Effect of thinning in birch stands: A review

Abstract

The genus birch is one of the most widespread tree genera in the northern hemisphere. Most of the species of the genus Betula are pioneer trees forming early succession – pioneer stands after disturbances. Thinning in pioneer stands should therefore reflect these biological assumptions. The effects of thinning were divided into: the effects on production parameters, on additional regeneration and on site microclimate. Thinning, or increased tree spacing, promote a longer and wider living crown, which stimulates the diameter growth of the released trees. The stronger and earlier the intervention the more intense and sustained the response. A strong diameter growth (increment) is a key tool for achieving high-quality birch timber. An optimal thinning regime can further increase the resistance of birch to snow and wind damage. Released birch trees tend to be more resistant to drought. Birch stands under light thinning are more productive than unthinned stands, while heavy thinning leads to a reduction in overall biomass and volume of productivity. This potential loss can be compensated in birch management by increased production of quality timber in a shortened rotation. By optimizing the thinning, the subsequent regeneration of late-succession trees in these birch stands can be supported. The degree of canopy opening should reflect the site and the requirements of the tree species of the subsequent regeneration – interventions will be stronger in drier sites and for more light-demanding species.