Willow (Salix spp.) and aspen (Populus tremula) regrowth after felling by the Eurasian beaver (Castor fiber): implications for riparian woodland conservation in Scotland

1. A proposed trial reintroduction of the Eurasian beaver (Castor fiber L.) to Scotland has recently been approved (May 2008). A previous proposal Was turned down by the licensing authority, partly over the perceived risks to woodland within a Special Area of Conservation. 2. This paper presents data oil two years of willow (Salix spp.) and aspen (Populus tremula L.) regrowth following tree Felling by captive beavers within two large semi-natural enclosures ill eastern Scotland. Both willow and aspen are highly preferred by beavers. 3. Regrowth of Willow sterns was quantified from Cut Stumps. felled logs and partially severed ('incompletely felled') trees, and compared With growth of steins in the canopies of untouched willows. 4. Maximum annual regrowth was observed in incompletely felled trees, followed by cut stumps and then unfelled control trees. Mean regrowth rates were ca 18 m regrowth per metre or measured tree section per year, ill incompletely Felled trees. This was approximately 12 times more annual regrowth than that observed ill unfelled trees. despite apparently selective browsing of the regrowth of incompletely felled trees by roe deer. 5. Although incompletely felled willows represent a relatively small component of felling activity (9% of all felled willow), they contribute disproportionately to the biomass of beaver-engineered riparian woodlands. creating a more multi-layered habitat structure. 6. Willow regrowth ill inundated areas was avoided by deer, and harvesting of regrowth by beavers was rare. 7. Significant regrowth from 11 stumps of aspen in 2 years post-felling Occurred by suckering. with 85 Stickers of mean height 2.1 m being recorded, all of which were subsequently avoided by browsing deer and beavers. S. These data Suggest that rapid regeneration of willow and aspen Will Occur in riparian Woodlands in the event of major felling activity by Eurasian beaver. even in the presence of low to moderate levels of roe deer browsing and that the conservation status of both these trees or the wider habitats that they form Would not be threatened by a Well planned and managed reintroduction of beavers to Scotland. Copyright (C) 2008 John Wiley & Sons, Ltd.