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

Abstract
The effect of browsing damage by red and roe deer on Sitka spruce girth was examined on two sets of trees. One set had leader damage histories from planting to age 11 (by which time nearly all trees were too tall to have leaders browsed), the other set, with older trees, had damage histories from age 5 to age 11. The impact of leader browsing on the growth of these trees was examined up to 15 to 20 years after leader damage monitoring stopped. In a Generalised Linear Mixed Model, browsing and other leader damage were found to be highly correlated with trees having multiple trunks. A mixed model was used to investigate the relationships of several factors with tree girth, and trees with a single trunk throughout the study were compared with all trees, including multi-trunked. In all model runs, initial height of trees (either age 0 or age 5) had the largest significant effect on tree girth, being positively correlated. In all-tree runs, the effect of multiple trunks on growth was negative and usually highly significant, being second only to initial tree height in explaining final girth. At sites with full damage histories, soil wetness also had a significant negative effect on growth, whereas at the other sites, altitude and the extent of unplanted ground around a tree were significant in later years. On average there was less leader browsing, and consequently fewer multiple-trunk trees, on plots with high stocking density. The effects of these results in relation to different forest management options are discussed.
Year
2009
Category
Refereed journal
Output Tags
SG 2006-2011 P3 Environment - Miscellaneous