Historically, human-ignited fires were responsible for the extensive tallgrass ecosystems found east of the Mississippi River. More recently, fire was been the single best tool for restoring and conserving tallgrass prairie communities. Mowing is an often recommended substitute for fire, although there has been little evaluation of how well mowing mimics fire. In 2005 we re-sampled a tallgrass prairie remnant in southern Wisconsin that had been originally sampled in the 1940s and had been re-sampled in the 1970s, using 2 m x 2 m permanently located plots. Max Partch conducted the first two studies using 180 plots. In 2005 we re-sampled 114 of those plots; skipping those located in a flood plane, which is now dominated by Phalaris arundinacea and other invasive species.

Results/Conclusions

We were initially surprised when the data revealed a substantial change between 1940s and 1970s and little change between 1970s and 2005. Previous studies in Wisconsin prairie remnants documented severe declines among species with small seeds, short-stature, and nitrogen-fixing capacity. In this study, these groups of plants increased substantially between 1948 and 1978. There was also a doubling of species density (1948: 12.3 spp./4 m²; 1978: 25.1, and 2005: 25.5). In our view, the dramatic changes from 1948 to 1978, followed by relative stability were the result in changes in management practices. The site was harvested for hay prior to the 1948 sampling and had been frequently burned since the early 1950s. This study indicates the differential effects of fire versus hay-mowing that must be considered in conserving tallgrass prairie.