Print PageA major factor limiting the scale and distribution of tallgrass prairie reconstructions is competition with agricultural land use. In Wisconsin, the percentage of farmers using management intensive rotational grazing (MIRG) is growing, and farmers utilizing this production system may be able to sustain restored prairies on their farms due to MIRG farmers’ attention to appropriate timing and intensity of defoliation, as well as to providing adequate rest for regrowth. In the central tallgrass prairie, grazing by cattle and bison has been demonstrated to increase plant community evenness through selective grazing of highly-productive C4 grasses, which facilitates increased abundance of rarer forbs by reducing competition for light, moisture, nutrients, and other resources. Whether or not grazing would demonstrate similar effects on dominance and evenness in the prairie peninsula region east of the Mississippi River (where the cooler, wetter climate is less favorable for C4 grass growth) has been contested but has not been experimentally tested. We utilized reconstructed mesic prairies (10 years old) and switchgrass monocultures (two years old) to explore the interaction of plant diversity and management intensity. We applied early spring burns to all plots in 2009 and 2010. Plots were assigned MIRG, mowing, or no disturbance (control) treatments, and management treatments were applied in June and July of each year. Each year, we used the point-line intercept method to sample plant community composition in early June prior to management and following management during peak standing biomass.
Results/Conclusions
We found that restored prairies were dominated by plants that have evolved to avoid or tolerate grazing (Poa pratensis, Helianthus grosseserratus, Bromus inermis, Sorghastrum nutans, and Andropogon gerardii). Helianthus grosseseratus and many subdominate composite species were defoliated by mowing but not by cattle. Multivariate nonparametric tests (ANOSIM) indicate that by the end of the period studied, composition of mowed plots was significantly different from control plots, but grazed plots and control plots did not differ significantly in composition. Switch grass monocultures were dominated by Panicum virgatum throughout the study period. However, July mowing affected Panicum virgatum regrowth more significantly than grazing. Defoliation facilitated invasion by species from adjacent prairie plots as well as nonnative species, and species richness of both native and nonnative plants was greater in mowed and grazed switchgrass plots than in control plots. ANOSIM indicated that community composition of mowed plots was significantly different than control plots.
