Status of alien plant species in eight State NaturalAreas in Eastern Wisconsin

An annotated list of the non-native plant species found in eight eastern Wisconsin natural areas and their relative abundances in 1988 is presented. Except for European buckthorn, aliens were scattered and at low densities, several found mainly along trails. The most seriously invaded sites were Sanders Park and Muskego Park, areas with numerous hiking trails and relatively open, oak-dominated canopies. INTHDCOOTCN Since the advent of Europeans into Wisconsin, most of the state's natural plant communities have been greatly altered through a variety of artificial disturbances (e.g., lumbering, grazing, agriculture, settlements, industry). Many of the best remaining areas have been designated as state Natural Areas by the Scientific Areas Preservation Council and the Department of Natural Resources. A "Natural Area" may be defined as "a tract of land or water so little modified by man's activity or sufficiently recovered that it contains intact native plant and animal communities believed to be representative of. the presettlement landscape" (Tans and Dawson 1980). These remnants of our natural heritage are used for scientific research and education by preserving natural diversity and allowing natural processes to proceed without human interference. As such, they serve as reference sites to which other, more disturbed areas may be compared. A potential threat to the integrity, quality, and usefulness of natural areas is the introduction and establishment of non-native plant species which may become weedy. Throughout the world, alien species have become common, and, at times, harmful members of the local vegetation. Witness cheatgrass (Bromus tectorum) in the rangelands of the American West (Mack 1981), saltcedar (Tamarix chinensis) along river channels of the Southwest (Graf 1982), prickly-pear cactus (Opuntia spp.) in Australia (Ehrlich and Birch 1967), the Eurasian honeysuckle (Lonicera x bella) (Barnes and Cottam 1974) and the European buckthorn (Rhamnus cathartica) (Leitner 1985) in the open woodlands of southern Wisconsin. It is therefore important to monitor periodically natural areas and report on the status of exotics. As part of a program by the Department of Natural Resources to acquire