The distribution of the above-ground biomass of two 35-year-old alder (Alnus incana) stands growing on an Oxalis-Myrtillus site and an Oxalis-Maianthemum site, as well as their total annual production and the amounts of nutrients bound in the annual production are examined in the study. An attempt is made to estimate the effect of whole-tree harvesting carried out at different times of the year on the loss of nutrients. There were considerable differences in the stage of development of the stands owing to the differences in site fertility. The biomass of the above-ground part of the tree stand was 33,6 t/ha in the Siilinjaervi experiment and 69.2 t/ha at Nakkila. The annual productin was 5,3 t/ha and 6,4 t/ha respectively. The alder stands consumed the following amounts of nutrients to produce one tonne of biomass: 16,7 kg N, 1,1 kg P, 5,1 kg K and 5,8 kg Ca. On the average, around 73% of the nitrogen, 46% of the phosphorus, 78% of the potassium and 93% of the calcium bound each year in the stand were returned to the ground in the litterfall. The ground vegetation accounted for 13% of the annual biomass production of the whole stand at Siilinjaervi. The ground vegetation utilized considerably more potassium, phosphorus and calcium to produce one unit of dry matter than the tree stand, and approximately the same amount of nitrogen. There were no clear differences in nutrient removal between whole-tree harvesting carried out at different times, partly owing to the internal cycling of nutrients within the trees and partly to the fact that part of the leaves shed when harvesting was carried out.
