Comparing Hybrid Populus Clones For SRF Across Northern Italy After Two Biennial Rotations: Survival, Growth And Yield.

Short rotation forest (SRF) plantations of hybrid poplar clones are currently attractive for Italian farmers due to the availability of public grants and the potential for producing wood chips for energy production. Growth and dendromass yield of new clones of hybrid poplars (specific to SRF plantations) were evaluated after two biannual rotations across northern Italy within a network of experimental fields established in spring 2003 on three sites of low (Bigarello), medium (Vinovo) and high fertility (Mira). Soil preparation, planting density (5900 trees ha-1), weed control, tree water status, and biannual mechanical harvesting were homogeneous across the sites. Nitrogen fertilization was applied only in Mira (300 Kg N ha-1). In all sites, survival was high for almost all clones, and stem density increased dramatically, with a parallel decrease of stem dimensions, after the first coppicing. In Bigarello, with limiting soil conditions, there was not significant difference among clone biannual yields, which varied from 10.3 (first rotation) to 14.2 (second rotation) Mg ha-1 in dry matter (dm). In the medium and high fertility sites of Vinovo and Mira, there was significant difference in clone yields, with the new clones performing better than control clones (I-214 and Lux). In Mira, mean biannual yield increased from 30.2 to 40.3 Mg dm ha-1 from the first to second biennial rotation cycle. The network of experimental plantations showed a yield variability in relation to soil fertility, with a range of new clones of hybrid poplar performing better than traditional ones in medium and high site conditions.