PARENT SESSION
Wednesday, August 9, 8:00-11:30 am
COS 58 - Temperate deciduous forest ecology
Sultana, Mezzanine Level, Cook Convention Center
Presiders: G Wang
Simplified floral diversity and the legacy of deer overabundance in Great Smoky Mountains National Park.
Griggs, Jennifer 1, Webster, Christopher*,1, Jenkins, Michael2, Rock, Janet2, 1 Michigan Technological University, Houghton, MI2 National Park Service, Gatlinburg, TN
ABSTRACT- Protected areas worldwide serve as refuges for biodiversity and are often critical components of rare plant conservation strategies. However, locally overabundant herbivore populations may greatly reduce their effectiveness. In order to improve our understanding of changes in understory composition associated with high deer abundance in areas otherwise protected from habitat destruction, we quantified understory plant community change over a 25 year period in Cades Cove, Great Smoky Mountains National Park, US. Cades Cove has a long and well-documented history of white-tailed deer (Odocoileus virginianus Zimm.) overabundance, with densities reaching 43 deer km-2 during the late 1970s. Between 1978 and 1979, nineteen 20 x 50 m permanent, long-term monitoring plots were installed in the Cove (each containing 25 randomly placed 1 x 1 m quadrants). Plots were resampled summer 2004. Over the sampling interval, mean coverage of herbaceous species declined significantly (p<0.001). Declines in individual forest types ranged from 57% in mixed conifer-hardwoods to 85% in successional pine stands. While declines in species richness were not statistically significant for all forest types, 46 herbaceous species recorded across all plots during the 1970s were absent in 2004. Additionally, distance measures of community dissimilarity declined significantly suggesting that the herbaceous layer has become increasingly homogenized. While some compositional changes were associated with forest succession, ordination analysis suggests that browsing by white-tailed is a primary driver of understory change, with browse sensitive species (e.g., trilliums and orchids) associated with increasing physical distance from Cades Cove.
Key words: deciduous forest, herbaceous layer, herbivory