Theory has shown that environmental fluctuations may promote coexistence through the storage effect, but testing this theory has been limited by a lack of appropriate data. Multiple empirical case studies are needed to establish the generality of the storage effect and determine its importance relative to other coexistence mechanisms. We used long-term demographic data from four semiarid plant communities to test for the conditions of the storage effect and quantify its strength using simulations of empirically parameterized models.

Results/Conclusions

Our comparative test produced two main results. First, we found that interannual climate variability had a stabilizing effect on historical coexistence in all four semiarid plant communities: Species had higher simulated long-term, low-density growth rates in variable than constant environments. This result was robust to model assumptions. Second, our models predicted that many species would persist even in the absence of temporal variability, indicating that other coexistence mechanisms are operating. However, this result was sensitive to assumptions about the composition of the resident community. Our analysis indicates that climate variability may help stabilize coexistence in many plant communities, meaning that efforts to forecast the impact of climate change on species diversity must consider changes in climate means and also variances.