Combined data on plant species abundance and composition from LTER and other grasslands in the United States, 1943 - 2010

Understanding how biotic mechanisms confer stability in variable environments is a fundamental quest in ecology, and one that is becoming increasingly urgent with global change. Several mechanisms, notably a portfolio effect associated with species richness, compensatory dynamics generated by negative species covariance and selection for stable dominant species populations can increase the stability of the overall community. While the importance of these mechanisms is debated, few studies have contrasted their importance in an environmental context. We compiled nine long-term datasets of grassland species composition to evaluate the strength of biotic mechanisms of community stability and assess how these mechanisms change across precipitation gradients. Data were collected in replicate plots over time at nine different sites throughout the US (replicates within a site range from 5-100, plot sizes from 0.1 m² to 17 m²; minimum 9 years, maximum 30 years). Species abundance was measured as either percent cover, biomass, or allometrically-derived biomass. At all sites the measurement techniques and management regimes remained constant over the collection period, and the data collection methods were not relativized. For example, sites in which species composition were measured as percent cover do not require their estimates to sum to 100. For sites with long-term experimental treatments, only the control plots were included. These data have been presented in: Lauren M. Hallett, Joanna S. Hsu, Elsa E. Cleland, Scott L. Collins, Timothy L. Dickson, Emily C. Farrer, Laureano A. Gherardi, Katherine L. Gross, Richard J. Hobbs, Laura Turnbull, Katharine N. Suding. 2014. Biotic mechanisms of community stability shift along a precipitation gradient. Ecology 95:1693–1700. http://dx.doi.org/10.1890/13-0895.1