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 yearspartly as a result of pressures to restore and expand nativewoodlands but also due to renewed interest in birch as a treecapable of producing quality timber. Despite the many advantagesof birch as a commercial timber tree—ease of establishment,fast growth on good sites, high value timber and a short rotation,it has a poor reputation in Britain largely as a result of thepoor form of the existing, mainly unmanaged resource. The followingpoints need to be considered if stands of quality birch treesare to be produced in an economical timescale. (1) Sites: silverbirch needs good sites that are relatively well drained withlight mineral soils. Downy birch does well on moist to wet sites.(2) Regeneration: natural regeneration through a shelterwoodis the preferred system of regenerating birch as some overheadprotection is beneficial to germination success. About 20–40seed trees should be left per hectare. Good ground preparationand control of grazing are essential. The vast majority of seedlingsare recruited in the first year of the regeneration cycle thereforeplanting should be considered if the initial regeneration successis poor. Direct seeding is also a successful method of regeneration.Birch readily regenerates naturally into suitably prepared openareas next to existing birch woods but these should not be toobig, e.g. gaps or strips 20–60 m wide have been suggestedin the literature. (3) Maintenance: density of regenerationneeds to be reduced to about 2500–3000 stems ha^–1by the time the trees are about 3–6 m tall. Birch seedlingsmust always be taller than the competing vegetation. (4) Thinning:thinning should begin when the mean height of the stand is about8–10 m. At this point at least half the number of treesshould be removed with the emphasis on retaining dominants andco-dominants of good form. The aim is to maintain about halfthe height of the tree as living crown to sustain a high rateof growth. Additional thinnings will be required at intervalsof 5 to 7 years and final thinning should leave around 300–500stems ha^–1. (5) Rotation: a rotation of 40–50 yearsis possible on good sites and perhaps 50–55 years on lessfavourable sites.