Effects of red deer exclusion on the corticolous and terricolous cryptogam community of Atlantic woodland

Abstract

Deer exclosures are often used to encourage woodland regeneration in the Scottish Highlands. However, dense saplinggrowth,intheabsenceofreddeer(Cervus elaphus),withinexclosurescouldposeathreattointernationally important lichen communities on mature oaks in open woodland. Cryptogam communities associated with the lower trunks of oak trees (Quercus × rosacea Bechst.) were compared from several blocks, inside and outside three exclosures, in Atlantic oak woodland north of Loch Maree, Wester Ross, Scotland. Epiphyte data were collected from three different height zones on both the north and south aspects of oak trees. Terrestrial cryptogam communities, sapling density, shrub cover and height were also compared. Data were analysed using linear mixed effects models. Mean Lobarion lichen cover and species richness was significantly lower on both aspects of oak trees within exclosures in quadrats from more than one zone. Sapling density, dwarf-shrub height and coverweresignificantlygreaterwithinexclosures.Terrestrialcryptogamdiversityandspeciesrichnessweresignificantly lower inside exclosures. The data suggest that increased shading by saplings around mature oaks in open woodland has had a detrimental effect on Lobarion lichens after 17‐22 years of exclosure. Alternative strategies for encouraging woodland regeneration without harming the Lobarion lichen community are discussed.