DEPENDENCE OF SILVER BIRCH (Betula pendula Roth.) STEM VOLUME ON DIAMETER AT BREAST HEIGHT AND TREE HEIGHT

Abstract

The study assessed silver birch (Betula pendula Roth.) stem volume using sectional stem measurements. Data from 130 model trees were analysed, comprising 1,595 measurement records. Diameter at the root collar and diameter at 1.3 m height were measured before felling, whereas sectional stem measurements were taken after the trees had been felled. Stem volume was calculated using the frustum formula, and the Huber method was additionally applied for comparison. Four stem volume models were analysed: a single-variable diameter model, a single-variable height model, a multiple linear model, and a logarithmic model. The mean stem volume calculated by the frustum formula was 0.440 m³, while the mean volume calculated by the Huber method was 0.438 m³. The diameter model explained 95.2% of stem volume variation, the height model explained 74.2%, the multiple linear model explained 96.3%, and the logarithmic model showed the highest accuracy with a coefficient of determination of 0.9876. Comparison of stem volumes calculated by the frustum formula and the Huber method showed that the results were practically identical.