Numerical Simulation of Crown Fire Hazard in Bark Beetle Infested Lodgepole Pine Forests

Due to increased extent and severity of bark beetle outbreaks and forest fires, there has been an increased interest by policy makers, land managers and the public in possible interactions between these two disturbance agents. A lack of empirical data, and fire behavior modeling methods which cannot adequately represent spatially heterogeneous fuels complex and do not consider fire-fuel-atmospheric interactions has lead to confusion and controversy over the interactions between bark beetles and fire. However, recently developed physics-based models are capable of addressing such variability and complex interactions. The broad goals of this dissertation are to utilize a combination of field collected fuels data and physics based simulations to assess changes in fire behavior for two periods of time following bark beetle outbreaks in lodgepole pine forests across a range of stand compositions and arrangements and levels of bark beetle-caused tree mortality.;Chapters 2 and 3 of this dissertation describe the results of two modeling experiments which investigate fire behavior following a mountain pine beetle outbreak during the 'red' stage. My results indicate that the amount of crown fuel consumption and the intensity of crown fires were linearly related to increasing levels of MPB-caused tree mortality. In addition, there were complex interactions among mortality, stand structure and tree spatial arrangement which influenced fire behavior. However, in chapter 3 my results indicate that increased crown fire potential immediately following bark beetle infestations is also dependent upon the fire intensity generated by the pre-outbreak surface fuels complex.;In Chapter Four, I extended my analyses investigate fire behavior following a mountain pine beetle outbreak during the 'grey' stage. When mountain pine beetle mortality was between 25--55 percent of susceptible trees, there was an increase in crown fire behavior. I further found that when mortality levels were above 55 percent there are significant increases in surface fire intensity and the total fire power. I found that pre-outbreak forest composition and arrangement along with the magnitude of tree mortality influenced crown fire behavior during the "grey" stage.