Nutrient Budgets in Forests Under Increased Biomass Harvesting Scenarios

A developing bioeconomy and the need for alternate sources of energy are promoting a more intensive procurement and use of forest biomass. While it is a fact that increased biomass harvesting generates greater nutrient losses from forest ecosystems relative to stem-only harvesting,the use of nutrient budget approaches as a decision support tool in managing forests under intensive biomass removal is uncommon. This lack of use can be explained by several factors including: large uncertainties in predicting certain fluxes, the poor representation of nutrient dynamics following harvest in nutrient cycling models,the lack of representation of biological feedback,the lack of appropriate validation,and finally the lack of maps of specific soil properties that would be required to predict nutrient budgets over forest landscapes. This review documents the impact of intensive biomass extraction on nutrient cycling and discusses the gaps in knowledge and the uncertainties associated with nutrient budgets. It identifies research and development issues that need to be resolved for making forest nutrient budgets more reliable and more useful to address the questions regarding the environmental sustainability of intensive biomass harvesting.