PS 25-50 - CANCELLED - Response to precipitation variation suggests resilience declines under climate change in early successional grassland communities

Background/Question/Methods

The composition of a plant community (e.g., community diversity, relative abundance of exotic species) can influence its resilience to resource limitation as well as its ability to take advantage of high resource availability. Simultaneously, resource availability can impact community composition. Given that Eastern US growing-season precipitation is predicted to become increasingly variable, with increases in both droughts and pulse rainfall events, we explored feedbacks between composition and water availability response on long-term productivity. Specifically, we used two decades (2000-2020) of annual net primary productivity (ANPP) data from 30 plots in early successional grassland communities at the Kellogg Biological Station LTER, south-central Michigan, USA. We identified growing seasons of drought and highly wet conditions and evaluated variation in ANPP as a function of species richness, diversity (H'), and exotic abundance. We additionally considered the response of these factors to water availability.

Results/Conclusions

Exotic abundance was negatively associated with ANPP drought resistance and also with the community’s ability to increase productivity in response to wet years. For one drought year, diversity was positively associated with resistance to drought. Unexpectedly, species richness tended to be negatively correlated with drought recovery. Both diversity and exotic abundance increased with current moisture availability, while species richness declined as a function of prior growing season moisture. Our results support previous studies showing that species diversity acts as a resilience mechanism, while exotic species decrease community resilience. Observed feedbacks between community properties and moisture availability response (i.e., wet years facilitating exotic species, but exotics reducing drought resilience and wet-year productivity) suggest that both resilience and productivity may decline under the variable precipitation projected for eastern North America.