The impacts of partial cuts on carbon stocks remain uncertain due to elevated post-harvest windthrow mortality that may counteract the positive effects of thinning on stand growth. This study evaluated the effects of partial cuts and tree mortality on aboveground carbon stocks eight years after harvest in jack pine forests. The experimental design included 24 sites with varying harvest intensities: unharvested control, moderate (30–35 %), and heavy (40–50 %) thinnings. Dendrochronological analyses and allometric equations were used to quantify carbon in live and dead biomass (snags, broken, and uprooted trees). Increases in individual tree carbon stocks between the pre-harvest year and the eighth year post-harvest were lower in controls and similar among partial cut treatments. Eight years after harvest, live carbon stocks per hectare were 41 % lower in the heavy thinning than in unharvested stands but remained similar between moderate thinning and control treatments. Larger trees and those growing closer to skidding trails showed greater increases in carbon stock, with the latter exhibiting a 33 % higher increase on average. Mean total deadwood carbon stocks were 55 % higher in the control than in the partial cuts due to reduced snag carbon in harvested stands. Uprooting was influenced by harvest treatment and proximity to skidding trails, while stem breakage was driven by tree characteristics (height, age, and competition) and distance to trails. The proportion of snags was explained by mean annual wind speed. These findings suggest that moderate thinning could sustain forest carbon stocks with prescriptions aiming at maintaining snag carbon stocks.

White pine decline in managed forests has led to the adoption of ecosystem-based management using natural disturbances, mainly surface fire. However, other natural disturbances, such as spruce budworm (SBW), are present in the native range of white pine but are rarely considered in the management of this species. SBW outbreaks are expected to change in frequency and severity under climate change, increasing the need to understand if and how this disturbance will affect the dynamics of white pine regeneration. In this study, we evaluated the impacts of an SBW outbreak on white pine and balsam fir regeneration and identified environmental variables that affect regeneration dynamics. We evaluated six defoliated and six control study plots in white pine stands close to the northern limit of the Québec’s temperate forest. In each plot, we counted white pine and balsam fir seedlings and measured structural (diameter, height), and abiotic (gap fraction, soil type) variables. White pine seedling density was three times greater in defoliated plots than in controls. By contrast, there was no significant difference in balsam fir seedling density between disturbance types. Seedlings of both species were taller in defoliated plots than in control plots. Overall, the SBW outbreak promoted white pine seedling density and height growth. This research contributes to our understanding of the effects of SBW outbreaks on white pine regeneration dynamics, and it will help forest managers to select harvesting methods that emulate SBW-modulated stand characteristics.

Mining and more recent e-waste recycling have contributed trace elements (TEs) to the environment. However, the occurrence of emerging technology-critical elements (TCEs), including rare earth elements (REEs), remains poorly reported. Our study aims to i) investigate the spatial distribution of TEs, including TCEs, across different environmental matrices; ii) compare measured concentrations in water and sediment against environmental quality guidelines; and iii) assess potential risks to human health from fish consumption. In this study, we sampled water, sediment, and fish tissues (muscle and liver) across six boreal lakes near the historically mining region of Rouyn-Noranda, home to North America's largest copper smelting and recycling facility (Horne Smelter). Concentrations of TEs (e.g., Cu, Se) were higher in lakes closest to the smelter. Similarly, some TCEs (i.e., Ti, Co, Tl) followed this same spatial distribution pattern, suggesting that their release may be linked to historical and current mining activities. Conversely, REEs displayed distinct spatial patterns, likely influenced by geological sources rather than pollution. Several TEs (e.g.,

Our study explored the spatiotemporal dynamics of spruce budworm (SBW) defoliation in Quebec’s boreal forests, highlighting how climatic factors, historical defoliation, and landscape heterogeneity intersect. SBW outbreaks are a major disturbance in these ecosystems, with significant ecological and economic repercussions—underscoring the need to understand the mechanisms that drive them. Although previous research has linked warming temperatures and past defoliation patterns to more severe outbreaks, their localized effects remain poorly characterized. Our aim is to clarify these localized processes and support more targeted forest management strategies. We employed an adjacent-category autoregressive (ACAR) model specifically designed for ordinal defoliation data spanning 1992–2022. Defoliation was categorized into three severity levels: none, light, and moderate/severe. Key climate variables — most notably spring and summer temperatures, as well as precipitation — were obtained from BioSIM and assigned to each landscape unit (LU). After fitting individual ACAR models to each LU and confirming their adequacy via the Portmanteau test, we identified the best models using the Akaike Information Criterion (AIC). A clustering analysis then grouped LUs with comparable model parameters into distinct ecological response clusters. Our findings reveal that temperature exerts a non-linear influence on SBW defoliation: while warmer spring and summer conditions can initially facilitate larval survival, exceedingly high temperatures reduce defoliation by surpassing larval thermal tolerance and disrupting phenological synchrony with host trees. Additionally, strong autoregressive feedback values (β1,β2) underscore the cumulative effect of past defoliation—trees weakened by previous outbreaks become more susceptible to subsequent infestations, triggering feedback loops that endanger long-term forest health. Through clustering, we identified five distinct landscape groups. The more homogeneous clusters (Clusters 4 and 5) displayed either relatively stable precipitation patterns or pronounced temperature variability, each with high silhouette scores (0.55 and 0.24, respectively), indicating clear opportunities for targeted management. Meanwhile, heterogeneous clusters like Cluster 1 (silhouette score: −0.43) exhibited overlapping characteristics that warrant further investigation. Overall, these results emphasize the importance of localized management approaches that account for climatic thresholds and historical defoliation patterns. Pinpointing temperature extremes and incorporating the impacts of cumulative defoliation can guide both the timing and intensity of interventions. Future research may integrate additional spatial factors, such as forest composition and connectivity, to refine outbreak predictions further. Ultimately, adaptive, multi-scale management is essential for maintaining the resilience of boreal forests in a changing climate.

Abstract Introduction Mining activities can lead to the formation of degraded, barren, or metal-contaminated ecosystems. Resource-poor ecosystems such as rocky outcrops are more sensitive to mining degradation, and their natural regeneration can be challenging due to soil erosion, lack of resources or seeds, and soil acidification. Objectives Our aim was to test the effectiveness of using locally collected bryophyte (Ceratodon purpureus [Hedw.] Brid.) mats as a restoration treatment to protect and promote the establishment of tree seedlings in mining-polluted rocky outcrops in Rouyn-Noranda (Canada). Methods The bryophyte restoration treatment inspired by natural succession processes was compared to a control, where only local soil was used as substrate, and to a liming treatment that increases soil pH. The three treatments were applied to sixty 1???1?m?units located on five outcrops at various distances (1.9?26.9?km) from the pollution source. Four tested tree species were each seeded at a density of 100?seeds/m2 on all units. Results The bryophyte treatment had a positive effect on the establishment success of Jack pine seedlings (Pinus banksiana Lamb.) with an establishment rate of 12% compared to 5 and 4% for liming and control treatments, respectively. Wind exposure had a significant negative effect on seedling establishment, potentially masking any negative effects of soil heavy metal concentration, which were not statistically significant. Conclusions Our strategy using bryophytes and mimicking natural succession has the potential to effectively regenerate trees in degraded rocky outcrops.

Young plantation trees are often highly vulnerable to insect herbivory in ways that are difficult to predict as underlying mechanisms linked to plant traits and natural enemy pressure interact in context-dependent ways. We compared bottom-up and top-down forces acting on spruce budworm (Choristoneura fumiferana) on young white spruce (Picea glauca) trees in plantations vs in natural regeneration under hardwood canopy. The spruce budworm is the most important outbreaking conifer defoliator in Eastern Canada, and we aim to better understand budworm herbivory on young trees, given its importance for post-outbreak forest succession. We conducted a 4-year field survey in Northwestern Québec, Canada, to compare plant phenology, budworm density, defoliation rates, predator populations, and parasitism between the two habitats. We also designed manipulative experiments with sentinel larvae to assess bottom-up and top-down forces in these habitats. The field survey showed earlier budburst phenology in plantation trees, affecting synchronization with budworm emergence from diapause. Field survey results also included slightly higher budworm density and lower larval parasitism in plantations, but no significant difference in current-year growth defoliation. The bottom-up experiment showed slightly better budworm biological performance, indicated by higher pupal mass, in plantations. The top-down experiment suggested slightly higher predation and parasitism in the natural forests. Together, our results show how mechanisms controlling insect defoliator populations are context-dependent. In plantations both bottom-up and top-down pressures on the spruce budworm appear slightly eased, leading to marginally better biological performance and higher population density of this forest pest. However, differences are so minor that no impact on defoliation is observed.

Windthrow is a natural disturbance affecting forest dynamics, characterized by tree uprooting or stem breakage when wind forces surpass tree anchorage strength or stem resistance. Windthrow mortality has been related to several ecological biotic and abiotic factors. However, the influence of natural root grafting on windthrow mortality remains unknown. This research evaluated the influence of root grafting on windthrow mortality by excavating root systems of jack pine (Pinus banksiana) in four windthrow-affected riparian buffers and analyzing root grafts using a dendrochronological approach. Our results revealed that natural root grafting decreased the uprooting likelihood but increased the propensity for stem breakage. In addition, root grafting occurred more frequently in trees closer to one another. These results suggest that root grafting influences the windthrow mortality type, with tree proximity being a good predictor for root grafting. This study provides valuable insights into windthrow dynamics, particularly relevant for managing windthrow mortality following partial harvesting and riparian buffers, conserving soil, and mitigating the impacts of windthrow events in the face of climate change.

There are ongoing debates among different stakeholders about which forest and ungulate management strategies will sustain high levels of timber and animal harvest and maintain important ecosystem functions under climate change. Ungulate-forest interactions are complex, including periods where forest regeneration is sensitive to browsing pressure, making it difficult to predict the consequences of a given strategy over time. To aid decision-making, we simulated the impacts of moose browsing on forest succession under 18 different combinations of moose (Alces alces) harvest rate levels and forest management scenarios in a boreal forest landscape in southern Sweden given projected changes in forest growth due to climate change. We found that the current management practices are important for sustaining a moose-forest system. Increasing moose harvest rates led to slightly smaller moose populations, larger estimates of landscape carrying capacity, and less biomass removal of Scots pine (Pinus sylvestris), a commercially valuable species. However, minor changes in the moose harvest were hardly affecting timber production. Increasing the timber harvest rotation time led to the highest estimates of Scots pine biomass, while thinning younger cohorts lead to the highest estimates of Norway spruce (Picea abies) biomass. These changes came without much effect to moose population dynamics. However, the increased broadleaf production scenario had a very large positive effect on total aboveground live biomass of deciduous species and on landscape carrying capacity and moose density. This scenario subsequently resulted in the greatest estimates of biomass removal of Scots pine, highlighting the tradeoffs associated with increased moose production.

In Canada, clearcutting is the most widely used silvicultural system in boreal forests despite potential impacts on forest simplification and biodiversity loss. Retaining mature trees is suggested to maintain stand structure and biodiversity, especially for promoting the regeneration of shade-tolerant species. Partial harvesting is considered a promising alternative to the clearcutting system as a means of integrating ecological, economic, and social objectives into silvicultural planning; however, this approach must be developed for use in natural boreal forests. Here, we evaluate the effects of silvicultural treatments on natural regeneration in stands of natural even-aged mature black spruce (Picea mariana (Mill.) B.S.P.), 18 years after cutting. In 2003, in the Saguenay and North Shore regions of Quebec, an experimental design of fully randomized blocks was established across six sites, each containing two forest stand types (younger and older stands) and six silvicultural treatments. In 1 512 microplots, we categorized all tree seedlings by species and height class and assessed a dominant seedling for growth-related variables, and microenvironment. We found that 18 years after treatment, mini-strip shelterwood harvesting produced the highest black spruce seedling density (39 765 seedlings/ha). In contrast, clearcutting produced a seedling density that was three times lower than uniform shelterwood harvesting but demonstrated a twofold increase in seedling terminal shoot length growth. Mineral soil, spot scarification, moss cover with Polytrichum spp., and distance from residual strips positively correlated with black spruce seedling density. Our study highlights the potential of shelterwood systems as a silvicultural alternative to clearcutting for promoting black spruce regeneration in Canadian boreal forests.