Managing Urban Forests for Sustainability

DETAILED REVIEW ABOUT THE ACQUIRED
KNOWLEDGE
GIOVANNI SANESI
In recent years, there has been a growing interest at different levels (scientific, technical, political) in urban and periurban forestry
(UPF) and in the system of green spaces, known as ‘Green Infrastructure’ (GI), as well as in the benefits (i.e., ecosystem services) that
these environmental resources provide to improve the quality of life in our cities. Less attention, however, has been paid to the mainte-nance
of UPF.
From a scientific point of view, current research interest has taken three main directions. Firstly, one of the recent mainstream con-cerns
economic issues and refers, in particular, to governance. In their review, Lawrence et al. (2013) gave five examples of urban fore-stry
governance from across Europe and illustrate the use of a framework to describe governance in these contexts.
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2 - URBAN FORESTS MANAGEMENT www.emonfur.eu
A second group of scientific interest concerns the analysis of the
growth and structure of urban forests. Semenzato et al. (2011) de-termined
the relationships between tree age and various parame-ters
of tree size in order to develop models to predict the growth
of the most important species of urban forests in northeastern
Italy.
Richnau et al. (2012) investigated the stand structure of 10 yo-ung
urban woodlands. The authors demonstrated that the cur-rent
canopy structures could be classified into different two- and
three-layered structural types, and that these had evolved as a
combination of differences in management frequency and initial
species composition. Marziliano et al. (2013) assessed urban fo-rest
plantations in terms of tree height growth, crown width and
vertical structure, using tree inventory data which had been col-lected
in an urban park as a case study. Basing on the obtained
results, the authors pointed out that during the earlier stages af-ter
planting, the trees reach high levels of growth (tree height
and crown width), regardless of the taxonomic unit. The results
show that in temperate climates, the maximum longitudinal
growth can be achieved in less than 30 years.
The third and more consistent mainstream is linked to benefits.
This topic is developed in Chapter 4.
Understanding which are the resources required by management
is an obvious priority. Therefore, it is important to take inventory
of urban green spaces, focusing mostly on trees rather than on
urban forests. We need to have comparable data, even if they are
derived from varied backgrounds or from different geographical
and environmental contexts.
In the matter of data standardization, the tree software suite
from the USDA Forest Service provides urban forestry analyses
and benefits assessment tools (http://www.itreetools.org/), and
it is a highly valuable source. This instrument is distributed
worldwide and currently boasts more than 11,000 users (mainly
public administrations).
For each management model it is necessary to understand which
features or contributions should be further considered (refer to
Chapter 4 for this topic). The management of an urban forest
must also take into account the origin of the forest itself. Today,
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we have primarily got to face green systems of artificial origin,
which often consist of a few tree species and even fewer shrub
species. These arboreal systems or forestry plantations are often
characterized by a low resilience that exposes them to damage
from biotic (e.g., fungi and insects) and abiotic (e.g., wind and
water stress) factors. This resilience may be even lower in areas
subjected to the effects of ‘Global Change’ or in urban settle-ments
characterized by a considerable Urban Heat Island (UHI)
effect.
Although there is a close relationship between plant models, ma-nagement,
and user preferences, research has not adequately
dealt with this topic yet. The variations in planting design and sil-viculture
can lead to considerable differences between the struc-ture
(vertical and horizontal) and visual appearance of woodland
stands, even in the early stages, as observed by Nielsen and Jen-sen
(2007). With regard to the preferences of the forest land-scape,
it should be stressed that users make judgments that vary
greatly depending on the geographical, social and cultural deve-lopment.
Another topic that has not been sufficiently analyzed by the re-search
community is the cost of forestry plantation and manage-ment.
It is evident that the costs of forest plantations are minor
compared to those of urban parks. However, it is equally true
that, as a rule, they should be compared with models in which in-tensive
silviculture thinning and other forest activities are ge-nerally
higher than those of traditional forestry. In these con-texts,
a collaboration among different stakeholders would be desi-rable
as well as new models of governance (Andersson et al.,
2013).
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References
Andersson, K., Angelstam, P., Elbakidze, M., Axelsson, R., Degerman, E.,
(2013) Green infrastructures and intensive forestry: Need and opportunity
for spatial planning in a Swedish rural–urban gradient. Scandinavian Jour-nal
of Forest Research, 28(2): 143-165.
Lawrence, A., De Vreese, R., Johnston, M., Konijnendijk van den Bosch,
C.C., Sanesi, G. (2013) Urban forest governance: Towards a framework for
comparing approaches. Urban Forestry & Urban Greening, 12(4): 464-
473.
Marziliano, P.A., Lafortezza, R., Colangelo, G., Davies, C., Sanesi, G.
(2013) Structural diversity and height growth models in urban forest plan-tations:
A case-study in northern Italy. Urban Forestry and Urban Gree-ning,
12(2): 246-254.
Nielsen, A.B., Jensen, R.B. (2007) Some visual aspects of planting design
and silviculture across contemporary forest management paradigms – Per-spectives
for urban afforestation. Urban Forestry & Urban Greening, 6:
143–158.
Richnau, G., Wiström, B., Nielsen, A.B., Löf, M. (2012) Creation of multi-layered
canopy structures in young oak-dominated urban woodlands - The
'ecological approach' revisited. Urban Forestry & Urban Greening, 11(2):
147-158.
Semenzato, P., Cattaneo, D., & Dainese, M. (2011). Growth prediction for
five tree species in an Italian urban forest . Urban Forestry & Urban Gree-ning,
10, 169-176.
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2.2
UPF’S PECULIARITIES MANAGEMENT
PAOLO NASTASIO, ROBERTO COMOLLI
The intensity of the fruition is generally the main element characterizing UPF compared to the generality of the forests present in a
broad territorial context. Considering the origin, in many cases unnatural, of this type of populations and their resulting reduced eco-logical
stability, it leads to a greater fragility compared to forestry contexts that, although being subject to disturbances of various na-ture
over time, will obtain a guaranteed higher level of resilience thanks to the complexity of biological factors that have evolved and
continue to do so to this day. An artificial urban or peri-urban forest is a tree plantation, which is very similar to a woody plantation
where the biodiversity is contained and the homeostatic level is reduced accordingly. The phytosanitary problems may be severe and
are often underestimated compared to wood plantations that resemble them in many ways: in fact, there are rare cases where chemi-cal
treatments are carried out for the containment of adversities. It is almost as if the search for naturalness, first pursued by the plan-
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ner and then by the manager, must also substantiate in abstai-ning
from practices that are considered disruptive compared to
the development of natural dynamics. Moreover, even though an
arboriculture system that yields revenue is considered harmful
(ex. specific defoliation by a moth), it can be considered a positi-ve
factor for the development of overall naturalness (protein sup-ply
in the ecological chain). Urban and peri-urban forests form
the joining link in terms of intensity and management costs,
among the urban greenery systems and natural suburban areas.
The maintenance practices are among the most intensive among
forest complexes and the least intensive in respect to conventio-nal
urban greenery (parks, gardens, tree-lined pathways). Of
course, the management approach of recently built artificial ur-ban
forests must be decidedly differentiated from natural forests
in close proximity of urban centers and even near many cities.
With recently built artificial forests, once the engraftment of fo-rest
planting stock is ensured through the containment of infe-sting
species and the necessary supplementary irrigation within
the first 3-5 years after planting, the main problem that will arise
is the gradual adjustment of density through progressive thin-ning,
so as to also tend to the competition between species in or-der
to orient the composition and structure of the population to-ward
the objectives that were predetermined during the planning
stage. The choice of the initial moment of the interventions is the
most critical element and can only derive from a number of speci-fic
factors that are both stational and from the project (in particu-lar,
the planting density and the species used) which must be
analyzed from time to time. Moreover, intervening too early is
certainly unnecessary and expensive (even harmful if one wants
to take advantage of the competition for obtaining sustained lon-gitudinal
increments). However, intervening too late can weaken
the structure as a whole and penalize the smaller growing species
that would find themselves damaged by the more exuberant spe-cies
for excessive shading or competition, and not to mention the
inevitable damage caused during the process of the cutting of the-se
trees that are considered excessively large compared to the po-pulation
average. It would certainly be advantageous to perform
frequent thinning interventions of low intensity, but the econo-mic
factors will compel one to compromises. Even the perception
of public opinion, in which the significance of the interventions
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of the removal of surplus trees should always be explained in
advance, should lead to frequent but light interventions. It can-not
be excluded that certain forest formations can be left to free
and natural evolution, refraining from any intervention. The choi-ce
may be linked to reasons that are experimental or for greater
economic sustainability. In these cases the maintenance for just
pedestrian and bicycle paths can be reduced, in which the safety
of its visitors must be guaranteed, including expressly advising
them to not leave the pathways.
With regards to soil, within UPF management particular atten-tion
must be given in order to avoid compaction. This type of de-gradation,
especially due to localized trampling and the transit of
mechanical means, will cause a reduction of soil porosity (in par-ticular,
macroporosity), increasing the bulk density of the soil.
While a forest soil of good quality, with normal organic matter
content, has a topsoil bulk density of 1.0-1.2 kg dm-3 or less, a
compacted soil can obtain values of up to 1.6-1.8 kg dm-3; com-paction
can cause serious difficulties to the percolation of water,
soil aeration and root penetration, sometimes rendering them al-most
impossible.
Since it often takes a long period of time to return to normal bulk
density conditions, even in the absence of mechanical compres-sion,
there is the need to avoid soil compaction also during the
phase of the UPF establishment, giving attention to the compac-tion
caused by the mechanical means used for the heavy han-dling
of soil. Sometimes the subsoil is compacted, while the
overlying topsoil, artificially led, has almost normal bulk density.
In this case, the subsurface compaction reduces the thickness of
the soil and the volume of soil that is exploitable by the roots.
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STRUCTURAL STABILITY AND SECURITY
FABIO CAMPANA
One of the most important aspects, in sense of integrity, for the security of people who frequent urban and peri-urban forests is the
structural condition of trees of which they are composed, in particular, trees of large sizes.
The structural stability of a tree depends on the typical characteristics of a tree species, such as hardness, elasticity and the tensile
strength of the woody tissues, but also the individual characteristics of each specimen, which may present structural defects such as
included bark, the asymmetric development of foliage, poor anchorage of the root system and so on.
In the contexts of frequent use as UPF often are, the potential danger of a tree is determined not only by its size and condition of struc-tural
stability, but also from its position. A tree that has structural defects that render it unstable is extremely dangerous if it is located
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in the proximity of main pathways or bike paths that cross a hi-ghly
frequented forest. Or along a pathway used for environmen-tal
education activities, where many children usually pass
through, whereas the danger is greatly reduced if the same tree is
located in a densely wooded area that is without pathways,
perhaps caused by the spontaneous evolution of vegetation for
naturalistic purposes.
Interventions that can redu-ce
the danger of unstable
trees are normally quite ex-pensive,
especially if they
involve large specimens.
For the studies must be car-ried
out by trained experts
who are equipped with spe-cial
equipment for felling
or pruning at high altitu-des,
removing dried and un-stable
branches, or for con-taining
the development of
the crown in order to redu-ce
the load at the level of
the trunk and roots.
Due to the economic impact of these interventions and the limi-ted
availability of resources, individuals who are usually respon-sible
for the maintenance of UPF must take into account several
factors for determining which trees are to be monitored with par-ticular
attention, which need to have studies of stability carried
out, and, when necessary, interventions of pruning or felling.
Therefore, it would be quite useful to have the territory mapped
according to the frequency of use, identifying the more potential-ly
dangerous areas where more resources should be invested in
order to maintain the highest level of security possible, and possi-bly
regulating the frequency of maintenance for the areas of low
attendance. Without a doubt
one appropriate solution
would be to define the procedu-res
of periodic and program-med
testing of the safety condi-tions
of trees, for example, by
the preparation of specific pro-tocols
of control.
With reference to forests of un-natural
origin, it should be no-ted
that a correct planning and
maintenance can lead to the
development of forests that
are more secure from a frui-tion
point of view. The use of
species suitable to the environ-mental
context, the correct di-sposition
within the popula-tion,
the phytosanitary condition, adequate spacing between indi-vidual
trees, and thinning interventions carried out at opportune
moments are all factors that can contribute to the development
of stable trees and more secure forests from a structural point of
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view. In particular, during the development of young stands, it is
very important to intervene with thinning operations when the
crowns begin to enter into competition for space and sunlight, so
as to avoid the phenomenon of “slenderness”, that is the forma-tion
of trees that are slender, tall and with apical crowns.
In all the cases where there are potentially dangerous trees in
proximity of highly frequented locations and generally in urban
contexts (rows of streets, public and private green areas), it is
possible to refer to a survey methodology that has been wide-spread
for years in many countries, in particular, in Europe and
the USA called Visual Tree Assessment - VTA (Mattek & Breloer,
1994). VTA consists of visual biomechanical assessment criteria
of a tree. After the identification of external symptoms, depen-dent
on possible structural defects, an in-depth study is perfor-med,
supported by the use of specific tools, such as the Resisto-graph,
pulse hammer, sonic tomograph and fractometer. The ex-tent
of the defects is then measured and the resulting class of risk
is determined. The operator will then have certain elements at
his disposal and will be able to decide what appropriate measu-res
to take.
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REFERENCES
Società Italiana di Arboricoltura http://www.isaitalia.org
International Society of Arboriculture http://www.isa-arbor.com
Prof. Dr. Claus Mattheck http://www.mattheck.de
ULTRASONIC, ELECTRIC AND RADAR MEASUREMENTS FOR ASSES-SMENT
OF LIVING TREES - Luigi Sambuelli, Laura Valentina Socco, Al-berto
Godio
http://areeweb.polito.it/ricerca/engel/ris/sam/mieipaper/trees.pdf
Demetra Cooperativa Sociale - VTA
http://www.demetra.net/servizi/servizi-specialistici/vta/
Fitoconsult – Analisi di stabilità
http://www.fito-consult.it/servizi/analisi-di-stabilita-n/analisi-di-stabilita
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2.4
PRESERVATION AND PHYTOPATHOLOGICAL
CONDITIONS
ALESSANDRO RAGAZZI, BEATRICE GINETTI, SALVATORE MORICCA
Diseases of forest trees in an urban setting
Whenever one of the normal growth processes of a tree (covering the whole range of its life functions, from its uptake of nutrients and
water out of the soil, to the operation of its organs of reproduction) no longer functions, one can speak of a tree disease.
A disease starts when the complex relationship between a tree, a pathogen, and the environment within an ecosystem is disturbed.
This happens whether the ecosystem is natural, or, as with the UPFs, anthropogenic. The agents that infect forest trees in cities are ge-nerally
the same as those that infect trees in forests, especially if the tree species are the same. For this reason it is the urban environ-ment
that shapes the life cycle of a pathogen, the way in which it expresses its pathogenicity, and the symptoms it causes. Any anthro-
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pogenic activity makes an ecosystem ‘artificial’, and this has re-percussions
on the occurrence, frequency, assembly and interac-tions
of potential pathogens in urban forests. In an urban con-text,
interactions between trees and pathogens arise and cannot
be compared to those that are found in natural forests. First of
all, the climate of a city often changes the growth rhythms of tre-es,
adversely affecting their response to disease agents (since citi-es
are ‘urban heat islands’). In cities trees also tend to suffer
from human activities such as asphalting, paving, excavations,
etc., and from incompetent pruning that impairs tree health.
Then there are also the negative effects that urban pollution has
on tree vigour, gas leaks that emit substances toxic to trees, and
salt spread on the roads to melt ice in winter. The soil in a city is
obviously not the same as the soil in a natural environment: in
cities the soil tends to be more compact and impermeable, with
negative consequences on the soil fauna and microorganisms,
causing an absence of the conversion of organic material. All the-se
factors combine to produce a premature senescence of trees,
which favours the pathogen at the expense of the tree. These pro-blems,
exacerbated as they are by the adverse conditions of an
anthropogenic environment, are made still worse by the global
warming that is now taking place. For more information about
the management of UPFs designed to improve the health of ur-ban
trees see “Urban forest health assessment under climate
change scenarios”.
In a seriously deteriorated environment such as has been descri-bed,
it is particularly important to choose suitable and certified
healthy germplasm so as not to introduce any further pathogens
into a system that is already weakened. Any potentially harmful
pathogens must be promptly identified and controlled to prevent
their spread to other areas, whether natural or anthropogenic.
The globalisation of the nursery trade over the last few decades
has permitted the spread of exotic invasive pathogens, which of-ten
found in their new areas host plants that had not co-evolved
with them, and that as a result are more susceptible to them. Ma-ny
species of pathogens have recently been introduced into Italy,
among which the quarantine pathogen Phytophthora ramorum
(see “Foliar blight and shoot dieback caused by Phytophthora ra-morum
on Viburnum tinus in the Pistoia area, Tuscany, central
Italy”), included in the A2 List of the EPPO (European Plant Pro-tection
Organisation), deserves mention. To prevent the spread
of this pathogenic oomycete, the Commission of the European
Union on 19 September 2012 passed its Decision no. 2002/757/
CE, ‘Provisional emergency phytosanitary measures to prevent
the introduction and the spread within the Community of
Phytophthora ramorum, a Decision that was amended on 29
April 2004 with Decision no. 2004/426/CE, and on 27 March
2007 with Decision no. 2007/201/CE, these last stipulating mea-sures
of prevention and control. Other pathogens have been
found more recently in Italy (see “Root Rot and Dieback of Pinus
pinea caused by Phytophthora humicola in Tuscany, central
Italy”), some in the context of the EMONFUR Project (see
“Phytophthora acerina sp. nov., a new species causing bleeding
cankers and dieback of Acer pseudoplatanus trees in planted fo-rests
in northern Italy” and “First Report of Phytophthora taxon
walnut in Lombardy, North Italy”).
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Dead wood
Dead wood left lying on the soil benefits the environment when
the wood is decayed by fungi and invertebrate organisms. Howe-ver,
some of these organisms, especially those that already in-fected
the tree before it died, may continue to live (some as sapro-phytes)
and infect other plants, for which they then become a
continuing source of inoculum.
Soils with abundant decaying matter are managed differently de-pending
on whether the soils are productive farmlands, natural
reserves, urban parks, or periurban parks. In the case of parasi-tes
that have invaded parks from outside, it may be necessary to
remove the dead wood from parks as well.
Leaving decaying wood on the ground should be avoided for rea-sons
of tree health, especially in artificial plantings such as parks,
where all the vegetation is - more or less - of the same age, and
only a few species are grown, all adapted to the same site. When
an infectious disease breaks out, it is necessary to remove all
dead wood from the ground, especially if the causal agent is a ne-crotrophic
fungus, that has its origin outside the park, because
this can infect not only the trees in the park itself, but also other
trees in the vicinity.
Wood chips
Wood chips are used in many parks to construct paths and
walkways or they are deployed on the ground in order to make
organic substance but, if they derive from infected trees, they
may preserve the pathogen infecting the tree and contribute to
its spread.
An example is furnished by an experiment carried out by the
Work group ‘Laboratorio boschi’ (Forest laboratory) set up at Par-co
Nord Milano: it was found that Botryosphaeria dothidea, a
plurivorous fungus which causes cankers on many tree species,
remained viable on the wood chips of maple trees for long pe-riods
of time at temperatures of 40°C and higher.
It is therefore advisable not to use any wood chips from infected
trees unless they are preventively heat-treated at temperatures
over 60°C. It is in any case vital to examine the wood chips for in-fective
agents.
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Wood thinning and its effects on tree health
Wood thinning, among other forest operations, may damage the
trees left standing and tree regeneration. The damage caused by
thinning may be related to a number of factors: the method of
harvesting, the site characteristics, and the amount of wood thin-ned
out (Bettinger et al., 1998; Fjeld and Granhus; 1998, Spinelli
et al., 2010).
A study on the effects of wood thinning in an artificial Corsican
pine stand in the village of Valle Gelata, a few kilometres from
the centre of Viterbo, found that 410 out of 901 tree trunks exami-ned,
or 45.5%, were damaged by wood thinning (Mattioli et al.,
2013).
Damage to the tree trunks favours the penetration and spread of
pathogens, causing diseases which, quite apart from the direct
economic loss, also affect a range of soil factors. The hundreds of
trees felled in the two sub-plots in the Parco Nord Milano (one
thinned, the other left unthinned) caused damage, though but
slight, to the trees that were left standing, and this certainly fa-voured
the penetration and spread of many endophytic patho-gens.
Wood thinning-out has a number of effects: it changes the leaf
area index (LAI), transpiration, the amount of water available in
the soil, soil temperature and soil humidity. Thinning initially re-duces
the LAI of the canopy, which in turn reduces the amount
of solar radiation admitted. Subsequently the LAI returns to its
previous levels, but it is concentrated over a smaller number of
trees (Todaro et al., 1997).
When the same LAI is spread over a smaller number of trees, it
means that each tree has a greater leaf mass than before. The in-crease
in leaf mass is due to a greater amount of light entering
the thinned plot. The greater leaf mass represents a larger “terri-tory”
for the parasite to colonise. The parasite (fungus, bacte-rium,
virus, phytoplasm or insect) considers as its territory the
single plant organ, which it begins to colonise, whether as an
epiphyte or an endophyte.
Since the basimetric area of the trees in the thinned-out plot is
not only smaller, but also has the highest frequency of potentially
pathogenous endophytes, it is tempting to think that the lower
tree density with its improved growing conditions makes the tre-es
less susceptible to stresses of any kind. In reality, however, the
lower tree density produces an increase in the leaf mass, and the
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old problem still remains the same: the endophytes now coveres
a greater amount of “territory” than before.
Urban forestry is still in its infancy in Italy, although it is beco-ming
increasingly important. Consequently there are as yet only
few studies on how silvicultural treatment, and especially forest
thinning-out, affects soils whose prime purpose is to satisfy the
demands of tourism and recreation (Mattioli, et al., 2013).
Forest thinning-out is certainly necessary for the renewal plan,
both in natural forests and in the park areas that we have been
discussing. The problem as it appears from our data, however, is
that thinning usually triggers a whole series of collateral effects,
like an increased amount of inoculum disseminated by some pat-hogens.
Our study is probably the first to demonstrate that forest thin-ning-
out may cause an increase in the incidence of some endo-phytic
fungi in forest trees.
Phytosanitary felling
Phytosanitary felling serves to reduce the inoculum of certain pat-hogens,
or to cure diseased trees. This type of felling is designed
to prevent or control animal and plant parasites, unless otherwi-se
prescribed by quarantine measures (Decisions) enforcing con-trol,
or by the relevant circulars. In this case reference must be
made to the regulations of the individual regions.
In Tuscany for example article 49 of the Regulation for the enfor-cement
of the Forestry Law (L.R. 39/00), entitled ‘Prevention
and control of animal and plant parasites of forest trees’, states:
The owners of forest trees must immediately inform the Provin-ce
or the “Comunità Montana” (the administrative unit of a local
mountain area) of any parasitic attacks harmful to their trees,
and of any damage to their trees from any other cause. The pro-vince
or the mountain community will inform the ARPAT (Agen-zia
regionale per la protezione ambientale della Toscana, Regio-nal
agency for environmental protection of Tuscany), which will
specify the action to be taken to control the damage.
Phytosanitary felling has been proposed and carried out in two
areas involved in the EMONFUR Project, Parco Nord Milano
(see “Monitoring the phytosanitary status of North Park-Milan .
Diagnosis and integrated management strategies”) and Boscoin-città
(see “New taxa of Phytophthora invading italian forests and
plantations”), both in Milan.
Criteria to protect urban forest trees
The concept of urban forest, and the habit of viewing green open
spaces as urban forests, has changed the approach to the manage-ment
of these spaces, and especially the approach to tree health.
Consequently, plant pathogens (mainly fungi) and insects are
now almost the only organisms thought to be a real cause of suffe-ring
to urban trees, which are already weakened by other stress
factors that are an intrinsic part of the urban environment, or
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that are due to errors in urban forest management, and primarily
in planting.
This situation is exacerbated when exotic and potentially invasi-ve
organisms are introduced from other continents, or even from
other areas.
The complex problem of dealing with the health of urban trees
growing in parks, and almost incessantly exposed to harmful fac-tors,
requires specific programmes of integrated control. It is ne-cessary
to take practical, especially silvicultural steps to address
the predisposing factors, which cause disease over the long term;
but it is equally necessary to consider the immediate, ‘inciting’
factors that require control in the short term, in order to safe-guard
the green spaces that already exist (Tiberi and Roversi,
1991; Capretti and Ragazzi, 2009).
From a purely practical point of view, it is recommended that:
• dead or diseased trees should be felled in winter
• sawdust should not be produced or allowed to escape when
trees are felled or pruned
• wounds should be protected by spraying with copper salts
• felling debris should be removed and burnt
• stumps should be eliminated
• all wounds are to be avoided
• trees if at all should be pruned only in the winter months
• large pruning wounds should be protected with polyvinyl glue
containing a broad-spectrum antibiotic, or with an organic
mastic
• large pruning wounds should be periodically inspected for to
assess their healing
• propagating material should not be introduced from areas
where a harmful pathogen has been reported
• park personnel should be well trained
• new plantings should be established at a proper distance
from existing plantings
• resistant clones should be used in new plantings
• pest control regulations should be observed.
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Monitoring
The health of urban and periurban forest trees should be careful-ly
monitored not only to safeguard the health of the trees and en-sure
a proper management of the green spaces overall, but also
to protect those who visit these green spaces (see “The importan-ce
of monitoring tree health”). Urban forest trees are exposed to
various stresses that impair their vigour and cause premature
ageing, that makes them more susceptible to pathogens, and that
also causes the loss of branches, or the sudden overthrow of the
whole tree. There are a number of forms to monitor tree vigour,
and which can be employed with urban forest trees (see “Examp-le
of a form to monitor tree vigour” and other examples). The va-riables
that are usually considered are: per cent leaf fall and chlo-rosis,
wood rot, injury to various tree organs, carpophores, dead
branches or twigs, epicormic shoots, symptoms such as bark can-kers
and/or exudates, microphyllia, etc. As far as the EMONFUR
project itself is concerned, the only variables considered in the
protocol are: leaf fall and chlorosis, depending on the monitoring
form employed (see the “Monitoring form”). Particulars of the
work carried out and the results obtained are shown as at-tachments
(see “Phytosanitary monitoring within the European
project” and “Phytopathology Unit. Report of the activities”).
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Regulations for urban and periurban cutting for tree
health to be adopted at a European level
The need for cutting should be obviated by growing the trees in
suitable conditions and with proper spacing between them. Cut-ting
large branches should be avoided; it is advisable to cut the
smaller branches, which are more easily compartmentalised by
the tree.
In the case of cutting made necessary by trunks breaking off, inju-ry
to the tree, or impairment of proper tree shape: the branch or
twig that is cut must be trimmed down and the cutting wound
must be protected.
Cutting made necessary by necrotic areas or cankers: the tree
should be cut where the wood is still healthy, some 15-20 cm be-low
the dead part, and the cutting wound must be protected.
Cutting of dead branches: it is necessary to make the tree safe;
this involves eliminating not only dead branches but also bran-ches
with large cankers.
Crown thinning: this is essential wherever leaf-inhabiting fungi
are common, since the lower humidity of a thinned crown offers
a less favourable environment to many fungi. A thinned crown is
also more easily blown through by winds without causing dama-ge,
and this avoids wounds, which are preferential entry points
for canker-causing fungi.
Tree branches should always be cut near buds or inserts of other
branches, so that the tree can form tissue to heal the cutting wo-unds.
Depending on the length and hence the weight of the branch, the
first cut should be at the distal end of the tree, dividing the
branch to be cut into three parts, and first cutting the apical end
of the branch.
An example of an intervention on different types of oak forests
(natural forests, artificial stands, parks) infected with the agent
of “charcoal canker” Biscogniauxia mediterranea (Franceschini):
• the inoculum was reduced by felling all infected trees and pru-ning
branches with die-back or with charcoal cankers.
• all pruning waste was burnt on site, or removed, taking care
however to cover the material with canvas while it was being
removed.
• if the charcoal canker agent has not yet reached epidemic pro-portions,
the trees should be grown as coppice with stands.
The forest clearing that this brings about hampers the further
spread of the fungus, which can then be contained with a furt-her
cutting of branches.
• if, on the other hand, the charcoal canker agent has reached
epidemic proportions, the trees should be grown as stands
and coppice or converted to high stand. In that case, rather
than trying to prevent the further spread of the fungus, which
has become ubiquitous, it is more important to maintain the
humidity of the soil at high levels in order to prevent any risk
of drought stress, which would favour the fungus invading
the tree.
131

2.5
NATURAL EVOLUTION AND REGENERATION
BENEDETTO SELLERI, RICCARDO TUCCI
Regeneration is of a natural origin when new entities are born directly from the seeds following natural dissemination (zoochory or
anemochori), or suckering originating from root plates or root systems of trees already present in the wood. It can occur either gra-dually
under the cover of foliage, or in a more abrupt manner after a natural event (such as after a fire or windthrown to the ground)
or a silvicultural intervention (thinnings of strong intensity, clear cutting, gaps celearcuts, thinning at juvenile age, etc.) which would
remove some of the ground vegetation, leaving the ground uncovered.
132

Advantages of natural regeneration
The main advantages of natural regeneration over artificial (Pius-si
1994, as amended) are as follows:
1. ensures a permanent cover of the ground, protecting it from
leaching and erosion, and stabilizes the microclimate, while en-suring
the ability of adapting to the most demanding and deli-cate
species, including nemoral flora;
2. in a situation of an abundance of seed and mixed forests it
would allow a rational distribution of the species and, at the
moment of juvenile thinning, the high number of entities
would allow to preemptively make a good quality selection,
both interspecific and intraspecific;
3. provides seedlings with a root system that is more vigorous
and further developed in depth, and therefore a higher ancho-ring
capacity to the ground and a greater possibility of rea-ching
a circulating solution with the land;
4. allow the preservation of local ecotypes that have a better adap-tation
to the environment where the trees live and therefore a
greater chance of survival;
5. there are no costs for the harvesting of seeds, nursery bree-ding,
transport and reforestation (hole digging, tree planting
location, eventual wetting and weeding).
Actions and techniques that can be put into place to en-sure
natural regeneration
From a silvicultural point of view, the link between the evolution
of a forest and natural regeneration comes from the fact that favo-rable
conditions for the regeneration of the forest are not only
created by regeneration felling. They are also performed by thin-ning
at juvenile age, which give way to all the favorable condi-tions
of the process (regulation of the specific component, forma-tion
of plant litter, creation of a favorable microclimate for the al-teration
of the plant litter, correct level of light radiation to the
ground). It should be borne in mind that the needs and tempera-ment
of the various species, considering that light-loving species
(oak, ash and pine trees in primis) require adequate solar radia-tion
shortly after the seedling stage, and therefore large enough
holes (even in relation to the height of the surrounding forest
stands). The sciaphilous species (linden, beech, fir, hackberry,
yew, holly, etc.) are able to live in dim light for many years, some-times
decades, until they are able to find the opportune moment
to fully develop - in relation to the coverage that is present above
them. If it is kept dense, then it will not allow them to survive.
133

Within certain contexts of a particular anthropogenic pressure,
the factors that may render the affirmation of a natural regenera-tion
difficult are human foot traffic and, at times, acts of vanda-lism.
A remedy for these problems is not quite simple. Concrete
action, in addition to surveillance which is, however, extremely
difficult to implement within the forest stands, is to create ele-ments
of deterrence at the access of an area where it is hoped the-re
would be an affirmation of a regeneration. The elements of de-terrence
can be constituted by plant elements such as impene-trable
bramble bushes and shrub belts, or large trunks. Otherwi-se,
one must resort to a true delimitation of the affected areas
through the use of forest fencing.
In fact, some of the disadvantages of natural regeneration (depen-ding
heavily on edaphic and climatic factors, it runs the risk of
being insufficient or unevenly distributed or having a sponta-neous
mixing ratio among species that is not desired) can be com-pensated
by silvicultural activities. This affirmation is correct
even in the presence of shoot sprouts (root or from coppice), for
the unwanted species can be contained or eliminated by mainte-nance
(in particular, with the presence of significant growths of
coppice shots that are oblique, straight, poorly shaped and de-void
of future).
Regarding tree stems that are generated in an agamic manner
(especially coppice stock), in particular, for species “of the futu-re”,
one must proceed with the choice of one or more erect stems
that will be left less straight and with greater potentiality, even
with respect to the available air space above.
SEE: FAO (2010) the “Assisted Natural Regeneration” (ANR)
consider weeding, fertilizing, thinning, selective logging.
(FAO 2014 Planted forest. Definitions
http://www.fao.org/forestry/plantedforests/67504/en/)
The link between the regeneration and evolution of a forest is
well illustrated by Piussi (1994) “the process of regeneration re-presents
a moment of transition between two successive genera-tions
of trees, in which one may be able to make decisions and
implement interventions which will shape the new generation
in the manner we want it.”
The choice of treatment (intermittent cut, successive cuts or gaps
clearcuts) will produce a different structure of the forest, which
in turn may be more or less suitable with respect to a certain
ecosystem service (ex. landscape). With this type of UPF, as well
as that of the safety of users and the equlibrium with the environ-ment,
considerable attention should be given to the aesthetic-or-namental
aspect. Even according to the type of ground vegeta-tion,
clear cutting should be avoided with species over large
areas, and should eventually be performed with patch cuts in
such a way as to tend toward an uneven-aged structure - at least
to groups, and without leaving the land completely uncovered
and adjusting the cutting to the needs of species that are to be
maintained.
REFERENCES
Piussi, P. 1994, Selvicoltura generale. UTET, Torino
134

2.6
INCREASE OF BIODIVERSITY
EMILIO PADOA SCHIOPPA
The increase of biodiversity in urban forests and urban parks means to increase the number of species and habitats too. Genetic level is
meaningless in this kind of environment (but genetic integrity must be considered).
An island effect (sensu Mac Arthur & Wilson, 1967) has been demonstrated in several studies. A bigger park has more species inside (fi-gure
1), and a park closest to source areas (so normally far from the city center) has more species.
Considering this point of view ecological planning may play a very important role. If we can choose were and how make a new park all
those aspects may be taken into account. In some case we can also detect that a larger forest surface will have a bigger number of spe-cies.
135

There is also a clear relationship between species diversity and
environmental heterogeneity. In figure 2 this relationship (mea-sured
in 13 parks of Milano, comparing bird and habitat diver-sity)
is clearly detectable (from Sanesi et al. 2009). Forest areas,
open habitats, waters will have different birds specialist (i.e. for
forest woodpeckers, skylarks in hopen habitats and several birds
linked to water).
Moreover individual abundance may be – at least for some spe-cies
– an important goal to reach. Of course should be conside-red
that this might not be a goal to reach for any species.
For example, a typical urban species such as the pigeon should
be contained, rather than made to expand (Conover, 2002).
In urban forests management of trees may become relevant. Seve-ral
studies explained how animal and plant populations may in-crease
depending on forest structure management. Choosing so-me
target species, and selecting some management elements
(i.e. tree dimensions) we can detect a relationship. As an examp-le
in Sanesi et al. (2009) DBH has been investigated to see if the-re
is a relationship with bird abundance. The DBH of the closest
100 trees surrounding each point-count within a radius of 100 m
was measured.
136
Figure 1. Number of species and distance from center in urban parks
(from Sanesi et al., 2009)
Figure 2 – relation between habitat heterogeneity (green line)
and bird diversity (yellow line).
Both habitat and bird diversity have been measured with Shannon diversity index

DBH values were then analyzed in relation to species abundance
values considering the following intervals of DBH: minimum,
first quartile, median, third quartile, and maximum. Such inter-vals
were used to derive input data for an additional regression
model. For each DBH interval, the observed species abundance
was compared with the average abundance across all the point-counts
and used those observations with higher values to con-struct
an “optimal” model of the DBH distribution (figure 3, gre-en
line). All the other observations were instrumental for crea-ting
a “minimal” model of this distribution (figure 3, red line).
This approach has been used in previous studies (Massa et al.
2003) and it follows the assumptions that: an high level of abun-dance
is generally preferable for birds in urban settings (Bock
and Jones 2004); that birds select forest with high values of
DBH, mature urban forest; and that species in urban environ-ments
are likely to occur within heterogeneous and uneven-aged
forest vegetation (Blair 1996; Donnelly and Marzluff 2006; Sand-ström
et al. 2006).
The term “forest herbs” means shade-tolerant species, generally
associated also to mature humus.
Several studies (e.g.Whigham, 2004) show that ecological cha-racteristics
of forest herbs make them bad colonizers, with very
slow dispersion mechanisms: their survival depends on forest
conservation and low level of natural or anthropic disturbance.
Decisive factors become the type of forest management, the age
of the vegetation (in case of reforestations), the size and the pre-sence
of ecological networks fit to allow the species to move insi-de,
such as wide and well-structured hedgerows or ancient
woody patches close to the forests we want to be colonized.
Milan hinterland and Po plain near it are Italian examples of ex-periments
to improve forest herbs in selected reforested sites,
using seeds, bulbs or plants taken away from sites nearby. Forest
age, spontaneous woody species and level of disturbance have be-en
previously assessed. The results of these experiments show
that the species planted are still alive and they sometimes ex-panded,
such as in Parco Nord Milano (Brusa, 2012).
137
Figure 3 – DBH and abundance for blue tit (from Sanesi et al., 2009)

Other experiments have been carried out by ERSAF (Regional
Authority for Agricultural and Forest Services) in several refore-sted
areas, and successively monitored (e.g. Nespoli, 2010). Also
in these patches, forest herbs (e.g. Vinca minor, Fragaria vesca
and Brachypodium sylvaticum) are still alive and they sometimes
expanded.
Restocking of forest herbs in reforestation sites is a good practice
to promote their presence; otherwise would be very difficult for
these plants to colonize woody habitat, just because of their limi-ted
dispersion capability. In anthropic environment landscape
matrix is often characterized by urban sprawl or intensive agricul-ture,
void of ecological networks and ancient or conserved woody
patches.
Since forest herbs are shade-tolerant, it is clear that it would be
possible to plant them when the canopy is enough to allow these
species to grow up: projects already finished show that after ten
years it would be possible to start planting forest herbs.
Finally, it is important to underline that the selection of forest
herbs depends on preliminary studies, such as ecology and struc-ture
of vegetation, presence of invasive alien species, availability
of forest herbs to be transplanted. Several in situ and ex situ stu-dies
show that not all forest herbs have the same germination ra-te,
so it is important to select the suitable ones (Cerabolini et al.,
2004).
References
Blair, R.B. 1996. Land use and avian species diversity along an urban gra-dient.
Ecological Applications 6(2):506–519.
Bock, C.E., and Z.F. Jones. 2004. Avian habitat evaluation: should coun-ting
birds count? Frontiers in Ecology and Environment 2(8):403– 410.
Brusa G., Bottinelli A., Castiglioni L.R., Cerabolini B., 2012. La flora erba-cea
nemorale nel Parco Nord Milano. Informatore Botanico Italiano, 44:
153-158
Cerabolini B., Ceriani R.M., De Andreis R., Villa M. (2004) Il Centro per la
Flora Autoctona della Regione Lombardia. Informatore Botanico Italiano
36(1):309-312
Conover, M. R. (2002). Resolving Human-Wildlife Conflicts: The Science
of Wildlife Damage Management, Lewis Publishers, ISBN 156670538X,
Boca Raton, Fla
Donnelly, R., and J.M. Marzluff. 2006. Relative importance of habitat
quantity, structure, and spatial pattern to birds in urbanizing environ-ments.
Urban Ecosystems 9:2, 99
Massa, R., L. Bani, D. Massimino, and L. Bottoni. 2003a. Foreste e biodi-versità
faunistica in Lombardia. La biodiversità delle foreste valutata per
mezzo delle comunità degli uccelli. Collana “C’è vita nel bosco.” Edizioni
Regione Lombardia – Agricoltura, 123 pp. (in Italian).
Nespoli L., 2010. Confronto ecologico tra boschi spontanei e rimboschi-menti
in ambito planiziale. Elaborato finale. Università degli Studi di Mila-no,
Corso di Laurea in Scienze Naturali, Dipartimento di Biologia, Sezione
di Botanica Sistematica e Geobotanica. Relatore prof. C. Andreis
Sandström, U.G., P. Angelstam, and G. Mikusinski. 2006. Ecological diver-sity
of birds in relation to the structure of urban greenspace. Landscape
and Urban Planning 77:39–53.
138

Sanesi, G., Padoa Schioppa, E., Lorusso, L., Bottoni, L., & Lafortezza, R.
(2009). Avian Ecological Diversity as an Indicator of Urban Forest Func-tionality.
Results from Two Case Studies in Northern and Southern Italy.
Arboriculture & urban forestry, 35(2), 80-86.
Whigham D.F., 2004. Ecology of woodland herbs in temperate deciduous
forests. Annu. Rev. Ecol. Evol. Syst. 35:583-621
139

2.7
POLLUTANTS MITIGATION AND CARBON
SEQUESTRATION
GIOVANNI SANESI , GIUSEPPE COLANGELO, ROBERTO COMOLLI
Due to the progressive urbanization of the population, cities are increasingly becoming larger and larger, and consequently are prime
centers of pollutants production. The anthropogenic activities cause strong emissions of gas (CO2, NOx, SOx, NH4, etc..) and particula-te
matters (PM 10 and PM 2.5).
Over the years, the CO2 and other greenhouse gases (GHG) have become of great importance in view of the effects of Global Warming,
concerning their concentration in the atmosphere. Therefore, since the end of the Nineties (Kyoto Protocol, 1997), there have been ta-ken
measures to reduce the GHG or to increase their storage and ink in different ecosystems.
140

Literature on urban trees and environment highlights the positi-ve
contribution to air quality provided by the deposition of pollu-tants
in the vegetation canopy, bark and root system, by the se-questration
of atmospheric CO2 in woody biomass and by the re-duction
of temperatures.
In particular, forests, trees and vegetation play an important role
in the storage of carbon dioxide, as well as in the absorption of
other gaseous pollutants.
The Kyoto Protocol includes forests in the accounting of CO2 and
thus many researches have been carried out in this area.
Ryan et al. (2010) showed what could be the role of forests in the
U.S. to offset the carbon dioxide emissions. U.S. forest growth
and harvested wood products currently offsets 12-19% of U.S. fos-sil
fuel emissions. Forestry trees carbon storage differs from ot-her
mechanisms that control atmospheric CO2 (e.g. ocean) becau-se
forests have a life span and cycle during which CO2 vary with
forest age. Trees storage carbon through photosynthesis: leaves
capture the energy by sun shine and convert CO2 from the atmo-sphere
and water into carbohydrates that are used for the growth
of new above and below ground biomass (e.g. leaves, wood, and
roots). The 50% of the CO2 that is converted into carbohydrates
is respired by vegetation to maintain their metabolism, and the
other 50% provide biomass for new leaves, wood, and roots. Due
to life cycle, over time the trees grow older and gradually provide
to the ground dead parts (e.g. branches, leaves, roots, etc.); in-sects
and microorganisms decompose this dead mass, releasing
CO2 back to the atmosphere, but a percentage of the carbon still
remains in the soil. Attending the results of research, live and
dead trees contain about 60% of the carbon in a mature forest,
and soil and forest litter contain about 40%. The net long-term
CO2 source/sink dynamics of forests change through time as tre-es
grow, die, and decay. The carbon varies with forest age, clima-te
and soil condition. The trees can cyclically produce biomass
that can be used as a fuel or as a construction material. Depen-ding
on the different destination carbon can be released into the
atmosphere with different methods and timing.
The role of urban forests in the carbon cycle is definitely lower
than that of the traditional forests, but takes on a dimension that
is not sufficiently emphasized. From the Chicago Project (Novak,
1994), especially in the U.S., studies have been conducted on the
absorption capacity of CO2 and other pollutants by urban fo-rests.
Novak and Crane (2002) estimated U.S. urban forests sto-re
700 million tonnes of carbon with a gross carbon sequestra-tion
rate of 22.8 million t C/yr. The same authors estimated the
U.S. average urban forest carbon storage density is 25.1 t C/ha,
compared with 53.5 t C/ha in forest stands. Davies et al. (2011),
in the city of Leceister (UK), estimated 231.521 tonnes of carbon
stored within the above-ground vegetation, equating to 3.16 kg
C/m2 of urban area, with 97.3% of this carbon pool being associa-ted
with trees rather than herbaceous and woody vegetation. At-tending
this research results domestic gardens can store just
0.76 kg C/m2, which is not significantly different from herba-ceous
vegetation land cover (0.14 kg C/m2). The greatest above-ground
carbon density is 28.86 kg C/ m2, which is associated
with areas of tree cover on publicly owned ⁄managed sites. Simi-
141

lar data for carbon storage and sequestration by urban forests ha-ve
been recorded in Shenyang (China) by Liu and Li (2012) and
in Karlsruhe (Germany) by Kändler et al. (2011). Less quantity of
carbon store has been detected in warm climate condition and
dry summer as Barcelona (Spain) by Chaparro and Terradas
(2009) or in Oakland (USA) by Nowak (1993). These results indi-cate
that the C storage and sequestration rate varied among ur-ban
forest types with different species composition, age structu-re,
and climate situation. All these results can be used to help as-sess
the actual and potential role of urban forests in reducing at-mospheric
CO2 in different latitudes. These results can provide
insights for technicians, decision-makers and citizens to better
understand the role of urban forests, and make better manage-ment
plans for urban forests.
The above-ground biomass and the tree growth can be calculated
at tree levels using allometric equations. These equations are pri-marily
derived from forested areas in Europe, North America
and Asia (Pastor et al.,1984; Zianiis and Mencuccini, 2004; Zia-nis
et al., 2005;Tabacchi et al., 2011); currently, there are also
equations, in terms of tree growth, for urban trees (McHale et al.,
2009; Semenzato et al., 2011; Marziliano et al., 2013). If multiple
equations are available for a species, they can be combined to
produce a generalized result (Pastor et al., 1984; McHale et al.,
2009). If no species-specific allometric equation exists, an equa-tion
derived from all broadleaf ⁄ coniferous trees can be used.
The above-ground biomass can be esteemed using similar appro-ach
(Jackson et al.,1996; Cairns et al., 1997).
It’s important the conversion from fresh to dried weight biomass
and the conversion from biomass to a carbon storage.
142
The Vertical Wood: on balconies of a private building in Milan
trees were planted to absorb pollutants.

For this operation we can use conversion factors (e.g. Nowak,
1994; Milne & Brown 1997; Nowak and Crane, 2002).
The allometric equations approach can be coupled with field sur-veys
or remote sensing approach (e.g. Davies et al. 2011; Liu and
Li, 2012).
Pollutants mitigation
The pollutants removal is another important effect of the urban
trees presence even though the pollutant uptake rates decrease
when decreasing tree canopy cover or changing the forest structu-re.
In the urban environment, pollutants are released from many
anthropogenic sources such as industry, combustion of fossil
fuels in vehicular traffic, and energy production. Among them
transport is the most significant source of air pollution due to the
increasing of element such as lead, NO2, chromium, CO, O3,
NH4.
Trees remove gaseous air pollutants by uptake via leaf stomata or
plant surface. Once inside the leaf, gases diffuse into intercellular
spaces and may be absorbed by water films to form acids or react
with inner-leaf surfaces. Trees also remove pollution by intercep-ting
airborne particles. Some particles can be absorbed into the
tree, though most particles that are intercepted are retained on
the plant surface. The intercepted particle often is re-suspended
to the atmosphere, washed off by rain, or dropped to the ground
when leaf and twig fall (e.g. Nowak, 2006). Consequently, vegeta-tion
is only a temporary retention site for many atmospheric par-ticles.
However literature investigated the impact on the functio-nality
of trees that can cause negative consequences and can de-grade
the urban environmental quality by an increase in water
use and the release of volatile organic compound (VOCs) emis-sions
that might lead to secondary formation of ground-level ozo-ne.
The role of the soil
The plant biomass (aboveground and underground) is able to ac-cumulate
large amounts of carbon (in the form of organic mat-ter)
in woody tissues, thereby sequestering and limiting the gre-enhouse
effect of CO2. However, the storage is only temporary,
although it can last for decades or centuries: at the end of the life
cycle of the forest, the organic carbon can be re-released (combu-stion
of wood, dead organic matter mineralization). Immobiliza-tion
of a longer-term (centuries or millennia) is that which oc-curs
in soil: the dead organic matter, especially of plant origin,
reaches the ground and is accumulated on the surface (litter),
but especially at depth along the entire thickness of the profile,
where it undergoes transformations of chemical type that make
it very resistant to microbial attack and degradation. The organic
matter strongly influences the characteristics and behavior of the
soil and its fertility is the foundation of agronomic and forestry:
it has a positive influence on the porosity, the water holding capa-city,
the ability to release nutrients for plants, etc.
Also urban soils can have a potential role for storing a large amo-unts
of Soil Organic Carbon (SOC) and, thus, can contribute in
143

the mitigation of atmospheric CO2 concentrations. Lorenz and
Lal (2009) estimated the amount of SOC stored in urban soils is
highly variable in space and time, and depends among others on
soil parent material and land use. Attending the results of these
authors the SOC pool in 0.3-m depth may range between 16 and
232 Mg/ha, and between 15 and 285 Mg/ha in 1-m depth.
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Semenzato, P., Cattaneo, D., Dainese, M., 2011. Growth prediction for five
tree species in an Italian urban forest. Urban Forestry and Urban Gree-ning
10 (3), 169–176.
Tabacchi G, Di Cosmo L, Gasparini P (2011) Aboveground tree volume
and phytomass prediction equations for forest species in Italy. Eur J Fo-rest
Res 130:911-934
Zianis D, Mencuccini M (2004). On simplifying allometric analyses of fo-rest
biomass. Forest Ecology and Management 187: 311–332
Zianis D, Muukkonen P, Mäkipää R, Mencuccini M (2005). Biomass and
stem volume equations for tree species in Europe. Silva Fennica Mono-graphs
4, pp. 63.
145

2.8
THE URBAN HEATH ISLAND (UHI). HOW TREES
CAN MITIGATE THE UHI AND HEAT PEAKS;
EXPERIENCES FROM DIFFERENT LATITUDES
GIOVANNI SANESI, LUIGI MARIANI, SIMONE PARISI, GABRIELE COLA
Cities and urban settlements are characterized by urban patterns resulting from the spatial organization of urban elements, namely
building curtains and canyons, street rows, paved surfaces and parks. The urban patterns interact with climatic factors (wind, solar ra-diation,
precipitation, etc.) and determine the wide variety of microclimates that characterize each urban area (Geiger et al., 2009; Oke,
2002; Stull, 1997). This, in turn, gives rise to the significant increase of urban air temperature that contrasts with the surrounding tem-perature
in rural areas, known as the Urban Heat Island (UHI) effect. The UHI effect is strongly modulated by synoptic and mesoscale
146

circulation patterns (main strength during dynamic anticyclonic
weather conditions) and is more evident during night-time hours
(the UHI peaks at sunrise).
UHI studies began with Bowen in 1926, and more recently with
Lewis (1995), Geiger et al. (2009), Munn (1966), and Oke (2002)
embracing analyses performed in very different macroclimates,
such as the subarctic (Hinkel et al., 2003), the tropics (Priyadarsi-ni
et al., 2008), mid-latitudes (Solecki et al., 2005; Offerle et al.,
2005), and the Mediterranean (Mihalakakou et al., 2004). These
studies are based on remote sensing monitoring (e.g., satellite da-ta)
or different types of data resulting from direct measurements
gathered by standard or mobile weather stations.
The quantitative study of the time and space evolution of the
UHI for a specific urban pattern and as a function of the time
and space evolution of other micrometeorological variables (e.g.,
solar radiation, relative humidity, and prevailing winds) is rele-vant
for urban planning and management policies (Mariani and
Pangallo, 2005). Among the most promising applications of such
studies, there is the appropriate selection of green areas (e.g.,
tree species and varieties, shrubs and grasses, and orientation of
tree rows and bushes) in the more general context of the urban
pattern project (e.g. shape, height, size, and orientation of buil-dings
and urban canyons). Moreover, these studies can be a use-ful
support to the management choices of urban green spaces
and to the utilization of urban green areas (Borgström et al.,
2006; Baycan-Levent and Nijjkamp, 2009; Lo and Jim, 2012;
Jim and Shan, 2013).
Many micrometeorological studies have described the UHI effect
and quantified the influence of different urban traits, paying par-ticular
attention to planning and mitigation (Hamada et al.,
2013). Nevertheless, a systematic characterization of the UHI
phenomenon in time and space is difficult to obtain, since each
urban area is a collection of microclimates and is prone to dyna-mic
and impacting transformation processes. For more details
on the UHI, see http://www.urbanheatislands.com/. In this con-text,
the segmentation of the urban pattern into concentric belts
(from the inner city center toward the suburbs and rural areas),
which are homogeneous in terms of UHI, is a useful theoretical
approach (Oke, 2002). However, this approach has some
drawbacks when is applied to cities with dendritic patterns,
which is the case of most major Italian cities where the urban/ru-ral
limit is hardly recognizable. A further significant limitation is
represented by urban green areas and parks, which create consi-stent
discontinuity in the urban network and, consequently, in
the UHI (Lafortezza et al., 2009). A review of the urban greening
effects on the UHI in different macroclimates was carried out by
Bowler et al. (2010), while Grimmond et al. (2010) reviewed the
physical approaches to urban energy balance simulations in the
context of the International Urban Energy Balance Models Com-parison
Project.
147

Communities can take a number of steps to reduce the UHI ef-fect:
• increase areas covered with grass and well-watered trees (mi-tigation
from shadowing and latent heat released in place of
sensible heat);
• create green roofs (also called "rooftop gardens" or "eco-roofs")
and green walls;
• install cool—mainly reflective—roofs and pavements.
These strategies are inter alia approved by The United States En-vironmental
Protection Agency
(http://www.epa.gov/heatisland/)
References
Baycan-Levent, T., Nijjkamp, P. (2009). Planning and management of ur-ban
green spaces in Europe: Comparative analysis, Journal of Urban Plan-ning
and Development, 135 (1), pp. 1-12.
Borgström, S.T., Elmqvist, T., Angelstam, P., Alfsen-Norodom, C. (2006).
Scale mismatches in management of urban landscapes Ecology and Socie-ty,
11 (2), art. no. 16.
Bowler D.E., Buyung-Ali L., Knight T.M., Pullin A.S., 2010. Urban gree-ning
to cool towns and cities: A systematic review of the empirical eviden-ce,
Landscape and Urban Planning 97 (2010) 147–155.
Geiger, R., Aron, R. and Todhunter, P., 2009. The Climate Near the
Ground, 7th edn. Lanham, MD: Rowman & Littlefield.
Grimmond et al., 2010. The International Urban Energy Balance Models
Comparison Project - First Results from Phase 1, Journal of applied meteo-rology
and climatology, Vol. 49, 1268-1292.
Hamada, S.; Tanaka, T.; Ohta, T., 2013. Impacts of land use and topo-graphy
on the cooling effect of green areas on surrounding urban areas.
Urban Forestry & Urban Greening vol. 12 issue 4 2013. p. 426-434.
Hinkel, K.M., Nelson, F.E., Klene, A.E. and Bell, J.H. 2003. The urban
heat island in winter at Barrow, Alaska. Int. J. Climatol. 23, 1889–1905.
Jim, C.Y., Shan, X. (2013), Socioeconomic effect on perception of urban
green spaces in Guangzhou, China, Cities, 31, pp. 123-131.
Lafortezza R., Carrus G., Sanesi G., Davies C. (2009). Benefits and well-being
perceived by people visiting green spaces in periods of heat stress.
URBAN FORESTRY & URBAN GREENING, vol. 2, p. 97-108, ISSN: 1618-
8667, doi: 10.1016/j.ufug.2009.02.003.
Lewis, J.M., 1995: The Story behind the Bowen Ratio. Bulletin of the Ame-rican
Meteorological Society, 76, pp 2433–2443.
148

Lo, A.Y.H., Jim, C.Y. (2012). Citizen attitude and expectation towards gre-enspace
provision in compact urban milieu Land Use Policy, 29 (3), pp.
577-586.
Mariani L., Pangallo G.S., 2005. Approccio quantitativo all'analisi degli
effetti urbani sul clima (Quantitative approach to the analysis of the urban
effects on climate), Rivista italiana di agrometeorologia, 2, 31-36 (in Ita-lian).
Mihalakakou G., Santamouris M., Papanikolaou N., Cartalis C., Tsangras-soulis
A., 2004. Simulation of the Urban Heat Island Phenomenon in Me-diterranean
Climates, Pure Appl. Geophys. 161 (2004) 429–451.
Munn R.E., 1966. Descriptive micrometeorology, Academic Press, 198 pp.
Offerle B., Grimmond C.S.B., Fortuniak K., 2005. Heat storage and anthro-pogenic
heat flux in relation to the energy balance of a central european
city centre, Int. J. Climatol. 25: 1405–1419.
Oke T.R., 2002. Boundary layer climates, Taylor & Francis, 464 pp
Priyadarsini R., Wong N.H., Cheong K.W.D., 2008. Microclimatic mode-ling
of the urban thermal environment of Singapore to mitigate urban
heat island, Solar Energy, 82, 727–745.
Solecki W.D., Rosenzweig C., Parshall L., Pope G., Clark M., Cox J., Wienc-ke
M., 2005. Mitigation of the heat island effect in urban New Jersey, Envi-ronmental
Hazards 6 (2005) 39–49.
Stull R.B., 1997. An introduction to boundary layer meteorology, Kluwer
Academic Publishers, Dordrecht, 670 pp.
149

2.9
LANDSCAPE
BENEDETTO SELLERI
The issue of landscapes is of an essential importance among the objectives of UPF management; for when it comes to urban and sub-urban
areas it is particularly important that the forests are perceived as a sense of beauty, due in particular to their naturalness in rela-tion
to the anthropized context they can be found in. Current research and experiences carried out in Italy and abroad have shown
that particularly important aspects regarding the landscape of UPF concern the forest edges, sunlight and the presence of clearings,
appreciation and protection of particular spaces, and finally the “diversification” perceptive of the ecosystem.
These aspects are acted upon appropriately by silvicultural interventions such as thinning, cutting, pruning, underplanting, and
through maintenance interventions.
150

Forest edges
A forest edge constitutes an element of a landscape that is of par-ticular
importance for it is quite visible. It is for this reason that
it should be considered the subject of particular attention, both
during the project planning phase and during management inter-ventions
of thinning or reforestation, depending on the type of
edge to be obtained:
• whether there should be a penetrable view or not from within
the forest
• with a natural tendency both in terms of design and structure
• variable from a chromatic point of view. That is, with species
characterized by particular florescence, autumn fructifications
or colors of leaves
• variable from a structural point of view with trees of large sizes
in the foreground, or with a gradual transition from shrubby
elements of modest sizes to arboreal elements that become tal-ler
and taller
Chromatic variability of a forest edge in Park Expo, Osaka, Japan
151

Forest edge with a penetrable view, Parc du Sausset, France Diversified cuts of grassland at Parc du Sausset (France) in order to allow easy and
sustainable usability
152

Sunlight
From a recent study carried out within the EMoNFUr project on
PNM, it was verified that users of UPF appreciate sunlight inside
of forests. The greater presence of sunlight leads to the creation
of sparse forest areas and small clearings that also become spa-ces
for resting, relaxing and playing, and the diversification of
the ecosystem with an increase in biodiversity. This objective is
pursued through selective thinning from above or with small
gaps clearcuts.
The enhancement and protection of particular spaces
With selective pruning and thinning out, forest areas should be
protected and appreciated where there are:
• stretches or streams of water
• focal points or viewpoints
• trees that are particularly beautiful for poise, structure or size
• trees with a particular build, appropriate for children playing,
climbing or hiding
• walking trails
153
Forest edge of an urban park in Leipzeig, with agricultural crops
Clearing with a small pond in Halde Rheinelbe, Ruhr

These areas should be in plain view, turned into transit and resting areas so that they can be accessed and appreciated by as many
people as possible.
154
Clockwise from top-right:
• Viewpoint in a public park in Berlin
• View of a “focal point” in Gleispark Frin-trop,
Ruhr
• Canal in the forest of an urban park
in Leipzeig

155
Clockwise from top-right:
• Sloping tree used for children playing in a
park in Amsterdam
• Playful use of a dried out tree trunk in an ur-ban
park in Leipzeig
• Raised walkway in a forest in Floriade
(Netherlands)

156
Clockwise from top-left:
• Access ramp in a forest in Floriade
(Netherlands)
• Raised walkway at Shoneberger.
The raised part of the pathway invites users
to respect the grass fields so that they are not
trampled on
• Walkway among the tree crowns at Park
EXPO in Osaka, Japan

The “diversification” of the landscape
Elements which can diversify a landscape should be inserted in
UPF. A well-structured forest landscape is more “interesting”
and at the same time may create situations that would allow a
better insight into the forest.
The same forest structure could also be diversified per area, plan-ning
out a differentiation of silvicultural treatments, and alterna-ting
forest areas with diverse structures that are vertical (mono-planes,
biplanes or stratified), horizontal (more or less dense) or
more or less filled with shrubbery.
Dead trees on the ground and woodpiles are elements of diversifi-cation.
Leaving several dead trees on the ground will allow peop-le
to observe the structure of trees and, in the case of rooted tre-es,
their root system. Moreover, making woodpiles available will
create a potential play area for children.
In conclusion, outside of forests, elements of diversification
which should also be protected and appreciated are hedges and
tree rows of particular value.
157
Dead tree trunk left in the forest (Riserva Naturale Statale Bosco del-la
Fontana, province of Mantova) and conveniently treated in order
to increase animal biodiversity

2.10
HEALTH AND WELL-BEING
GIOVANNI SANESI, GIUSEPPE CARRUS
The World Health Organization’s (WHO-HFA 2002) defines health as not merely the absence of illness but as a general state of physi-cal,
social, and mental wellbeing. How important are UPFs to urban quality and to wellbeing? In urban environments, UPFs have de-monstrate
to represent ameliorating factors of some climatic features related to heat stress and to provide comfortable outdoor set-tings
for urban residents (Lafortezza et al. 2009). Tzoulas et al. (2007), on a literature review of a wide body of interdisciplinary stu-dies,
argued that urban and periurban green spaces (i.e., green infrastructure and UPFs) can provide healthy environments and physi-cal
and psychological health benefits to people residing within and nearby them. An extensive Dutch study by Maas et al. (2006), loo-ked
at the relationships between public health and greenness of people’s living environment. Their research indicated that people li-ving
in urban areas generally are less healthy than people living in areas that are more natural. They argued that green spaces are mo-re
than just a luxury, but are rather a requirement to maintain or improve the public health of urban populations.
158

Mitchell and Popham (2007) confirmed that a higher proportion
of green space in a given residential area is associated with better
health outcomes, but they were unable to say whether this was
simply because people in these parts of the city were wealthier or
because there was a causal relationship in play. However, this
study shows that green space can help in reducing income-rela-ted
health inequalities. A healthy population also implies equitab-le
access to good local environments, hereby including effective
communication, participation and involvement in local decision-making
process. For this reason, we have to rethink our relation-ship
between cities and the UPFs.
More recently, various studies showed that access to green space
in urban areas is associated with improved overall well-being, in-cluding
benefits related to both physical and mental health (Bow-ler
et al., 2010, Lee and Maheswaran, 2011, Logan and Selhub,
2012; van den Berg et al., 2010). Wilker et al., (2014) associated
green spaces with health benefits in terms of post-stroke survi-val.
The relationship between green spaces and wellbeing is not
still clear; UPFs and trees may be associated with lower exposure
to ambient air pollution, extreme heat, and noise. Proximity and
accessibility to green spaces offers opportunities for physical acti-vity
and social interactions; access to green space has been asso-ciated
with personal wellbeing, lower stress levels and better co-gnitive
functioning (see for example Carrus et al., 2013; Hartig et
al., 2011; Park et al., 2010, Van Den Berg et al., 2007). A review
on the physiological effects of experiencing green spaces, forest
and trees was recently provided by Haluza et al. (2014).
Finally, in these last years a more recent stream of studies is inve-stigating
the role of green spaces in promoting factors such as so-cial
cohesion, personal self regulation and prosociality. An intere-sting
field experiment recently conducted by Guéguen and Stefan
(2014) showed for example that individuals are more willing to
help other people after a short walk in an urban park.
From a policy making perspective, Nowak and Dwyer (2007) al-so
argued that the benefits of green space in towns depend on ap-propriate
management practices, so that we would need a better
understanding of these benefits and a better understanding of
the costs that are generated from the provision and maintenance
of urban forests. Since many of the benefits are not market-ba-sed,
these authors argued for the need of environmental econo-mics
to quantify and assign monetary value to urban forest servi-ces,
in order to allow decision makers to make more direct com-parisons.
The aim is to deliver the appropriate benefits to any lo-cality.
Urban forestry sees the urban forest as an ecosystem
within and extending beyond the urban system and aims to
analyze the interactions between the natural and socio-economic
systems.
In brief, the provision of adequate green space in urban settings
seems crucial for the promotion of public health. The current po-pulation
of Europe enjoys better health than any generation sin-ce
the beginning of humankind. People today have a longer life
expectancy than ever before (WHO-HFA 2002). However, longe-vity
and quality of life might not necessarily be the same thing,
and there is a continuing concern to improve the quality of life of
large sectors of populations, in particular in view of the progressi-
159

ve increasing of urban population worldwide. The state of the en-vironment
in cities is consequently of great importance to most
Europeans; on the other hand, environmental problems, from
the global to the local level, are often rooted by the increasing ur-ban
activities and by the pressure they put on natural resources.
References
Bowler, D.E., Buyung-Ali, L.M. , Knight, T.M., Pullin, A.S. 2010. A sy-stematic
review of evidence for the added benefits to health of exposure to
natural environments. BMC Public Health, 10 (2010), p. 456 .
Carrus, G., Lafortezza, R., Colangelo, G., Dentamaro, I., Scopelliti, M., Sa-nesi
G. (2013) Relations between naturalness and perceived restorative-ness
of different urban green spaces. Psyecology 4 (3), 227-244
Guéguen, N., Stefan, J., (2014). ''Green Altruism'': Short Immersion in
Natural Green Environments and Helping Behavior. Environment and Be-havior
published online 1 July 2014.
Hartig, T., Berg, A., Hagerhall, C., Tomalak, M., Bauer, N., Hansmann,
R. Ojala, A., Syngollitou, E., Carrus, G., van Herzele, A., Bell, S., Ca-milleri
Podesta, M.T., Waaseth, G. 2011. Health benefits of nature expe-rience:
psychological, social and cultural processes,. K. Nilsson (Ed.) et al.,
Forests, Trees and Human Health, Springer, Netherlands, pp. 127–168.
Haluza, D., Schönbauer, R., Cervinka, R. (2014) Green Perspectives for Pu-blic
Health: A Narrative Review on the Physiological Effects of Experien-cing
Outdoor Nature. Int J Environ Res Public Health. May 2014; 11(5):
5445–5461.
LAFORTEZZA, R., CARRUS, G., SANESI, G., & DAVIES, C. (2009). Bene-fits
and well-being perceived by people visiting green spaces in periods of
heat stress. Urban Forestry & Urban Greening, 8, 97-108.
Lee, A.C. , Maheswaran, R. 2011. The health benefits of urban green spa-ces:
a review of the evidence J. Public Health, 33: 212–222.
Logan, A.C. Selhub, , E.M. 2012. Vis medicatrix naturae: does nature “mi-nister
to the mind“? BioPsychoSoc. Med., 6 , p. 11.
Maas J, Verheij RA, Groenewegen PP, de Vries S, Spreeuwenberg P
(2006) Green space urbanity, and health: how strong is the relation? J Epi-demiol
Community Health 60:587–592
Mitchell, R., & Popham, F. (2008). Effect of exposure to natural environ-ment
on health inequalities: An observational population study. Lancet,
372, 1655-1660.
Nowak DJ, Dwyer JF (2007) Understanding the benefits and costs of ur-ban
forest ecosystems. In: Kuser JE (ed) Urban and community forestry in
the Northeast. Springer, New York, pp 25–46
Park, B., Tsunetsugu, Y., Kasetani, T., Kagawa, T., Miyazaki, Y. 2010.
The physiological effects of Shinrin-yoku (taking in the forest atmosphere
or forest bathing): evidence from field experiments in 24 forests across Ja-pan.
Environ. Health Prev. Med., 15: 18–26.
Tzoulas K, Korpela K, Venn S, Yli-Pelkonen V, Kaźmierczak A, Niemela J,
James P (2007) Promoting ecosystem and human health in urban areas
using green infrastructure: a literature review. Landsc Urban Plan 81(3,
20):167–178.
VAN DEN BERG, A. E., HARTIG, T., & STAATS, H. (2007). Preference for
nature in urbanized societies: Stress, restoration, and the pursuit of sustai-nability.
Journal of Social Issues, 63, 79-96.
Van den Berg, A.E., Maas, J. , Verheij, R.A., Groenewegen, P.P. 2010. Gre-en
space as a buffer between stressful life events and health. Soc. Sci.
Med., 70: 1203–1210.
WHO-HFA (2002) World Health Organisation regional office for Europe.
Statistical Data Base Health for all (HFA-DB)
Wilker, EH, Wub, CD., McNeely, E., Mostofsky, E., Spengler, J., , Welle-nius,
GA., Mittleman MA., 2014. Green space and mortality following
ischemic stroke. Environmental Research, Volume 133: 42–48.
160

BOX
WORKSHOP:
MAINTENANCE OF UPF
ELISA BARBANTE
On November 14, 2013 the workshop “The silvicultural man-teinance
of urban and peri-urban artificial forests. Prospects
and criticalities”, sponsored by the EMoNFUr (LIFE + 10
ENV/IT/399) project was held at Palazzo Lombardia in Mi-lan.
The first part was dedicated to the presentation of the
EMoNFUr project and the management of UPF, with inter-ventions
related to the instruments developed within the proj-ect
and the main results of the carried out monitoring.
161

Professor Sanesi, with the presentation titled “Silvicultural inter-ventions
and thinning in urban forest plantations”, analyzed is-sues
relating to the subject of silvicultural interventions, the spe-cificity
of urban forestry systems and several significant expe-riences
within the urban context.
The second part of the day was entirely dedicated to the mana-gement
of UPF and thinning, leading to the experiences had
and the good practices that were adopted. The urban and peri-urban
forest plantation have purposes and functionalities that
differ from traditional ones. The methods of silvicultural inter-ventions
to be implemented and their intensity mainly depend
on the ecosystem services that are considered priorities, with
particular reference to those that are in support of biodiversity,
carbon sinks, and social and landscape aspects.
Beginning with the different experiences had in the Lombardy
territory, the main issues concerning the maintenance of the
UPF were addressed, in particular: the issue of thinning in a
new lowland forest and in lowland wood, thinning aimed at
preventing the growth of alien species, prevention and phytosa-nitary
measures with the cases of Parco del Ticino and the Cen-
162

tro di Forestazione Urbana di Boscoincittà, and the increase of
the usability of urban forests with the case of Parco Nord Mila-no.
The working groups have addressed issues concerning the ob-jectives
and criteria that should guide the silvicultural choices
made and the involvement of volunteers in the management
and maintenance of UPF, thus representing a moment of deba-te
and discussion among the stakeholders involved with the ma-nagement
of UPF.
The objectives and criteria that guide the silvicultural choices
made, in particular with regards to thinning, should support
usability and accessibility, ensure safety (diseased trees, wildli-fe,
harmful associations), pursue the highest biodiversity possib-le
in order to redevelop an environment that is similar to a natu-ral
one, allow economic sustainability by acting on the organi-zation
of the works, the involvement of more individuals and
the relationship with the wood sector, promote the increased
stability of forests, the spreading of the culture of forests in or-der
to raise awareness and explain to citizens the choices of
necessary maintenance, even if they are at times unpopular.
Two interventions regarding the involvement of stakeholders in
the maintenance of UPF were presented by Nina Caferelli of
the Associazione di volontariato La Risorgiva that operates at
the Bosco della Giretta, and Sergio Pellizzoni of the Italia No-stra
association that carries out its work activities at Boscoincit-tà
(CFU – Centro di Forestazione Urbana).
As far as the stakeholders’ role in the maintenance of UPF is
concerned, the working group identified aspects and activities
that are capable of involving volunteers and citizens.
All the WS material can be downloaded at this link.
BOX
163

BOX
THE FOREST
MAINTENANCE
ACTIVITIES IN THE
RUHR’S PARKS
PAOLO NASTASIO
The management of urban and peri-urban forests is general-ly
characterized by a high intensity when it is compared to
the care and maintenance that characterize the average of
a forest coverage on a regional scale. However, in several
particular contexts, less intensive management methods may
be adopted, including choices of non-intervention which
would intensify natural evolution, reducing any intervention
and human guidance in the development of populations to a
minimum.
164

This is the case with a number of forest areas located within the
Emscher Regional Park, which was possible to visit during the
study trip in the Ruhr area. In particular, newly formed forest
sites were visited which, in many cases, originated from the
spontaneous processes of forest colonization that followed the
accumulation of inert material that derived from the mining in-dustry
(residue from the crushing and washing of coal). In the
mines still active the process of forestation is instead accelera-ted
by the obligation imposed to the concessionaire by the pu-blic
authorities to progressively provide afforestation works of
newly formed stands. The process of natural colonization was
favored by the presence of abundant mother trees present in
the surroundings, where birch is considered the essential and
primary pioneer element.
The following insertion to consider is that of European ash and
sycamore, and a good cortege of shrubbery. The scarcity or
complete absence of invasive non-native species is seen as posi-tive,
if an exception is made for red oak which, however, is wil-lingly
tolerated in the region. The presence of robinia is less
common, a species which in some cases was introduced volun-tarily.
The two aspects that better distinguish the management of the
visited forests are:
•The lower overall intensity of maintenance interventions, hi-ghlighted
by the state of apparent abandonment of many
areas to unhindered evolution
•A less exaggerated attention to the aspects linked to the safe-ty
of visitors.
165

These aspects are strongly correlated. The costs of forest main-tenance
are kept to a minimum, and the intraspecific and inter-specific
competition and natural succession help guide the fo-rest
structure towards forms that are progressively and more
ecologically stable. Without human intervention to help shape
and guide a forest structure it will find itself with considerable
amounts of standing dead mass (typically with the replacement
of birch) that will be tolerated, provided that there are no well-frequented
paths, in which case safety measures would have to
be taken.
The presence of significant amounts of dead wood greatly in-creases
the biodiversity of areas of relatively recent formation
(saproxylic fungi, insects, ornithofauna etc.). Even the mainte-nance
of internal paths appears to be carried out with very litt-le
care: trails that are barely useable, unsuitable for the disa-bled,
which, however, help to increase the sense of the appa-rent
naturalness of the areas, and in any case, integrate with
the main pedestrian and bicycle traffic that is often well plan-ned
and cared for.
The attention to safety is certainly present, but appears to be
less influenced by “accident neurosis” that seems to prevail
with forest and urban park administrators. The legal and cultu-ral
context seems to lay more responsibility on the end-users of
the natural areas and the parents of young visitors, obligating
them to a greater awareness of the inherent risks in visiting
such natural spaces. A prime example is the lack of protection
separation between the visited forest areas and active railway
lines, or the aforementioned tolerance of standing dead trees
bordering the main pathways, which requires full observance
of the pathways themselves or a conscious acceptance of the
risks for those who venture into the middle of the forest.
BOX
166

2.11
UPF GOVERNANCE AND MANAGEMENT,
SLOVENIJA CASE STUDY
ANDREI VERLIČ, URŠA VILHAR, ROBERT HOSTNIK, ANŽE JAPELJ
National level strategy for GI of UPF
Spatial development strategy of Slovenia (2004) defines "green system" as the integrity of landscape components within the boundari-es
of a town or settlement area. The green system’s components of a town are individual parts of open space, which differ in function,
structure, and degree of naturalness, yet are still interrelated. UPF are included and discussed as one of the components of green sy-stem.
GI is not separately mentioned.
167

National forest programme (2007) deals with UPF in relation to
the social aspects of forests with the objective to significantly con-tribute
to the quality of life, in particular to the health of all citi-zens.
It lists several guidelines, as maintaining free access of the
public to forests, increasing the share of state and municipally
owned forests in the proximity of larger cities, adapting forest
management, and strengthening the educational function of fo-rests.
GI is not specifically defined.
Operative Spatial Planning Act (OGRS 33/2007, 57/2012) defi-nes
relationships among different spatial acts, their contents and
types. It defines green areas as ones that contribute to the impro-vement
of quality of life in settlements; therefore their state
should not be detoriated by development of settlements. It hi-ghlights
that green areas should have a special planning focus on
the level of detailed urbanistic plans of specific settlements (mu-nicipal-
level planning).
Act on forests (OGRS 30/1993, 17/2014) provides basis for decla-ring
urban forests as special-purpose forests and defines basis
for special management regimes.
Nature conservation act (OGRS 56/1999, ... 41/2004) and Natu-ra2000
acts refer to GI as element of potential conservation of
biodiversity in dense-settlements areas.
Regional level strategy for GI of UPF
System of spatial planning on regional level is in preparation and
is not formally implemented yet. Nevertheless, the system of re-gional
planning for forest lands exists since 1950s. Every 10
years, Regional forest management plans are regularly prepared
by Slovenia Forest Service for 14 regions. Regional forest manage-ment
plan includes the category of "forests of special purpose"
which are defined as forests with particularly emphasized envi-ronmental
or social functions. UPF are mainly included in this
category. Regional forest management plans define locations of
forests of special purpose and provide general objectives and gui-delines
for their management. Regional forest management
plans cover a forest areas of 50.000 to 140.000 ha.
168

Managing Urban Forests for Sustainability

Managing Urban Forests for Sustainability

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