Date of Graduation

Spring 5-14-2020

Document Type

Project/Capstone

Degree Name

Master of Science in Environmental Management (MSEM)

College/School

College of Arts and Sciences

Department/Program

Environmental Management

First Advisor

Aviva Rossi

Abstract

Wildfires in the mixed conifer forests of California’s Sierra Nevada have been a common and natural disturbance for thousands of years, historically occurring every 3 to 30 years. The flora and fauna of the mixed conifer forest have evolved to depend on low to moderate severity wildfires for reproduction, foraging, and habitat. However, the Sierra Nevada has experienced dramatic environmental changes over the past ~150 years as a result of three main factors: wildfire suppression, climate change, and habitat loss. Because of the threat wildfires pose to human lives, property and timber harvest, they have been suppressed to an extent that has completely altered mixed conifer ecosystems. One of the changes to these ecosystems is increased vegetative fuel density, which can result in stand-replacing mega fires. To mitigate these high-severity mega wildfires, forest managers incorporate various fuel reduction methods into forest management plans. These impacts can have negative effects on forest ecosystems, degrading ecosystem characteristics that are critical for adapting to climate change. Thus, the two main objectives of this paper are to compare and contrast four different fuel reduction methods based on their effectiveness to (I) reduce wildfire risk and (II) promote climate change resiliency. The four fuel reduction methods are: low thinning, canopy thinning, selective thinning, and prescribed fire. These four fuel reduction methods have been compared in syntheses tables for the two main objectives. Qualitative and quantitative metric data, based on a literature review, were used to compare the optimal effects of each fuel reduction method. It was found that prescribed fire or thinning with prescribed fire resulted in the most optimal effects when considering both reduced wildfire risk and climate change resilience. However, tree mortality and the risk of fire escaping controlled boundaries are increased during prescribed fire operations. Additionally, results showed that all four fuel reduction methods displayed both positive and negative effects, depending on the metric used to evaluate the objective, which suggests that appropriate application of fuel reduction methods is highly variable depending on the goals and the environment. For example, canopy thinning alone may have desirable effects when prescribed fire is financially unfeasible or unsafe due to proximity to buildings. Applying prescribed fire is the most optimal fuel reduction method in most forest conditions; however, it is recommended that forest managers evaluate forest structure, density, and tree species prior to selecting the most appropriate fuel reduction method for their situation.

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