Laura M. Ladwig, David A. Rogers and Ellen I. Damschen
Department of Zoology, University of Wisconsin-Madison,
Department of Biological Sciences, University of Wisconsin Parkside, David.Rogers@uwp.edu
Across the Midwest, less than one percent of pre-settlement prairies exist today – having been largely converted to agriculture via Euro-American settlement. These remnant communities often manifest in tiny, widely scattered and marginal populations of questionable viability. Understanding how the remaining remnants respond to both historical and changing environmental conditions is critical to managing their continued presence on the landscape. We are revisiting 62 prairie remnants in southeastern Wisconsin that were originally surveyed in the 1950s by Philip Whitford, working out of UW-Milwaukee. At each site in the original survey, a list of all vascular species was made, based on observations made at multiple visits during the growing season. At approximately half of the sites, quantitative measures of abundance were also estimated, using 20, 1/4m2 quadrats, spaced evenly throughout the site. With these data, we ask how prairie remnants have changed over the past 60 years and how these changes correlate with land-use history and local environmental conditions. As expected, remnants prairies have changed considerably over the past 60 years, with a range of 15-70% species loss at individual sites. Species loss was nonrandom and was concentrated in species with low height, small seeds and lacking vegetative reproduction. Woody plant density increased dramatically between the 1950s and today, with some sites being totally lost to forest conversion with only an occasional prairie species surviving in edge or gap microhabitats. At the site level, management by fire was the most important variable, with fire-managed sites losing fewer of the original species and generally maintaining a higher floristic quality. In general, prairie remnants along railroad corridors persisted better than did remnants in other settings, particularly those wet prairie remnants that survived into the 1950s along field edges. Apparently, extensive “improvements” (drainage tile, ditches) have effectively eliminated these remnants from the current agricultural landscape, further reducing the total remnant area in SE Wisconsin and reducing the probability of metapopulation persistence, even in higher quality remnants. The UWM Field Station’s Benedict Prairie, Kenosha County, is one of our study areas.