Fire Impacts on Rangeland Hydrology and Erosion in a Steep Sagebrush Dominated Landscape

Wildfire is a major ecological process and management issue on sagebrush dominated rangelands throughout the western United States. Fire in these systems can induce soil water repellency and increase runoff and erosion. Few data are available to quantify fire induced hydrologic impacts on rangelands or to determine the persistence of such impacts. Small plot-scale (stratified over shrub coppice and interspace microsites) and concentrated flow simulation methodologies were used to quantify spatial and temporal variation in fire induced hydrologic impacts on steep sagebrush dominated rangelands. Fire impacts on interrill runoff and erosion and induced soil water repellency were primarily restricted to shrub coppice microsites; shrub coppice sites exhibited significant reduction in infiltration capacity and increased interrill sediment yield following wildfire. The greatest impact observed was the effect on overland flow dynamics. Extensive removal of ground cover and microtopography by wildfire concentrated overland flow into rills and significantly increased runoff and erosion rates. Mean rill depth, velocity, and sediment concentration were greater in burned areas than unburned areas immediately following wildfire and decreased as litter and plant basal cover increased through four growing seasons post-fire. The findings provide a relative index of overland flow and erosion risks and the rate of hydrologic recovery following fire in sagebrush dominated rangelands.