00/00309 Case study of 85 m 3 floating drum biogas plant under hilly conditions

Abstract

1500 Stumps of pubescent birch (Betula pubescens Ehrh.) and silver birch (Betula pendula Roth) were studied in four localities in middle and southern Sweden with different site conditions. The naturally regenerated birches were 3 to 19 years old. The stumps were sampled in 15 mm diameter classes from seed-sown trees. Living dormant buds were counted on four segments of the stumps: 0–10 cm above ground, between ground and mineral soil (humus layer), between mineral soil and the first thick root (> 5 mm) and below the first thick root.As a general rule, the pattern of buds on the 1500 birch stumps examined showed differences between localities more than between species. Between 5 and 28% of the buds were situated above ground. There were significant differences between number of buds per stump above ground level and below ground level on both species. The mean number of buds per stump fluctuated between 22 and 129 on both species depending upon locality and forest site. The number of buds was highest on peatland. The distance between ground level and the deepest bud was highest on peatland. Deep peat is a condition for increasing buds. Only on localities with thin humus layer (1–2 cm) did buds emerge in the ground-first thick root layer.Practical implications are given. To manage a birch stand for biomass production, 10–25 cm high stumps should be left on peatland to get a sufficient stand of sprouts, but on localities with thin humus layer (sandy soils and farm land) low stumps may be left. In contrast, to avoid sprout production on peatland the stump must be cut at ground level or just below. On mineral soils total removal of the stump is not recommended because of the risk of damaging conifer roots.