|Robichaud, Peter - USDA-USFS|
|Spaeth, Kenneth - NRCS|
Submitted to: Catena
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 17, 2008
Publication Date: March 17, 2008
Citation: Pierson, F.B., Robichaud, P.R., Moffet, C.A., Spaeth, K.E., Williams, C.J., Hardegree, S.P., and Clark, P.E. 2008. Soil water repellency and infiltration in coarse-textured soils of burned and unburned sagebrush ecosystems. Catena 74:98-108. Interpretive Summary: Post-fire increases in runoff and sediment yield on rangelands are often attributed to fire-induced water repellent soil conditions and removal of vegetation and ground cover. Few data are available to address these fire effects on infiltration and runoff from mountainous sagebrush-dominated landscapes. Soil water repellency, infiltration, and runoff were assessed after two wildfires and one prescribed fire in three steep, sagebrush-dominated watersheds underlain with coarse-textured soils. Annual variability in naturally occurring water repellency had a greater impact on infiltration than fire effects. 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. The findings indicate post-fire increases in runoff and erosion on mountainous sagebrush systems with naturally high soil water repellency are more influenced by fire removal of ground and canopy cover than fire effects on soil water repellency and that the these impacts may exhibit short-term fluctuations due to annual variability in the strength of water repellent soil conditions.
Technical Abstract: 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 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 for coarse-textured sagebrush landscapes with high pre-fire soil water repellency, post-fire increases in runoff and erosion 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.