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Title: Hydrologic vulnerability of western US rangelands in the wake of woodland encroachment and increasing wildfire activity

Author
item Williams, Christopher - Jason
item Pierson Jr, Frederick
item AL-HAMDAN, OSAMA - University Of Idaho
item KORMOS, PATRICK - Boise State University

Submitted to: Trans American Geophysical Union
Publication Type: Abstract Only
Publication Acceptance Date: 12/9/2013
Publication Date: 12/9/2013
Citation: Williams, C.J., Pierson, F.B., Al-Hamdan, O.Z., and Kormos, P.R. 2013. Hydrologic vulnerability of western US rangelands in the wake of woodland encroachment and increasing wildfire activity. Presented at the American Geophysical Union Annual Fall Meeting, December 9-13, 2013, San Francisco, CA.

Interpretive Summary:

Technical Abstract: Pinyon and juniper woodlands have dramatically increased their range in the past 150 years and currently occupy more than 30 million ha of the western US. Range expansion has primarily occurred through encroachment into sagebrush rangelands. Woodland expansion and infill on western rangelands have altered the ecological structure and function of these ecosystems and have made much of the western US prone to large severe wildfires. Early succession woodlands are now burning in large, high-severity wildfires due to heavy woody-fuel loading and extensive horizontal-to-vertical fuel connectivity. Tree infill on late-succession woodlands coupled with extreme fire weather has increased the occurrence of large, high-severity woodland fires in recent decades. We investigated the effects of woodland encroachment and burning on hydrologic vulnerability at multiple woodlands and at a sagebrush rangeland in the early stages of woodland encroachment. Artificial rainfall and overland flow simulations were paired with vegetation and soil measures to evaluate ecohydrologic ramifications of woodland encroachment and burning at multiple spatial scales and over time. Our results provide insight into the ecohydrologic consequences of landscapescale conversion of sagebrush rangelands to woodlands and the effects of increasing wildfire across this domain in the western US.