Impacts of geology and topography on plant species distributions in the White Mountains, eastern California.

摘要

This research seeks to understand landscape-scale interactions between plant species distributions, the underlying geology, and surface topography. These studies began with the question: Why do plants grow where they do in the central and southern White Mountains and northern Inyo Mountains of eastern California? These questions were approached from remote sensing and multivariate statistics perspectives. Hyperspectral remotely sensed imagery was employed to map both surficial geology and plant communities across the range. In the process, a strategy for mapping arid species distributions was developed, and the importance of seasonality on remotely sensed data was evaluated. The second perspective uses multivariate statistics to create species-specific links with environmental variables in a GIS framework. Through statistical analyses, species tolerances along complex environmental gradients were estimated and used to create predictive maps of species distributions. By modifying the input environmental variables, species responses to increased temperatures were forecasted, and the species at greatest risk of local extinction were identified. The analyses of remotely sensed imagery and multivariate statistics are not exclusive of each other. Remotely sensed data were combined with topographic and geologic data as environmental inputs in the multivariate analyses, to produce more accurate maps of species distributions and to better understand species-environment relationships.; An additional study examining the age of the Barcroft pluton in the central White Mountains is included. The pluton occupies a northeast-trending fault, the so-called Barcroft structural break, that separates the Mesozoic White Mountain Peak metavolcanic suite on the north from uppermost Precambrian-Lower Cambrian platform metasediments to the south. Field data show that the pluton intruded the metavolcanic suite, but previously published U-Pb zircon ages indicate the metavolcanics are younger than the pluton. New U-Pb zircons ages from four samples within the Barcroft pluton were measured using a Sensitive High Resolution Ion Microprobe - Reverse Geometry (SHRIMP-RG). The resulting 206Pb/238U ages indicate that the Barcroft pluton was emplaced at 165 Ma, within the ranges of previously published dates.