Long-term effects of leader browsing by deer on the growth of Sitka spruce (Picea sitchensis)

This study aimed to show the long-term consequences of leader browsing by deer on growth of\udSitka spruce in plantations and took place in Glenbranter Forest in western Scotland. Browsing and\udother leader damage were monitored at 11 sites until age 11 years when nearly all trees were too\udtall to have leaders browsed. Impact on girth growth was examined up to 15 – 20 years later. The\udoccurrence of multiple-trunk trees was strongly related to browsing frequency, and their main trunks\udhad smaller mean girth than single-trunk trees. There was less leader browsing and hence fewer\udmultiple-trunk trees at higher tree stocking densities. Relationships between tree girth and several\udfactors were investigated in separate analyses for single-trunk trees and all trees. The initial height\udof trees always had the largest signifi cant effect on tree girth, being positively related; trees in older\udstands signifi cantly benefi ted from edge position. In all-tree runs, the effect of multiple trunking was\udnegative and usually highly signifi cant, being second to initial height in explaining fi nal girth. Our\udresults suggest that planting at high stocking density for good-quality timber is likely to reduce deer\udbrowsing and multiple trunking compared with the strategy of less-dense planting required for pulp