The relationships between environmental variability, species diversity and community stability are highly debated. For example, environmental variability can destabilize species populations through increased stochasticity. However, it can also stabilize species diversity by structuring species tradeoffs (i.e., if different species are favored by different environmental conditions but can persist across unfavorable conditions). Scaling up, species tradeoffs may stabilize community properties (such as primary production) in variable environments if an increase in one species compensates for a decline in another.
I employ long-term data analysis and synthesis to identify broad temporal patterns of biodiversity and to contextualize site-level research. For example, precipitation is a limiting resource in most grasslands, and may drive site-level differences in biodiversity. Early in my doctoral work I collaborated with a Long-Term Ecological Research (LTER) team to test controls on community stability along a precipitation gradient in US grasslands. A significant finding was that biodiversity-stability relationships shifted along the gradient – high richness lead to community stability in mesic systems, whereas species tradeoffs increased stability in variable systems.
My experimental research tests the mechanisms underlying observational patterns. In our LTER synthesis, California grasslands exhibited the highest degree of species tradeoffs and precipitation variability. For my dissertation research, advised by Dr. Katharine Suding, I explored this relationship using rainfall and grazing manipulations. I found that rainfall variability increased species diversity by structuring species tradeoffs, and that moderate grazing enhanced this effect by promoting functional diversity. Further, species tradeoffs increased the stability of community properties such as total cover because an increase in one species could compensate for the decline in another. As a postdoc, I am collaborating with Drs. Katharine Suding, Whendee Silver and Andrew Moyes to extend this research to test the implications of tradeoffs for many community and ecosystem-level responses (e.g., above and belowground biomass, soil nutrient cycling, carbon sequestration).