Wind erosion and dust flux from plot to landscape scale: Disturbance effects exemplified by fire and grazing

Background/Question/Methods

Wind erosion and dust flux in and from dryland ecosystems have important ecological implications over a range of spatial scales and are fundamental to many basic ecosystem processes such as nutrient cycling, litter decomposition, and fluxes of energy and resources. Despite the growing recognition of the ecological importance of wind erosion within areas of biogeosciences, geomorphology, and atmospheric sciences, the ecological community at large has generally focused on this issue to a much lesser degree, precluding a better understanding of the multi-scale ecological consequences of aeolian processes in dryland ecosystems. Although dryland ecosystems cover a substantial fraction of the Earth’s land surface, relatively few measurements of aeolian sediment transport have been made within these systems, especially following disturbance such as fire and grazing. Aeolian sediment transport in dryland systems is strongly influenced by disturbance, as well as the spatial density of roughness elements, which is largely determined by woody plant height and spacing. However, the few existing measurements of aeolian sediment transport within these systems have not been systematically evaluated with respect to disturbance and gradients of woody plant cover. Here we report new field-based measurements of aeolian sediment transport for twelve study plots in disturbed and undisturbed semiarid grasslands in southern Arizona.  Aeolian sediment transport was measured using a series of BSNE samplers located at five heights above ground in each plot. 
Results/Conclusions

Our site-specific results indicate that disturbance can have a large effect on aeolian sediment transport at the plot scale and that the type and intensity of disturbance plays an important role in determining the magnitude and the severity of the response. To assess trends in aeolian sediment transport at the landscape scale, we compared our site-specific findings to other recently published measurements and evaluated these results with respect to disturbance and gradients of woody plant cover. Our findings suggest that for relatively undisturbed ecosystems, shrublands have inherently greater aeolian sediment transport than grasslands, woodlands and forests because of fundamental differences related to the height and spacing of woody roughness elements within these systems. Furthermore, our findings suggest that wind erosion and dust flux following disturbance spans a relatively small range in woodlands and forests, an intermediate range in shrublands, and the largest range in grasslands. More generally, these collective results highlight important interactions between vegetation and disturbance on wind erosion, which in turn has important ecological implications spanning plot to landscape scales and greater.