Sitka spruce silviculture in Scottish forests

Abstract

SynopsisSitka spruce is the most important species grown in Scottish forests thanks to its high yield potential, site tolerance and wood properties. It is easily raised from seed or cuttings, and can be readily established and tended under a wide range of site conditions using uncomplicated silvicultural techniques. Spaced furrow ploughing and site drainage are normally required for afforestation; and cultivation may also be desirable prior to restocking. Planting at 2500 trees/ha is done in late winter and spring. Weed control may be necessary, particularly to prevent Calluna-induced growth check. On poor sites, repeated fertiliser application prior to canopy closure can be essential to ensure satisfactory growth, and use of nursing mixtures may be worthwhile. Wherever possible, pole stage crops are thinned regularly to enhance stem quality and diameter growth, but on high windthrow hazard sites the onset of windthrow can be delayed by leaving crops unthinned. After an economic rotation of forty-five to sixty years, crops are clear felled and replanted. During establishment, deer control measures are often required to prevent browsing damage. Damage by insects and fungi is seldom serious, provided that bark-feeding insects are controlled by insecticide at time of replanting, and development of fungal butt rot is minimised by urea treatment of fresh stumps.