LAUSR

Abstract Seedbanks are essential for forest resilience, and disturbance interactions could potentially modify seedbank availability, subsequent forest regeneration patterns, and successional trajectories. Regional mountain pine beetle outbreaks have altered forest structure and seedbanks in fire prone-landscapes across western North America and could influence forest regeneration. We examined the drivers of lodgepole pine recruitment across a gradient of fire severity from fire that burned through gray-phase outbreak conditions in central interior British Columbia, Canada. We considered ten potential drivers of lodgepole pine recruitment including: fire severity, mountain pine beetle outbreak severity, cone abundance, branch retention, open cones, exposed soil, snag fall, snow accumulation, climate moisture deficit, and frost events, as well as the contribution of unburned fire refugia to lodgepole pine recruitment. In 2016, we inventoried 83 plots that spanned gradients of outbreak severity, burning conditions, and fire severity across three fires that burned through lodgepole pine dominated forests with gray-phase conditions that had moderate to high mortality. We used generalized linear models to evaluate drivers of variability in seedling recruitment. Our analyses affirm that wildfire is a critical mechanism for lodgepole pine seedling recruitment. For plots that burned as crown and surface fire, recruitment densities were two or six times greater compared plots that experienced light surface or were fire refugia, respectively. Recruitment was driven by cone abundance indicating the importance of an available seed source. In fire refugia, recruitment was three times greater during the post-outbreak period compared to before outbreaks, suggesting cone senescence from mortality and/or xeriscent-cueing of cones. The unevenness in recruitment across gradients of outbreak and fire severity contribute to the heterogeneity of stand initiation across these landscapes that may be important for mediation of subsequent outbreaks.