ABSTRACT
We conducted floristic surveys of Horseshoe Lake Conservation Area (HLCA), a 3,702 ha refuge that was established in 1927. It is owned and managed by the Illinois Department of Natural Resources to provide habitat for migratory waterfowl. Fishing, deer hunting, camping, and wildlife observation are secondary uses of the refuge. Goals of this study were to conduct a floristic survey of HLCA, characterize existing plant communities, document threatened and/or endangered plant species, and compare results with other studies in the region. Based upon a floristic study of a portion of the area during 1968-72 and 25 collecting trips during 1993-94, a total of 685 taxa in 366 genera and 112 families were documented. One-hundred forty one (20.6%) were non-native to the study site. Thirteen taxa were state listed as threatened or endangered. A comparison with ten additional study areas in the region indicates that floristic relationships exist at the family and genus level. The families Asteraceae, Poaceae, Cyperaceae, Fabaceae, and Polygonaceae and genera Carex, Quercus, and Polygonum were most important. The use of percent non-native taxa can be utilized to determine past and present anthropogenic disturbance to a site.