Impacts of mountain pine beetle outbreak and wildland fuel reduction treatments in Jasper National Park, Alberta, Canada

Abstract

Wildland fuels are deviating from traditional described fuel complexes due to climate- mediated pressures and anthropogenic alteration. However, technological advances have also increased the capacity to obtain fuels information at higher detail across the landscape to capture these changes. Quantifying fuel baselines in disturbed and altered states is paramount to understanding the impact on wildland fire potential. This thesis examines fuels that deviate from traditional fuel types in the montane region of Jasper National Park, Alberta, Canada using field measurements and coincident airborne lidar data. First, the impacts of mountain pine beetle on fuels over a range of severity within the same temporal phase of outbreak are investigated. With increasing severity, overstory and subcanopy fuel loading significantly lowered, forest floor composition became more herbaceous, and organic layer loading increased. Severely impacted stands also exhibited less than half the amount of coniferous seedling recruitment than lightly impacted stands, which could signal a shift in regeneration away from closed-canopy conifer stands in this region. Second, fuel treatment efficacy over two decades was evaluated using field and lidar-derived canopy metrics. Though surface fuels in field-measured stands remained similar over time, stem density, canopy cover, canopy bulk density, and canopy base height varied significantly over time since management. Stand-level fire modelling at dry to extreme weather percentiles (90th – 97th) predicted that stem density and canopy fuels were sufficiently reduced to prevent active crown fire in treated stands, but surface fuels and low canopy base height were conducive to torching of individual trees in most scenarios and treatment years. This research provides critical insight into the variability within both managed and disturbed fuels over time, and the potential impact on fire behaviour as high fire weather indices occur more often in a warming climate.