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.

Boreal forest soils store more carbon than the aboveground vegetation and play a critical role in the global carbon cycle and ecosystem function. Despite their importance, the long-term impacts of forest management on soil organic carbon (SOC) remain unclear, especially in boreal forests with contrasting climatic conditions. This study assesses the effects of commercial thinning on SOC stocks (20-year post-treatment) in black spruce stands across two boreal regions in Québec: the warmer, drier Abitibi and the colder, wetter Cote-Nord, accounting also spatial variability from skidding strips. We measured SOC stocks at three soil depths (forest floor, mineral layer: 0–15 and 15–30 cm) in both thinned and unmanaged stands, using bulk density and SOC concentration. Soil pH, cation exchange capacity (CEC), and macronutrients were also conducted to characterize soil fertility. Thinning had no effect on total SOC stocks of the whole profile in either region, but horizon-specific differences were detected. A decrease in forest floor SOC stocks was observed in Côte-Nord, whereas SOC stocks in Abitibi remained similar. These contrasting outcomes reflect regional differences in soil fertility (higher CEC, potassium in Abitibi) and climatic conditions which may have influenced vegetation regrowth and, consequently, SOC stocks’ recovery over time. Although SOC stocks decreased in skidding strips, their small proportion within the stand minimized their effect on total SOC stocks at the plot level. Overall, the study emphasizes the need to consider climatic and soil context, as well as limited spatial extent of skidding strips, in evaluating silvicultural impacts on boreal carbon sequestration.