Hutten, M.A. 2015. Yosemite Region nitrogen deposition patterns in the composition of lichen communities. Ph.D. Dissertation, Oregon State University, Department of Botany and Plant Pathology.
Over 300 epiphytic lichen tissue samples were collected throughout Yosemite National Park in the Sierra Nevada mountains of California. The lichen samples were tested for nitrogen concentrations and the vast majority of samples were found to exceed the critical load for nitrogen content for this region. Using GIS the researchers were able to show spatially that this region exceeded critical loads (thresholds at which the element in question starts to effect ecological change) in 68% of sampled sites. Lichen tissue concentration of nitrogen has been calibrated to throughfall nitrogen deposition measurements in past studies and has been shown to correspond to kilogram/hectare/year throughfall deposition rate of nitrogen. This was done using standard linear regression with three different lichen species. From there they used nonparametric multiplicative regression to extrapolate for the landscape level. This model was then overlayed in ArcGIS with a California-wide nitrogen deposition model, to see the differences. This much higher resolution model (10x10 meters) highlighted areas where the California-wide model (4000 x 4000 meters) was underestimating critical load exceedances, primarily at higher elevations. This study found differences between sites due to elevation and topography, the researchers cautioned against using traditional krigging, which assumes equal variance in all directions. This thesis work is very applicable to mine because it deals with the same species of lichens, same pollutants of interest (nitrogen), and Yosemite is just north of my study area.











