Silviculture and stand dynamics in Scots pine forests in Great Britain; implications for biodiversity

Abstract

There are 241,000 hectares of Scots pine forest in Great Britain or about 10 percent of the total forest area. Traditionally, a distinction has been drawn between a small area of native pinewoods with high conservation value in northern Scotland and the younger plantations of Scots pine to be found in many parts of Britain. The latter have been primarily managed for timber although they are now expected to meet multipurpose objectives including enhanced biodiversity. Silvicultural practices in the plantations are based upon a system of clear felling and artificial regeneration. However, older plantation stands can be colonised by rare species previously thought to be confined to the native pinewoods. The structure of Scots pine stands of different ages is examined using modern concepts of stand dynamics. The analysis highlights that the native pinewood stands have features characteristic of «old-growth» such as: a lower stocking density; more large trees; greater variation in diameter; a clumped distribution of stems; and appreciable quantities of standing deadwood. By contrast, most plantation stands have higher stocking densities, less variation in diameter, more uniform spacing and limited amounts of deadwood. By quantifying these structures it becomes possible to propose thinning regimes which can be introduced into plantations to accelerate the development of old-growth conditions without undue sacrifice of timber values. Natural disturbance histories in British pinewoods indicate a return period for stand replacing events (fire, windthrow) of once every 100 years which suggests that a maximum of 10 per cent of the pine resource should be managed as old growth stands. The age structure of some remnant pinewoods shows a lack of younger age classes and the desired old-growth habitat will diminish over time unless suitable plantation stands are managed as potential old-growth habitat. The maintenance of biodiversity in British pinewoods requires an integrated approach that applies to both the native pinewoods and the plantation stands.