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18
Legend
“0” ecosystem service of no value (this symbol refers also to soil groups that provide a significant number of
disservices);
+++: ecosystem service of high value;
++: ecosystem service of medium value;
+: ecosystem service of low value.
Brackets are used to introduce intermediate scores
Survey, mapping and quality assessment of urban soils (mainly for
Technosols
) is a very
complicated and complex task. Human activities have played an overwhelming role in the
distribution of soil or parent materials with different pedogenetic processes.
Strategies for sampling and methods for data spatialization and management, different from those
of the conventional pedological methods, must be planned. Great variability of soil types in very
narrow spaces makes it impossible to adopt a soils distribution model to guide the survey. For the
same reasons the existing soils databases can be useful only to define the soil "potentially" present
in urban areas, but not as a source for punctual soil information.
Despite these difficulties the knowledge of soils is of fundamental importance in order to develop
management policies of urban green spaces and for food security.
The urban and peri-urban areas are those most affected by the dynamics of land use/land cover
changes. Therefore, it makes it essential understand how such soils can be managed, rehabilitated
or reconditioned to support green infrastructure or urban agriculture.
Studies in various world cities show that compaction, low content of organic matter and
contamination, generally due to atmospheric deposition from various sources and past land uses,
are the most common problems of urban soils.
Also some soils of Rome record high values of heavy metals (Pb, Pt, Ba, Cu, Zn), mainly near the
main road or in correspondence of past human activity.
The content of heavy metals in soils is highly dependent on geochemical behaviour, pedogenic
processes and anthropogenic influences. Nevertheless, their accumulation in the soils is
considerable because they are persistent.
Contamination of urban soils by heavy metals may represent, therefore, a serious problem for
human health due to the possible presence of high concentrations in places normally frequented by
highly sensitive subjects, as in urban gardens, or for their passage in the chain food by means, for
example, the consumption of agricultural products.
For this reason is necessary to know the characteristics of the soils not only to quantify the
ecosystem services that would be lost due to urbanization but also to evaluate their quality,
especially if used for recreational use or for urban agriculture.
Thus, heavy metals in urban and suburban soils can be successfully used as indicators for the
evaluation of the environmental contaminations by hazardous metals due to anthropogenic and
industrial activities or a high natural content. The study of geochemical contamination, allows
differentiation of anthropogenic pollution from the one linked to the geological characteristics
(natural background value), and provides useful information on the impact of human activities. It is
important for the implementation of suitable measures of long-term prevention and for planning a
monitoring of soil and environment quality.
1.3 Planning addresses
Urban forestry includes “
the management of trees and forest resources in and around urban
community
for the physiological, sociological, economic, and aesthetic benefits
”
22. Thus urban
forestry includes the set of all trees and shrubs existing in urban and periurban areas. So this definition
includes not only wood areas, but also green belts and tree-lined rows. Considering the aims of the
forestry intervention and the site characteristics, it is possible to consider different typologies of urban
forests: for example to mitigate climate change and to increase biodiversity it would be better to create
a new wooded area, while for atmospheric pollutants abatement and for anti-noise barriers it would be
chosen primarily tree-lined rows, especially in urban areas.
22
Definition of “
urban forestry
” by the Society of American Foresters (Helms, J. (Ed.), 1998.
The Dictionary of Forestry
. Society of
American Foresters, Bethesda.), approved also in Europe (Konijnendijk, C.C., Ricard, R.M., Kenney, A. e Randrup, T.B., 2006.
Defining
urban forestry – A comparative perspective of North America and Europe
. Urban Forestry & Urban Greening 4: 93-103).