Total vertical sediment flux and PM10 emissions from disturbed Chihuahuan Desert surfaces

Abstract

Desert surfaces are typically stable and represent some of the longest-lived landforms on Earth. For surfaces devoid of vegetation, the evolution of a desert pavement of gravel and small stones protects the surface from erosion by wind and water and vegetation further protects the surface in arid and semi-arid rangelands. The susceptibility of the land surface to wind erosion is enhanced by mechanical damage to the desert pavement or vegetation losses resulting from fire or grazing. Despite the relatively rich literature on the effects of grazing and fire on plant community composition, land degradation, and the productivity of arid landscapes, little is known about the effects of moderate grazing or fire on the erodibility of soils in desert grasslands and shrublands. Here we investigate the effects of simulated moderate grazing, simulated livestock trampling, and of fire on the resulting wind erodibility and dust emissions of the affected soil surfaces. We surveyed 24 plots of the same size, 6 m × 0.6 m, at a research site in the northern Chihuahuan Desert including 6 plots in a shrub-grass ecotone, 12 plots in an adjacent grassland, and 6 plots in an area that had been burned by a natural wildfire 6 months earlier but had no vegetation recovery due to the time of year and drought. To evaluate the various effects of disturbances on the susceptibility of the surface to wind erosion and dust entrainment, replicates of three plots underwent different treatments including clipping, trampling, fire, and tillage. We subsequently tested each of the treated plots with a portable field wind tunnel run at 12.6 m s− 1. We found that moderate grazing and fire did not result in great soil loss in desert grasslands but that shrublands were more seriously affected by grazing and fire. Total removal of vegetation and disturbance of the soil surface did result in greater than order of magnitude increases of vertical sediment flux and greater than three-fold increases of dust emissions.