High white-tailed deer density has negative impact on tallgrass prairie forbs1

ANDERSON, R. C., E. A. CORBETT, M. R. ANDERSON, G. A. CORBETr, AND T. M. KELLEY (4120-Department of Biological Sciences, Behavior, Ecology, Evolution, and Systematics Section, Illinois State University, Normal, Illinois 61790-4120). High white tailed deer density has negative impact on tallgrass prairie forbs. J. Torrey Bot. Soc. 128:381-392, 2001.-We studied the effect of deer browsing on prairie forbs under conditions of high deer density (30 to 42 deer km -2) on a single remnant tallgrass prairie in the Illinois Department of Natural Resources' Heidecke Lake Fish and Wildlife Area in northeastern Illinois. Almost no grasses or sedges were browsed and the frequency of browsing of graminoids was nearly the same in deer exclosure and reference plots. In contrast, deer browsed 3.5% to 18.9% of the standing crop of forb stems depending upon time of sampling. Deer selectively browsed 26% percent of the 100 species of forbs sampled in at least one of nine samples taken over three growing seasons. However, most species (17 of 26 selected species) were selected in only one sample. Highest browsing intensity occurred during late June and early July. Flowering stems of 3 species of forbs were significantly less abundant in the reference plots than in the exclosure plots, indicating a potentially adverse effect of deer browsing on the reproductive success of these prairie forbs. Deer are most likely to influence prairie vegetation by causing a shift in plant species abundance and competitive abilities in a way that favors grasses over forbs and reduces prairie plant diversity.