Biomass production and allometric above- and below-ground relations for young birch stands planted at four spacings on abandoned farmland

Abstract

The objective of the study was to quantify above- and below-stump biomass of silver (Betula pendula Roth) and downy (Betula pubescens Ehrh.) birches planted at four spacing intervals and growing on two soil types on an area of farmland. The 12-year-old birches had been grown at four spacings (1.3, 1.5, 1.8 and 2.6 m) on two sites: one on medium clay soil and the other on fine sand soil. The dry weight of the stem, branches, leaves, stumps and roots was estimated by drying and weighing sub-samples. The projected leaf area (PLA) m-2 of trees, leaf area index of stands and basic density (kg m -3)of stems were also estimated. A significant greater dry weight of stem, branches, stump and roots and species and spacing for pendula birch were found. The root length of silver birch was significantly greater than that for downy birch and for both species the root length was greatest at the widest spacing (2.6 m). There was also a significant difference between leaf weights of birch of the same species growing on the two soil types. Significant differences were also found between PLA and species, and for both species, between PLA spacing. Basic density of stems was significantly different between soil types. Equations for estimating the above-ground biomass and root biomass from diameter at breast height were developed for birches growing on fine sand and on medium clay soils. The total biomass production per hectare on fine sand was higher for silver birch (19.9-65.9 tonnes ha-1), than for downy birch (13.0-48.3 tonnes ha-1). On medium clay soil, total biomass production for silver and downy birches was 30.8-52.8 and 16.8-42.8 tonnes ha-1, respectively. © Institute of Chartered Foresters, 2007. All rights reserved.