Predicting effects of different harvesting intensities with a model of nitrogen limited forest growth

The anticipated increasing utilisation of forest biomass necessitates impro ved understanding of its long-term consequences on forest productivity. We have used a model of carbon and nitrogen fluxes to predict effects of diffe rent management regimes in Norway spruce stands at three levels of fertilit y. Stands with high production are the least sensitive to intensified harve sting, partly because these stands occur in regions with high nitrogen depo sition which compensates for the removal in nitrogen in harvests. Intensifi ed thinning with stem-only removal is the management that affects productiv ity least followed by whole-tree harvesting at clear-fellings. Whole-tree t hinnings are less beneficial and shortened rotation times the least desirab le from a production point of view. Increases in total biomass harvests are at the expense of stem harvest, which can mean a conflict between volume a nd value. The importance of secondary vegetation as is also discussed. (C) 1999 Elsevier Science B.V. All rights reserved.