Impact of whole-tree harvesting and compensatory fertilization on growth of coniferous thinning stands

A series of 16 field experiments was established to quantify the growth response of first-thinning stands of Pinus sylvestris and Picea abies to whole-tree harvesting (WTH), and to estimate the need for nutrient compensation. The experiments were undertaken in Finland, Norway and Sweden and represent a wide range of climatic and soil conditions. The biomass and nutrient amounts removed were estimated on the basis of felled sample trees. On average, WTH reduced tree volume growth in both pine and spruce stands (5% and 6%, respectively) during the first 10-year period. The growth reduction was counteracted by fertilization (NPK) and the results indicate that the reduction was an effect of reduced N supply. The inclusion of various site descriptive variables in the linear models did not explain variation in growth response to WTH. Since the growth reductions due to WTH after 10 years were still present, the observation period needs to be extended. (C) 2000 Elsevier Science B.V. All rights reserved.