Individual Function and Community Processes in Desert Annuals

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This proposal is to investigate the functional biology of Sonoran Desert winter annual plants in order to provide insights into their population and community dynamics. Annual plants are a major component of arid land plant communities. Ecologists are interested in the mechanisms that allow species to coexist and hence maintain species diversity. We have previously documented long-term population and community dynamics of a community of Sonoran Desert annuals. This ecosystem has highly variable precipitation. Plants respond to this variability in species-specific ways that result in the idiosyncratic schedules of reproductive success. This partially uncorrelated reproduction contributes to these species coexistence in ways that are now understood mathematically. The goal for this proposal is to understand how this variation in performance among species, which contributes to their coexistence, is a function of their physiology and morphology. We will collect various types of physiological, morphological and stable isotope data on plants growing in their natural habitats. This will uncover variation in functional biology that determines how different co-occurring species experience environmental variation and hence coexist. The previously collected long-term population dynamic data on this community have given us a unique window on how environmental variation can contribute to biodiversity by decoupling the temporal pattern of reproductive success. This project allows us to explain the underlying biology that creates the differential response to variation that is in turn responsible for two important ecological phenomena: species coexistence and diversity. The results of the work are also germane to management plans for desert systems.