Characterizing the Drivers of Northern Mixed-Grass Prairie Plant Community Composition

Northern mixed-grass prairies are recognized for their high biodiversity but are becoming increasingly threatened by conversion to agricultural rangeland. To determine how grazing by cattle or reintroduced bison may impact these plant communities, we examined the primary drivers of northern mixed-grass prairie plant communities, assessed the heterogeneity of community composition at two sites with differing land use histories, and identified factors important for heterogeneity in these prairie communities. Overall, community characteristics were similar across sites, but community composition differed markedly across short distances. Both landscape traits, including elevation, slope, and precipitation, and grazing pressure were primary drivers of community composition. While bison-grazed sites had lower grazing pressure, both relative cover and richness of native plant species were higher in cattle-grazed sites. As both sites were historically cattle grazed, our results suggest that management legacies play a large role in northern mixed-grass prairie community composition and the benefits of bison grazing may only become apparent after a substantial amount of time since reintroduction.