INCREASED ABUNDANCE OF EXOTIC PLANTS BENEATH FOREST CANOPY GAPS FACILITATED BY WHITE-TAILED DEER HERBIVORY

Abstract

The combination of deer overpopulation, frequent or intense windstorms, and invasions of exotic plants can profoundly affect forest understory composition. This research examined deer herbivory in 14 forest canopy gaps created by Hurricane Ivan in 2004 at Catoctin Mountain Park near Thurmont, Maryland. Deer population density in the park was 34 deer/km 2 in 2006. Percent cover of 117 species of exotic and native herbaceous plants was measured inside 28 paired open or deer-exclosed 5x5 meter plots. Factorial repeated measures ANOVA revealed that deer affected the native and exotic plants in significantly different ways (F = 11.357, P = .002), although overall plant abundance was not reduced (F = .716, P = .405). Three years of herbicide treatments did not significantly reduce exotic plants in the fourth year. Reduction of overabundant deer populations will increase native plant abundance and reduce the successful invasion of exotic plants beneath canopy gaps.