MANAGING BIRCH WOODLANDS FOR THE PRODUCTION OF QUALITY TIMBER

Interest in silver birch (Betula pendula Roth) and downy birch (Betula pubescens Ehrh.) has greatly increased in recent years partly as a re sult of pressures to restore and expand native woodlands but also due to renewed interest in birch as a tree capable of producing quality ti mber. Despite the many advantages of birch as a commercial timber tree -ease of establishment, fast growth on good sites, high value timber a nd a short rotation, it has a poor reputation in Britain largely as a result of the poor form of the existing, mainly unmanaged resource. Th e following points need to be considered if stands of quality birch tr ees are to be produced in an economical timescale. (1) Sites: silver b irch needs good sites that are relatively well drained with light mine ral soils. Downy birch does well on moist to wet sites. (2) Regenerati on: natural regeneration through a shelterwood is the preferred system of regenerating birch as some overhead protection is beneficial to ge rmination success. About 20-40 seed trees should be left per hectare. Good ground preparation and control of grazing are essential. The vast majority of seedlings are recruited in the first year of the regenera tion cycle therefore planting should be considered if the initial rege neration success is poor. Direct seeding is also a successful method o f regeneration. Birch readily regenerates naturally into suitably prep ared open areas next to existing birch woods but these should not be t oo big, e.g. gaps or strips 20-60 m wide have been suggested in the li terature. (3) Maintenance: density of regeneration needs to be reduced to about 2500-3000 stems ha(-1) by the time the trees are about 3-6 m tall. Birch seedlings must always be taller than the competing vegeta tion. (4) Thinning: thinning should begin when the mean height of the stand is about 8-10 m. At this point at least half the number of trees should be removed with the emphasis on retaining dominants and co-dom inants of good form. The aim is to maintain about half the height of t he tree as living crown to sustain a high rate of growth. Additional t hinnings will be required at intervals of 5 to 7 years and final thinn ing should leave around 300-500 stems ha(-1). (5) Rotation: a rotation of 40-50 years is possible on good sites and perhaps 50-55 years on l ess favourable sites.