Desertification, Soil Nitrogen Mineralization, and the Fractal Nature of Soil Spatial Variation in J. Occidentalis Communities of Central Oregon (Ecosystem Studies): VPW

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The proposed research tests three hypotheses relating decertification to changes in the fractal nature of soil properties and to soil food webs in big sagebrush/bluebunch wheatgrass communities in central Oregon which are grazed and being invaded by Juniperus occidentalis subsp. occidentalis. The hypotheses will be tested by sampling soils in two sites, with and without J. occidentalis, according to a fractal sampling design; analyzing samples for organic carbon, total nitrogen, moisture content, pH, soil fauna, and nitrogen mineralization rates; calculating the fractal dimension of the data by fitting straight lines to log-log semivariograms; and comparing the shapes of the semivariograms and their fractal dimensions between the sites. The research is significant because it tests a hypothesis developed in deserts of the southwest U.S. stating that decertification may occur as invasion of wood plants in grassland ecosystems as the result of grazing, which increases the spatial heterogeneity of soil water and nutrients, but recognizes the fractal nature of soil spatial variation, i.e. that they have self-affinity and detail as a wide range of spatial scales, and attempts to relate the patterns of variation to the structure of soil food webs. The results of this research will contribute to understanding of geographical and ecological processes affecting the long term use of semi-arid ecosystems. The project furthers VPW program objectives to provide opportunities for women to advance their careers in science or engineering through research, and to encourage other women to pursue careers in these areas through the investigators' enhanced visibility as role models on the host campuses. In this project, the proposed activities which contribute to the second objective include: teaching a course entitled, "Soil spatial Variability and Forest Ecology;" leading reading and discussion groups; advising; and organizing a series of guest seminars to be presented by women scientists working in fields related to the subject of soil spatial variability and forest ecology.