Ecological boundaries for sustainable biomass harvest in production forests.

The rapidly increasing demand for tree biomass for industrial applications and energy, added to ongoing demands for timber, requires more intensive use of production forests (i.e., tree production systems). Demands for biomass trigger whole tree harvesting (WTH), partially replacing conventional stem only harvest (SOH). WTH involves removal of stem and branches and causes higher removal of nutrients in forests compared to SOH. WTH may be ecologically unsustainable since it may decrease nutrient pools of the forest production system, causing a decline in productivity and ecosystem integrity during following rotations. Yet, it is unclear under which conditions current-day-practices of biomass harvest are ecologically sustainable or not, especially concerning the nutrient poor sandy soils on which a major part of the Dutch production forests is located. We aim at providing science-based guidelines for ecologically sustainable biomass harvest. We propose to assess how tree species, soil and management influence the balances of biomass, nutrients, and carbon in production forests. We will evaluate the effects of harvest intensity and management on forest biomass, nutrient and carbon balances, and recovery on nutrient poor sandy soils. Based on this new experimental information, a nutrient budget model will be validated to optimize ecologically sustainable management for biomass yields for different forests on nutrient poor sandy soils. The model will serve as a decision support system for forest managers and forest policy makers to evaluate biomass yield from ecological sustainability principles. This application will provide new guidelines to use Dutch forests in an sustainable way under increasing demands.