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United States Department of Agriculture

Agricultural Research Service

Title: Runoff and erosion effects after prescribed fire and wildfire on volcanic ash-cap soils

Authors
item Robichaud, Peter - FOREST SERVICE
item PIERSON, FREDERICK
item Brown, Robert - FOREST SERVICE

Submitted to: USDA Forest Service, Joint Fire Science Program, Final Report
Publication Type: Government Publication
Publication Acceptance Date: March 20, 2007
Publication Date: March 20, 2007
Citation: Robichaud, P.R., Pierson, F.B., and Brown, R.E. 2007. Runoff and erosion effects after prescribed fire and wildfire on volcanic ash-cap soils. In: Page-Dumroese, D., Miller, R., Mital, J., McDaniel, P., Miller, D., Technical Eds. Volcanic-ash-cap derived forest soils of the Inland Northwest: Properties and implications for management and restoration, November 9-10, 2005, Couer d’Alene, ID. Proceedings RMRS-P-44, U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fort Collins. 220 p.

Interpretive Summary: THE HYDROLOGIC IMPACTS OF BURNING WERE STUDIED ON ASH-CAP SOILS IN IDAHO AND MONTANA. THE STUDY WAS DESIGNED TO DETERMINE IF THE SEVERITY OF BURNING INFLUENCED OBSERVED AMOUNTS OF RUNOFF AND EROSION. RESULTS INDICATED THAT THE ASH-CAP SOILS HAD HIGH NATURAL RATES OF RUNOFF DUE TO WATER REPELLENT SOIL CONDITIONS. HOWEVER, UNBURNED ASH-CAP SOILS HAVE LOW EROSION RATES DUE TO THICK PROTECTIVE DUFF LAYERS. WHEN ASH-CAP SOILS ARE BURNED AND THE DUFF LAYER IS REMOVED, EROSION RATES CAN DRMATICALLY INVREASE ESPECIALLY DURING HIGH INTENSITY RAINFALL EVENTS.

Technical Abstract: AFTER PRESCRIBED BURNS AT THREE LOCATIONS AND ONE WILDFIRE, RAINFALL SIMULATIONS STUDIES WERE COMPLETED TO COMPARE POSTFIRE RUNOFF RATES AND SEDIMENT YIELDS ON ASH-CAP SOIL IN CONIFER FOREST REGIONS OF NOTHERN IDAHO AND WESTERN MONTANA. THE MEASURED FIRE EFFECTS WERE DIFFERENTIATED BY BURN SEVERITY (UNBURNED, LOW, MODERATE, AND HIGH). RESULTS INDICATE THAT THIS DRY, UNDISTURBED ASH-CAP SOIL EXHIBITS HIGH RUNOFF RATES AND IS NATURALLY WATER REPELLENT AT THE SURFACE. HOWEVER, THE UNBURNED, UNDISTURBED ASH-CAP SOIL IS NOT HIGHLY EROSIBLE DUE THE PROTECTIVE DUFF LAYER ON THE SURFACE. WHEN ASH-CAP SOIL WAS EXPOSED TO PROLONGED SOIL HEATING (HIGH SEVERITY BURN), SURFACE WATER REPELLENCY WAS DESTROYED AND A STRONG WATER REPELLENT LAYER OCCURRED A FEW CENTIMETERS BENEATH SATURATED; THUS MAKING THE SOIL ABOVE THE WATER REPELLENT LAYER HIGHLY ERODIBLE-ESPECIALLY DURING HIGH INTENSITY RAINFALL.

Last Modified: 7/28/2014
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