Biomass equations for determining fractions of pendula and pubescent birches growing on abandoned farmland and some practical implications

Biomass production was estimated in 10 stands each of pendula birch (Betula pendula Roth) and pubescent birch (Betula pubescens Ehrh.) growing on abandoned farmland. The pendula birch stands were located in Sweden at latitudes ranging from 66° to 58°N, and their total age varied from 8 to 32 years. Pubescent birch stands were located at latitudes ranging from 66° to 60°N, and their total age varied from 6 to 20 years. A modified “mean tree technique” was used to estimate biomass production; i.e. the tallest tree was chosen for sampling. The actual mean total dry weight above stump level was 71 tonnes ha−1 (range, 6 to 175 tonnes d.w. ha−1) for pendula birch stands and 27.3 tonnes ha−1 (range, 7 to 61 tonnes d.w. ha−1) for pubescent birch stands. In addition to estimating conventional dry weights of trees and tree components, specific leaf area, total surface area and LAI, among other measures, were estimated.