Use of turtlehead ( Chelone glabra L.) and other herbaceous plants to assess intensity of white-tailed deer browsing on Allegheny Plateau riparian forests, USA

Abstract

One of the key factors affecting the integrity of forest ecosystems in portions of the eastern United States is heavy browsing by overabundant populations of white-tailed deer ( Odocoileus virginianus Zimmerman). Deer impacts to upland forests of the Allegheny Plateau in northwestern PA, USA, have been especially intense: high levels of deer browsing over the past 60 years have strongly influenced forest pattern and process. Riparian forests of the region are rich in herbaceous plant species, but virtually nothing is known about how deer browsing may influence the structure and function of these systems. Moreover, reliable techniques for assessing and monitoring deer impacts on riparian forests are lacking. The goal of this study was to determine whether the common riparian herbaceous plant turtlehead, Chelone glabra L., is a useful indicator species with which to assess and monitor the intensity of deer browsing in the herbaceous layer of Allegheny Plateau riparian forests. The percentage of C. glabra stems browsed by deer was significantly correlated with intensity of browsing on the herbaceous community during one sample period, but stem height, an attribute used widely in other studies of browse indicator species, was poorly correlated with intensity of browsing. Three other herbaceous plant species, Aster divaricatus L., A. prenanthoides Muhl. and Impatiens capensis Meerb., were preferentially browsed by deer and show promise for use as indicators of browsing intensity in riparian forests. Variability in deer browsing intensity on C. glabra across sites and sample periods suggests that use of an assemblage of herbaceous browse indicator species is preferable to sole reliance on C. glabra for assessing and monitoring browsing impact.