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ARS Home » Pacific West Area » Burns, Oregon » Range and Meadow Forage Management Research » Research » Publications at this Location » Publication #285811

Title: Postfire soil water repellency in pinon-juniper woodlands: Extent, severity, and thickness relative to ecological site characteristics and climate

item ZVIRZDIN, D - Brigham Young University
item Madsen, Matthew
item ROUNDY, B - Brigham Young University
item PETERSEN, S - Brigham Young University
item ANDERSON, V - Brigham Young University

Submitted to: Ecology and Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/2017
Publication Date: 4/20/2017
Citation: Zvirzdin, D.L., Madsen, M.D., Roundy, B.A., Petersen, S.L., Anderson, V.J. 2017. Postfire soil water repellency in pinon-juniper woodlands: Extent, severity, and thickness relative to ecological site characteristics and climate. Ecology and Evolution. 7:4630-4639.

Interpretive Summary: Soil water repellency is a condition caused or intensified by wildfire that can contribute to soil erosion and decrease vegetation recovery. Few studies have identified the magnitude of this problem in piñon-juniper (PJ) woodlands. Our objectives were to quantify how much water repellency there typically is following fire and develop a knowledge base of the environmental controls influencing the extent and severity of soil water repellency. We established study sites at 41 locations spread across major wildfires that burned during the 2009 fire season. Our results showed a strengthening in soil water repellency (i.e. greater extent and severity) as canopy cover and tree age increase, and soil pH and relative humidity decrease. These results are concerning as piñon-juniper woodlands are predicted to increase in cover over the next few decades. In addition, trends in global climate change will likely reduce relative humidity throughout the Intermountain West. Accordingly, we expect post-fire soil water repellency to intensify in the coming years. Land managers can use the information provided in this study to better guide management decisions with respect to soil water repellency.

Technical Abstract: Wildfires can create or intensify water repellency in soil, limiting the soil's capacity to wet and retain water. The objective of this research was to quantify soil water repellency characteristics within burned piñon–juniper woodlands and relate this information to ecological site characteristics. We sampled soil water repellency across forty-one 1,000 m2 study plots within three major wildfires that burned in piñon–juniper woodlands. Water repellency was found to be extensive—present at 37% of the total points sampled—and strongly related to piñon–juniper canopy cover. Models developed for predicting SWR extent and severity had R2adj values of 0.67 and 0.61, respectively; both models included piñon–juniper canopy cover and relative humidity the month before the fire as coefficient terms. These results are important as they suggest that postfire water repellency will increase in the coming years as infilling processes enhance piñon–juniper canopy cover. Furthermore, reductions in relative humidity brought about by a changing climate have the potential to link additively with infilling processes to increase the frequency and intensity of wildfires and produce stronger water repellency over a greater spatial extent. In working through these challenges, land managers can apply the predictive models developed in this study to prioritize fuel control and postfire restoration treatments.