49 / 55
47
characteristics (Agnelli et al., 201
0 56). Furthermore, compost can contribute to improve soil
water retention;
•
Mycorrhizal inocula and biostimulants. These include different products and, generally, they
are specie-specific. Some increase root apparatus retake after plantation (also increasing
resistance to stresses). Furthermore they increase nutrient supply. When using mycorrhizal
inocula, it is important that roots maintain a good humidity to support mycorrhiza
development. Among biostimolants, the most used are seaweeds, especially in range biologic
management, because they are natural fertilizers and, furthermore, they can contribute to the
prevention of several diseases thanks to the supply of vitamins and oligoelemens, etc.;
•
Artificial mixes. They are artificial substrata which tolerate footfall and allow roots
development, so without threaten plants vitality. Then they are particularly useful near streets
or on pavements. In general they are composed of a rocky matrix, of soil, which insinuate
between matrix pores, and of an artificial binder.
•
Finally, sometimes, if soil lacks in one or more elements, it could be necessary to resort to chemical
manuring, at least for first months after planting. Anyway, it is appropriate to assess in advance the use
of manures and fertilizers, which if from a side can help a rapid retake of the new plants, in the other
side can cause later imbalances (for example in presence of good nutrient supply, roots can be
stimulated to grow too much).
2.2 Planting
A properly planted tree will be more tolerant of adverse conditions and require much less
management than one planted incorrectly. In the following paragraphs a description is given of how to
correctly execute some major planting interventions, once soil has been properly prepared.
2.2.1 Planting patterns
When planning a forestation project (also after specific surveys), it is necessary to define how
many trees will be planted in the selected area and a specific planting density has to be chosen (how
many trees per hectare). In case of vast surfaces, a preliminary signing on the soil of each single site
where seedlings will be bedded out can be useful (Figure 5)
.
Figura 5
-
Example of preliminary signing with stakes and caution tape in a green area of Rome
When choosing the planting pattern it is advisable to prefer the one that allows abatement of costs
(for example a linear, regular designs if high mechanization has to be used
) 57. However, in order to
realize a more natural and woodland-like plantation it is advisable to opt for non-linear and irregular
planting model
s 58(no straight rows, but, for example, a sinusoidal pattern), with trees species with
56
Agnelli A., Bellasio C., Boschi C., Colangelo G., Ferrini F., Fini A., Lafortezza R., Mishra S., Nicese F., Pellegrini S., Sanesi G., 2010.
Impiego del compost di qualità nel verde urbano. Una scelta di sostenibilità
. NET n. 51 Confservizi Cispel Toscana.
57
A planting pattern 2,5x1,5 m allows the way to a compact tractor among rows (Lassini et al., 1998. Forestazione urbana per la Lombardia.
Regione Lombardia e Azienda Regionale delle Foreste).
58
In the past regular planting patterns were mainly used, but in more recent planting geometric scheme has been replaced with planting
arranged along curve lines (Marziliano P.A., Lafortezza R., Colangelo G., Villa G., Colombo T., Selleri B., Tucci R., Sanesi G., 2009.