DISSERTATION RESEARCH: Riparian Tree Dynamics: Learning How to Restore Non-equilibrium Communities

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River regulation in California's Central Valley has altered hydrologic conditions and impaired reproduction of riparian tree populations that evolved with pre-settlement cycles of flooding and summer drought. The goal of this research is to develop a predictive understanding of recruitment and survival of the cottonwoods and willow species that dominate the crucial initial phase of riparian community development. Targeted field studies and controlled experiments will be conducted to parameterize and validate a conceptual model of hydrogeomorphic, phenologic, and ecophysiological factors driving cottonwood and willow recruitment on the lower Tuolumne River, CA. The model integrates length of seed release and viability periods, field conditions of water table dynamics and soil moisture, and seedling survival thresholds in response to water table recession. The studies will provide quantitative information necessary for resource managers to model cost-effective strategies to restore natural recruitment processes to Central Valley riparian woodlands. This project is important scientifically because it tests a general conceptual model integrating hydrology, ecology, and ecophysiology in a non-equilibrium system within a field-based resource management context. Broader impacts of this project include optimizing reach-wide flow restoration scenarios, evaluating current floodplain restoration projects, disseminating results to agencies for restoration planning, and mentoring undergraduates in research methods.