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Timing and Magnitude of Soil Erosion in Owens Valley, California: A Combined 137Cs and 210Pbex Approach

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Author: Evans, Guy Nathaniel
Advisor: Kaste, James M.
Committee Members: Hancock, Gregory S.; Bagdassarian, Carey
Issued Date: 2010-05-24
Subjects: Owens Valley
Soil erosion
Cesium
Lead
URI: http://hdl.handle.net/10288/2067
Description: Soil erosion poses a major threat to the sustainability of soil resources in both natural and agricultural ecosystems and is considered a key contributor to desertification in arid and semi-arid regions. While studies have tried to resolve linkages between soil erosion and other environmental influences, attempts to connect soil erosion to these processes over time is often inhibited by the lack of a detailed decadal-scale soil erosion history. The study presented here examines erosion rates in Owens Valley, California and possible linkages to a recent episode of drought, water withdrawal, and live vegetation loss in 1986-1992. The study used a modification of the standard 137Cs and 210Pbex technique in which a mass balance advection-diffusion erosion model is used to connect 137Cs and 210Pbex soil bulk inventories to past erosion. Cs-137 is generally more sensitive to total erosion while Pb-210 inventories are sensitive to both total erosion and erosion timing. By combining the two isotope bulk inventories in a model and comparing them with measurements collected in the field, it was possible to constrain both erosion timing and magnitudes. This is in contrast to single-isotope models which do not present results with regards to erosion timing. This study found a higher likelihood of erosion in more recent years, particularly during and following the drought period of 1986-1992. However, significant spatial variability was observed and some soil cores were more consistent with episodic erosion while others were consistent with a relatively constant erosion rate. The average erosion magnitude for the region was 1.2± 0.65cm over 54 years or 2.5 t ha-1yr-1.
Degree: Bachelors of Science in Geology


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