NUTRIENT CYCLING IN ENERGY FOREST PLANTATIONS

Knowledge about growth and nutrient uptake dynamics within and between seasons, internal nutrient cycling, decomposition and mineralization of litter as well as nutrient losses due to harvest and leakage in energy forest plantations are reviewed. These topics, especially in connection to willow plantations, will be presented and discussed, and where possible, comparisons with other fast growing deciduous tree species like grey alder and poplar will be made. A nitrogen budget during the two first rotations of a willow plantation on good agricultural soil is presented. It is concluded that the fertilizer need in well established and high yielding (>>12 tonnes stems, dry weight, ha-1 year-1) stands is small, about 30 kg N ha-1 yr-1, due to an efficient recycling of N from litter and the relatively low nutrient content in the harvested biomass (stems).