Native plant species richness and diversity are important and widely used metrics of grassland ecosystem health. However, surprisingly little information on their variability through time and in response to specific stressors or ecological factors is available. We are using eight existing long- and short- term datasets from throughout the central United States to assess ranges in variability of native plant species richness and diversity and to determine the predictive value of factors such as weather, soil characteristics, grazing, fire, and exotic species for changes in native plant richness and diversity.

Results/Conclusions

Our preliminary results indicate that grazing has a larger long-term impact on the absolute value and variability of native richness than does fire, while the patterns are less clear in terms of native diversity. Our results also show a strong negative response of native richness and diversity to nitrogen fertilization with native diversity being more variable over time than native richness. Additionally, as the proportion of exotic species increases, the interannual variability of native species richness also increases.