Conservation Biology of Eastern Tallgrass Prairie: Integrating Issues of Management and Restoration for the 21st Century
Taft, John .
Composition, Structure and Diversity Patterns in Small Prairie Remnants.
Are small, isolated preserves of tallgrass prairie floristically sustainable? To approach this question, three pioneer cemetery prairies in east-central Illinois were examined to determine whether species diversity, composition, and structural patterns in “edge” zones (outer 10 meters) differed from “interior” portions. A stratified sampling design was established using permanently marked transects oriented perpendicular to the long axis of the three prairies; vegetation data were collected in 50 cm x 50 cm quadrats along each transect. These prairie remnants, all protected as nature preserves, range from 1.29 to 1.62 ha in area; each is bordered primarily by cropland and mowed non-native grassland. The null expectations were no differences between edge and interior zones and no change over time. Native species density (species/quadrat) formed a unimodal pattern across each site. Distance from edge to peak levels of species density ranged up to 25 m. Average native species density in edge and interior zones was 10.17 and 13.62, respectively, and average non-native species density in edge and interior zones was 2.05 and 1.42, respectively; both differences were statistically significant. Percent non-native species in edge zones was positively correlated with percent non-native in interior zones. Edge vegetation was characterized by greater abundance of woody species and non-native C3 grasses; however, sites differed individually in composition of edge and interior portions. Data from one site resampled five years post baseline indicate there were within-site differences in the patterns of change. One-half of the site was stable while native species density declined significantly in the edge zone of the other half. These prairies support a rich diversity of native species; however, patterns suggest they are smaller than they appear. Further monitoring will determine whether the edge vegetation is encroaching on interior portions or whether these isolated remnants provide a stable refugium for prairie plant species.
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1 - Illinois Natural History Survey, Division of Biodiversity and Ecological Entomology, 1816 S. Oak Street, Champaign, IL, 61820, US
Presentation Type: Symposium or Colloquium Presentation
Location: Williford B/Hilton
Date: Wednesday, July 11th, 2007
Time: 11:00 AM