Abstract Climate-induced fire regime shifts may reduce post-fire recovery and erode the resilience of the boreal forests. The eastern North American boreal zone is often dominated by near-monospecific stands of black spruce (BS, Picea mariana), a tree species with regeneration traits that are adapted to stand-replacing fire. While post-fire vulnerability of immature BS stands has been extensively studied, no study has evaluated post-fire regeneration of mature BS stands and its ecological determinants at the subcontinental scale. This study assessed the fire resilience of mature BS forests and the effects of major environmental drivers on post-fire regeneration. We analysed an extensive network of 536 mature BS-dominated stands that were affected by 21 fires (1995?2016) across a 50,400?km2 boreal landscape in eastern North America. We first quantified post-fire seedling density (seedlings/ha) of BS and co-occurring tree species to determine the proportion of plots affected by low levels of BS regeneration and potential shifts toward jack pine (JP, Pinus banksiana) or broadleaved species. We then analysed the effects of seed bank condition, fire characteristics (severity and seasonality) and seedbed conditions on post-fire BS regeneration. One-third of the plots exhibited low-regeneration levels, particularly in stands that were dense and closed-canopy prior to the fire. A relatively minor proportion (one-fifth) also experienced compositional changes, mainly toward JP. Generalized linear mixed-effect models indicated that higher pre-fire BS basal area and greater post-fire cover of unburned living Sphagnum promoted post-fire BS regeneration, whereas high-severity crown fires and spring fires had negative effects. Synthesis. Based on a dataset of unprecedented size and spatial extent in eastern Canada, our study provides the first robust assessment of the fire resilience of mature BS forests. A third of pre-fire mature closed-canopy stands are expected to transition into open woodlands, a change that could persist for centuries. While mature BS-dominated forests are generally considered more fire-resilient than younger stands, our study raises concerns about their capacity to persist and maintain ecosystem services under the projected climate-driven increases in burned area and severity.

Wood processing, mining, and recreational infrastructures facilitate the transport and establishment of woodboring insects. Longhorn beetles (Coleoptera: Cerambycidae) are woodborers that typically develop in stressed or dead trees and are inadvertently transported in wood products, creating opportunities for exotic species to invade and expand their range around infrastructures. To understand how these infrastructures influence longhorn diversity, abundance, and potential invasions, we sampled longhorn beetles in 2021 and 2022 from 11 sawmills, 10 mines, 11 campgrounds, and 12 control (unmanaged) forest sites throughout northwestern Quebec (Canada) using broadly attractive blends of pheromone and host volatiles to assess infrastructure-related shifts in community composition compared to undisturbed forest stands. The most abundant species observed across all infrastructures was Monochamus scutellatus scutellatus Say, comprising over 60 % of the total individuals collected, followed by Monochamus mutator LeConte (17 %) and Tetropium cinnamopterum Kirby (7 %). We did not record any exotic species; this absence may reflect community-level resistance from diverse native longhorn assemblages. Sawmill sites had the highest diversity and evenness and showed increased abundance of several common native species. However, longhorn communities varied more with forest composition than infrastructure type. NMDS distinguished longhorns linked to balsam fir from those associated with Jack pine, like M. mutator and Rhagium inquisitor Linnaeus, and separated beetles in white spruce and pine, such as Tetropium cinnamopterum Kirby and T. schwarzianum Casey, from those in early-succession hardwoods. Increased abundance of longhorns near sawmills came from diverse forest types. We do not find evidence for increased invasion risk near infrastructures, but ongoing surveillance remains crucial.