Long-term effects of short rotation forestry with willows and poplar on soil properties

Abstract

Short rotation forestry is a promising tool for biomass production. In order to determine long-term effects of short rotation forestry on chemical, biochemical and physical soil properties we have investigated two former arable sites with willow and poplar clones (Salix and Populus spp.) in northeast Germany. The organic carbon and the total nitrogen contents of the sandy topsoil increased up to 4.0 g kg−1 and 0.2 g kg−1, respectively after 12 years. The C/N ratio was higher under short rotation forestry caused by the stronger C than N accumulation. The contents and reserves of plant available phosphorus and potassium were decreased significantly from the 6th to the 12th year, but the plant supply was still sufficient without fertilization. The pH in the topsoil was significantly lower under willow clones than under poplar clones. Higher dehydrogenase activity of the soil was measured under poplar and willows than at tree-less control plots. The bulk density decreased and the porosity of the soil increased under short rotation forestry. In conclusion the major long-term effects of short rotation forestry on arable used Cambisols were the accumulation of organic matter followed by slightly improved soil physical conditions and increased soil biological activity.