Agroforestry systems for the production of woody biomass for energy transformation purposes

In the temperate zone, agroforestry systems come increasingly into focus as, they offer an approach for the production of fuelwood, thus matching the increasing demand for a self-supply with bioenergy in rural decentralized areas. Because of the large area potential of marginal land, research activities aimed at a reliable estimation of the minimum productivity of fast-growing tree species under most unfavourable site conditions. Two agroforestry systems were established on reclaimed mine sites in NE-Germany (Lusatia) and Central Germany (Helmstedt). The yield potential and the sustainability of yields were studied for different clones of poplar (Populus spp.), willow (Salix viminalis L.), and black locust (Robinia pseudoacacia L.), considering different rotation periods (3-, 6-, and 9-year-rotation) and approaches of soil amelioration (mineral fertiliser, compost). On both sites the highest yields of woody biomass were found for R. pseudoacacia L. regardless of rotation period and amelioration measures. on loamy substrates in the Helmstedt mining district, all tree species and clones responded positively to soil amelioration measures. In the agroforestry system in Lusatia, special emphasis was given to the interaction between trees (R. pseudoacacia) and crops (Medicago sativa L.). Considering the land equivalent ratio (LER), R. pseudoacacia hedgerows have practically no negative influence on yields of M. sativa. Hence, with regard to an increasing demand for woody biomass, alley cropping with R. pseudoacacia and crops such as M. sativa may provide a promising alternative for future land use in the temperate zone. (c) 2006 Elsevier B.V. All rights reserved.