Karpotųjų (Betula pendula Roth.) ir plaukuotųjų (Betula pubescens Ehrh.) beržų paplitimas pelkinėse augavietėse

Abstract

Studies of the ecological distribution of silver and downy birches in boggy (natural and drained) sites were conducted in 45 birch stands (older than 10 years) and in 25 former clearcut areas (up to 10 years of age), where no economic measures were applied.

It was found that in high fens and intermediate type bogs not only downy, but also silver birches occur, the amount of which in the species composition of birch stands decreases with increasing age of birch stands, e.g, within 2–5 yr. old birch stands silver birch comprises about one-third (30.6±3.6 %)of all birch trees. Later, with the age of birch stands, the amount of silver birches gradually decreases and in mature stands remain only individual trees (3.2±1.7 %). The species composition of birch stands (the portion of silver and downy birches in stand species composition) on natural (undrained) boggy sites is mostly preconditioned by the depth of ground water. In the first 1-3 (5) years after felling silver birches in high fens and intermediate type bogs comprise about one-third (30.6±3.6 %) of all birch trees, then in low bogs silver birches grow only in young stands up to 10 years of age, comprising 5.0 %.

The ascertained variation range of birch stand species composition on boggy drained forest sites has been significantly high, reaching 50–80%. In undermature and mature birch stands, growing in drained low bogs, silver birches comprise respectively 42.8±21.5% and 62.9±8.8%, meanwhile in natural (undrained) low bogs they occur in exceptionally rare cases.