Date of Award:

8-2023

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Wildland Resources

Committee Chair(s)

Larissa L. Yocom

Committee

Larissa L. Yocom

Committee

Eric Thacker

Committee

James A. Lutz

Abstract

Fuel treatments are land management activities that reduce living and dead flammable materials on the landscape to mitigate undesirable wildfire behavior and effects. Common treatments in the western United States include mechanical methods such as thinning and mastication, prescribed burns, and chemical methods, such as herbicide application. Treatments usually have multiple objectives, including reducing fire intensity, protecting natural and cultural resources, slowing or disrupting a potential future fire’s path, supporting ecosystem health, and reestablishing low to mid severity fire cycles in ecosystems. Although treatments can potentially modify fire behavior and ecological health, they generally cannot prevent fires from igniting, eliminate fires from occurring, or consistently stop active fires from spreading. The majority of fuel treatments are never encountered by wildfire, which limits our understanding of effectiveness. In Utah, treatments are primarily implemented by the U.S. Department of the Interior Bureau of Land Management (BLM) and U.S. Department of Agriculture Forest Service (USFS). In order to increase understanding of fuel treatment effectiveness, I conducted a statewide study, including 3,208 fuel treatments and 1,558 wildfires on BLM and USFS managed lands across Utah from 1997 to 2019. The objective of my study was to evaluate treatment effectiveness using four metrics: 1.) Encounter rates, 2.) Burn severity, 3.) Manager reports and 4.) Ecological health. In Chapter 2, I summarized treatment and wildfire distributions and calculated a treatment encounter rate of 8.7%. I also analyzed burn severity in 48 treatments in forested vegetation, finding that treatments significantly reduced burn severity, especially in areas that had been treated repeatedly. Finally, manager observations from treatments encountered by fire were summarized, with findings that managers reported fuel treatments to be effective in the majority of encounters. Chapter 3 evaluated ecological health in juniper mastication treatments, using field measurements, and found no treatment effect on cheatgrass, bare ground, or sagebrush density post-fire. In conclusion, fuel treatments were effective in their primary goals of altering fire behavior and effects, based on the metrics of burn severity and manager reports. However, fuel treatments were seldom encountered by wildfire, and juniper mastication treatments were ineffective at improving the measured ecological health metrics. These findings suggest that expanding treated areas to improve encounter rates will increase the circumstances in which treatments are effective.

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