Bark-stripping of common buckthorn by goats during managed browsing on bur oak savannas

Abstract

Goats are being used increasingly to manage woody invasive plants in woodland habitats, but their speci c impacts on those plants over a period of time during active, periodic browsing has not been documented. This study investigated bark-stripping by goats browsing on common buckthorn in savanna habitats, focusing on possible size-selective feeding and the cumulative effects of repeated, periodic browsing over a 3-year period. When surveyed after the rst browsing period, bark was stripped selectively on buckthorn stems 20 to 60 mm in diameter. Approximately 60% of all stripped stems were completely girdled, but only 14-17% of stems were bark-stripped. After ve browsing periods, 66% of standing stems displayed bark stripping and 39% were completely girdled. Buckthorn densities were reduced by 90% compared to the rst browsing period, the decline resulting mostly from consumption of foliage and terminal shoots of small (<20 mm) buckthorn and bark-stripping resulting in top-kill in intermediate-sized (20-60 mm) plants. Large buckthorn (>60 mm) were largely unimpacted by goats. Relatively few (28%) seedling buckthorn were browsed by goats, although >90% of 2 nd -year plants were browsed. Buckthorn can be managed in part via goat browsing, but repeated, periodic browsing over several to many years may be necessary to produce a signi cant impact, and other techniques will be needed to eliminate large, seed-producing plants.