Predictions regarding future climate change vary greatly among regions, and these predictions include directional changes such as more arid conditions in the US Southwest (Seager et al. 2007), as well as an expectation of greater interannual variability (Easterling et al. 2000). Ecologists are charged with identifying biotic communities and ecosystems most at risk for declines in diversity and functioning, which first requires an understanding of how diversity and ecosystem function respond to current temporal and spatial variation in climate, including interannual climate variation. In many systems there is great interannual variation in climate, making long-term observations of species composition and ecosystem functioning essential for documenting these climate-composition-function relationships.