EARTH SURFACE PROCESSES AND LANDFORMS Earth Surf. Process. Landforms 34, 193–203 (2009) Copyright © 2009 John Wiley & Sons, Ltd. Published online in Wiley InterScience (www.interscience.wiley.com) DOI: 10.1002/esp.1703 John Wiley & Sons, Ltd. Chichester, UK ESP Earth Surface Processes and Landforms EARTH SURFACE PROCESSES AND LANDFORMS Earth Surface Processes and Landforms The Journal of the British Geomorphological Research Group Earth Surf. Process. Landforms 0197-9337 1096-9837 Copyright © 2006 John Wiley & Sons, Ltd. John Wiley & Sons, Ltd. 2006 Earth Science Earth Science 9999 9999 ESP1703 Research Article Research Articles Copyright © 2006 John Wiley & Sons, Ltd. John Wiley & Sons, Ltd. 2006 Prescribed-fire effects on rill and interrill runoff and erosion in a mountainous sagebrush landscape † Prescribed-fire effects on rill and interrill runoff and erosion Frederick B. Pierson, 1 * Corey A. Moffet, 2 C. Jason Williams, 1 Stuart P. Hardegree 1 and Patrick E. Clark 1 1 United States Department of Agriculture – Agricultural Research Service, Northwest Watershed Research Center, Boise, Idaho, USA 2 United States Department of Agriculture – Agricultural Research Service, U.S. Sheep Experiment Station, Dubois, Idaho, USA Received 31 December 2007; Revised 13 March 2008; Accepted 7 April 2008 * Correspondence to: Frederick B. Pierson, Supervisory Research Hydrologist, US Department of Agriculture – Agricultural Research Service, Northwest Watershed Research Center, 800 Park Boulevard, Plaza IV, Suite 105, Boise, Idaho 83712, USA. E-mail: fred.pierson@ars.usda.gov † This article is a U.S. Government work and is in the public domain in the U.S.A. ABSTRACT: Changing fire regimes and prescribed-fire use in invasive species management on rangelands require improved understanding of fire effects on runoff and erosion from steeply sloping sagebrush-steppe. Small (0·5 m 2 ) and large (32·5 m 2 ) plot rainfall simulations (85 mm h –1 , 1 h) and concentrated flow methodologies were employed immediately following burning and 1 and 2 years post-fire to investigate infiltration, runoff and erosion from interrill (rainsplash, sheetwash) and rill (concentrated flow) processes on unburned and burned areas of a steeply sloped sagebrush site on coarse-textured soils. Soil water repellency and vegetation were assessed to infer relationships in soil and vegetation factors that influence runoff and erosion. Runoff and erosion from rainfall simulations and concentrated flow experiments increased immediately following burning. Runoff returned to near pre-burn levels and sediment yield was greatly reduced with ground cover recovery to 40 per cent 1 year post-fire. Erosion remained above pre-burn levels on large rainfall simulation and concentrated flow plots until ground cover reached 60 per cent two growing seasons post-fire. The greatest impact of the fire was the threefold reduction of ground cover. Removal of vegetation and ground cover and the influence of pre-existing strong soil-water repellency increased the spatial continuity of overland flow, reduced runoff and sediment filtering effects of vegetation and ground cover, and facilitated increased velocity and transport capacity of overland flow. Small plot rainfall simulations suggest ground cover recovery to 40 per cent probably protected the site from low-return-interval storms, large plot rainfall and concentrated flow experiments indicate the site remained susceptible to elevated erosion rates during high-intensity or long duration events until ground cover levels reached 60 per cent. The data demonstrate that the persistence of fire effects on steeply-sloped, sandy sagebrush sites depends on the time period required for ground cover to recover to near 60 per cent and on the strength and persistence of ‘background’ or fire-induced soil water repellency. Published in 2009 by John Wiley & Sons, Ltd. KEYWORDS: Erosion; infiltration; fire; rangeland; runoff; sagebrush; water repellent soils Introduction Changing climate conditions and conversion of sagebrush- steppe (Artemisia spp.) vegetation to cheatgrass (Bromus tectorum L.) have increased the frequency of landscape- scale wildfires in lower elevations in the Great Basin, USA (Whisenant, 1990; Miller et al., 1999; Miller and Tausch, 2001). At higher elevations, historical fire suppression activities have led to dense stands of sagebrush and encroachment of woody plants such as western juniper ( Juniperus occidentalis Hook). Prescribed-fire is increasingly being used as a tool for fuels reduction and to manage woody plant encroachment in these communities. Increased runoff and erosion following fire in semi-arid rangelands, chaparral and forests has been well documented (Meeuwig, 1971; DeBano, 1981; Simanton et al., 1990; Robichaud, 2000a,b; Johansen et al., 2001; Pierson et al., 2001, 2002, 2008a). Post-fire increases in runoff and erosion have been commonly associated with development or enhancement of soil water repellency (DeBano et al., 1970; Inbar et al., 1998); removal of surface soil-protective ground cover (Morris and Moses, 1987; Johansen et al., 2001; Pierson et al., 2001, 2008a), reduced aggregate stability (Shakesby and Doerr, 2006) and alteration of soil organic matter (DeBano et al., 1998). These fire-induced effects alter infiltration rates, increase and concentrate overland flow, and facilitate sediment transport. Although general causal agents for post-fire effects on runoff and sediment yield are well documented, fire rehabilitation and prescribed fire plans must address site-specific impacts and the spatial and temporal scale of fire effects.