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United States Department of Agriculture

Agricultural Research Service

Title: Hydrologic Impacts of Fire on Steep Intermountain Sagebrush-Steppe Rangeland

Authors
item Pierson, Frederick
item Carlson, D - UNIVERSITY OF IDAHO
item Spaeth, K - NRCS

Submitted to: International Journal of Wildland Fire
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 20, 2002
Publication Date: July 24, 2002
Citation: Pierson, F.B., Carlson, D.H., and Spaeth, K.E., Impacts of wildfire on soil hydrological properties of steep sagebrush-steppe rangeland, v. 11, no. 2 p. 145-151.

Interpretive Summary: The impact of wildfire on infiltration and erosion was examined on steep slopes with sandy soils and sagebrush/bunchgrass vegetation. Densely vegetated north-facing slopes were compared to sparsely vegetated south- facing slopes under both burned (moderate and high severity) and unburned conditions. Both fire severity and slope aspect strongly influenced the impact of the fire on infiltration and soil erosion. South-facing slopes had the least infiltration and the greatest rates of erosion following the fire. Infiltration rate was significantly less and erosion was significantly greater on severely burned south slopes as compared to those experiencing only moderate burn severity. Fire severity had little effect on the hydrology and erosion of north-facing slopes. Despite differences in infiltration, runoff from all burned and unburned slopes began within 2 to 4 minutes following the start of rainfall. Differences in surface water storage and soil and vegetation characteristics were the primary cause of differences in infiltration between burned and unburned slopes. The roughness of the soil surface and associated ground cover after the fire were important factors in controlling runoff and erosion under the dry soil and vegetation conditions found on these steep rangelands. Results from this study will aid future efforts to understand and mitigate the impact of rangeland wildfires.

Technical Abstract: Fire impacts on infiltration and interrill erosion were examined using simulated rainfall one year following a rangeland wildfire. Densely vegetated north-facing slopes were compared to sparsely vegetated south- facing slopes under both burned (moderate and high severity) and unburned conditions. Both fire severity and slope aspect strongly influenced the impact of fire on infiltration capacity and soil erodibility. South-facing slopes had the least infiltration and the greatest rates of interrill erosion following the fire. Infiltration rate was significantly less and interrill erosion was significantly greater on severely burned south slopes as compared to those experiencing only moderate burn severity. Fire severity had little effect on the hydrology and erosion of north-facing slopes. Despite differences in terminal infiltration rates, runoff from plots of all treatment combinations (burned and unburned slopes) began within 2 to 4 minutes following the start of simulated rainfall. Differences in initial storage capacity and soil and vegetation structure were the primary determinants of total infiltration. Post-fire microtopography and associated ground cover appear to be important determinants of the potential for increased runoff and interrill erosion under conditions of dry antecedent soil moisture on these steep rangelands.

Last Modified: 11/24/2014
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