Research note. Effects of stand structure, composition and treatment on bark-stripping of beech by grey squirrels

Abstract

Beech (Fagus sylvatica L.) is particularly vulnerable to bark-stripping by grey squirrels (Sciurus carolinensis Gmelin), especially when it is medium-sized and growing rapidly with a high average phloem volume. Patterns of bark-stripping are best explained as a consequence of agonistic behaviour, food-seeking or learning, which is amplified by tree-growth factors, including phloem volume and bark-structure (Shorten, 1954; Taylor, 1966, 1969; Mackinnon, 1976; Kenward, 1982, 1983; Rowe, 1984; Rowe and Gill, 1985; Kenward and Parish, 1986; Gurnell, 1987; Kenward et al., 1988a, b, 1996; Kenward, 1989; Gill, 1992; Kenward and Dutton, 1996; Mountford, 1997). Bark-stripping seems more intense in stands that have been silviculturally thinned, i.e. where growth rate and phloem volume have increased, and accordingly modified patterns of stand treatment have been proposed (Kenward et al., 1988a; Kenward and Dutton, 1996). This note records supporting evidence for the influence of thinning on the intensity of barkstripping. It relates to Lady Park Wood, a mixed deciduous woodland growing on and above steep slopes on Carboniferous limestone overlooking the river Wye (UK), where stand dynamics and the growth rate of individual trees have been closely observed for over 50 years (Peterken and Jones, 1987, 1989; Mountford, 1994, 1997; Peterken and Mountford, 1995, 1996, 1998). The reserve comprises a non-intervention area containing both old-growth and young-growth stands, and an adjacent compartment which had a similar composition and treatment history until a part was thinned in 1982.