Recovery of browse-sensitive tree species following release from white-tailed deer Odocoileus virginianus zimmerman browsing pressure

Abstract

Deer browsing encourages the development of a vegetation dominated by non-browse or browse-tolerant species at the expense of those sensitive to browsing. For restoration or management of forests, it is crucial to understand how browse-sensitive species recover following release from browsing. As these species re-establish, or achieve former levels of dominance, they must compete with a newly established vegetation. We examined recovery of eastern hemlock Tsuga canadensis (L.) Carr, a shade-tolerant, browse-sensitive tree species, following release from intensive browsing. To examine patterns of recovery over time we used data collected from three forest sites in northern Wisconsin, USA. In an intensely browsed forest, eastern hemlock was the leading dominant in the tree stratum. However, it was absent from the seedling and sapling strata where sugar maple Acer saccharum Marsh. was the dominant species. Twelve years of protection from white-tailed deer Odocoileus virginianus browsing resulted in establishment of hemlock seedlings not present in adjacent browsed areas. In a 27-year-old exclosure, under a canopy of shade-tolerant species, there was apparent recovery of hemlock to a diameter distribution typical of an all-aged forest. In forests subjected to continuous and intensive browsing pressure from the early part of this century, periods as long as 70 years may be required for shade-tolerant trees to achieve size class distribution characteristic of all-aged forests.