Microtopography and soil-surface materials on semi-arid piedmont hillslopes, southern Arizona
1992
Parsons, A.J. | Abrahams, A.D. | Simanton, J.R.
Many semi-arid piedmont hillslopes are vegetated by a sparse shrub community. The shrubs are commonly located atop small mounds of fine materials whereas the intervening inter-plant areas are swales with a desert pavement surface. The hypothesis that such microtopography and distribution of soil surface materials of a hillslope in southern Arizona (USA) result from the effects of rainsplash erosion was tested. It is shown that the protection afforded by shrubs to the ground surface beneath them results in differential rainsplash. More sediment is splashed into the areas beneath shrubs than is splashed outward. Furthermore, surface materials of small mounds have the same size distribution as sediment transported by rainsplash. The mounds, however, are not wholly accumulation features. Some of the difference in elevation between the mounds and the interplant swales is due to removal of sediment from the swales by overland flow. Desert pavement forms in the swales as a lag deposit that results from the water sorting action of rainsplash erosion. Inasmuch as the microtopography and distribution of soil surface materials on the studied hillslope are a consequence of the present shrub vegetation, they must have formed in the century or so since this vegetation replaced the former grassland.
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