Corey Moffet | The Samuel Robert Noble Foundation (original) (raw)
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ABSTRACT Wildfire is a major ecological process and management issue on sagebrush dominated range... more ABSTRACT 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.
Wildfire is an important ecological process and management issue on western rangelands. Major unk... more Wildfire is an important ecological process and management issue on western rangelands. Major unknowns associated with wildfire are its affects on vegetation and soil conditions that influence hydrologic processes including infiltration, surface runoff, erosion, sediment transport, and flooding. Post wildfire hydrologic response was studied in big sagebrush plant communities on steep slopes with coarse-textured soils. Significant rill erosion was observed following both thunderstorm and rapid snowmelt events. Rainfall simulation and controlled overland flow techniques were used to study post-fire effects on infiltration, and interrill and rill erosion processes on burned and adjacent unburned areas. Results indicate that burn severity and the development of water repellent soil conditions play significant roles in determining infiltration and interrill erosion rates, particularly on shrub coppice dunes characterized by high surface litter accumulations. The most dramatic and long-lasting affect of fire was on rill erosion processes by reducing ground cover needed to slow and spread water as it moves across the soil surface. Ongoing research efforts are aimed at characterizing the hydrologic impacts of prescribed fire used as a tool to manage vegetation and mitigate the impacts of catastrophic wildfire events.
Millions of dollars are spent each year in the United States to mitigate the effects of wildfires... more Millions of dollars are spent each year in the United States to mitigate the effects of wildfires and reduce the risk of flash floods and debris flows. Research from forested, chaparral, and rangeland communities indicate that severe wildfires can cause significant increases in soil water repellency resulting in increased runoff and erosion. Few data are available to document the effects of fire on the spatial and temporal variability in soil water repellency and potential impacts on infiltration and runoff on sagebrush-dominated landscapes. Soil water repellency, infiltration and runoff were assessed after two wildfires and one prescribed fire in three steep, sagebrush-dominated watersheds with coarse-textured soils. Water repellency was generally greater on unburned hillslopes and annual variability in water repellency had a greater impact on infiltration capacity than fire effects. The most significant impact of fire was canopy and ground cover removal on coppice microsites. Infiltration rates decreased on coppice microsites after fire even though soil water repellency was reduced. Fire-induced reduction in infiltration resulted from the combined effect of canopy and ground cover removal and the presence of naturally strong water repellent soils. Removal of ground cover likely increased the spatial connectivity of runoff areas from strongly water repellent soils. The results indicate that for coarse-textured sagebrush landscapes with high pre-fire soil water repellency, post-fire increases in runoff are more influenced by fire removal of ground and canopy cover than fire effects on soil water repellency and that the degree of these impacts may be significantly influenced by short-term fluctuations in water repellent soil conditions.
ABSTRACT Wildfire is a major ecological process and management issue on sagebrush dominated range... more ABSTRACT 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.
Wildfire is an important ecological process and management issue on western rangelands. Major unk... more Wildfire is an important ecological process and management issue on western rangelands. Major unknowns associated with wildfire are its affects on vegetation and soil conditions that influence hydrologic processes including infiltration, surface runoff, erosion, sediment transport, and flooding. Post wildfire hydrologic response was studied in big sagebrush plant communities on steep slopes with coarse-textured soils. Significant rill erosion was observed following both thunderstorm and rapid snowmelt events. Rainfall simulation and controlled overland flow techniques were used to study post-fire effects on infiltration, and interrill and rill erosion processes on burned and adjacent unburned areas. Results indicate that burn severity and the development of water repellent soil conditions play significant roles in determining infiltration and interrill erosion rates, particularly on shrub coppice dunes characterized by high surface litter accumulations. The most dramatic and long-lasting affect of fire was on rill erosion processes by reducing ground cover needed to slow and spread water as it moves across the soil surface. Ongoing research efforts are aimed at characterizing the hydrologic impacts of prescribed fire used as a tool to manage vegetation and mitigate the impacts of catastrophic wildfire events.
Millions of dollars are spent each year in the United States to mitigate the effects of wildfires... more Millions of dollars are spent each year in the United States to mitigate the effects of wildfires and reduce the risk of flash floods and debris flows. Research from forested, chaparral, and rangeland communities indicate that severe wildfires can cause significant increases in soil water repellency resulting in increased runoff and erosion. Few data are available to document the effects of fire on the spatial and temporal variability in soil water repellency and potential impacts on infiltration and runoff on sagebrush-dominated landscapes. Soil water repellency, infiltration and runoff were assessed after two wildfires and one prescribed fire in three steep, sagebrush-dominated watersheds with coarse-textured soils. Water repellency was generally greater on unburned hillslopes and annual variability in water repellency had a greater impact on infiltration capacity than fire effects. The most significant impact of fire was canopy and ground cover removal on coppice microsites. Infiltration rates decreased on coppice microsites after fire even though soil water repellency was reduced. Fire-induced reduction in infiltration resulted from the combined effect of canopy and ground cover removal and the presence of naturally strong water repellent soils. Removal of ground cover likely increased the spatial connectivity of runoff areas from strongly water repellent soils. The results indicate that for coarse-textured sagebrush landscapes with high pre-fire soil water repellency, post-fire increases in runoff are more influenced by fire removal of ground and canopy cover than fire effects on soil water repellency and that the degree of these impacts may be significantly influenced by short-term fluctuations in water repellent soil conditions.