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UBC Theses and Dissertations

The effects of single-objective management on disturbances in central interior dry forests of British Columbia Leclerc, Marc-Antoine François


Mule deer are an important game species, and have become the focus of applying a particular silvicultural treatment that enhances habitat while allowing timber harvesting. Mule deer winter range management (MDWRM) involves the proportional removal of trees based on their diameter and abundance resulting in a multilayered, Douglas-fir dominated forest with a clumpy tree distribution. I assessed changes in forest stand attributes brought about by MDWRM through time and how these attributes related to stand susceptibility to the western spruce budworm, Douglas-fir beetle, and wildfire using a randomized complete block single factor mixed-effects model with subsampling. In the short-term, MDWRM significantly changed (p<0.05) forest stand attributes by decreasing sub-canopy tree density and basal area, canopy cover, leaf area index, and increasing large surface fuel load. In the long-term, most attributes recovered to untreated levels. Relative to untreated stands, treated stands maintained a multilayered structure and an abundance of Douglas-fir trees thus their susceptibility to the western spruce budworm did not change through time. In the short-term, a reduction in mature host-tree density lowered susceptibility to the Douglas-fir beetle. With subsequent forest recovery, long-term susceptibility did not differ relative to untreated stands. In the treated stands the likelihood of crown fire was greater shortly after than longer after treatment. This was likely due to more large surface fuels immediately following treatment. In addition, I extrapolated the effects of MDWRM across eligible stands of interior British Columbia in a hypothetical simulation to evaluate the current and forecasted landscape-level fire risk. The forecasted forest under widespread application of MDWRM resulted in a homogenized landscape dominated by low fire risk. Further, widespread application of MDWRM may result in a fire resilient landscape, but with consequences for other ecological processes. The present study contributes to our understanding of the relationship between single-objective management and subsequent stand susceptibility to biotic and abiotic disturbances. I concluded that understanding this relationship should play an important role in responsible resource management.

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