ANALYSIS OF PRAIRIE RESTORATIONS AT ROCK SPRINGS ENVIRONMENTAL CENTER, DECATUR, ILLINOIS.

The vegetation of five prairie restorations at Rock Springs Environmental Center was examined during the 1999 to 2001 growing seasons. At this site, five tracts, totaling 12.1 ha, were developed as prairie restorations of varying ages on former farmland starting in 1977. Within these five restorations, 164 plant species were documented, 133 of which were native to Illinois. Andropogon gerardii had the highest importance value for all tracts combined with a total of 42.7 (out of 200) followed by Schizachrium scoparium (31.8), Solidago spp. (26.4), Sorghastrum nutans (16.9), Chamaechrista fasciculata (14.5) and Securigera varia (12.7). Sorensen's Index of Similarity between the tracts ranged from 53.97 to 72.97 while the Floristic Quality Index (FQI) ranged from 18.6 to 25.8; the overall FQI for all tracts combined was 32.3. An analysis of invasive species showed that Securigera varia had a significant negative impact on both species richness and diversity. According to Sorensen's Index of Similarity and cluster diagrams, the tracts are becoming more similar. In addition, based on the FQI, the quality of the flora in the prairie restorations increases with the tract age. [ABSTRACT FROM AUTHOR]