Ecology of Scots Pine in the Scottish Highlands

The formation of viable seeds by the surviving fragments of native pine forest in the Scottish Highlands is generally adequate. Seeds and seedlings are destroyed by a wide variety of animals from slugs to voles and chaffinches, but the present state of soil and vegetation within and surrounding the pine woods is a more serious threat to regeneration than these. Seedlings on thick, felted moss and litter layers are liable to desiccation in only moderate spring drought, while a growing season wetter than average can result in the asphyxiation of seedling roots in unhumified Sphagnum mats and dense, colloidal or fibrous peats. Repeated burning of forest and moorland, coupled with extensive and uncontrolled animal-grazing, has produced a vegetation completely dominated by raw humus-forming species and a biologically inactive humus; thus adding acute nitrogen deficiency to the intrinsic lack of phosphorus in the substrata. Mineral-deficient seedlings are checked in their growth and rendered all the more sensitive to shading and competition for nutrients by coarse herbaceous and shrubby vegetation as well as to defoliation by animals. The fencing of large areas for forest plantations on ground formerly utilized by wintering red deer has channelled these animals on to the unfenced areas of native pine forest. Regeneration of pine in the various pine and mixed woodland communities and the success with which pine invades non-woodland vegetation are described. The methods that have been used in encouraging natural regeneration and assisting it by seed sowing on prepared ground have been outlined. It is concluded that the pure pine stands of the present day are largely artifacts and that they have a limited future as self-maintaining entities; intensive management will be required for the native forests to be retained as they are and it may well be that the pine will only achieve self-perpetuation in a forest of mixed composition and intimately mixed age structure which has yet to be produced.