Document Type

Thesis

Date of Degree Completion

Spring 2019

Degree Name

Master of Science (MS)

Department

Resource Management

Committee Chair

Megan Walsh

Second Committee Member

Jennifer Lipton

Third Committee Member

Michael Pease

Abstract

The historic fire regime of the forests of the Eastern Cascades, Washington, has been described as one of high-frequency, low-severity fires using fire scar analysis. Over the past few centuries, the historically open, park-like ponderosa pine-dominated stands have been significantly altered due to Euro-American land use change such as fire exclusion, grazing, mining, and logging. The eventual encroachment of shade-tolerant species has resulted in a high-density forest structure that promotes rare, but extreme fire behavior and heightened susceptibility to insect attacks. As a result, the current disturbance regime is significantly less frequent and of higher severity, posing risks to forest resilience by changing its fundamental structure. The purpose of this study is to understand how land use change has altered the structure and composition of the Teanaway Community Forest (TCF). This research requires 1) remote sensing techniques to reconstruct the vegetation history and extent of the forest and to characterize the overall effects of land use change in the TCF and 2) the Forest Vegetation Simulator to predict future disturbance scenarios within individual stands in the TCF. Landsat imagery from years 1984, 2000, 2013, and 2017 were classified according to stand density and multispectral characteristics to assess changes in forest structure and composition. It was found that throughout the TCF, a continuous transition from more open ponderosa pine and mixed-conifer forest to uncharacteristically overstocked grand fir-dominated forest has occurred, which have drastically increased the potential for extreme fire behavior. These changes are due primarily to modern land use changes, including fire suppression, harvesting of large-diameter, fire resilient trees, grazing of fine fuels, and building of roads, which have allowed the over-accumulation of hazardous fuels capable of supporting high-intensity wildfire. The FVS simulated that potential fire hazard will increase drastically over the next century due to increasing fuel loads and progression into later forest seral stages. When fire does occur in the TCF, high rates of tree mortality and economic repercussions can be expected. However, restoring the forest structure and composition to more closely emulate historic conditions will decrease wildfire severity potential and increase forest resilience to wildfire.

Available for download on Saturday, July 18, 2020

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