Why some species are consistently more abundant than others, and predicting how species will respond to global change, are fundamental questions in ecology. Long-term observations indicate that plant species with high stoichiometric homeostasis for nitrogen (HN), i.e., the ability to decouple foliar N levels from variation in soil N availability, were more common and stable through time than low HN species in a central US grassland. However, with 9-yrs of nitrogen addition, species with high HN decreased in abundance, while those with low HN increased in abundance. In contrast, in climate change experiments simulating a range of forecast hydrologic changes - extreme drought (2-yrs), increased rainfall variability (14-yrs), and chronic increases in rainfall (21-yrs) - plant species with the highest HN were least responsive to changes in soil water availability. These results suggest that HN may be predictive of plant species success and stability, and how plant species and ecosystems will respond to global-change driven alterations in resource availability.