Saturday, 15 July 2006

Soil Surface Properties of Mojave Desert Landforms.

Daniel R. Hirmas and Robert C. Graham. Univ of California Riverside, 1419 Hallberry Dr., Riverside, CA 92507

Many important one-dimensional soil processes in arid environments are strongly linked to surface properties such as infiltration rate, plant and rock cover, texture, and structure. Correlation of these properties with parts of the landscape will enhance quantitative landscape models of pedogenesis. The objectives of this study were to: (1) quantify surface properties of several major and component landform surfaces in the Mojave Desert, (2) determine the spatial distribution of these surface properties, and (3) interpret the spatial distribution of these properties from a landscape-modeling (3-D) context. The study area is located in Johnson Valley, Mojave Desert which contains several alluvial basins, composing approximately two-thirds of the total area, which are interrupted by igneous and metamorphic bedrock of hills and mountains. The ages of alluvial fans in the area range between late Pleistocene and middle Holocene. Soils are largely classified as Entisols and Aridisols, often containing argillic horizons, duripans, and various stages of calcic and petrocalcic horizon morphologies. Annual precipitation for the area ranges from 76 to 127 mm and falls predominantly between the months of November and March. Vegetation is dominated by creosote bush. Major and component landforms were delineated in the bounding mountains and piedmont slopes of the landscape. We hypothesized that the difference in the variability within and between landforms would be greater on the piedmont than in the mountains. On both piedmont and mountain slopes, surface properties are important to the three-dimensional movement of water and sediment across a desert landscape.

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