Plant Community Shifts in Response to Fire and Bison in a Restored Tallgrass Prairie

To redress prairie loss, managers seed former agricultural lands and reinstate key ecosystem processes with prescribed fires and reintroduction of native grazers to create restored prairies. Bison (Bison bison) were almost hunted to extinction in the late 1800s but are recovering and have recently been reintroduced to restored prairies for their ecosystem engineering roles. The effects bison and fire have on remnant (never-plowed) prairie vegetation are well documented. However, there is little known about how bison will impact plant communities in restored prairies. These effects are most likely driven by reduction of competition from grasses and increased heterogeneity from disturbance. This study aimed to quantify bison impacts on vegetation in a chronosequence of restored prairie with varied burning regimes. We found that plant diversity decreased with restoration age and did not differ among either grazing or fire treatments. However, grazed sites displayed more variation within plant community composition. Older restorations tended to be more similar in species and functional group composition in comparison to younger sites. Although the roles of bison and fire were not as important in these first three years after reintroduction as predicted, changes in composition suggest that bison effects may become more apparent in later years as grazing drives different compositional trajectories.