High leaf tissue density grassland species consistently more abundant across topographic and disturbance contrasts in a North American tallgrass prairie

Abstract

Understanding the coupling between plant functional traits and abundance provides insight into the often hidden forces that structure plant communities. To better understand the coupling between leaf traits and abundance of grassland species in a mesic North American grassland, we measured specific leaf area (SLA) and its two components, tissue density and thickness for 125 grassland species. Plants with high tissue density were more abundant over a 17-year period across a range of environments: uplands, grazed and ungrazed watersheds, and frequently and infrequently burned watersheds. The consistent relationships between leaf tissue density and abundance across ecological contrasts imply that belowground resource availability constrains community composition independent of grazing and burning regimes. Leaf tissue density did not explain species abundance in lowlands, where belowground resources are the highest. Neither did it explain the differential abundance of species between grazing or fire frequency contrasts, suggesting that changes in burning or grazing select for species based on other traits. Relative to leaf tissue density, SLA was a poor predictor of abundance, reinforcing a long-observed—but often ignored—call that measurements of SLA need to be coupled with thickness measurements in order to effectively predict the performance of species. More generally, future research needs to investigate which belowground resources control community composition in the grassland and whether the importance of water or nutrients change with burning and grazing.