimo, gli alberi sono una potente medicina per larchitettura quando larchitettura è
malata. Laddove il prodotto architettonico è discutibile, né esistono ragionevoli speranze di
migliorarlo, spesso non rimane che unultima soluzione: prescrivere la messa a dimora di
gruppi o filari di alberi che con la loro naturale bellezza riescono, quasi a stendere un velo sui
peccati dellarchitettura.
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1° ELENCO degli ALBERI MONUMENTALI (D.G.R. n. 37 8157 del 30.12.2002)
ALBERI MONUMENTALI
con procedimento in corso per lapposizione del vincolo (fase di pubblicazione)
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158
ALBERI MONUMENTALI
con procedimento avviato (fase di ulteriore accertamento delle caratteristiche)
Consiglio regionale
del Piemonte
Legge regionale 3 aprile 1995, n. 50.
Tutela e valorizzazione degli alberi monumentali, di alto pregio naturalistico e
storico, del Piemonte.
(B.U. 12 aprile 1995, n. 15)
Art. 1.
(Finalita)
1. La Regione Piemonte individua, in attuazione dellarticolo 5 dello Statuto gli alberi, i filari e
le alberate monumentali, di interesse paesaggistico-ambientale e storico-culturale presenti
sul territorio regionale e ne promuove la tutela e la valorizzazione.
2. Sono inclusi nella competenza della presente legge anche gli alberi, i filari e le alberate gia
sottoposti a vincolo di tutela da parte della legislazione regionale e nazionale.
Art. 2.
(Definizione)
1. Ai fini della presente legge sono considerati alberi, filari ed alberate monumentali di interesse
storico-culturale e ambientale-paesaggistico:
a) alberi isolati o facenti parte di formazioni boschive naturali o artificiali che per eta o
dimensioni possono essere considerati come rari esempi di maestosita o longevita;
b) alberi che hanno un preciso riferimento ad eventi o memorie rilevanti dal punto di vista
storico o culturale;
c) filari ed alberate di particolare pregio paesaggistico, monumentale, storico-culturale, ivi
comprese quelle inserite nei centri urbani.
Art. 3.
(Censimento)
1.La Giunta Regionale, entro sessanta giorni dalla approvazione della presente legge adotta,
con propria deliberazione, la metodologia di rilevazione ed una scheda di identificazione
allo scopo di predisporre il censimento degli alberi, dei filari e delle alberate monumentali di
interesse paesaggistico-ambientale e storico-culturale.
2. Il censimento deve raccogliere in particolare dati ed informazioni relativi a:
a) localizzazione;
b) proprieta;
c) caratteristiche floristiche e dendrometriche;
d) descrizione delle caratteristiche monumentali o storico-culturali o paesaggistico-ambientali
che motivano linclusione nel censimento;
e) condizioni fitosanitarie, vulnerabilita, rischi ed eventuali interventi necessari per garantire
la conservazione.
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3. Singoli cittadini, Organi ed Enti pubblici o Associazioni possono segnalare alla Giunta
Regionale lesistenza di alberi, filari o alberate aventi le caratteristiche descritte allarticolo
2.
4. La Giunta Regionale sentito il parere obbligatorio e vincolante della Commissione Tecnica
di cui allarticolo 4, predispone ed aggiorna periodicamente lElenco degli alberi, dei filari e
delle alberate monumentali, di interesse paesaggistico-ambientale e storico-culturale della
Regione Piemonte, che viene pubblicato integralmente sul Bollettino Ufficiale della Regione
Piemonte.
5. Gli alberi, i filari e le alberate inseriti in tale elenco devono essere individuati negli
strumenti urbanistici comunali ai sensi dellarticolo 24 della legge regionale 5 dicembre
1977, n. 56.
6. Linclusione nellelenco di cui al comma 4 comporta, ai sensi dellarticolo 9 della L.R. 56/
1977 listituzione del vincolo di cui alla legge 29 giugno 1939, n. 1497 sulla protezione delle
bellezze naturali e panoramiche.
Art. 4.
(Commissione tecnica per la tutela e la valorizzazione degli alberi,
filari ed alberate monumentali)
1. È istituita la Commissione Tecnica per la tutela e la valorizzazione degli alberi, filari ed
alberate monumentali.
2. La Commissione e composta da:
a) Assessore ai Beni ambientali e paesaggistici o suo delegato con funzioni di Presidente;
b) Assessore ai Beni culturali o suo delegato;
c) rappresentante dellIstituto per le piante da legno e lambiente (I.P.L.A.);
d) rappresentante della Soprintendenza per i beni ambientali ed architettonici del Piemonte;
e) rappresentante del Corpo Forestale dello Stato;
f) rappresentante della Facolta di Scienze Forestali dellUniversita di Torino.
Svolge le funzione di Segretario della Commissione un funzionario del Settore Beni ambientali
e paesaggistici della Regione nominato con decreto del Presidente della Giunta Regionale.
La Commissione e validamente costituita quando sia stata nominata la maggioranza dei
suoi membri.
3. La Commissione formula parere obbligatorio e vincolante alla Giunta Regionale in merito
alla inclusione nellelenco di cui allarticolo 3 degli alberi, filari e alberate di cui e stata
predisposta la scheda di identificazione.
4.La Commissione esprime inoltre parere in ordine ai finanziamenti per gli interventi di cura
ordinaria e straordinaria, nonche di valorizzazione di cui agli articoli 5 e 6.
5. La Commissione esprime altresi parere obbligatorio e vincolante sulleventuale abbattimento
degli alberi, filari e alberate inclusi nellElenco di cui allarticolo 3.
6.La Commissione si riunisce su convocazione del Presidente, su richiesta dellAssessore dei
Beni ambientali e paesaggistici o dellAssessore ai Beni culturali, o su richiesta di almeno un
terzo dei suoi componenti.
7.Le riunioni della Commissione sono valide con la partecipazione della maggioranza assoluta
dei componenti.
8.La Commissione dura in carica cinque anni e scade con lo scioglimento del Consiglio
Regionale. Essa svolge la sua attivita finche non siano insediati i nuovi componenti.
9.Ai membri della Commissione spettano per ogni riunione i gettoni di presenza e le eventuali
indennita di rimborso spese previste dalla vigenti leggi regionali in materia.
Art. 5.
(Interventi di cura ordinaria e straordinaria)
1.La Regione Piemonte eroga contributi per la cura ordinaria e straordinaria degli alberi,
dei filari e delle alberate inclusi nellelenco di cui allarticolo 3.
2.Gli interventi di cui al comma 1 sono eseguiti dai proprietari o dagli aventi diritto, su
richiesta propria o della Regione Piemonte, a seguito di parere obbligatorio e vincolante di un
esperto nominato dalla Giunta Regionale.
160
Art. 6.
(Interventi di valorizzazione)
1. La Giunta Regionale, anche su istanza dei proprietari o degli aventi diritto, puo promuovere
iniziative di valorizzazione degli alberi, filari ed alberate inclusi nellelenco di cui allarticolo
3, al fine di divulgarne la conoscenza ed il significato della tutela, nonche per migliorare il
contesto territoriale ed ambientale circostante.
Art. 7.
(Norme finanziarie)
1. Agli oneri necessari per il conseguimento dei fini di cui alla presente legge, valutati in lire
20 milioni per lanno finanziario 1995, si provvede mediante una riduzione di pari ammontare,
in termini di competenza e di cassa, del capitolo 15190 dello stato di previsione della
spesa per lanno finanziario 1995 e mediante listituzione, nello stato di previsione medesimo,
di apposito capitolo con la denominazione Spese per la tutela e la valorizzazione degli
alberi, dei filari e delle alberate di interesse monumentale e con lo stanziamento di
competenza e di cassa di lire 20 milioni.
2. Il Presidente della Giunta Regionale e autorizzato ad apportare, con proprio decreto, le
occorrenti variazioni di bilancio.
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IL CENSIMENTO E LA GESTIONE DEGLI ALBERI MONUMENTALI: LESPERIENZA DELLA
REGIONE LOMBARDIA
P. Lenna, G. Galasso
Regione Lombardia - Direzione Generale Qualità dellAmbiente - Struttura Azioni per la Gestione delle
Aree Protette e la Difesa della Biodiversità - Milano (MI) Italia
Premessa
La Lombardia, regione densamente popolata e ad alto indice di sviluppo, tra le prime in
Europa per tasso di occupazione e reddito, conserva ancora gioielli naturali di altissimo
valore nonché scorci di paesaggio legati al passato e alle tradizioni delluomo. Un patrimonio
che, ventanni fa, la Regione Lombardia ha deciso di salvaguardare attraverso listituzione
dei Parchi regionali, delle Riserve e Monumenti naturali e dei Parchi locali di interesse
sovracomunale. Un sistema di pianificazione territoriale che ha consentito di gestire con
forme differenziate di tutela più del 20% del territorio e che, oggi, costituisce la solida base
della rete ecologica lombarda, inserita nella più vasta strategia di conservazione della natura
in Europa.
La Regione Lombardia è stata la prima in Italia a istituire un Assessorato allEcologia,
nellormai lontano 1970, e anche con la sua attività legislativa in materia di parchi e riserve
ha svolto un ruolo pionieristico. Già nel 1973, con la legge regionale n. 58 ha posto sotto
tutela biotopi e geotopi di interesse naturalistico e scientifico e ha dato lavvio alla istituzione
dei primi parchi (Ticino, 1974; Nord Milano, 1975; Groane, 1976 e Colli di Bergamo (1977).
Dieci anni più tardi è stata approvata la legge regionale 86/1983 Piano regionale delle aree
regionali protette. Norme per listituzione e la gestione delle riserve, dei parchi e dei monumenti
naturali nonché delle aree di particolare rilevanza naturale e ambientale, ben 8 anni in
anticipo sulla normativa nazionale (l. 394/1991). Da alcuni anni il sistema lombardo delle aree
protette è ancora più articolato. La Regione Lombardia ha infatti avviato nuove forme di
tutela del territorio in base alle ultime direttive comunitarie in materia di habitat e specie. Al
31 dicembre 2003 il sistema risultava così articolato:
· 1 Parco nazionale;
· 21 Parchi regionali;
· 4 Parchi naturali;
· 60 Riserve naturali;
· 27 Monumenti naturali;
· 45 Parchi locali di interesse sovracomunale;
· 176 Siti di importanza comunitaria (di cui 85 già approvati dalla Comunità Europea);
· 8 Zone di Protezione Speciale.
Le azioni di tutela riguardano però non solo le aree protette ma lintero territorio regionale,
grazie al coinvolgimento di tutti i soggetti istituzionalmente preposti (Comuni, Comunità
montane e Province) e alla sempre maggior sensibilità e disponibilità del mondo accademico,
delle associazioni e dei privati. Un esempio significativo di questa collaborazione è proprio il
censimento degli alberi monumentali. La Lombardia è forse la Regione italiana che ospita la
più ampia varietà di specie arboree, grazie alla diversità di ambienti che ne caratterizzano il
territorio, dai grandi bacini lacustri insubrici alle montagne alpine e appenniniche, fino alle
campagne planiziali con gli esemplari sopravvissuti alla meccanizzazione agricola. Linventario
e la tutela delle piante più meritevoli assume, inoltre, un ulteriore significato più prettamente
scientifico, rendendo possibile lo studio di questi alberi eccezionali nel tentativo di scoprire
se devono la loro lunga vita, oltre al caso che li ha preservati, anche al loro patrimonio
genetico, che può averli resi più idonei di altri a sopportare e superare le difficoltà, le
malattie e i danni che gli anni portano con sé.
La Regione Lombardia, attraverso la collaborazione delle Province, ha avviato sin dal
1989 il censimento degli alberi monumentali. Da allora è iniziato un importante lavoro di
stimolo e di coordinamento e, nel corso di diverse riunioni, è stato predisposto un protocollo
per attribuire agli esemplari arborei la qualifica di monumentale, raccogliere i numerosi dati
e archiviarli. Il percorso di lavoro via via condiviso è stato il seguente:
1. rilevamento 1a fase: raccolta di segnalazioni da parte di volontari,
2. rilevamento 2a fase: verifica da parte di tecnici,
3. predisposizione di uno schedario provinciale,
4. predisposizione di un data-base possibilmente collegato a un gis,
5. pubblicazione di uno stralcio dei risultati,
6. tutela, allinterno del Piano territoriale di coordinamento provinciale (PTCP), degli alberi
monumentali individuati
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Una fase successiva potrebbe prevedere lo stanziamento di fondi per la manutenzione straordinaria
degli alberi monumentali stessi: potature, interventi di dendrochirurgia ecc.
Numerose Province hanno iniziato celermente il lavoro di censimento: alcune lo hanno già concluso e
hanno pubblicato i loro dati; altre hanno già inserito gli alberi monumentali individuati allinterno del loro
PTCP; altre ancora hanno appena avviato lattività. La prima Provincia a intraprendere la fase esecutiva
dellindagine è stata Pavia. Nel contempo è stato organizzato un seminario il 18 novembre 1997 a Milano e
sono state realizzate due pubblicazioni, una del 1999 relativa alla sola Provincia di Sondrio e una del 2000
relativa alle Province di Brescia, Milano, Pavia e Sondrio:
AAVV., 1999 - Alberi monumentali della Provincia di Sondrio. 1o censimento. Provincia di Sondrio, Azienda
Regionale delle Foreste, Sondrio.
AAVV., 2000 - Gli alberi monumentali della Lombardia. Regione Lombardia, Il Verde Editoriale, Milano.
Scheda di rilevamento e informazioni raccolte
Per lesecuzione del censimento è stata predisposta una scheda informatizzata che permette di rendere
omogenei e confrontabili i dati raccolti nei diversi contesti territoriali e amministrativi; gli stessi dati potranno
quindi essere elaborati e resi su cartografia GIS. La scheda, realizzata in Microsoft-Acceess e aggiornata
nel corso del 2003, permette di descrivere ciascun albero, filare o gruppo di alberi attraverso la raccolta di
informazioni su: localizzazione, tassonomia, aspetti di monumentalità, caratteristiche morfologiche e
biologiche, condizioni vegetative e sanitarie.
Tale scheda è stata redatta per essere utilizzata sia nella fase di prima indagine territoriale, durante la
quale il personale incaricato si limiterà a compilare solo le voci per le quali è in grado di fornire uninformazione
esauriente, sia nella successiva fase di verifica specialistica. La scheda è articolata nelle seguenti sezioni
tematiche.
Numero della scheda, data del rilievo, estremi del rilevatore
Localizzazione geografica
Riporta lambito territoriale del rilievo, ovvero la Provincia, il Comune, la località e, se disponibile, lindirizzo;
ove necessario viene descritto brevemente lambito in oggetto e il percorso necessario per raggiungere
lesemplare, facendo riferimento a elementi di facile individuazione sul tracciato (cartelli indicatori, case
isolate, bar ecc.). Laddove reperibili sono riportati anche i dati catastali (numero di foglio e di mappale),
soprattutto se ci si trova in ambito privato. Sono infine indicati i dati relativi allesposizione, alla pendenza
media e al tipo di ambiente (urbano o extraurbano).
Tassonomia e carattere del rilevamento
Oltre al nome scientifico è indicato se si tratta di un esemplare singolo, di un filare o di un gruppo di
alberi. Nel caso di raggruppamento viene specificato il numero degli individui.
Aspetti di monumentalità
Un esemplare arboreo può essere definito monumentale in base a diversi criteri:
· monumentalità architettonica: esemplari legati a edifici di elevato valore storico-culturale;
· monumentalità paesaggistica: piante collocate in un contesto territoriale di elevato valore estetico o la cui
presenza caratterizza un certo luogo;
· monumentalità storico-culturale: limportanza della pianta è legata a particolari eventi della storia locale,
tradizioni, leggende ecc.;
· monumentalità legata alla forma;
· monumentalità legata alla rarità botanica: si riferisce a specie non tipiche dellambiente in cui crescono
(es. piante ben sviluppate al di fuori dalla loro tipica fascia bioclimatica) e poco rappresentate numericamente;
· monumentalità dimensionale: legata alla circonferenza.
Laspetto di monumentalità dimensionale viene selezionato direttamente dal programma, che tiene
conto dei valori di circonferenza inseriti nella descrizione fisionomica. Inizialmente i limiti dimensionali
erano correlati alla zona bioclimatica di Gams; tuttavia ci si è presto svincolati da questa e attualmente
sono stabiliti i seguenti limiti regionali, anche se ogni Provincia può discostarsene per meglio adattarli alla
sua realtà locale:
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Descrizione fisionomica
In questo parte della scheda sono descritte le caratteristiche morfologiche e biologiche,
quali laltezza, la circonferenza del fusto, il diametro della chioma e il portamento:
· tronco: è indicato se è monocormico o policormico;
· portamento: arboreo, arbustivo, prostrato o rampicante;
· n° fusti: è indicato il numero dei fusti di un individuo policormico;
· circonferenza: è misurata in centimetri a petto duomo (a 130 cm dal suolo); in caso di
albero policormico si riporta la somma delle circonferenze di tutti i fusti;
· altezza: è espressa in metri, valutata o misurata; se lalbero è policormico si riporta
laltezza del fusto più elevato;
· età: età stimata o misurata, indicata mediante un intervallo di anni: <100, 100-200, >200;
· diametro della chioma: è indicato il diametro medio della chioma, espresso in metri;
· forma della chioma: è indicato se espansa, pendula, colonnare o piramidale;
· carattere della chioma: è indicato se obbligata o naturaliforme; questo dato fornisce una
prima indicazione in merito ad eventuali interventi quali ad esempio potature;
· altezza del 1° palco: è indicata laltezza da terra, espressa in metri.
Quadro vegetativo
Il quadro vegetativo fornisce una prima valutazione generale dello stato di salute
dellesemplare arboreo:
· vigore vegetativo: buono, medio o scarso;
· seccume: assente, incipiente o diffuso;
· microfillia: assente, significativa o evidente; questo carattere si riferisce a foglie dalle
dimensioni più ridotte rispetto al normale sviluppo, sintomo da imputare allazione di diversi
agenti biotici e abiotici quali stress idrico, carenze nutrizionali, attacchi fungini, inquinamento
ecc.;
· riscoppi: assenti o presenti; trattasi di rami provenienti da gemme dormienti, che si sviluppano
a seguito dellazione di diversi fattori quali stress idrici, funghi, virus ecc.
Quadro strutturale
Questa sezione è finalizzata a fornire indicazioni generali circa la stabilità meccanica e
considera le seguenti regioni anatomiche:
· aspetto dellapparato radicale: buono, medio o scarso;
· aspetto del colletto: buono, medio o scarso;
· aspetto del fusto: buono, medio o scarso;
· aspetto della chioma: buono, medio o scarso;
· aspetto delle branche: buono, medio o scarso;
· note: breve descrizione dei sintomi rilevati.
Quadro fitosanitario
Viene indicata leventuale presenza di infestazioni, infezioni o carpofori, specificando
lagente patogeno e la collocazione anatomica:
· infestazioni: riferite a parassiti quali insetti e acari;
· infezioni: riferite a malattie fungine, virali e batteriche;
· carpofori: presenza di corpi fruttiferi fungini appartenenti a specie dei generi Armillaria,
Ganoderma, Phellinus, Phomes, Rosellinia ecc.
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Interventi effettuati
Si tratta di informazioni aggiuntive relative alla storia dellesemplare monumentale, segnalate
laddove siano evidenti o confermate da informazioni attendibili; se possibile sono specificate
la tipologia e la localizzazione:
· potatura: di rimonda, di diradamento, di contenimento ecc.; effettuata su branche primarie
ecc.
· consolidamenti: effettuati con lutilizzo di cavi in acciaio passanti o altro; localizzati a livello
di branche primarie ecc.;
· ancoraggi: cavi in acciaio, funi ecc.;
· altro: altri dati, tra i quali concimazione, trattamenti antiparassitari ecc.;
· note: sono indicate le eventuali operazioni future consigliate.
Informazioni sul terreno
È indicato il tipo di copertura e il grado di costipamento del suolo ai piedi della pianta:
· terreno: nudo, inerbito, cespugliato, pavimentato o impermeabilizzato;
· caratteristiche: debolmente compattato, mediamente compattato, fortemente compattato;
· altro.
Quadro minacce
Viene segnalato quale elemento di disturbo può minacciarne lintegrità:
· errata gestione: presenza di grossi tagli di potatura, irrigazioni eccessive o inesistenti,
carenze nutrizionali ecc.;
· urbanizzazione: presenza di cantieri di lavoro in corso che possono pregiudicare la pianta
(scavi per servizi, marciapiedi, parcheggio dauto in prossimità dellesemplare) ecc.;
· instabilità del terreno: presenza di cedimenti del versante o aree a franosità diffusa che
possono mettere in pericolo la stabilità dellesemplare;
· fuoco: esemplari ubicati in zone soggette a incendio;
· rischio di taglio: esemplari ubicati in aree di sviluppo urbanistico che rischiano labbattimento;
· altro.
Quadro vincoli
Sono segnalati i vincoli esistenti in base alla normativa vigente: vincolo idrogeologico,
vincolo ex l. 490/1999.
Quadro tutela
È indicato se lalbero censito è stato inserito ufficialmente: a) nellelenco degli alberi
monumentali, riportando gli estremi del relativo atto amministrativo provinciale, b) nel Piano
Territoriale di Coordinamento Provinciale e/o se è c) Monumento naturale ai sensi della l.r.
86/1983.
Attribuzione di punteggi agli alberi monumentali e ripartizione in classi di merito
Uno degli scopi del censimento degli alberi monumentali è quello di poterli tutelare
attivamente, anche mediante lo stanziamento di fondi per la loro manutenzione straordinaria.
Per fare questo è però necessario attribuire a ogni albero un punteggio che permetta di
stilare, a livello provinciale, delle graduatorie di priorità. La Provincia di Sondrio è stata la
prima a proporre un sistema che giunge a distribuire gli alberi in tre categorie: I° élite, I° e
II°. Alla fine del 2003 la Provincia di Como, nel corso della revisione della scheda di rilevamento,
ha proposto un nuovo sistema che è stato condiviso da tutte le Province; esso, lavorando
attraverso lapplicazione di tre filtri successivi, ripartisce gli alberi in tre classi di merito
(classe 1, classe 2, classe 3).
Il primo filtro tiene conto dei criteri di monumentalità. A ogni albero viene attribuito
automaticamente un punteggio in base ai parametri Aspetti di monumentalità inseriti nella
scheda. La monumentalità dimensionale contribuisce molto meno degli altri aspetti nella
formazione del punteggio; la misura della circonferenza sarà determinante durante lapplicazione
del secondo filtro. Gli esemplari censiti vengono così ripartiti in tre classi provvisorie. Le
classi 2 e 3 provvisorie passano al secondo filtro, mentre quelle della classe provvisoria 1
saltano direttamente al terzo e ultimo filtro.
Il secondo filtro agisce sui parametri dimensionali, cioè sulla circonferenza, e, come
detto, agisce soltanto sulle classi provvisorie 2 e 3. Per ogni esemplare la selezione si base
sul confronto tra la sua circonferenza, il limite minimo di soglia per quella specie (vedi
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Aspetti di monumentalità) e il valore medio per quella specie (calcolato automaticamente e
solo per i valori rilevati oltre la soglia minima).
Il terzo filtro si basa sul punteggio attribuito automaticamente ai singoli esemplari in base
al Quadro vegetativo, al Quadro strutturale e al Quadro fitosanitario della scheda di
rilevamento. Come detto, il sistema tiene conto della media delle circonferenze. Di conseguenza
ogni volta che vengono caricate nuove schede i valori e i relativi punteggi possono variare.
Pertanto il procedimento di attribuzione dei punteggi e la successiva ripartizione in classi di
merito, entrambi automatizzati, dovranno avvenire alla fine del censimento.
Lo schema seguente illustra il procedimento logico adottato dai tre filtri successivi.
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Svolgimento del Censimento e risultati
Come detto, la Regione Lombardia a partire dal 1989 ha promosso e contribuito, con
proprie risorse tecniche e finanziarie, al censimento di tali monumenti vegetali, partendo
dalle Province di Pavia, Milano, Brescia e Sondrio, caratterizzate da condizioni socio-ambientali
diverse tra loro e sufficientemente rappresentative delleterogeneità territoriale regionale. Ai
censimenti hanno collaborato attivamente i Comuni, il Corpo forestale dello stato, lEnte
regionale per i servizi agricoli e forestali (ERSAF), le scuole, le associazioni ambientaliste e i
privati, sia in quanto proprietari di alberi notevoli sia in qualità di studiosi e cultori della
materia. Le Guardie ecologiche volontarie (GEV), in particolare, grazie alla loro radicata
conoscenza del territorio, hanno rappresentato un riferimento insostituibile nella rilevazione
di un grande numero di esemplari altrimenti sconosciuti.
Provincia di Pavia
Pavia è stata, come detto, la prima Provincia lombarda a iniziare nel 1989 il censimento
degli alberi monumentali, affidando lincarico a professionisti esterni allAmministrazione.
Trattandosi della prima esperienza attuata a livello regionale, lo studio è stato seguito in
tutte le sue fasi da un gruppo di lavoro interdisciplinare formato da studiosi e professionisti di
diversa estrazione (botanici, agronomi, forestali, architetti, paesaggisti e storici). Tale gruppo
di lavoro, attraverso lesame delle esperienze già maturate in altre realtà italiane ed estere,
ha elaborato delle linee guida sia per lorganizzazione della fase dei rilievi di campagna sia per
la successiva disamina dei dati raccolti.
Dallindagine territoriale sono state escluse tutte le aree già tutelate comprese nel Parco
del Ticino e nelle Riserve naturali. La fase di prima raccolta delle segnalazioni e di verifica di
quelle trasmesse da parte di alcuni Comuni è stata portata a termine dalle Guardie ecologiche
volontarie, che sono state coinvolte in forza della loro passione per la natura e la specifica
conoscenza dei luoghi; un breve corso mirato ha consentito alle GEV di acquisire le informazioni
di base indispensabili alla conduzione dellindagine sul territorio. Le segnalazioni, poi, sono
state vagliate da tecnici esperti (agronomi, forestali e botanici) sulla base delle informazioni
riportate sulle schede di campagna e della consultazione del materiale fotografico allegato; i
rilievi che hanno superato la prima fase di selezione a tavolino sono stati sottoposti a una
successiva verifica sul posto. In seguito, i risultati della verifica sono stati esaminati mediante
lapplicazione di un criterio di analisi elaborato ad hoc dal gruppo di lavoro.
Trattandosi dellesperienza guida per la Lombardia, i criteri di riferimento per individuare le
piante di interesse monumentale, derivati dalla letteratura e da esperienze condotte fuori
regione hanno determinato una selezione piuttosto marcata delle piante già nella fase di
prima raccolta delle segnalazioni. Pertanto, per la Provincia di Pavia il numero complessivo
dei rilievi risulta, mediamente, inferiore a quello registrato nelle successive esperienze dove
sono stati usati, viceversa, nuovi criteri derivati proprio da questo primo censimento.
In un secondo momento, terminato nel 2002, il censimento è stato riverificato e integrato
coi dati delle aree protette. Il lavoro è stato commissionato a professionisti esterni
allAmministrazione, che si sono avvalsi della collaborazione del Corpo forestale dello stato.
Attualmente gli alberi monumentali sono stati inseriti allinterno del PTCP con una norma che
ne salvaguarda la conservazione, fatta salva la possibilità di abbattimenti per problemi di
stabilità o fitopatologici.
Risultati:
segnalazioni raccolte nella prima fase 247,
segnalazioni sottoposte a verifica
224,
alberi monumentali
31 (esemplari singoli: 26; gruppi: 4; filari: 1),
generi botanici più rappresentati
Quercus (5), Castanea (4), Populuss (4).
Provincia di Milano
La Provincia di Milano ha avviato il censimento nel 1992, organizzando un gruppo di lavoro
interdisciplinare composto da tecnici interni allAmministrazione. Anche in questo caso sono
state escluse le aree protette.
Le GEV non hanno potuto completare la prima fase del censimento a causa di alcuni
problemi organizzativi; pertanto la Provincia ha provveduto a conferire a un professionista
esterno lincarico di portare a termine la fase di rilievo di campagna e la verifica delle
segnalazioni inviate da parte di alcuni Comuni. Sia durante lesecuzione dei rilievi sia nella
successiva analisi delle informazioni sono stati sostanzialmente utilizzati i criteri messi a
punto nel corso del precedente studio della Provincia di Pavia; ciò ha consentito di sottoporre
la metodologia a un valido test di verifica che ha permesso di affinare lapproccio tecnico-
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metodologico, adattandolo alla realtà provinciale del milanese. Una volta elaborato lelenco
degli alberi monumentali, la Provincia ha avviato, nel 1997, una fase di sperimentazione
invitando i Comuni a richiedere, dietro presentazione di un progetto, lerogazione di un
finanziamento per sottoporre alcuni esemplari a interventi di tutela e manutenzione
straordinaria; in totale sono stati impegnati e spesi circa 35.000.000 £ per 17 alberi.
Attualmente gli alberi monumentali sono stati inseriti allinterno del PTCP (approvato con
delibera di consiglio provinciale 14 ottobre 2003, n. 55, pubblicata sul B.U.R.Lombardia serie
inserzioni, n. 45 del 5 novembre 2003) con una norma (art. 65) che ne salvaguarda la
conservazione, fatta salva la possibilità di abbattimenti per problemi di stabilità o fitopatologici.
Dal punto di vista della cartografia del PTCP, in scala 1:25.000, la localizzazione è di tipo
ideogrammatico e quindi indicativa. In ogni caso, il Comune può chiedere alla Provincia la
localizzazione puntuale, disponibile in scala 1: 10.000.
Risultati del censimento:
segnalazioni raccolte nella prima fase
alberi monumentali
1.103,
223,
Quercus (352), Celtis (164), Platanus (126).
Tra il completamento del censimento e lapprovazione del PTCP, lelenco degli alberi
monumentali è stato aggiornato, giungendo a 233 segnalazioni corrispondenti a 1399 esemplari:
esemplari singoli
filari monospecifici
gruppi monospecifici
gruppi plurispecifici
146
22
60
5
corrispondenti a 146 esemplari,
corrispondenti a 27 esemplari.
Provincia di Brescia
La terza Provincia che ha intrapreso il censimento degli alberi monumentali è stata Brescia
che, nel 1994, ha incaricato professionisti esterni allAmministrazione. Anche in questo caso
sono state escluse le aree protette. Data la complessità territoriale che caratterizza il
bresciano è stato fondamentale il coinvolgimento delle GEV, la cui motivazione è stata
alimentata anche grazie alla organizzazione di un breve corso formativo, utile sia per delineare
un quadro generale degli obiettivi sia per fornire le adeguate precisazioni operative per una
corretta conduzione delle indagini di campagna. Inoltre, ciascun gruppo di Guardie ecologiche
volontarie è stato puntualmente seguito da un responsabile che ha operato in stretto contatto
coi coordinatori provinciali del progetto e coi professionisti incaricati. Nellambito
dellorganizzazione del lavoro si è tenuto conto di quanto emerso dalle due precedenti
esperienze, sia per lo svolgimento dellindagine di campagna sia per la successiva fase di
verifica e analisi delle informazioni raccolte. Con la Provincia di Brescia, tra laltro, il censimento
si è esteso ad altre unità di paesaggio non interessate dagli studi precedenti (aree lacustri,
prealpine e alpine), la qual cosa ha reso possibile lintegrazione degli elenchi degli alberi
censiti con le specie tipiche della flora mediterranea e delle quote altimetriche più elevate.
Risultati:
alberi monumentali
608,
339,
Fagus (177), Quercus (135), Taxodium (103).
Provincia di Sondrio
La Provincia di Sondrio ha dato il via al censimento nel 1997, avvalendosi della collaborazione
dellAzienda regionale delle foreste (ARF, oggi ERSAF). Lindagine ha interessato, a differenza
delle altre province, tutto il territorio coinvolgendo anche le aree protette.
Sullesempio della linea operativa seguita nelle altre province lombarde, il censimento si è
articolato in una fase iniziale di campagna e nella successiva verifica delle segnalazioni.
Innanzitutto le schede di segnalazione sono state distribuite a tutti i Comuni e agli operatori
di vari Enti e associazioni che si occupano a vario titolo di ambiente (es. GEV, Enti gestori dei
Parchi, CAI, Legambiente e WWF), opportunamente informati e addestrati. Altre schede
sono state distribuite anche a privati cittadini tramite comunicati stampa diffusi per mezzo di
giornali, radio e televisione. Le segnalazioni acquisite durante la fase di rilievo sono state
sottoposte a un primo riscontro comparativo che ha condotto a scartare tutti gli esemplari
che non raggiungevano una determinata soglia minima, calcolata applicando i risultati ottenuti
nelle altre province e modulata attraverso valutazioni specifiche legate al particolare ambito
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territoriale. La verifica specialistica e la successiva analisi statistica dei risultati sono state
condotte da personale tecnico specializzato. La particolare configurazione orografica della
provincia ha permesso di arricchire ulteriormente le informazioni disponibili a livello regionale,
integrando lelenco delle specie censite con lintroduzione di quelle prevalentemente alpine.
Il numero finale degli alberi monumentali non è particolarmente elevato, sia a causa dello
sfruttamento forestale dei boschi ancora in atto in questa provincia sia per la scarsa presenza
di dimore storiche che, in altre province, hanno garantito la conservazione di alcuni esemplari
nel corso degli anni divenendo, pertanto, fonte di numerose segnalazioni.
Probabilmente gli alberi monumentali individuati verranno inseriti allinterno del PTCP con
una norma che ne salvaguardi la conservazione, fatta salva la possibilità di abbattimenti per
problemi di stabilità o fitopatologici.
Risultati:
alberi monumentali
212,
168,
Castanea (24), Fagus (18), Larix (11).
Provincia di Bergamo
Il lavoro, svolto su tutto il territorio provinciale comprese le aree protette, è iniziato nel
1998 ed è ormai in conclusione. Nella fase di raccolta dei dati ci si è avvalsi della preziosa
collaborazione di GEV, aree protette, Comuni, Corpo Forestale dello Stato e varie associazioni
naturalistiche e ambientali; la loro attività ha prodotto circa 1.150 segnalazioni. Per la
successiva verifica tecnica ci si è affidati a tecnici esterni alla Amministrazione, coordinati
dallOrto Botanico di Bergamo. Le segnalazioni ritenute monumentali sono circa 400 e
attualmente si sta valutando quali inserire allinterno del PTCP con una norma che ne salvaguardi
la conservazione, fatta salva la possibilità di abbattimenti per problemi di stabilità o
fitopatologici.
Provincia di Lodi
Il lavoro, svolto su tutto il territorio provinciale comprese le aree protette, è iniziato nel
1999 ed è ormai entrato nella fase finale. Lincarico è stato affidato a un tecnico esterno alla
Amministrazione. Nella fase di raccolta dei dati ci si è avvalsi della preziosa collaborazione di
GEV, aree protette e Comuni; la loro attività ha prodotto circa 700 segnalazioni. Attualmente
sono stai selezionati circa 100 esemplari da sottoporre alla verifica tecnica.
Provincia di Como
Il lavoro, svolto su tutto il territorio provinciale, è iniziato nel 2001 ed è ormai entrato
nella seconda e ultima fase. La ricerca, a partire dallesperienza maturata nelle altre Province,
è stata caratterizzata da una fase iniziale di predisposizione delle azioni da intraprendere; a
tal fine è stato nominato un apposito Tavolo tecnico-scientifico. È stata anche verificata
lesistenza di precedenti e analoghi lavori, attività che ha consentito il recupero dei dati di
censimenti compiuti negli anni 90 da parte del WWF e del Corpo Forestale dello Stato. Nella
fase di raccolta dei dati si è cercato di coinvolgere, oltre alle GEV, le scuole, i Comuni e le
Associazioni, anche i numerosi edifici e ville storiche con parco e/giardino vincolati ai sensi
della normativa vigente. Questo lavoro ha prodotto circa 500 segnalazioni da sottoporre alla
successiva verifica tecnica. Nel corso del lavoro si è anche compiuta una rivisitazione della
scheda di rilevamento e del relativo data-base di archiviazione e di calcolo dei punteggi.
Provincia di Lecco
Il lavoro, svolto su tutto il territorio provinciale, è iniziato nel corso del 2002 ed è ormai
entrato nella seconda e ultima fase. Lincarico è stato affidato al WWF. Nella fase di raccolta
dei dati ci si è avvalsi dei volontari del WWF, mentre con le GEV si sta procedendo alla
georeferenziazione degli esemplari sinora segnalati. La prima fase di raccolta dati ha prodotto
circa 850-900 segnalazioni, che saranno sottoposte alla verifica tecnica da parte di un
esperto forestale del WWF.
Sempre con la collaborazione da parte delle GEV si stanno individuando dei percorsi
turistici alla scoperta degli alberi monumentali della provincia; attualmente si sta lavorando
su circa 15 itinerari.
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Provincia di Cremona
Il lavoro di censimento è iniziato nel 2004. Come dato di partenza si è tenuto conto di una
pubblicazione sui giardini della provincia; questi sono poco più di 100 e oltre la metà hanno
almeno un albero monumentale. Per garantire la completezza del censimento sono state
coinvolte non solo le GEV ma anche le aree protette e il Gruppo Floristico Cremonese.
Provincia di Mantova
Il lavoro è iniziato nel 2004, affidandosi a professionisti esterni alla Pubblica Amministrazione.
Sinora è stata inviata un questionario ai Comuni e alcuni hanno già risposto comunicando
dati interessanti. Ci si avvarrà anche della collaborazione delle aree protette e delle associazioni
ambientaliste e naturalistiche.
Provincia di Varese
Il lavoro è iniziato nel 2004, affidandosi a professionisti esterni alla Pubblica Amministrazione.
In ogni caso ci si avvarrà anche della preziosa collaborazione di GEV, Comuni, aree protette
e associazioni, che nella altre Province hanno contribuito in modo significativo alla fase
iniziale di raccolta dei dati.
Prospettive e sviluppi
Nel complesso si può affermare che il censimento degli alberi monumentali in Regione
Lombardia ha sinora prodotto ottimi risultati. Per completare e migliorare il lavoro si prevede
di promuovere le seguenti azioni:
· completare i censimenti ancora in corso o appena iniziati;
· estendere i censimenti anche allinterno delle aree protette, inizialmente escluse nelle
Province di Brescia e Milano;
· aggiornare in continuo i censimenti già conclusi;
· prevedere, man mano, linserimento degli alberi monumentali allinterno dei PTCP;
· prevedere linserimento dei dati in Carta Naturalistica della Lombardia;
· prevedere finanziamenti per lesecuzione di perizie e di interventi conservativi (potature,
dendrochirurgia ecc.); i fondi potrebbero essere liquidati alle Province in proporzione agli
alberi censiti; le Province, in seguito, dovrebbero predisporre un bando oppure convenzionarsi
con una ditta che provvederà a verificare tutti i casi segnalati intervenendo ove il caso;
· prevedere una serie di pubblicazioni divulgative provinciali e una pubblicazione regionale;
· prevedere una norma di legge che tuteli gli alberi monumentali e preveda lerogazione di
fondi.
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LESPERIENZA GESTIONALE DELLE PUBBLICHE AMMINISTRAZIONI NELLAMBITO
DELLA TUTELA E VALORIZZAZIONE DEGLI ALBERI MONUMENTALI: IL CASO DELLA
REGIONE VENETO
E. Piutti, G. Bullo, A. Vieceli
Azienda Regionale Veneto Agricoltura, Agripolis Legnaro (PD)
1. Premessa
Il tema degli alberi monumentali è di estrema attualità oltre che particolarmente
affascinante e di grande rilievo per la storia dellintero territorio nazionale e del paesaggio
che lo definisce. Infatti, tutela e conservazione di questi beni vegetali nasce da motivazioni
sia paesaggistiche che ambientali in quanto è riconosciuto che gli alberi, soprattutto quelli di
grandi dimensioni, costituiscono la componente più appariscente ed emozionale di qualsiasi
luogo e ricoprono un ruolo fondamentale nel determinarne il valore.
Gli alberi sono una delle forme di vita più antiche della terra, silenziosi testimoni
dellevoluzione dellumanità e del passaggio del tempo. La consapevolezza che tali monumenti
naturali, caratterizzati da unelevata ricchezza genetica che li rende tanto forti da superare
le siccità più lunghe e resistere ai freddi più intensi, siano giunti fino ai giorni nostri dopo una
lunga e complessa evoluzione attraverso i secoli deve far riflettere anche sul loro valore
storico-culturale e testimoniale. Gli alberi monumentali, inoltre, costituiscono un peculiare
elemento del patrimonio architettonico ed artistico, caratterizzando ed arricchendo gli ambienti
esterni di ville, residenze e palazzi storici, dove spesso sono potuti sopravvivere salvaguardati
da eventi bellici e dalle modificazioni urbanistiche degli ultimi decenni. Vanno così considerati
come beni preziosi da tutelare e conservare nel tempo, costituendo globalmente un patrimonio
naturale e paesaggistico con valenza composita meritevole di attenzione.
Un albero monumentale ha perciò un grande valore ecologico, estetico e culturale e va
valorizzato in quanto componente della memoria collettiva e componente significativa dei
paesaggi.
Tuttavia, a causa della longevità e senescenza, degli interventi di ripristino e
dellinterferenza con le infrastrutture adiacenti, gli alberi monumentali sono piante molto
vulnerabili e maggiormente soggette a deperimento. Strettamente connesse alla loro presenza
sono le problematiche relative alla manutenzione ed al ripristino ambientale ed architettonico
nonché allo spinoso problema delle responsabilità, della gestione e del tipo degli interventi,
trovandosi spesso in aree pubbliche e ad elevata valenza sociale.
2. La situazione normativa regionale e nazionale a supporto del censimento e della
catalogazione
Soprattutto dagli anni 90 la maggior parte delle Regioni si sta dotando di norme per la
tutela, la valorizzazione e la conservazione del patrimonio vegetale di alto pregio e, più
specificatamente, degli alberi monumentali.
Molti sono i lavori disponibili di censimento e schedatura delle piante monumentali, avviati
dalle singole amministrazioni ed associazioni ambientaliste e culturali. La metodologia seguita
è quella già utilizzata per il censimento del verde urbano (impiego di un sistema informativo
geografico e di schede di rilevamento informatizzate per la raccolta delle caratteristiche
morfologiche, fitosanitarie e di stabilità, strutturazione di un database per la programmazione
e la gestione degli interventi e costi di manutenzione, ecc.). Numerosi ormai sono gli esempi
sia a livello regionale italiano che internazionale di elenchi e pubblicazioni sugli alberi monumentali
in ampi ambiti territoriali o più specificatamente di quelli in ville, parchi e giardini.
3. Lesperienza gestionale delle pubbliche amministrazioni: la Regione Veneto
3.1 Quadro storico
Nel Veneto il primo organismo istituzionale ad occuparsi di alberi monumentali è stato il
Corpo Forestale dello Stato che nel 1982 ha effettuato un censimento che ha interessato gli
alberi che come singoli soggetti arborei hanno una propria individualità per essere
eccezionalmente vecchi, per essere stati protagonisti di episodi storici o per essere legati
alla vita di grandi uomini o di Santi. Liniziativa, lanciata al livello nazionale nellestate del
1982 e condotta dal personale del Corpo Forestale dello Stato, ha censito, in Veneto, 57
alberi.
La Regione Veneto, nellambito dei lavori di redazione del Piano Regionale di Coordinamento,
ha avviato, nel 1987, un censimento degli alberi monumentali della Regione. Tale censimento
è stato articolato per provincia e a tal fine è stata elaborata una scheda. I lavori di rilievo,
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eseguiti dal WWF, hanno dato luogo ad una pubblicazione per ogni singola provincia censita,
curata dalla Segreteria regionale per il territorio dal titolo I grandi alberi della Provincia di
.. Il censimento, sospeso nel 1995, ha consentito la pubblicazione di 5 Province su 7 con i
seguenti risultati:
Successivamente alcune amministrazioni provinciali hanno effettuato autonomamente
attività di censimento. E il caso, ad es., della Provincia di Padova che ha eseguito un
censimento e una catalogazione degli alberi monumentali presenti nel suo territorio. I dati
sono stati inseriti in un programma di gestione informatico. Per ogni singolo albero censito è
stata effettuata lindagine di stabilità secondo il metodo VTA (Visual Tree Assessmant),
consentendo così di individuare leffettivo stato di salute degli alberi e i soggetti a rischio
nonché di raccogliere gli elementi per poter mettere in atto le misure di salvaguardia. Il
censimento è stato inoltre arricchito da una ricerca storica. Gli alberi censiti dalla Provincia
di Padova sono 92. Anche lAmministrazione Provinciale di Venezia, visto il mancato
completamento del censimento regionale ha deciso di procedere in proprio al censimento
degli alberi monumentali presenti sul proprio territorio, che è stato completato nel 2002. Il
lavoro è stato reso noto con una pubblicazione che descrive 166 degli alberi censiti.
3.2 La Legge Regionale del Veneto n. 20 del 9 agosto 2002
3.2.1 Finalità e definizioni
La legge regionale n. 20/2002 Tutela e valorizzazione degli alberi monumentali, detta
norme per lindividuazione degli alberi monumentali di alto pregio naturalistico e storico, di
interesse paesaggistico e culturale presenti nella Regione Veneto. Il testo di legge definisce
come alberi monumentali di alto pregio naturalistico e storico e di interesse paesaggistico e
culturale:
a) gli alberi isolati o facenti parte di formazioni boschive naturali o artificiali che per età o
dimensioni possono essere considerati come rari esempi di maestosità o longevità
b) gli alberi che hanno un preciso riferimento a eventi o memorie rilevanti dal punto di vista
storico o culturale o a tradizioni locali.
3.2.2 Competenze
La legge regionale individua lAzienda Regionale per i settori agricolo, forestale e agroalimentare, Veneto Agricoltura, ente pubblico economico della Regione Veneto, quale soggetto
competente per listituzione dellelenco regionale degli alberi monumentali, incaricando la
stessa di definire la metodologia di rilevazione e i contenuti informativi della scheda tipo, che
dovrà almeno contenere i dati caratteristici di vegetazione e i criteri di tutela. Linserimento
nellelenco regionale degli alberi monumentali avviene su proposta diretta delle Province, dei
Comuni, delle Comunità Montane e degli Enti Parco oppure a seguito di segnalazioni di singoli
cittadini o associazioni ai medesimi enti che trasmetteranno a Veneto Agricoltura la
segnalazione corredata da un proprio parere. La scheda tipo e lelenco regionale degli alberi
monumentali sono pubblicati nel Bollettino Ufficiale della Regione del Veneto. Lelenco verrà
aggiornato periodicamente. Oltre a Veneto Agricoltura, le strutture regionali interessate
sono i Servizi Forestali e i Servizi Fitosanitari che assicurano rispettivamente lassistenza per
gli aspetti agroforestali e fitopatologici in merito agli alberi dellelenco.
3.2.3 Valorizzazione e tutela
LAzienda Regionale Veneto Agricoltura, le Province, i Comuni, le Comunità Montane e gli
Enti Parco promuovono iniziative di pubblicizzazione e di valorizzazione degli alberi inclusi
nellelenco al fine di divulgarne la conoscenza, il significato di tutela nonché per migliorare il
contesto territoriale e ambientale circostante. Gli alberi inseriti nellelenco sono segnalati
come Albero Monumentale Protetto. I Comuni riportano nel proprio strumento urbanistico
generale gli alberi monumentali protetti e le relative aree di pertinenza dettando apposita
normativa di tutela. Gli interventi per una corretta manutenzione e conservazione degli alberi
monumentali sono autorizzati dal Comune previa acquisizione di un parere tecnico delle
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strutture regionali competenti in materia di servizi forestali e fitosanitari. È vietato a chiunque
abbattere, danneggiare o comunque modificare la struttura degli alberi monumentali inseriti
nellelenco regionale, salvo pareri degli enti competenti. Labbattimento dei alberi inclusi
nellelenco può avvenire per esigenze di pubblica incolumità o per esigenze fitosanitarie e
comunque dopo aver accertato limpossibilità ad adottare soluzioni alternative. I comuni e le
strutture regionali competenti in materia di servizi forestali e fitosanitari vigilano sullapplicazione
delle disposizioni della presente legge.
3.3 Metodologia utilizzata
Sulla base delle finalità e delle disposizioni della legge regionale n. 20/2002, lAzienda
Regionale Veneto Agricoltura ha predisposto un piano triennale di lavoro dal 2003 al 2005.
Fase 1
a. Organizzazione, da parte di Veneto Agricoltura, di un incontro a livello regionale al quale
sono stati chiamati a partecipare tutti gli Enti e le Associazioni che si sono occupati in
passato o che si occupano oggi di alberi monumentali nonché gli Enti Territoriali interessati
dalla Legge per la futura applicazione del vincolo; nellincontro è stato illustrato il contenuto
della Legge e presentata la bozza di programma di lavoro che ha dato luogo ad un
partecipato e costruttivo dibattito.
b. Istituzione di una Commissione Tecnica Consultiva costituita da un rappresentante di
Veneto Agricoltura, della Direzione Foreste ed Economia Montana della Regione Veneto,
del Servizio Fitosanitario Regionale, del Dipartimento TESAF (TErritorio e Sistemi AgroForestali) dellUniversità di Padova, del Corpo Forestale dello Stato, della Soprintendenza
per i Beni architettonici ed il Paesaggio del Veneto, dellAssociazione Nazionale Comuni
dItalia e del WWF - sezione regionale del Veneto. La Commissione ha il compito di fornire
a Veneto Agricoltura il proprio parere tecnico in merito allinclusione degli alberi nellelenco
regionale. Svolge inoltre un ruolo consultivo in merito alla definizione della scheda tipo per
il rilevamento, alla definizione dei criteri di selezione e delle metodologie di rilevazione.
c. Determinazione dei requisiti che qualificano una pianta come monumentale e dei criteri di
selezione;
d. Raccolta e selezione del materiale pubblicato già esistente relativo alle piante già censite
e verifica della disponibilità di altri dati rilevati e non ancora pubblicati;
e. Definizione di una scheda tipo di censimento in linea con i requisiti richiesti dalla legge
regionale (art. 3 comma 2) e conforme sia agli standard di catalogazione e inventario
proposti dalla scheda PG Parchi e Giardini dellIstituto Centrale per il Catalogo e la
Documentazione del Ministero per i Beni e le Attività culturali;
f. Progettazione di un software per la gestione delle schede per ogni singola pianta
(localizzazione e georeferenziazione, informazioni amministrative, dati morfologici e botanici,
dati fitopatologici, dati storico-culturali, criteri di tutela, foto e bibliografia, ecc.)
Fase 2
a. Istituzione di un tavolo provinciale per la verifica della selezione eseguita sul materiale
pubblicato (fase 1.d.); sono chiamati al tavolo provinciale gli Enti Territoriali, gli altri Enti
Pubblici e le Associazioni interessati dallargomento (Servizi Forestali, Corpo Forestale
dello Stato, Servizi fitosanitari,);
b. Sopralluoghi in campo al fine di verificare e implementare le informazioni raccolte nelle
schede già esistenti, applicando i criteri e le schede di cui alla fase 1, così da ottenere un
primo inventario degli alberi monumentali;
c. Individuazione delle piante appartenenti al primo inventario con possibili problemi relativi
alla stabilità e allo stato fitosanitario;
d. Informatizzazione delle schede relative al primo inventario con georeferenziazione.
Fase 3
a. Approfondimento dello stato fitosanitario e verifica della stabilità per le piante per le quali
sono stati individuati problemi di sicurezza;
b. Cartellinatura delle piante inserite nel primo inventario: Regione Veneto Albero
monumentale;
c. Formulazione di indicazioni operative sulla pianificazione e sulle modalità di gestione del
patrimonio arboreo censito per i Comuni interessati (o gli Enti Gestori nel caso di Parchi o
Riserve);
d. Divulgazione: predisposizione di un link a tema su sito web dellAzienda Regionale Veneto
Agricoltura, produzione di un CD rom e di un depliant illustrativo del progetto.
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I principali aspetti da evidenziare nelle fasi di lavoro sono i seguenti:
- la costituzione della Commissione tecnica consultiva che consente di poter disporre del
contributo e della competenza di esperti afferenti a varie discipline;
- la predisposizione di due prospetti (Tabella 1 e Tabella 2) utili ai fini della classificazione di
una pianta come monumentale, in cui sono indicati vincoli e criteri di priorità per la scelta
delle piante da inserire nellelenco;
Tabella 1 - Vincoli per la classificazione delle piante monumentali
Deroghe a V1, V2 e V3 potranno essere ammesse con specifica motivazione
Tabella 2 Criteri di priorità per la classificazione delle piante monumentali
- la raccolta di tutti i censimenti realizzati nel Veneto in più di un ventennio di attività da
parte di vari Enti e Associazioni e avvio della selezione per lelenco regionale da questo
materiale raccolto;
- listituzione del tavolo provinciale che consente di poter disporre della competenza e della
conoscenza del territorio che di chi, per lavoro o per passione, percorre quasi quotidianamente
le aree dove vegetano gli alberi da selezionare;
- accanto allelenco degli alberi monumentali sarà redatto un elenco di alberi notevoli.
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4. Problematiche emerse
Le difficoltà finora incontrate nello sviluppo delle fasi di lavoro possono essere brevemente
sotto elencate:
1. Mancanza di documenti normativi nazionali di riferimento per la classificazione di piante
di pregio e per la omogeneizzazione della metodologia di rilievo e censimento
Infatti, se da un lato è consolidata lopinione che lalbero monumentale è un bene ambientale,
meritevole di conservazione e tutela, ancor oggi si deve purtroppo constatare che a livello
normativo nazionale le cose non sono ben chiare o per lo meno sussiste un approccio ancora
approssimativo legato a criteri di catalogazione non esplicitati e codificati in maniera univoca
per tutti. Ad oggi infatti, non è stato ancora proposto alcun protocollo operativo ufficiale, a
livello nazionale, sulle modalità di individuazione, di censimento, di catalogazione e di gestione
degli alberi monumentali, lasciando alle amministrazioni locali piena libertà sullorganizzazione
del lavoro. Il Decreto Legislativo n. 490 del 1999, così come il recentissimo Codice dei Beni
culturali e del Paesaggio (art. 10 punto 4 lett. f), pur sancendo limportanza del patrimonio
ambientale e paesaggistico, non considera esplicitamente lelemento albero come un bene
monumentale da conservare nonostante presenti un indiscutibile valore storico, estetico,
paesaggistico, ambientale. Inoltre, lattuale scheda Parchi e Giardini proposta dal Ministero
per i Beni Culturali e Ambientali (Istituto Centrale per il Catalogo e la Documentazione, 1994)
inquadra il bene parco o giardino, senza però considerare adeguatamente gli alberi quali
principali elementi vegetali che compongono e determinano il valore stesso del parco.
Infine, anche se vengono comunemente classificati alberi monumentali quelle piante
imponenti che suscitano meraviglia per unicità ed armonia, caratterizzate da longevità e
dimensioni notevoli, da forma o portamento molto particolari e rare, da essere considerate
rarità botaniche o collegate con edifici storici o monumentali, con fatti storici, tradizioni o
leggende, manca una metodologia standard di rilievo valida ad ampia scala; pertanto non è
possibile, o risulta difficile, fare confronti fra diverse realtà territoriali. Questo permetterebbe
di avere un approccio oggettivo alla catalogazione del bene da tutelare, slegato da criteri
soggettivi ed emotivi di valutazione, soprattutto nei casi di alberi che già sottostanno a
vincoli o che richiederebbero finanziamenti per interventi di manutenzione.
2) La legge non prevede le modalità di applicazione del vincolo
Una volta realizzato il primo elenco regionale degli alberi monumentali, sarà necessario
individuare le modalità di applicazione del vincolo.
3) Difficoltà a reperire finanziamenti e specifici contributi per gli interventi sia di tipo
fitosanitario che di messa in sicurezza degli alberi monumentali
Nella legge regionale del Veneto n. 20/2002 per la tutela e valorizzazione degli alberi
monumentali non sono previsti contributi specifici per la valorizzazione degli esemplari
monumentali individuati nellapposito elenco. Questo aspetto è molto delicato in quanto la
pianta monumentale può essere vista non come un pregio bensì come un onere dal singolo
proprietario o amministrazione comunale, impossibilitati spesso a far fronte alle spese di
manutenzione, restauro e messa in sicurezza. Quando lelenco degli alberi monumentali verrà
pubblicato nel Bollettino Ufficiale della Regione ed il vincolo di tutela diverrà quindi effettivo,
sarà indispensabile poter disporre di un finanziamento per lesecuzione degli interventi di
messa in sicurezza degli alberi.
5. Conclusioni
La finalità del lavoro promosso dalla legge regionale del Veneto sulla tutela e valorizzazione
degli alberi monumentali è quella di far prendere coscienza di questo enorme patrimonio
naturalistico ai cittadini veneti. La tutela e conservazione sono, in unottica di sviluppo
sostenibile e valorizzazione delle risorse ambientali, i primi e basilari strumenti per trasmettere
alle generazioni future limportanza e il rispetto di tale patrimonio.
Solo così ogni cittadino si potrà impegnare in prima persona per difendere questi giganti
della storia e potrà essere direttamente coinvolto in azioni di promozione e divulgazione
relative alla conoscenza e al significato storico-culturale del patrimonio arboreo paesaggistico
regionale. Infine, sarebbe auspicabile che i contributi di studio e il know-how prodotti dalle
singole regioni potessero confluire in un unico lavoro di sintesi a livello nazionale con
individuazione e definizione di criteri e metodologie organiche di catalogazione; ciò potrebbe
servire alla conservazione e gestione delle piante di pregio, al controllo fitosanitario e alla
messa in sicurezza nonché, forse, ad uneventuale pianificazione dei finanziamenti necessari
per gli interventi.
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6. Bibliografia di riferimento
AA.VV. 1990. Gli alberi monumentali dItalia: il Centro e il Nord. Ed. ABETE, Roma.
AA.VV. 1991. Grandi alberi e monumenti naturali nel Friuli-Venezia Giulia. Regione Autonoma del
Friuli Venezia Giulia, Az. Parchi e Foreste Regionali, pp. 223.
Corona P., Salbitano F. 2001. Aspetti progettuali e di gestione delle alberature urbane. EM Linea Ecologica 33(3): 11-25.
Credano V., Pirola A. 1975. La vegetazione della Provincia di Sondrio. Amm. Provinciale Sondrio,
Banca Credito Valtellinese, Sondrio.
Dalla Fior G. 1985. La nostra flora. Ed. G.B.Monauni, Trento 1985
Fenaroli L. 1967. Guida agli alberi dItalia. Ed. Marcello, Milano.
Gellini R. 1985. Botanica forestale (Testi I e II). Ed. CEDAM, Firenze
Hageneder F. 2001. Lo spirito degli alberi. Ed. Crisalide, pp. 439.
Harrison R.P. 1982. Foreste. Lombra della civiltà. Garzanti, pp.300.
Pignatti S. 1982. Flora dItalia. Edagricole, Bologna.
Provincia di Brescia. 1996. Alberi monumentali della provincia di Brescia. Il Verde Editoriale, Milano.
Provincia di Brescia. 1996. Censimento degli esemplari arborei monumentali del territorio della
provincia di Brescia da sottoporre a tutela ex L.R. 30.11.83 n.86. Il Verde Editoriale, Milano.
Provincia di Milano. 1996. Censimento degli esemplari arborei monumentali del territorio della
provincia di Milano da sottoporre a tutela ex L.R. 30.11.83 n.86. Settore Ufficio del Piano, Milano.
Regione Emilia-Romagna. 1991. Alberi monumentali dellEmilia-Romagna Censimenti e tutela
(Volume n.43). Assessorato Ambiente/Istituto Beni Culturali, Bologna.
Regione Lombardia. 1997. Direzione Generale Tutela Ambientale. Criteri e metodi per il censimento
degli alberi monumentali Documento tecnico. Milano.
Semenzato P. (a cura di) 1999. Il verde storico. Teoria e tecnica di conservazione e restauro.
Regione Veneto, Direzione Cultura e Az. Reg. Veneto Agricoltura, pp. 102.
Summary
This paper outlines the importance of veteran trees under the naturalistic, cultural,
social and landscape point of view. Then, it is referred the aim of the regional law for
defence and protection of veteran trees and the methodology proposed by the Regional
Agency Veneto Agricoltura to arrange the veteran tree list for the Veneto Region. Problems
faced during the work development are presented and discussed.
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IL SISTEMA REGIONALE PER LA CONSERVAZIONE DELLA NATURA.
LA TUTELA DEGLI ALBERI MONUMENTALI E LA CONSERVAZIONE DEL PAESAGGIO IN
PUGLIA
M. Saccomanno
Ufficio Parchi e Riserve Naturali, Assessorato allAmbiente Regione Puglia
La tutela del patrimonio di alberi monumentali assume una particolare rilevanza in Puglia in
relazione ad alcune specificità. Da un lato la regione appare essere quella con la più bassa
percentuale di boschi (149.400 Ha pari al 7,75% della superficie regionale), dallaltra la sua
posizione geografica gli ha conferito nel tempo un notevole patrimonio di biodiversità. La
Puglia è definita infatti regione delle dieci querce, due delle quali appaiono esclusive della
nostra regione (Quercus trojana webb, Quercus macrolepis), ospita con la foresta Umbra, la
più estesa formazione di latifoglie in Italia (circa 15.000 Ha), presenta estese formazioni di
Pinus halepensis.
Il carattere determinante della pianura e delle limitate pendenze ha favorito nei secoli la
forte riduzione del manto forestale, la cui presenza è testimoniata oggi proprio da vetusti
alberi isolati. La tutela di tali esemplari viene operata attraverso il Decreto legislativo 29
ottobre 1999, n° 490
Testo Unico delle disposizioni legislative in materia di beni culturali e ambientali che
agisce nei casi in cui vi è anche un valore storico del contesto di inserimento e dalla
normativa regionale L.R. n° 14 del 31-05-2001 Art. 30 Tutela paesaggistica degli alberi che
prevede la istituzione di un albo regionale dei monumenti vegetazionali. Per gli esemplari
dellalbo è previsto il divieto di espianto e un regime sanzionatorio per gli abusi.
La L. R. n.19 del 24-07-1997 Norme per listituzione e la gestione delle aree naturali
protette nella Regione Puglia prevede altresì allart. 2 - Classificazione delle aree naturali
protette listituto dei monumenti naturali.
Le azioni svolte sinora hanno riguardato una prima fase di conoscenza, favorita dalla
diffusione di una scheda di censimento e successiva valutazione e validazione delle segnalazioni
pervenute agli uffici regionali. Si sta procedendo inoltre ad un raccordo con altri enti (CFS,
Ispettorati Forestali regionali) per lazione di tutela e ulteriore indagine.
La problematica della tutela degli alberi monumentali non riguarda solo le specie di interesse
forestale, lo dimostra il caso del commercio ed espianto degli ulivi in Puglia. Si tratta di un
caso complesso per due motivi: da una lato le dimensioni del problema, dallaltro limportanza
economica della coltura dellolivo nella regione. In Puglia ci sono oltre 350.000 Ha coltivati ad
ulivi, pari al 25% della superficie regionale. Sono interessati tutti i comuni della regione.
Lulivo è il simbolo stesso del paesaggio pugliese.
Lulivo, specie originaria del medio oriente, mostra i primi segni della sua presenza in Puglia
in ritrovamenti preistorici tra Torre a Mare e Fasano (sud della provincia di Bari) risalenti al
Neolitico, in periodo databile a circa 5000 a.C. Per avere unidea dellimportanza dellulivo
nella cultura regionale basti pensare che le antiche monete, gli stateri e le dracme tarantine
del VI-V sec. a.C., riportano leffige di satiri coronati dulivo. La presenza dellulivo si sostanzia
in Puglia anche nei numerosi frantoi ipogei di epoca remota, attraverso la cui analisi è stato
possibile verificare come avveniva sin da tempi lontanissimi la spremitura delle olive.
Secondi i dati del 2000 lolivocoltura pugliese produce un reddito di 760 milioni di euro
allanno. Vi sono cinque D.O.P. di produzione e la sua importanza è tale che sono stati
realizzati quattro grandi itinerari turistici denominati vie dellolio. Sono attivi 1200 frantoi,
che trattano le 53 diverse varietà di olive coltivate in regione.
Vi sono 50 milioni di piante di ulivo in Puglia, di questi circa 15 milioni di esemplari sono
censiti come ultracentenari e si può certamente stimare un numero non inferiore ai tre milioni
di esemplari pruricentenari e dotati di particolare valore paesaggistico ed estetico.
La notevole longevità dellolivo, con esemplari che in Puglia raggiungono i duemila anni,
sembra legata in parte allestrema capacità rigenerante della specie , in grado di rinascere
dal tronco reciso, cosi come dai robusti germogli che si affacciano anche dalle parti più
antiche dell albero. Le aspre condizioni climatiche caratterizzate da aridità, un difficile
substrato con roccia affiorante a pochi centimetri dalla superficie, la frequenza degli incendi,
il delicato equilibrio tra metabolismo dellalbero e potature, conferiscono agli esemplari di età
più avanzata un alternarsi di legna secca dallaspetto pitreo e vasi turgidi, ricche di linfa,
diretti alle parti in vegetazione. Il risultato è uninsieme di sculture viventi dallaspetto
fortemente suggestivo. Ma questi caratteri di rusticità e di adattabilità, se da una lato ci
hanno consegnato una pregevole eredità paesaggistica ed economica, dallaltra si stanno
traducendo in penoso rischio di impoverimento del paesaggio pugliese, per la relativa facilità
177
dellespianto e della vendita degli esemplari più pregevoli esteticamente. Nonostante limpegno
di istituzioni e cittadini la Puglia perde giornalmente significativi pezzi della sua identità. Ulivi
secolari si acquistano, spendendo dai 2 a 8-10 mila euro a pianta, e vengono richiesti per
arredare i giardini del nord Italia e dellEuropa centrale.
Le dimensioni del problema determinano la estrema difficoltà di schedatura di tutti gli
esemplari rappresentativi e la complessità di varare norme che vietino lespianto senza
confliggere con le esigenze produttive e con il diritto dei proprietari.
Lunica normativa di riferimento è una vecchia legge emanata da Umberto II: il decreto
legislativo luogotenenziale n. 475 Divieto di abbattimento di alberi dolivo del luglio 1945.
La norma è nata nellimmediato dopoguerra per limitare la tendenza allespianto di ulivi per
ricavarne legna da ardere, con il fine di tutelare la produzione. La norma prevede il divieto di
abbattimento di alberi di olivo oltre il numero di cinque ogni biennio, tranne in caso di morte
fisiologica degli alberi, permanente improduttività o eccessiva fittezza dellimpianto.
Attualmente si stanno perseguendo due vie per la tutela di questo patrimonio. Una di
analisi e raccolta dati per una maggiore comprensione del problema, laltra di maggiore
sensibilizzazione della popolazione e di raccolta dei dati. I primi risultati mostrano che gli ulivi
pluricentenari sono raramente presenti in forma isolata, più spesso sono raccolti in
appezzamenti agricoli piuttosto omogenei. E il caso di Mass. Pettolecchia, nei pressi di
Fasano (Br) dove è stato messo in evidenza che vi sono 3000 ulivi pluricentenari, alcuni dei
quali millenari, in una relativamente ridotta superficie aziendale.
Tali aree possono comunque essere messe in evidenza con luso di ortofoto carte, grazie
al caratteristico sesto di impianto irregolare, che una volta individuato può essere verificato
attraverso lanalisi diretta dei siti. Resta da definire il modo con il quale intervenire sotto il
profilo normativo per tutelare questi particolari paesaggi produttivi. Per una maggiore azione
di sensibilizzazione si sta procedendo con la creazione di una scheda di censimento specifica
per lulivo. Infatti i caratteri morfologici che individuano le specie di interesse forestale
(diametro del tronco, altezza dellalbero) non si adattano allulivo.
La nuova scheda si basa piuttosto su alcune caratteristiche del tronco (forma spiralata,
aspetto dellapparato radicale, ecc.). Con questo sistema sarà facilitata lindividuazione degli
esemplari isolati ed anche dei contesti più rappresentativi, accanto ad unazione di
sensibilizzazione dei cittadini.
Non si tratta ancora della soluzione del problema, ma certamente di unazione che riteniamo
potrà portare in tempi medio-brevi ad una forte riduzione dellespianto e traffico di pezzi del
nostro paesaggio.
178
MONUMENTAL TREES AND RELICT VEGETATIONAL FORMATIONS OF THE PROVINCE OF
MATERA: INTERVENTIONS OF PROTECTION AND VALUE INCREASE
E.L. De Capua, C. Rugge
1. Introduction
The former denomination Lucania of Regione Basilicata, evokes what once was the
natural landscape of this Region, dominated by the forest (lucus) and testifying its ancient
sylvan-pastoral origins.
Also the lucanian forest landscape has suffered deep modifications through the ages.
Nevertheless interesting traditions have remained intact, which are tightly connected to
ancient uses and customs of the various civilizations that alternated in the territory at
different times. They concern celebrations and cults devoted to trees.
The presence of important forest resources, characterizing the Province of Matera, has
stimulated different studies, in particular on the relict vegetational realities, being rare ones,
as well as on the suggestive monumental trees that grow within its territory.
Such natural resources, connected to their historical and cultural aspects, represent
fundamental elements to build up an educational knowledge path about the environment,
underlining the signs that the human and natural history have handed down to us. In order
to reach this goal, the Province of Matera has started and extended a series of interventions,
aimed at protecting and raising the value of the forest resource in general and in particular
of the unusual patrimony represented by the monumental trees. These deserve to be preserved
for their noteworthy scientific-cultural and aesthetical value, being, moreover, important
testimonies of the native Italian wood patrimony.
2. History and cult of the tree in the province of Matera
Traditions and historical references about forests and trees offer very interesting hints
for the Lucanian territory and particularly for the province of Matera. The Greek civilization,
that mainly concerned the Metapontino Plain, introduced new cults and religious forms, to
be identified in the natural cycles.
In the classical age trees were object of cult and
humanized, as it happened for instance for Dafne, the mythical nymph transformed into
laurel, or for the fantastic forests populated by splendid female divinities called Driadi.
Already between the III and the VI century B.C., in the territory of Policoro (the ancient
Heraclea), the first laws concerning forest matters were passed. They still represent the
only document regarding the forest ecosystem in pre-Roman Age.
Besides offering accurate indications on the type of environment at those times, these
laws, written on bronze boards, enacted the obligation for farmers to replace the trees that
had been cut along the Agri river banks with others of the same species. In this way the
lands that were sacred to Dionisio and Atena would not be deprived of their natural beauties.
In the Roman Age the cult of the Italic god Silvano was widespread in the valley of the
river Sele. It was the god of the woods and the countryside, to whom Autumn propitiatory
rites were devoted. In the following centuries, the reduction of the forest surface mostly
concerned the hilly areas, that allowed better general conditions of life compared with the
ones in coast and mountain areas. In particular in the Lucanian territory, the work of
deforestation continued despite the special Law for the Basilicata passed in the 1904,
better known as Zanardelli Law, aimed at somehow stopping the devastation of Lucanian
woods. As in the rest of Italy, with the advent of Fascism, also in Basilicata the reforestation
and realization of urban parks favored a progressive change of the forest landscape. In fact
both the area of the Ionian coast and the one of the Materan hill, are dominated by the
presence of artificial settings of conifers, with a prevalence of Pinus halepensis, replacing
the natural formations merely reduced to relict evidence today.
The ancient pagan cult linked to the wood and tree is still strongly felt today by Lucanian
people and brought back to life through the celebrations of the May, celebrating the
nuptial rite between the prince of the trunks (Quercus cerris) and its top (Ilex aquifolium).
3. Vegetational patrimony and monumental trees
The natural environment of Basilicata shows extremely heterogeneous physical and
biological characteristics to which different vegetational landscapes correspond: from the
hilly to the mountain system, from the torrential basin to the duny environment and the
damp zones, from the natural parks to the reservations, not to forget the artificial
reforestations, the urban parks and the gardens.
179
The whole Region belongs to the Mediterranean climatic area, boasting the presence of
almost all its vegetational Plains. Within the Lucanian territory, in fact, you can find groups
of plants belonging to the thermo-Mediterranean Plain, that is strongly characterized by the
presence of thermopile vegetation, in particular sclerofilles such as the oleo-lentiscetis and
the Mediterranean pines. Or you can find vegetation belonging to the meso-Mediterranean
Plain where you can easily see the Leccio (Quercus ilex) and the thorny Oak (Quercus
coccifera). Moving from the valley of the Basento upward, these plains are overhung by the
supra-Mediterranean plain, with its characteristic deciduous oak woods, and by zones belonging
to the Mountain Mediterranean plain, where areas of forest with Abies alba grow.
In particular in the Province of Matera important relict vegetational evidence has survived.
The Wood of Policoro (Oriented Natural Reservation managed by the Province) represents
the last remains of what was the luxuriant forest maze of tall and deciduous trees ,
described by Norman Douglas, in 1907, when the English writer measured, inside the dense
brushwood, a lentisco having a three meter circumference. The present remains of the
wood represent what is left of the two complexes called wood of the Pantano soprano
and wood of the Pantano sottano, that were, up to some decades ago, one of the widest
plain forests in Southern Italy. It is a hydric wood linked to the Carici-fraxinetum angustifoliae,
dominated by the ossifillo Ash tree, with the presence of numerous other species, among
which the Rural Elm, the Farnia, the black Ontano, the Poplars and the Laurel. When not
subjected to systematic wood culture interventions, this forest had arboreal specimens of
considerable size, reduced to sporadic samples today.
Different areas of the Province of Matera along the Ionian coast belong to the same
context. Here important shrubby formations of the Mediterranean bush grow with a prevalence
of juniper and lentisco. The latter is present at various stages, from the gariga to the tall
bush, where the shrubby elements often exceptionally assume arboreal forms.
Among these, numerous specimens could be considered monumental trees due to the
exceptional sizes and the age, as well as their strange forms forged by the main wind,
blowing from the sea. In the province of Matera, within the territory of the Teresa Forest
, isolated specimens of Juniperus macrocarpa, whose age has been assessed about 110
years, have been individuated. In the Materan Comune of Montescaglioso, within the area
called the Monks Olive-grove, a small wood area of about half hectare still exists, mainly
composed of specimens of Pinus halepensis. In this group, formed by numerous plants of
more than one century, a specimen of over 110 years stands out. This specimen has got a
trunk with a four meter circumference growing up to about three meters and splitting itself
into two big branches of 70 cm of diameter each.
Moreover there are numerous specimens of deciduous oaks, typical of the upper plain, of
exceptional massive structure and longevity.
Among the innumerable examples, a specimen of Quercus pubescens, growing in the
place called Calla , in the Comune of Tricarico, stands out. Its age has been estimated to
be 600 years. It seems to be the oldest plant in whole Lucania, having a height of 16 m. and
a trunk circumference of 6,25 m. A further example of the extraordinary longevity of this
specimen is in the area called Pocco Hill in Oliveto Lucano. The Cersone, as it is called
by the inhabitants of Oliveto, is more than one hundred years, a height of 18 m. and a
circumference of 5,30 m. Among the suggestive calanchis of the Comune of Pomarico, in the
area of Melito Plain , four stately specimens of Pinus pinea grow. Their age has been
estimated to be about 160 years. They have a height of 30 m. and trunk circumference
between 2 and 3.5 m.
The following table sums up a list of the main plants having a particular naturalistic and
landscape value to be protected according to the Regional Law n. 42 of 22-5-1980, passed
with Decree by the President of the Regional Assembly of January 4 th 1988 n.3.
Tab.1 - List of the trees having major
naturalistic and landscape value in the Province of Matera
Kind Common Place Età(anni) C1,30(cm) Htot Posizione
Salix babylonica Aliano Acinello 25 175 14 isolated
Tamarixgallica Matera Cilvestri 50 140 3,50 isolated
Juniperusmacrocarpa Matera Forest Teresa 100 160 12 isolated
Phoenixdactiliphera Matera BorgoLa Hammers 100 220 8 isolated
Rhamnusalaternus Matera Forest Teresa 50 70 4 isolated
Quercus trojana Matera Farm S.Francesco 100 150 12 in group
Pinushalepensis Montesca-glioso Olive-grove deiMonaci 100 370 25 in group
180
Taxodium disticum Pomarico S. Felice 150 80 20 in group
Quercus pubescens OlivetoLucano Calle lily Rocco 300 530 18 isolated
Pinushalepensis OlivetoLucano Olive-grove / Accettura 50 270 18 isolated
Trembling Populus OlivetoLucano Scarrone 50 115 14 in to spin
Pinus pinea Pomarico Plan MelitoDemanio 150 307 30 in group
Salyxbabylonica Salandra Villa 35 80 12 isolated
Quercus pubescens Tricarico Calle lily 600 680 16 isolated
Fig. 1
An ancient Ceratonia siliqua in Montescaglioso (MT)
4. Interventions of protection and value raise
The Province of Matera intends to continue with the activity of preservation and value
raise of its own forest patrimony, by promoting a series of scientific and historical - naturalistic
studies aimed at defining the most appropriate ways of action and intervention. It has
undertaken for a long time scientific and geo-historical studies on the relict woods and on
the numerous monumental trees of the Province. The necessity of an interdisciplinary approach
is of fundamental importance, also because of the complexity of the territory and the
problems concerning the preservation of monumental trees. Such trees, being ancient and
very big specimens, need phytosanitary analysis, to prevent deterioration to take place,
and investigations about their stability. To such purpose the Province of Matera proposes to
collect the necessary data for the management and application of the appropriate culture
measures to adopt within a short period and over a longer one.
The numerous activities and implications coming out around a monumental tree have
given the idea for the institution of an Observatory on the relict woods and the monumental
trees of the Province of Matera. Given the institutional role of the Province, the realization
of informative didactic material on the monumental trees and what they represent is considered
to be of fundamental importance. The idea of promoting the monumental tree areas with a
series of initiatives connected to the local traditions is to be placed in the same context. So
that the places and the selected trees will not remain a closed reality but a well known one
that the public can enjoy, the realization of a suitable cartography is also essential. This will
be followed by the realization, where possible, of a series of paths, conceived in such a way
to focus the public attention on the important natural aspects and on the particularities
that can be seen there.
Conclusions
The structural and composition particularities of some woods contribute to define some
communities of considerable naturalistic value and, as to the monumental trees, some rare
examples of longevity and bulk, deeply connected to the culture and the popular traditions
of the territory. The census of the monumental trees taken till today represents only a part
181
of the vegetational patrimony of the Province that needs to be analyzed with greater detail.
The importance currently assumed by the monumental tree as a source of important
anthropological territorial information, requires an appropriate scientific and historical geographical search to be spread.
Having been recognized the essential value by now assumed by the environmental tourism,
the natural resources currently represent a crucial expectation of the traveler. The relict
woods and the monumental trees can represent, if correctly managed and protected, a
precious resource also in the field of the ecotourism and a further opportunity for the smaller
centers situated in the marginal territories of the Province.
Bibliography
ADAMESTEANU D., 1974 - La Basilicata antica. Di Mauro Editore.
CARELLI G., DE CAPUA E. L., LABRIOLA F., 2002 - Indagine preliminare sullo stato dei rimboschimenti
costieri del litorale Jonico di Policoro (MT). legno celulosa Carta, n.2
DE CAPUA E. L., 1995 Rinaturalizzazione delle pinete litoranee. Progetto redatto per la Provincia di
Matera.
DE CAPUA E. L.,1995 Il bosco di Policoro: vicende storiche e caratteri vegetazionali. Annali Accademia
Italiana di Scienze Forestali, Vol. 44.
GUALDI V., 1988. The maintenance and the improvement of the woods of the re3gionis center southern peninsular. National II° Congresso of forestry. Venice, 24-27 giugno,1998s
SPICCIARELLI R., 1996. You plant with trees Fathers The monumental trees of Lucani. Regional
suggestion of Basilicata.

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