Soil Water Repellency within a Burned Piñon–Juniper Woodland: Spatial Distribution, Severity, and Ecohydrologic Implications

Abstract

Soil water repellency is commonly found in piñon (Pinus spp.)–juniper (Juniperus spp.) (P‐J) woodlands and may limit site recovery after a fire. Understanding the extent of this problem and the impact it has on vegetation recovery will help guide land managers in conducting their restoration efforts. In this study, we (i) examined the spatial distribution and severity of post‐fire soil water repellency in a burned P‐J woodland, (ii) related ecohydrologic properties to pre‐fire tree canopy cover and post‐fire vegetation establishment, and (iii) demonstrated a geographic information system (GIS)‐based approach to extrapolate observed patterns to the fire boundary scale. During a 2‐yr period, several soil and vegetative measurements were performed along radial line transects extending from the trunk of burned Utah juniper [Juniperus osteosperma (Torr.) Little] trees to twice the canopy radius. Results indicate that water repellency patterns are highly correlated with pre‐fire tree canopy cover. Critical water repellency extended from the base of the tree to just beyond the canopy edge, while subcritical water repellency extended half a canopy radius past the edge of the critical water repellency zone. At sites where critical water repellency was present, infiltration rates, soil moisture, and vegetation cover and density were significantly less than non‐water‐repellent sites. These variables were also reduced in soils with subcritical water repellency (albeit to a lesser extent). Results were exported into a GIS‐based model and used in conjunction with remotely sensed imagery to estimate the spatial distribution of soil water repellency at the landscape scale.