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Urban Forest management - chapter 2


Published on - 3 capitolo del manuale *Urban and Periurban Forests. Management, monitoring and eco system services*.
Il manuale è stato concepito come un prodotto multimediale continuamente aperto ad aggiornamenti e arricchimenti. Rappresenta il risultato del lavoro di un équipe multidisciplinare che ha affrontato, da più punti di vista, il tema delle foreste urbane e periurbane, offrendo riflessioni, spunti e indicazioni tecnico/scientifiche in merito alla loro pianificazione, monitoraggio e manutenzione.
Per questo il manuale costituisce un utile strumento per tecnici, professionisti, amministratori coinvolti nella gestione del patrimonio verde urbano e periurbano.

Published in: Environment
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Urban Forest management - chapter 2

  2. 2. 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. 2.1 113
  3. 3. 2 - URBAN FORESTS MANAGEMENT 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 (, 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, 114
  4. 4. 2 - URBAN FORESTS MANAGEMENT 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). 115
  5. 5. 2 - URBAN FORESTS MANAGEMENT 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. 116
  6. 6. 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- 117
  7. 7. 2 - URBAN FORESTS MANAGEMENT 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 118
  8. 8. 2 - URBAN FORESTS MANAGEMENT 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. 119 Click HERE to download the Italian version
  9. 9. 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 2.3 120
  10. 10. 2 - URBAN FORESTS MANAGEMENT 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 121
  11. 11. 2 - URBAN FORESTS MANAGEMENT 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. 122 Click HERE to download the Italian version
  12. 12. 2 - URBAN FORESTS MANAGEMENT REFERENCES Società Italiana di Arboricoltura International Society of Arboriculture Prof. Dr. Claus Mattheck ULTRASONIC, ELECTRIC AND RADAR MEASUREMENTS FOR ASSES-SMENT OF LIVING TREES - Luigi Sambuelli, Laura Valentina Socco, Al-berto Godio Demetra Cooperativa Sociale - VTA Fitoconsult – Analisi di stabilità 123
  13. 13. 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- 124
  14. 14. 2 - URBAN FORESTS MANAGEMENT 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”). 125
  15. 15. 2 - URBAN FORESTS MANAGEMENT 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. 126
  16. 16. 2 - URBAN FORESTS MANAGEMENT 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 127
  17. 17. 2 - URBAN FORESTS MANAGEMENT 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 128
  18. 18. 2 - URBAN FORESTS MANAGEMENT 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. 129
  19. 19. 2 - URBAN FORESTS MANAGEMENT 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”). 130
  20. 20. 2 - URBAN FORESTS MANAGEMENT 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
  21. 21. 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
  22. 22. 2 - URBAN FORESTS MANAGEMENT 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
  23. 23. 2 - URBAN FORESTS MANAGEMENT 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 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. Click HERE to download the Italian version REFERENCES Piussi, P. 1994, Selvicoltura generale. UTET, Torino 134
  24. 24. 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
  25. 25. 2 - URBAN FORESTS MANAGEMENT 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
  26. 26. 2 - URBAN FORESTS MANAGEMENT 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)
  27. 27. 2 - URBAN FORESTS MANAGEMENT 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
  28. 28. 2 - URBAN FORESTS MANAGEMENT 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
  29. 29. 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
  30. 30. 2 - URBAN FORESTS MANAGEMENT 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
  31. 31. 2 - URBAN FORESTS MANAGEMENT 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.
  32. 32. 2 - URBAN FORESTS MANAGEMENT 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
  33. 33. 2 - URBAN FORESTS MANAGEMENT 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. References Cairns M.A., Brown S, Helmer E.H., Baumgardner G.A., 1997. Root bio-mass allocation in the world’s upland forests. Oecologia. 111:1-11. Chaparro, L. & Terradas, J. (2009). Ecological services of urban forest in Barcelona. Ajuntament de Barcelona: Àrea de Medi Ambient Institut Mu-nicipal de Parcs i Jardins. Davies, Z. G., Edmondson, J. L., Heinemeyer, A., Leake, J. R. & Gaston, K. J. (2011). Mapping an urban ecosystem service: Quantifying above-ground carbon storage at a city-wide scale. Journal of Applied Ecology, doi:10.1111/j.1365-2664.2011.02021.x Kändler, G., Adler, P. & Hellbach, A. (2011). Wie viel Kohlenstoff spei-chern Stadtbäume? Eine Fallstudie am Beispiel der Stadt Karlsruhe [How much carbon is stored by urban Trees – A case study from the city of Karlsruhe]. FVA-Einblick, 2, 7–10 (in German). Jackson R.B., Canadell J., Ehleringer J.R., Mooney H.A., Sala O.E., Schul-ze E.D., 1996. A global analysis of root distributions for terrestrial biomes. Oecologia. 108:389-411. Li, C., Li, X. (2012) Carbon storage and sequestration by urban forests in Shenyang, China. Urban Forestry & Urban Greening , Volume 11, Issue 2, 121–128. Lorenz, K., Lal, R., (2009) Biogeochemical C and N cycles in urban soils. Environment International, 35, 1–8. 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), pp. 246-254. doi: 10.1016/j.ufug.2013.01.006 McHale, M.R., Burke, I.C., Lefsky, M.A., Peper, P.J., McPherson, E.G., (2009). Urban forest biomass estimates: is it important to use allometric 144 Ryan et al., 2010
  34. 34. 2 - URBAN FORESTS MANAGEMENT relationships developed specifically for urban trees? Urban Ecosystems 12 (1), 95–113. Milne, R. & Brown, T.A. (1997) Carbon in the vegetation and soils of Great Britain. Journal of Environmental Management, 49, 413–433. Nowak, D. J. (1993). Atmospheric carbon-reduction by urban trees. Jour-nal of Environmental Management, 37(3), 207–217. Nowak, D. J. (1994). Atmospheric carbon dioxide reduction by Chicago’s urban forest. In E. G. McPherson, D. J. Nowak, & R. A. Rowntree (Eds.), Chicago’s urban forest ecosystem: Results of the Chicago Urban Forest Cli-mate Project (pp. 83–94). United States Department of Agriculture, Fo-rest Service. Nowak, D. J. & Crane, D. E. (2002). Carbon storage and sequestration by urban trees in the USA. Environmental Pollution, 116(3), 381–389. Nowak, D.J., Crane, D.E., Stevens, J.C. (2006) Air pollution removal by urban trees and shrubs in the United States. Urban Forestry and Urban Greening, 4 (3-4), pp. 115-123. Pastor, J., Aber, J.D. & Melillo, J.M. (1984) Biomass prediction using gene-ralized allometric regressions for some northeast tree species. Forest Eco-logy and Management, 7, 265–274. Ryan, M. G., Harmon, M. E., Birdsey, R. A., Giardina, C. P., Heath, L. S., Houghton, R. A., Jackson, R. B., McKinley, D. C., Morrison, J. F., Murray, B. C., Pataki, D. E., Skog, K. E. (2010) A Synthesis of the Scien-ce on Forests and Carbon for U.S. Forests. Issues in Ecology. Report Num-ber 13. 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
  35. 35. 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
  36. 36. 2 - URBAN FORESTS MANAGEMENT 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 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
  37. 37. 2 - URBAN FORESTS MANAGEMENT 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 ( 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
  38. 38. 2 - URBAN FORESTS MANAGEMENT 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
  39. 39. 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
  40. 40. 2 - URBAN FORESTS MANAGEMENT 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
  41. 41. 2 - URBAN FORESTS MANAGEMENT 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
  42. 42. 2 - URBAN FORESTS MANAGEMENT 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
  43. 43. 2 - URBAN FORESTS MANAGEMENT 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
  44. 44. 2 - URBAN FORESTS MANAGEMENT 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)
  45. 45. 2 - URBAN FORESTS MANAGEMENT 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
  46. 46. 2 - URBAN FORESTS MANAGEMENT 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 Click HERE to download the Italian version
  47. 47. 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
  48. 48. 2 - URBAN FORESTS MANAGEMENT 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
  49. 49. 2 - URBAN FORESTS MANAGEMENT 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
  50. 50. 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
  51. 51. 2 - URBAN FORESTS MANAGEMENT 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
  52. 52. 2 - URBAN FORESTS MANAGEMENT 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 Click HERE to download the Italian version
  53. 53. 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
  54. 54. 2 - URBAN FORESTS MANAGEMENT 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
  55. 55. 2 - URBAN FORESTS MANAGEMENT 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 Click HERE to download the Italian version
  56. 56. 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
  57. 57. 2 - URBAN FORESTS MANAGEMENT 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