Data collected from 183 poplar and 102 willow SRC experimental plots, located in Central-North Italy, were subjected to stepwise regression analysis to acquire information on the environmental factors affecting plant survival and productivity in the first two-year rotation cycle. Nine Populus ×canadensis Mönch, eight P. deltoids Bartr. clones and four hybrids of Salix matsudana Koidz were included in analysis. Independent variables were: annual and seasonal water availability (rainfall and irrigation), annual mean air temperature, soil texture, pH, N and organic matter content, planting density and management intensity. Dependent variables were: a) mean annual yield during the first two-year rotation cycle in tons per hectare per year of dry matter (Odt·ha ); b) plant survival at the end of the second year from planting (%). Water availability resulted the main variable driving plant survival and biomass production in both poplar and willow clones. Water availability appeared to be the principal factor affecting the establishment of poplar and willow energy plantations in the Po valley. Possible variations in the rainfall regime consequent to climate changes could seriously influence land suitability to SRC. Experimental data also indicate that choice of planting density may increase the biomass yield during the first two-year especially with P. deltoides clones.
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Keywords: Biomass production • Poplar • Willow • Short rotation coppice • Soil texture • Climate factors • Soil nutrient contents
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CRA -Agricultural Research Council, PLF -Research Unit for Wood Production Outside Forests, I-15033 Casale Monferrato (AL), Italy
IntroductionBiomass from short rotation coppice (SRC) is one of the possible alternatives to fossil fuels in Europe. Poplar and willow SRC plantations can produce large amounts of dry matter in a relatively short time (e.g. 1-2 years) maintaining their yield capacity throughout many years [1].During the last 5 years about 6000 hectares of energy plantations (Short-Rotation-Coppices, SRC) have been established in Italy, mainly in the Po valley, where biomass thermoelectric power plants are under construction, and the Regional Programs for Rural Development included a series of financial incentives to support the establishment and maintenance of SRC. The planted species were those recommended for the North and Central Italy by the National guidelines for energy plantations [2,3] namely poplars (Populus Cent. Eur.