The influence of plant functional traits on ecosystem responses to altered rainfall

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In the coming decades, ecological communities will experience numerous environmental changes, including shifting climates and invasion by exotic species. Plant and microbial communities may exhibit non-linear responses to these environmental changes as species encounter physiological thresholds that constrain their growth and reproduction. Ultimately, ecosystem responses to environmental change will depend both on short-term shifts in species physiology or growth, and long-term shifts in species composition. This project will help develop the understanding of ecosystem responses to environmental change that will be needed for sustainable long term management of chaparral ecosystems.Experimental, observational, and modeling approaches will be used to quantify chaparral ecosystem responses to altered rainfall regimes. Rainout shelters will be used to produce a gradient of rainfall quantity, and initial species composition of the experimental plots will be controlled by removing invasive annual grasses. Short-term physiological measurements will be taken on focal species, which will also be monitored over the course of the experiment to measure growth and survival. To complement these experiments, similar measurements will be taken on dominant plant species along a natural rainfall gradient across Southern California. Results from these experiments and surveys will be used to parameterize a Dynamic Global Vegetation Model to predict how predicted shifts in rainfall regimes will influence plant species composition and, ultimately, influence regional ecosystem processes.This project will contribute to undergraduate, graduate, and public education, it will provide data to the broader scientific community, and it will inform land-management agencies. The experiment will provide research opportunities both for undergraduate and graduate students. Further, the research will evaluate how invasion influences ecosystem responses to global change, and whether interannual variation in rainfall may create opportunities for native shrub restoration. Communicating these findings with relevant conservation and land-management organizations will be one of the most important outcomes from this experiment. Finally, the project will make all of the data available and support communication about the ecological impacts of global change through evening lectures in public venues.