Spatial patterns of conifer regeneration following Mountain pine beetle outbreak (Dendroctonus ponderosae) and mixed-severity wildfire: A point process model of disturbance interactions in the southern Selkirk Mountains, British Columbia

Mountain pine beetle (MPB) outbreaks and wildfire increasingly overlap across conifer forests of western North America, yet few studies have examined how prior beetle mortality shapes post-fire regeneration at fine spatial scales. We investigated seedling intensity of seven conifer species across three 4-ha plots within the 2015 Mt Midgeley Wildfire burn site in the Darkwoods Conservation Area, British Columbia, where mixed-severity fire followed MPB outbreaks by 1–11 years (median 7 years). Disturbance covariates were derived from classified Landsat time-series imagery using the differenced Normalised Burn Ratio (dNBR) for burn severity and the differenced Normalised Moisture Index (dNMI) for red-stage beetle mortality, both validated against field reference plots. Grey-stage MPB mortality was derived as the union of annual Landsat NDMI red-attack classifications from 2005 to 2011, identifying pixels in which beetle-killed canopies had ≥ 4 years to lose needles and collapse before the 2015 fire. Among 3886 mapped seedlings, spatial point pattern analysis revealed significant clustering for all species, with intensity governed by fire severity, distance to seed source, topography, and wind. Inhomogeneous Cox process models showed that areas of overlapping beetle mortality and high burn severity had significantly reduced lodgepole pine regeneration, while other conifers responded primarily to fire severity and seed source proximity. Results suggest that as beetle-fire intervals shorten under climate change, divergent regeneration trajectories between host and non-host species may alter successional outcomes and challenge the resilience of pioneering lodgepole pine cohorts.