Country Report: Italy. Cost Action non-native tree species for European forests

Considering the specific climatic conditions, Italy is one of the European countries most affected by the invasion of not native species. The country has been a centre of intense exchange and colonization of non-native biota as a result of human trade and migrations ever since ancient times (Blasi et al. 2007). The inventory of the Italian non-native flora of Celesti-Grapow et al. (2009), shows that in Italy there are 1,023 NNTS and sub species, about 13.4% of all the Italian flora. Among these not native species, 101 are tree species, in particular 32 gymnosperms, 69 angiosperms (Table 1). Many of these species have been introduced for ornamental and non-productive purposes. Comparing the Celesti-Grapow et al. inventory list (2009) and the listof tree and shrub species recorded during the second Italian National Forest Inventory (INFC2005), 34 species are common to both lists, out of which 15 are naturalized, 10 are casual and 9 showed invasive behaviour (Rizzo and Gasparini, 2011). Within the “forest” category of INFC2005 , the total number of NNTS trees (stems with diameter at breat height larger than 4.4 cm) represented 4.4% of the overall total number of trees while 2.7% was the proportion of invasive invasive species trees. Concerning the basal area and volume of invasive NNTS, the proportion was 1.9% and 1.8%, respectively, of the total basal area and volume of Italian forests (Rizzo and Gasparini, 2011). In Italy, despite the hard experimental work carried out at the beginning of the last century, the overall planted surfaces with NNTS are rather small. Only in some regions and for some species, such as Douglas fir in Tuscany, Pinus radiata in Sardinia, and Eucalyptus spp. in Sicily and Sardinia, the plantations cover large areas, causing a significant environmental and landscape impact, that was not always accepted by local people. After a primary impulse to use NNTS, due to public financing in South Italy and to strong demand of some companies, related to the paper industry in Tuscany during the 60s, the creation of new plantation and forestation activities with NNTS has had a relatively limited relevance in Italy. The future of wide NNTS plantations in Italy will be the conversion with native species. This process has already started in Sicily with Eucalyptus spp. Many alien plantations have already reduced significantly their consistency due to fires, pests and diseases as it happened to Pinus radiata in Sardinia, while small groups of exotic species included in conventional reforestation, will follow a policy of naturalization. Currently in Italy the possibility of further spread of NNTS, it can be considered only in the context of a productive plantations for wood production (Nocentini, 2010). Among NNTS tested in Italy the Douglas fir appears to be on a large scale the most interesting from the adaptive and productive point of view (Nocentini, 2010). The first Douglas fir in Italy was introduced in the 1878 in the Arboretum Pinetum P. Moncioni at Cavriglia (province of Arezzo, Italy). With more than 2,000 ha in Tuscany, the average productions reach and sometimes exceed 10 m3/ha/year in plantation 20-30 years old (Asoni et al., 1989; Ciancio et al., 1992). The forest biomass for energy production, enhancing research to optimize the use of Robinia pseudoacacia and Eucalyptus spp. in short-rotation forestry (SRF). However, particularly for Eucalyptus the commercial applications for energetic biomasses is not yet significant (Bisoffi et al., 2009). Currently is starting a new interest for Douglas fir wood production. In Italy the most widespread NNTS is Robinia pseudoacacia L., that accounts for 92.7% of the total number of trees of invasive exotic speciesand 92.9% of the total basal area of the same species (“High forest category” of INFC2005, natural and semi-natural forests) (Rizzo and Gasparini, 2011). The number and density of NNTS is highest in artificial land use types. Closed-canopy forests have long been cited as highly resistant to invasion. However, while invasion of forests (in particular by shade-tolerant NNTS) may be a slower process than the establishment of NNTS in disturbed or open ecosystems, the long-term effects are likely to be just as pervasive (Martin et al. 2009).