Biomass, biomass increment and nutrient cycling were studied in (1) a Scots pine (Pinus sylvestris) stand, (2) a Norway spruce (Picea abies) stand and (3) a mixed birch (Betula pubescens)/pine stand on a drained mire at Ilomantsi, eastern Finland in 1979-85. In addition, the effect of NPK and micronutrient fertilizer treatment was studied. Above-ground and root measurements were taken. These data formed the basis of stand biomass and nutrient cycle simulations of fertilized and unfertilized stands. The increases in biomass were greater in (1) and (2) in the fertilized simulation than in the unfertilized one. For (3), the effect of fertilization on biomass increment was small. In six years only part of the applied fertilizer had been fixed in the biomass of the model stands and proportionally less micronutrients than macronutrients. The potassium stores were small compared to the nutrient amounts fixed by the stands. This supports the notion that there is a shortage of potassium on deep-peat soils.

The effects of wood ash and PK fertilization on natural regeneration and sowing of Scots pine (Pinus sylvestris L.) were studied in field experiments on nitrogen-poor (Ntot 0.87–1.26%) peat substrates. The study material was derived from three drained, nutrient-poor pine mires (64°52'N, 25°08'E) at Muhos, near Oulu. The experimental fields were laid out in 1985 as a split-split-plot design including the following treatments: mounding, natural regeneration and sowing and fertilization; PK at a level of 400 and wood ash 5000 kg ha–1. The seedlings were inventoried on 648 circles and vegetation on 324 circles in July–August 1991. Changes in the vegetation were small and there were no statistical differences due to the fertilization treatments in the ground vegetation. PK or ash fertilization did not cause vegetational changes harmful to Scots pine regeneration on nitrogen-poor peatlands. Both sowing and fertilization significantly increased the number of pine seedlings, but not their height. Wood ash increased seedling number more than PK fertilizer. The number of seedlings varied from 7963 (control) to 42 781 ha–1 (mounding + sowing + ash). The number of pine seedlings even on non-mounded, non-fertilized naturally regenerated plots was adequate for successful regeneration. The number of birch seedlings varied more than that of pine (370–25 927 ha–1). Mounding especially increased the number of birches. The difference between PK fertilizer and ash was less pronounced than that for pine. In addition to the field studies the effects of ash and PK fertilizer on the germination of Scots pine seeds was studied in a greenhouse experiment. Soaking in ash solutions strongly reduced seed germination, while the PK solution was less harmful.