Thesis (M.S.)--Brigham Young University, Dept. of Geography. / Electronic thesis. Also available in print ed.

Thesis (M.S.)-- Brigham Young University. Dept. of Geography.

abstract: Biological soil crusts (BSCs) dominate the soil surface of drylands in the western United States and possess properties thought to influence local hydrology. Little agreement exists, however, on the effects of BSCs on runoff, infiltration, and evaporative rates. This study aims to improve the predictive capability of an ecohydrology model in order to understand how BSCs affect the storage, retention, and infiltration of water into soils characteristic of the Colorado Plateau. A set of soil moisture measurements obtained at a climate manipulation experiment near Moab, Utah, are used for model development and testing. Over five years, different rainfall treatments over experimental plots resulted in the development of BSC cover with different properties that influence soil moisture differently. This study used numerical simulations to isolate the relative roles of different BSC properties on the hydrologic response at the plot-scale. On-site meteorological, soil texture and vegetation property datasets are utilized as inputs into a ecohydrology model, modified to include local processes: (1) temperature-dependent precipitation partitioning, snow accumulation and melt, (2) seasonally-variable potential evapotranspiration, (3) plant species-specific transpiration factors, and (4) a new module to account for the water balance of the BSC. Soil, BSC and vegetation parameters were determined from field measurements or through model calibration to the soil moisture observations using the Shuffled Complex Evolution algorithm. Model performance is assessed against five years of soil moisture measurements at each experimental site, representing a wide range of crust cover properties. Simulation experiments were then carried out using the calibrated ecohydrology model in which BSC parameters were varied according to the level of development of the BSC, as represented by the BSC roughness. These results indicate that BSCs act to both buffer against evaporative soil moisture losses by enhancing BSC moisture evaporation and significantly alter the rates of soil water infiltration by reducing moisture storage and increasing conductivity in the BSC. The simulation results for soil water infiltration, storage and retention across a wide range of meteorological events help explain the conflicting hydrologic outcomes present in the literature on BSCs. In addition, identifying how BSCs mediate infiltration and evaporation processes has implications for dryland ecosystem function in the western United States. / Dissertation/Thesis / Masters Thesis Geological Sciences 2015

Moab, located in southeastern Utah, began as an agricultural village, in accordance with the economy of early Utah. However, Moab's growth was limited by a restricted physical site. The purpose of this study is to trace the development of the economic functions of Moab in relation to its resource base. Despite the physical limitations of the area, agriculture remained the chief economic activity up to the mid-twentieth century. Periodic booms in speculative mining were only temporary and not significant to the permant economy of the community.However, in the 1950s, a spectacular uranium boom brought unprecedented growth to the town. As the uranium boom slackened, economic and population decline threatened the town's new status. Potash production and tourist-service industries emerged to buoy up the sagging economy. Although the economy was aided by the addition of other activities, the sectors of the economy still remained disproportionately unbalanced in comparison to the norm. The future economic stability of the community remains questionable unless balance can be attained.