Precipitation affects water availability, which subsequently influences plant growth, species persistence, and productivity. Critically, global change is causing precipitation patterns to shift, which can lead to changes in plant community composition and may affect the capacity of plant communities to perform essential ecosystem functions. We can use rainout shelters to intercept incoming ambient rainfall and simulate future precipitation conditions to better predict how plant communities may respond to shifts in precipitation. 

Here, we aim to study if altered precipitation seasonality affects plant diversity and biomass by experimentally increasing spring precipitation via manual irrigation and decreasing summer precipitation using rainout shelters. Furthermore, there can be two experimental plots under a single rainout shelter allowing us to test the combined effects of multiple factors on plant communities. So in addition to manipulating precipitation seasonality, we will also manipulate the presence of insect herbivores using exclosures to quantify the independent and interactive effects of precipitation and insect herbivory on plant species richness, diversity, and biomass. The top-down effects of insect herbivores on plant communities can vary depending on plant water status, suggesting that precipitation and insect herbivory may have interactive effects on plant diversity, community composition, and biomass. 

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