Increment losses by full-tree harvesting in Norway spruce ( Picea abies)

Abstract

In three experiments, pre-commercial thinning has been carried out in three different ways. After felling, the trees in one treatment were immediately removed, in another treatment they were removed one growing season later, so as to leave the needles in the stand, and in a third treatment the felled trees were left in the stand. Three years after the establishment of the experiments it turned out that the basal area increment differed by 12% between the treatment where the felled trees were left in the stand as a whole, and the two other treatments. Since in one experiment the nutrient supply of nitrogen and phosphorus was increased significantly in the treatment where the felled trees were left in the stand, it is concluded that the increment differences between the treatments can be interpreted as the fertilizing effect of the slash when left in the stand.