Cofer, M. Shea , Walck, Jeffrey , Hidayati, Siti .
Determinants of species richness and exotic species invasion on cedar glades in middle Tennessee.
FIELD surveys of vascular plants on 40 cedar glades at Stones River National Battlefield in Rutherford County, Tennessee were conducted during the 2001-2003 growing seasons. Glades were delineated utilizing GPS, and geo-referenced data imported into ESRI ArcMap to obtain area, perimeter, distance from autotour road and degree of isolation for each glade. In addition, amount of disturbance was recorded. A total of 232 taxa was found with Andropogon virginicus, Croton monanthogynus, Juniperus virginiana, Panicum flexile and Ulmus alata being present on all glades. The exotics Ligustrum sinense, Leucanthemum vulgare and Taraxacum officinale occurred on the majority of glades. Lobelia appendiculata var. gattingeri, Leavenworthia stylosa and Pediomelum subacaule were the most frequent endemics. Richness of native, exotic and endemic species increased significantly with increasing area and perimeter and decreased with increasing isolation (P ≤ 0.0299). However, area was positively correlated with perimeter and isolation negatively correlated with area and perimeter (P ≤ 0.0021). Perimeter explained a greater amount of variation than area for native and exotic species, whereas area accounted for greater variation than perimeter for endemic species. The slope of the log-log relationship between area and total richness (0.17) was within the range reported for continental islands (0.12-0.19). Species richness was not related to distance to road (P ≥ 0.2023). Disturbed glades contained a significantly higher number of exotic and native species than nondisturbed ones, but they also were larger (P ≤ 0.0330). Invasion of exotic species was unrelated to native species richness, and it did not influence endemic species richness (P ≥ 0.5903). Thus, environmental conditions that support native species richness also favor exotic species richness contrasting with the diversity-resistance hypothesis for invasibility. Competitive interactions on glades may be less important than tolerance to (drought) stress for determining community composition.
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1 - Middle Tennessee State University, Department of Biology, Murfreesboro, Tennesee, 37132
Presentation Type: Oral Paper:Papers for Sections
Date: Tuesday, August 1st, 2006
Time: 8:30 AM