Individual function and community processes in desert annuals

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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).This project will investigate the physiology of Sonoran Desert winter annual plants in order to provide insights into their population and community dynamics and the mechanisms that allow species to coexist at high diversity. Annual plants are a major component of arid land, where precipitation is both low and highly variable. Plants respond differently to this variability in a manner that contributes to species coexistence. Species trade off maximal growth rate for efficient water use in different ways, resulting in distinct population dynamics. It has been shown that the species of this community that efficiently use water have lower temperature optima for photosynthesis. The goal for this proposal is to determine how variation in temperature optima and water use efficiency results in differences in population dynamics. A combination of natural observations, field and lab experiments and models of population dynamics will be used to determine if species are specializing to photosynthesize during different parts of the daily, storm front or seasonal cycle. Field experiments will manipulate precipitation pulse sizes and seasonal timing and the differential responses of species will be measured. The data will be used to forecast species-specific responses to changes in temperature and precipitation. This work will provide a unique framework for understanding how differences in physiology lead to important community properties: species coexistence and diversity. A more mechanistic community ecology and more ecologically grounded physiology will increase our understanding of how natural systems adapt to changing environments. This research will combine research and education in ways that train the ecological scientist of tomorrow. Undergraduate, graduate and postdoctoral students will gain hands-on scientific training. A graduate student will develop an educational kiosk that the hundreds of thousands of visitors to the University of Arizona's Biosphere 2 will interact with. Women and underrepresented ethnic and cultural groups will be encouraged to participate in this research in various ways including working with minority access programs on campus. The understanding gained from this work will have applications for resource management of desert systems in response to a changing climate.