Coastal Wetland Hydroecology: Multi-scale Links Between Near-surface Hydrologic Processes and Vegetation

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Coastal wetlands are critical environments for which hydrogeologic processes are poorly appreciated. We propose fundamental hydrologic-science research to understand the functional links between coastal wetland vegetation and transport processes involving subsurface water, dissolved salt, and heat. We hope to test the hypothesis that a plant "engineers" a beneficial environment, in part by controlling local salinity and soil moisture in a positive feedback system. We propose to study a salt marsh in the Palo Alto Baylands where we can engage in a combination of intensive field monitoring, low-altitude high resolution thermal and visual remote-sensing, and quantitative analysis based on multi-scale simulation. Our investigation would include inherent matters of spatial and temporal variability. Three nested models spanning scales from a single plant to a vegetation patch to the larger salt-marsh system will aid in quantifying the physical controls on the marsh-plant system. Based on two years of original field data for calibration, our models would quantify fluxes of water, salt, and heat on multiple scales. These models will enable us to test hypothesis and identify key controls on wetland hydroecology and to evaluate potential environmental impacts. This project will contribute to hydrologic science by providing data and multi-process models that will be broadly applicable to other salt-marsh environments. Potential contributions include understanding species-specific hydrologic response, which will improve understanding of physical controls on ecosystem function. Quantification of local gradients and their causes would provide insight into the role of near-surface hydrogeology in binding adjacent plant patches into a united ecologic community. Our salt-marsh system model can be used to explore scenarios related to restoration and environmental change. Our data and modeling results might improve quantification of near-shore submarine groundwater discharge. Outreach will be achieved via publications and presentations. The Baylands Nature Interpretive Center has agreed to provide us with a venue for public/private workshops on wetland hydroecology and the scientific basis for wetland restoration. Our proposed research cuts across disciplinary boundaries by contributing to the fields of coastal ecology and biogeochemistry by helping to better identify fluxes and hyporheic exchange of water, solute, and heat that are of interest to wetland and marine ecologists and biogeochemists. Our results are also of interest to those in the fields of landscape ecology, plant physiology, benthic zoology, near-shore marine ecology, and coastal engineering.