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Description
Riparian wetlands are an important natural resource that has been widely threatened by human activity. Marine Corps Base Camp Pendleton near Oceanside, California, is the location of some of the few remaining natural riparian habitats in southern California. Riparian wetlands along the Santa Margarita River provide habitat for several federally endangered species, heightening the need to guarantee the continued sustenance of the riparian vegetation. In the near future, groundwater levels at the base could decline due to the cessation of infiltration of treated sewage water. Since riparian vegetation requires water in the subsurface within the root zone to survive, a substantial drop in groundwater level may have a negative impact on the vegetation. Identification of a correlation between soil hydro logic properties and tree moisture stress may aid in the development of an easily applied and economically feasible method to predict the moisture stress status of the trees for an extended period of time. The current hydrologic conditions at seven sites on the Santa Margarita River floodplain were evaluated to attempt to identify a correlation between soil tension, soil volumetric water content, effective unsaturated hydraulic conductivity, and depth to groundwater with values of tree moisture stress measured predawn and midday (by other researchers). Soil hydrogeologic properties including grain size distribution, saturated vertical hydraulic conductivity, and soil water characteristic curves were determined utilizing laboratory methods. Depth to groundwater and soil tension conditions were measured in the field. Volumetric moisture content and effective unsaturated hydraulic conductivities were derived from soil tensions and laboratory derived soil water characteristic curves. A correlation with midday tree moisture stress was only evident with depth to groundwater. A correlation with predawn tree moisture stress was also evident with depth to groundwater, and there was a possible correlation with soil tension and volumetric moisture contents at select locations.
