Beever et al. modeled the impacts of cattle and burros grazing on soil and vegetation in the Mojave National Preserve among years and environmental gradients. Soil aggregate stability increased as the number of defecations decreased; indicating greater grazing pressure reduces soil stability. However, recovery of soil stability was not directly related to removal of grazing pressure, possibly suggesting that grazing was not the only factor affecting soil stability or that recovery would be a long-term process. Non-native plant species were more related to precipitation and environmental gradients when herbivores were present, however, after removal of grazing pressure, the number of non-native species was greater in areas with greater defecation, indicating that grazing and environmental factors are interacting to determine non-native species composition in this area. Based on the results of this study, the authors concluded that ecosystem dynamics in this, and any, system can only be fully understood when all spatial scales and sources of variability are accounted for.
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