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United States Department of Agriculture

Agricultural Research Service

Title: Wind Erodibility of Soils at Ft. Irwin, CA (Mojave Desert) Before and after Trampling Disturbance: Implications for Land Management

Authors
item Belnap, J. - USGS
item Phillips, S. - USGS
item Herrick, Jeffrey
item Johansen, J. - JOHN CARROLL UNIV

Submitted to: Earth Surface Processes and Landforms
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 5, 2005
Publication Date: N/A

Interpretive Summary: We compared wind erosion vulnerability of recently disturbed and control coarse sandy soils in the Mojave Desert near Barstow, California. Disturbance increased wind erosion vulnerability at all sites. Wind erosion vulnerability was indicated by the wind speed required to move soil particles. However, the wind speed required varied across sites. Statistical regression analyses showed that the decline in wind speed required to move sediment, and the corresponding rise in sediment yield, were significantly related to the biomass of biological soil crusts. However, chlorophyll a amounts were very low compared to chlorophyll a amounts found at other desert sites. Unlike these other sites, where chlorophyll a is higher and is often the most important factor our analyses showed that other factors were more important in determining the overall site susceptibility to wind erosion. These factors included soil texture (especially the fine, medium, and coarse sand fractions), rock cover, and the inherent stability of the soil (as indicated by subsurface soil stability tests). Thus, our results indicate there is a threshold of biomass below which biological crusts are not the determining factor in soil vulnerability to wind erosion.

Technical Abstract: Recently disturbed and “control” (i.e., less recently disturbed) sites in the Mojave Desert were compared for their vulnerability to wind erosion before and after being trampled. Before trampling, control sites had greater cyanobacterial biomass, soil surface stability, threshold friction velocities (TFV; i.e., the wind speed required to move soil particles) and sediment yield than sites that had been more recently disturbed by military maneuvers. After trampling, all sites showed a large drop in TFVs and a concomitant increase in sediment yield. Regression analyses showed that the decline in TFVs and the rise in sediment yield were significantly related to the biomass of biological soil crusts, as indicated by soil chlorophyll a concentrations. However, chlorophyll a amounts were very low compared to chlorophyll a amounts found at other desert sites. Unlike these other sites, where chlorophyll a is higher and is often the most important factor in determining TFV and sediment yield, multiple regression analyses showed that other factors at Ft. Irwin were more important in determining the overall site susceptibility to wind erosion. These factors included soil texture (especially the fine, medium, and coarse sand fractions), rock cover, and the inherent stability of the soil (as indicated by subsurface soil stability tests). Thus, our results indicate there is a threshold of biomass below which biological crusts are not the determining factor in soil vulnerability to wind erosion. Most undisturbed soil surfaces in the Mojave Desert region produce very little sediment, but even moderate disturbance increases soil loss from these sites. Because current weathering rates and dust inputs are very low, soil formation rates are low as well. Therefore, soil loss in this region is likely to have long-term effects.

Last Modified: 10/21/2014