Plains bison (Bison bison) were a keystone species that once roamed the Great Plains in the millions but have now largely been replaced by domestic cattle. While cattle and bison share similar ecological roles within grasslands, bison, unlike cattle, create bare-earth depressions (wallows) through dust-bathing. Historically, as bison followed fire across the Plains, wallows would have been abandoned from months to years, likely creating a mosaic of unique plant communities and ephemeral wetlands. This study takes advantage of a long-term bison reintroduction (30 years), which is factorially crossed with fire frequency (1, 2, 4, and 20-year fire intervals) at Konza Prairie Biological Station (KPBS), a native, unplowed tallgrass prairie. One disadvantage of this landscape-scale experiment is that bison cannot migrate long distances and are less likely to abandon some wallows. To circumvent this limitation, we established exclosures within the bison area to mimic migratory patterns of wallow and pasture abandonment. We conducted plant surveys in 120 plots (fenced and unfenced wallows and non-wallows; n=24) to determine if wallows contribute to plant diversity in tallgrass prairie and, thus, if bison provide distinct services that cattle do not. Our results show that wallows support unique plant communities, increase overall plant diversity, and increase phylogenetic diversity, which may contribute to increased functional diversity and resilience. Wallows also house unique soil microsites with greater clay content, and in some wallows (about 20%), long periods of standing water and/or high salt concentrations similar to brackish wetlands. Our results suggest that the removal of bison from Great Plains tallgrass prairie may have reduced the plant biodiversity and the extent of semi-aquatic ecosystems.