Date of Award:

5-2014

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Wildland Resources

Committee Chair(s)

Michael J. Jenkins

Committee

Michael J. Jenkins

Committee

Martin E. Alexander

Committee

Barbara J. Bentz

Committee

Edward W. Evans

Committee

Michael R. Kuhns

Abstract

Recent outbreaks of aggressive tree-killing bark beetles, including mountain pine beetle in lodgepole pine forests and spruce beetle in Engelmann spruce forests, have recently affected vast areas across western North America. The high levels of tree mortality associated with these outbreaks have raised concerns amongst fire managers and wildland firefighters about the possible effects on fire behavior potential, particularly crown fire potential, as crown fires (fires that consume part or all of tree crowns) hinder the ability of firefighters to conduct safe and effective fire suppression operations. The purpose of this research was to measure and characterize the changes in moisture content, chemical composition, and resulting flammability of foliage on bark beetle-attacked trees and to describe the implications of these changes on crown fire potential in affected forests.

Results indicated that bark beetle attack causes a significant decline in moisture content and change in chemical composition in lodgepole pine and Engelmann spruce tree foliage, which substantially increases foliage flammability. The results also suggested that the moisture content of dead foliage on mountain pine beetle-attacked lodgepole pine trees cannot be predicted using conventional models, so data were collected to develop and test new models. The implications of these changes on crown fire potential are dependent upon site specific factors such as outbreak duration, severity, and the structural characteristics of the forest. Based on our results, we believe that current fire behavior models are inadequate for accurately predicting crown fire potential in bark beetle-affected forests. In order to make significant progress in our understanding of crown fire potential in recently attacked forests, a substantial effort to document wildfire behavior in the field and/or to conduct experimental fires is needed.

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