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 res ponse 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 represen t a wide range of climatic and soil conditions. The biomass and nutrient am ounts removed were estimated on the basis of felled sample trees. On averag e, 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 c ounteracted by fertilization (NPK) and the results indicate that the reduct ion was an effect of reduced N supply. The inclusion of various site descri ptive variables in the linear models did not explain variation in growth re sponse to WTH. Since the growth reductions due to WTH after 10 years were s till present, the observation period needs to be extended. (C) 2000 Elsevie r Science B.V. All rights reserved.