Ecological Models for Assessing Functions of Hard Claypan Vernal Pool Wetlands in the Central Valley of California Using the Hydrogeomorphic (HGM) Approach for Wetland Assessment.
Date of Award
Doctor of Philosophy (PhD)
Oceanography and Coastal Sciences
William H. Patrick, Jr
Seven vernal pool complexes consisting of numerous shallow wetland depressions were sampled in Sacramento County, California, during the spring and early summer of 1998. Data were obtained to characterize ecological conditions within each complex and to develop models for assessing wetland disturbance and functions. Degree of disturbance, topographic features, soil profiles, and plant species composition and percent cover were examined. Pool area, volume, perimeter, maximum depth, distance from pool to pool, and percent of sample area were computed for 265 vernal pools. Additional detailed topographic and vegetative data were obtained at 68 vernal pools and soil profiles characterized at 64 vernal pools. Disturbance was computed quantitatively by integrating the type of disturbance and proximity to the pool into a single numeric index. This disturbance quotient provided a relative measure of vernal pool alterations. Data were analyzed using correlation analysis, stepwise discriminant analysis, and discriminant analysis to construct a model sensitive to disturbance. Results of the discriminant analysis indicated that three variables (disturbance quotient, maximum depth, and percent native to nonnative plant species) provided the best combination of factors to assess relative disturbance. A predictive model was developed using these three variables to accurately assign 92.8 percent of the pools to particular wetland areas indicative of different levels of alteration. Other variables that also related to disturbance included soil depth to the durapan and slope at the edge of the vernal pool. Five wetland functions were identified as being relevant to vernal pools and ecological models were developed for each function. These models were calibrated with data collected from the vernal pools to provide a relative measure of the functional capacity of vernal pool wetlands in the Central Valley of California. The ecological models can be used to assess the capacity of wetlands to perform different functions, calculate project impacts on those functions, compute mitigation requirements to offset unavoidable impacts, and assess mitigation success.
Clairain, Ellis Joseph Jr, "Ecological Models for Assessing Functions of Hard Claypan Vernal Pool Wetlands in the Central Valley of California Using the Hydrogeomorphic (HGM) Approach for Wetland Assessment." (2000). LSU Historical Dissertations and Theses. 7253.