Guidelines suistainable urban forestry ROMA_Eng

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new trees/shrubs. However, in protected areas, soil processing for forestry interventions is subjected to
restrictions provided for by Managing Authorities (such as in Rome the RomaNatura Authority) .
The main procedure consists in the ploughing or in the sub-soiling, with a variable depth in relation
to the existing soil conditions. In case of ploughing, soil horizons are overturned to improve airing of
the soil and to create the conditions for a better penetration of roots. However, especially in urban
environment, ploughing could be not suitable because it can bring less fertile layers on surface, or
worst, building waste and residues. Then, in these cases it is better to choose other procedures, such as
sub-soilin , which, differently from ploughing, does not modify soil stratification, but cut the soil
vertically, allowing to improve soil structure and airing and keeping superficial layers more operative.
For this procedure it is possible to use different equipment (tractors, scrapers, ploughs, etc.).
Finally, sometimes, it is necessary to realize other procedures aimed to further reshuffle soil
superficial layers and to improve their characteristics.
2.1.4 Manuring
Subsoil manuring in the implantation site allows to obtain a favorable environment for new plants,
facilitating their rapid achievement. Creating a suitable environment for roots development is even
more important in urban areas, which, as shown in previous paragraphs, can be characterized by
stresses and alterations and present a soil of scarce quality. Then, in these conditions, it could be
necessary a manuring, which, not only improves soil fecundity, but also physic and structural
characteristics (porosity, drainage, etc.). On the basis of site characteristics and fund availability, the
best kind of manuring intervention will be assessed each time. Manuring, however, is not always
necessary (for example in protected areas is not realized). There are different interventions that can be
used for improving soil characteristics before planting. Following the most common procedures are
described.
“Topsoil” consists in a supply of soil collected elsewhere, with the aim to improve chemical-physical
characteristics of the soil in the implantation sit . However, this practice is expensive and not always
justifiable when starting soil conditions are not so bad (in this case it could be better to choose other
interventions such as those described to follow). Furthermore, in this practice it is fundamental to
assess the area of origin of the collected soil (to assess if it is necessary to realize other interventions
before using the new soil, for example to add ameliorants). However, in particular adverse conditions
(original substratum very damaged), the addition of soil can be the best solution to maximize rooting
of plants and, consequently, the achievement of forestry intervention.
Ameliorants are organic matters added in planting holes with the aim to improve soil structure, airing
and water retention, so to reduce plantation stress and facilitate plants growing. It is a practice quite
widespread in urban environment where, as above-mentioned, soils can be very modified both from a
chemical (pH, nutrient supply) and a physical point of view (structure, porosity, water retention, etc.).
Ameliorants, in fact, are first choice matter for every environmental reclamation interventions (ANPA,
200 ).
The quantity of ameliorants to add depends on original substratum but, anyway, it has to be no less
than the 35% per soil volume, in relation to the addition of compost (5-10% in weight), 50-60% (or
more) if sand is added.
According to composition and effects on soil, different ameliorants can be distinguished, in details:
• Compost (the decomposed remnants of organic materials). Compost seems to return the best
results in degraded areas, especially in the season following implantation. Moreover, it
reproduces forest humus characteristics, being rich of microbial flora. Thus, the use of
compost of quality can represent the best choice if there is the need to supply an ameliorant
which not only help the reclamation of soil structure, but also its microbiological
52 Regional Law n. 29 of the 6th October 1997 “Norme in materia di aree naturali protette regionali” (“Rules on the subject of regional
protected areas”), establishes some important measures to consider in forestry interventions localized inside protected areas, such as the
prohibition to collect and to damage spontaneous flora and the prohibition to introduce exotic species.
53 Sub-soiling is a soil processing, generally in depth, which does not cause the soil horizons overturn, but facilitates roots penetration,
drainage and airing.
54 Ideal topsoil should be collected in the site of provenience and immediately used; if this is not possible, it should be stored in
accumulations high less than 2 meters, and, in case of a long period of storage, it should be sown with an appropriate mix of species to
reduce erosion, to maintain structure and to stimulate biotic activity (Bradshaw A., Hunt B., Walmsley T., 1995. Trees in the urban
landscape. E & FN SPON, London, pp. 272.). This practice can be useful also for reducing weed potentially present in the topsoil.
55 ANPA, 2002. Il recupero di sostanza organica dai rifiuti per la produzione di ammendanti di qualità. Manuali e linee guida 7/2002