Document: TIF-3-42-33
Persistence or extinction: A demographic analysis of elevated herbivore pressure in an herbaceous understory community.
KNIGHT, T.* 1, S.KALISZ 1, L.SMITH 2 and J.DAVIS 3
University of Pittsburgh, Pittsburgh, PA 15260 USA 1
Western Pennsylvania Conservancy, Pittsburgh, PA 15222-2075 USA 2
Beechwood Farms Nature Reserve, Pittsburgh, PA 15238 USA 3
Abstract:
Current deer numbers are creating significant disturbances in herbaceous communities in the eastern half of North America. To quantify the impact of a local recent and dramatic increase in deer herbivory, we monitored three pairs of large fenced exclosure and unmanipulated control plots over six years. While deer herbivory significantly influenced overall species richness, abundance, and composition of the herbaceous understory community, the herbaceous species exhibited dramatic variation in their responses to the presence of deer. A detailed analysis of Trillium grandiflorum indicated that deer impact both the stage structure and overall size of this long-lived perennial. Specifically, herbivory significantly decremented both above ground and below ground growth, and thus prevented plants from reaching the size threshold necessary to reproduce. Furthermore, the ratio of reproductive stems to percent cover indicated that deer herbivory reduced the demographic representation of reproductive individuals in six other common understory species. This study provides evidence for a demographic mechanism by which elevated deer browse reduces understory plant populations and ultimately alters community composition.
Keywords: herbivory, demography, forest understory
This abstract is being presented at: 4:15 PM in session:
Oral Session #17: Mammalian Herbivory.