Integrated Research on Aeolian Processes and Soil Biogeochemistry in the Desert Grassland of Southern New Mexico

Li, Junran, Department of Environmental Sciences, University of Virginia
Epstein, Howard, Department of Environmental Sciences, University of Virginia
Okin, Greg
Wiberg, Pat, Department of Environmental Sciences, University of Virginia
D'Odorico, Paolo, Department of Environmental Sciences, University of Virginia
Smith, James, Department of Civil & Environmental Engineering, University of Virginia

This dissertation is concerned primarily with a landscape-scale field experiment and associated aeolian sediment flux, soil nutrient loss, and soil nutrient heterogeneity measurements carried out in the Jornada Experimental Range in south-central New Mexico. There are four major new research chapters reflecting the thesis's fourfold purpose: (1) to investigate soil nutrient loss on plots with varying vegetation cover and wind erosion rates, (2) to examine changes of soil resource heterogeneity caused by wind erosion, (3) to evaluate the effects of sediment deposition on surface soil nutrient content and spatial heterogeneity, and (4) to evaluate a biogeochemical model for its utility in predicting the effects of wind erosion on long-term nutrient and vegetation dynamics . Different magnitude of sediment flux was encouraged with various levels of vegetation cover reduction, and was monitored with Big Spring Number Eight (BSNE) sediment samplers. Soil nutrient loss was calculated by comparing mean levels of soil nutrients before and after plant cover reduction over a three-year period. Results show that about 250f the surface soil C and N were depleted due to enhanced wind in three windy seasons. In investigating wind erosion and soil heterogeneity, a novel geostatistical method was developed. The overall results of wind on the grass cover reduction plots are the disappearance of small, strong fertile islands, which may be related to grasses; and the reinforcement of large fertile islands, which are likely related to mesquite shrubs. Soil heterogeneity in the downwind deposition dominated area was studied in a similar way as the upwind plots but was presented in a separate chapter (Chapter 5). Despite the change of general variations in surface soil nutrients, statistically significant changes in soil nutrient spatial patterns were generally not observed. iii Finally, a major biogeochemical model (CENTURY) for its utility in examining the effects of wind erosion in future arid land soil-plant dynamics was evaluating, with the consideration of different wind erosion intensities. The results indicate that current version of CENTURY, without an independent submodel of wind erosion, may substantially underestimate the nutrient depletion ability of aeolian processes in arid and semiarid ecosystems.

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PHD (Doctor of Philosophy)
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