Decadal-scale soil redistribution along hillslopes in the Mojave Desert

Crouvi, O. , Polyakov, V. O. , Pelletier, J. D. , Rasmussen, C.

2015 EARTH SURFACE DYNAMICS 2015   3(卷), 2(期), (251-264页)

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This study estimates the relative magnitude of decadal-scale soil redistribution (i.e., soil loss or gain) by slope wash using Cs-137 inventories measured in 46 soil profiles at four study sites in the Ft. Irwin area of the Mojave Desert of California, USA. The variability in Cs-137 inventories on a < 5m scale suggests that even for the same topographic position, there is large variation in runoff generation and flow continuity. Smaller average Cs-137 inventories that are suggestive of higher relative erosion rates are associated with more gently sloping sites that have a lower percentage of surficial rock-fragment and vegetation coverage. Individual Cs-137 inventories from all four sites are positively correlated with the percentage of rock fragments in the upper soil profile. The increase in rock-fragment cover (i.e., soil armoring) with increasing slope gradient appears to negate any potential increase in transport effectiveness with increasing slope steepness. This armoring, together with the sandy-loam soil texture characteristic of steeper slopes, hinders runoff and slope-wash erosion. Our findings are supported by soil data that suggest that these patterns are persistent for longer timescales (i.e., centuries and millennia).

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