Consequences of Piñon-Juniper Woodland Fuel Reduction: Prescribed Fire Increases Soil Erosion While Mastication Does Not

Abstract

Fire suppression has increased fuel load and the risk of catastrophic wildfire in forest and woodland ecosystems across the Western United States. In an effort to reduce fuel load and restore historical structure and function, land managers have implemented fuel reduction treatments on millions of acres. Reducing fuel loads protects people, structures, and in some cases, improves ecosystem health. However, the ecological risks of soil surface disturbance related to fuel reduction strategies, and subsequent soil erosion, may be significant in some cases. Here, we examined the effects of common fuel reduction strategies (mechanical mastication and two techniques for prescribed burning) on wind and water erosion in two upland pinon-juniper woodlands in SE Utah over 2 years. We also tested the impact of broadcast seeding coupled with fuel reduction as a way to mitigate erosional soil loss. Finally, we analyzed biotic and abiotic predictor variables to evaluate important drivers of soil erosion following fuel treatments. We found that both techniques for prescribed burning—pile burning and broadcast burning—increased wind-related sediment fluxes by an average of 11-fold and 58-fold, respectively. Mastication did not increase wind-related losses over untreated controls. Erosional fluxes measured at silt fences, that captured both wind- and water-driven sediments, followed similar trends with moderate increases from pile burning (fivefold) but larger increases from broadcast burning (17-fold). Seeding did not affect erosion rates. Our results suggest that prescribed fire significantly increases soil erosion in fuel-treated pinon-juniper woodlands and may be a degradation pathway when implementing treatments.