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Salt and sediment contributions to the Colorado River and its tributaries pose economic and environmental concerns for the United States and Mexico. Land use decisions promoting the aggregation of Mancos Shale derived soils are one way to reduce the transportation of salts and sediments to water resources. We used a simple field test of soil aggregate stability to determine the site characteristics influencing the soil stability of sedimentary marine shale in the Gunnison Gorge National Conservation Area in Southwestern Colorado. Ninety-six 1 m2 plots were intensively sampled to explore relationships between soil stability and the biological, chemical and physical site characteristics. Analysis of variance showed...
Soil surface roughness may significantly impact runoff and erosion under rainfall. A common perception is that runoff and erosion are decreased as a function of roughness because of surface ponding and increased hydraulic roughness that reduces effective flow shear stress. The objective of this study was to measure the effects of initial surface roughness on runoff and erosion under controlled laboratory conditions. Initially, rough and smooth surfaces were exposed to five simulated rainfall applications at 5% and 20% slopes. In all cases, runoff was delayed for the case of the initially rough surface; however, this effect was temporary. Overall, no statistical differences in either total runoff or erosion were...
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In a semi-arid, upland setting on the Colorado Plateau that is underlain by nutrient-poor Paleozoic eolian sandstone, alternating episodes of dune activity and soil formation during the late Pleistocene and Holocene have produced dominantly sandy deposits that support grass and shrub communities. These deposits also contain eolian dust, especially in paleosols. Eolian dust in these deposits is indicated by several mineralogic and chemical disparities with local bedrock, but it is most readily shown by the abundance of titaniferous magnetite in the sandy deposits that is absent in local bedrock. Magnetite and some potential plant nutrients (especially, P, K, Na, Mn, and Zn) covary positively with depth (3?4 m) in...
This study investigates how dust deposition samplers affect the grain size characteristics of the sediment they catch. Sediment samplers act as obstacles in the flow and their collection efficiency varies with the grain size and other factors. Some particle fractions are collected more efficiently than others, resulting in a modification of the original grain size distribution of the sediment. This paper presents wind tunnel results for five dust deposition samplers and five wind velocities ranging from 1 to 5 m s− 1. The catcher's effect on the grain size was apparent in all experiments. Dust accumulated in a catcher is finer than undisturbed dust. For the dust used in the tests the difference (in median grain...
We compared short-term effects of lug-soled boot trampling disturbance on water infiltration and soil erodibility on coarse-textured soils covered by a mixture of fine gravel and coarse sand over weak cyanobacterially-dominated biological soil crusts. Trampling significantly reduced final infiltration rate and total infiltration and increased sediment generation from small (0.5 m2) rainfall simulation plots (p<0.01). Trampling had no effect on time to runoff or time to peak runoff. Trampling had similar effects at sites with both low and very low levels of cyanobacterial biomass, as indicated chlorophyll a concentrations. We concluded that trampling effects are relatively independent of differences in the relatively...
The effect of rock fragment eccentricity on the deposition of airborne dust was examined in a wind tunnel. Eccentricity was defined as the ratioa/b, wherea is the longest andb the intermediate axis of the rock fragments. The effect of eccentricity on the deposition of dust on the pebbles, on the deposition of dust between and underneath the pebbles, and on total dust deposition (pebbles + interpebble space) was measured separately, and this for different values of pebble size, pebble flattening, cover density and wind speed. The more pebbles are elongated, the larger dust deposition on them will be. This effect is more pronounced as pebbles become larger, as they become less flattened, and as wind speed increases,...
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    map background search result map search result map Late Quaternary eolian dust in surficial deposits of a Colorado Plateau grassland: Controls on distribution and ecologic effects Late Quaternary eolian dust in surficial deposits of a Colorado Plateau grassland: Controls on distribution and ecologic effects