Bison Grazing in Eastern Tallgrass Prairie Does Not Alter Plant Diversity after Five Years

North American tallgrass prairie evolved with regular fire set by Indigenous people and grazing from large herbivores, including the plains bison (Bison bison). In contrast to uniform effects of prescribed fire, bison graze selectively, creating increased heterogeneity on the landscape. We examined plant community responses to reintroduced bison grazing in high-diversity native and restored tallgrass prairie in Illinois, USA. We evaluated plant community diversity and structure in paired grazed and ungrazed (fenced) plots. After 5 y of grazing at a relatively low target stocking rate of 1 animal unit per 5.2 ha (13 acres), there were no differences in plant community diversity, composition, nonnative:native species ratio, or visual obstruction readings between grazed and ungrazed plots. An interaction exists (or was found) between plant community type and grazing in which grazed savanna plots had greater grass relative abundance compared to ungrazed plots. Ongoing monitoring will evaluate long-term trends.