The effects of biomass harvest on nutrient budgets, productivity, and resilience of forests on poor sandy soils are unknown, since we lack science-based guidelines. This study will provide these guidelines based on a unique large-scale forest experiment and by using forest models.
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. Especially demand of woody biomass for energy is increasing since EU-directive of 2009/28/EC points out that we should promote greater mobilisation of our production forest in order to exploit the full potential of biomass for the development towards a bio-based economy. The demand of biomass for energy triggers whole tree harvesting, partially replacing conventional stem only harvest. Whole tree harvest involves removal of stem and branches and causes higher removal of nutrients out of forests systems compared to stem only harvest. As a result of decreasing nutrient pools through whole tree harvest within the forest production system, whole tree harvest may be ecologically unsustainable and may lead to a decline in productivity and ecosystem integrity during following rotations.
Current-day forest management
Not only the increasing demand of tree biomass can lead to a unsustainable system. Even the effects of current-day-practices of biomass harvest on the sustainability and resilience of production forests is still unknown. Especially for production forests located on poor sandy soils, questions rise about the long term stability of the nutrient budget and the implications of management on the productivity of the forest systems. The current-day-practices consist of a variety of sylvicultural systems, cutting methods and soil treatments. We aim to investigate the effects of the current-day-practices regarding tree species, harvest intensity, harvest/thinning methods and soil treatments on the balances of biomass, nutrients and carbon in production forest. Therefore we set up a unique large-scale forest experiment to assess the effects of the current-day-practices on the sustainability, resilience and recovery of the biomass, nutrient and carbon balance for production forests on poor sandy soils.
Science-based guideliness for sustainable biomass harvest
The final goal of this project is to derive science-based guidelines for sustainable biomass harvest from production forests. Therefore we will assess the nutrient balance based on the forest experiment. The data of al incoming (deposition and weathering) and outgoing (harvest and leaching) fluxes of this forest experiment will be used to validate a nutrient budget model. Based on this nutrient budget model we will simulate the nutrient budget during an entire rotation period under different management scenarios. The resulting output regarding the sustainability and recovery of the nutrient budget during the rotation 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.