Thinning Models Based on Profitability Calculations for Southern Finland

1992

35 S.

47 Lit. Ang.

Bandaufführung

2628

37302

The aim of the present study was to make financially optimal thinning models for Scots pine and Norway spruce stands. The main objective of the forest management was assumed to be the net present value of the future revenues from a forest stand at three and five per cent interest rates. Calculations concerned solely thinnings from below. In order to distinguish regional differences, thinning models were made separately for four sub-regions in southern Finland. The basic data consisted of relascope sample plots from the 7th and 8th National Forest Inventory in southern Finland. The calculations were carried out with MELA-software and the thinning models were made by using linear mixed model analysis. According to the calculations, thinnings were essential for the financial return of a forest stand. The profitability of the thinnings was due to the accelerated growth of the stand stock and the temporal distribution of the revenues. Due to the mortality, the profitability of the thinnings was accented in Scots pine stands. The thinning models based on the net present value of the future revenues resulted in remarkably heavier thinnings than those recommended by Forestry Center Tapio. Consequently, fewer thinnings were needed. Assuming a three per cent interest rate two to three thinnigs were made during the rotation. At the interest rate of five per cent, a single thinning usually sufficed for both Scots pine and Norway spruce stands. The financial return can be improved by intensifying and postponing the first thinning as per present recommendations. The postponement of the first thinning resulted in higher volume removed, bigger harvestable stems, and hence lower unit costs per thinning. The postponement of the first thinning was always profitable notwithstanding whether the successsive thinnings were made in accordance with the models presented here, or those of Tapio. The profitability of the postponement was accented in Norway spruce stands. Financially the best management regime for Scots pine and Norway spruce stands was to tend young stands at the mean heigth of 4-6m to a density of 2000 stems/ha, to postpone the first thinning to the mean heigth of 13m as earliest and to make 1-3 heavy thinnings during the rotation.