Post-Fire Variability in Aeolian Deposition in the Northern Great Basin

Aeolian processes play a significant role in the redistribution of sediment and nutrients in sparsely vegetated sagebrush steppe ecosystems. When fire is introduced to the landscape, decreased surface roughness and threshold friction velocity increase the mobility of surface sediments and burnt organic material. Once material is entrained, interactions between a dynamic atmosphere and complex topography control the spatial variability of aeolian deposition over a landscape. Our study uses over two years of continuous passive dust trap data to characterize spatial and temporal variations in the vertical flux of aeolian material following a fire in the northern Great Basin. Seasonal variation in aeolian mass flux is pronounced, with the fall months generating the largest magnitude dust flux. Immediately following fire, the mass flux of both sediment and carbon increased by four to eight fold within and proximal to the burned area until the first growing season. Samples impacted by fire contained 88% silt and clay sized material while undisturbed samples averaged 94% silt and clay sized material, indicating a temporary increase in the particle size distribution within the burned area. A geochemical comparison of regional and local dust and its sources also indicates a pulse of local sediment mobility following the fire through an increase in the concentrations of Titanium (found in local soil) and a decrease in the concentrations of Barium and Strontium (found in regional soluble salts). We interpret the cessation in local mobility after revegetation to adequate surface roughness provided by grasses and forbes which returned vertical fluxes of carbon and sediment to within pre-disturbance fluctuations. The preferential redistribution of locally derived material onto sheltered, leeward slopes and topographically low positions via aeolian processes adds a layer of complexity to the spatial variability of soil characteristics and the typical aspect controlled water-energy balance within the Great Basin. The results of this study will inform research on post-fire sediment and carbon redistribution, spatial variability of soil characteristics and landscape evolution in western rangelands.