Regional analyses assessing the vulnerabilities of forest ecosystems and the forest sector to climate change are key to considering the heterogeneity of climate change impacts as well as the fact that risks, opportunities, and adaptation capacities might differ regionally. Here we provide the Regional Integrated Assessment of climate change on Quebec's forests, a work that involved several research teams and focused on climate change impacts on Quebec's commercial forests and on potential adaptation solutions. Our work showed that climate change will alter several ecological processes within Quebec's forests. These changes will result in important modifications in forest landscapes. Harvest will cumulate with climate change effects to further alter future forest landscapes, which will also have consequences on wildlife habitats (including woodland caribou habitat), avian biodiversity, carbon budget, and a variety of forest landscape values for Indigenous peoples. The adaptation of the forest sector will be crucial to mitigate the impacts of climate change on forest ecosystem goods and services and improve their resilience. Moving forward, a broad range of adaptation measures, notably through reducing harvest levels, should be explored to help strike a balance among social, ecological, and economic values. We conclude that without climate adaptation, strong negative economic and ecological impacts will likely affect Quebec's forests.

Regional analyses assessing the vulnerabilities of forest ecosystems and the forest sector to climate change are key to consider the heterogeneity of climate change impacts but also the fact that risks, opportunities and adaptation capacities might differ regionally. Here we provide the Regional Integrated Assessment of climate change on Quebec’s forests, a work that involved several research teams and that focused on climate change impacts on Quebec’s commercial forests and on potential adaptation solutions. Our work showed that climate change will alter several ecological processes within Quebec’s forests. These changes will result in important modifications in forest landscapes. Harvest will cumulate with climate change effects to further alter future forest landscapes which will also have consequences on wildlife habitat (including woodland caribou habitat), avian biodiversity, carbon budget and a variety of forest landscape values for Indigenous peoples. The adaptation of the forest sector, will be crucial to mitigate the impacts of climate change on forest ecosystem goods and services and improve their resilience. Moving forward, a broad range of adaptation measures, notably through reducing harvest levels, should be explored to help strike a balance among social, ecological and economic values. We conclude that without climate adaptation strong negative economical and ecological impacts will likely affect Quebec’s forests.

In 2020, Quebec adopted a strategy to increase the quantity and quality of timber it produces. During a roundtable discussion held in the fall of 2021, experts in forestry and in related fields expressed their views on the new strategy and its implementation challenges. The main purpose of this article is to present the key observations from the roundtable. The observations addressed two themes: the general context in which the strategy was developed, and the context of its implementation on the ground. Although most of the panellists agreed on the relevance of such a strategy, particularly as regards to climate change mitigation and wealth creation, several questions remain. The challenge of harmonizing uses, regionalization, spatialization of management decisions, labour shortage, and uncertain ecosystem dynamics make it difficult to assess the strategy’s potential impact on the ground and its ability to achieve its targets.

En 2020, le Québec a adopté une stratégie nationale de production de bois (SNPB) afin d’augmenter la quantité et la qualité de la matière ligneuse produite. Au cours d’une table ronde tenue à l’automne 2021, des experts de la foresterie et de domaines connexes se sont prononcés sur cette nouvelle stratégie et sur les défis de mise en oeuvre qu’elle pose. L’objectif principal de cet article est de présenter les principaux constats émis au cours de cette table. Les constats ont été divisés en deux thématiques, soit le contexte général d’élaboration de cette stratégie et le contexte de sa mise en oeuvre en forêt. Bien que la plupart des panélistes s’entendent sur la pertinence de créer une telle stratégie, notamment en ce qui a trait à l’atténuation des changements climatiques et à la création de richesses, plusieurs interrogations persistent. Les défis d’harmonisation des usages, de régionalisation, de spatialisation des décisions d’aménagement, de manque de maind’oeuvre et de la dynamique incertaine des écosystèmes complexifient l’évaluation des retombées potentielles de la SNPB sur le terrain et sa capacité d’atteindre les cibles établies.

The objective of this study was to compare the accumulation over time of organic carbon (C) in soil and vegetation of abandoned agricultural lands left to natural vegetation succession or afforested with planted white spruce (Picea glauca (Moench) Voss) in Abitibi (Canada). The agricultural areas of this region originated from the clearing of forested lands in the late 19th -early 20th centuries. The aim was to determine whether afforestation of such lands is a relevant tool for C sequestration and climate change mitigation.

{Changing climates are altering the structural and functional components of forest ecosystems at an unprecedented rate. Simultaneously, we are seeing a diversification of public expectations on the broader sustainable use of forest resources beyond timber production. As a result, the science and art of silviculture needs to adapt to these changing realities. In this piece, we argue that silviculturists are gradually shifting from the application of empirically derived silvicultural scenarios to new sets of approaches, methods and practices, a process that calls for broadening our conception of silviculture as a scientific discipline. We propose a holistic view of silviculture revolving around three key themes: observe, anticipate and adapt. In observe, we present how recent advances in remote sensing now enable silviculturists to observe forest structural, compositional and functional attributes in near-real-time, which in turn facilitates the deployment of efficient, targeted silvicultural measures in practice that are adapted to rapidly changing constraints. In anticipate, we highlight the importance of developing state-of-the-art models designed to take into account the effects of changing environmental conditions on forest growth and dynamics. In adapt, we discuss the need to provide spatially explicit guidance for the implementation of adaptive silvicultural actions that are efficient, cost-effective and socially acceptable. We conclude by presenting key steps towards the development of new tools and practical knowledge that will ensure meeting societal demands in rapidly changing environmental conditions. We classify these actions into three main categories: re-examining existing silvicultural trials to identify key stand attributes associated with the resistance and resilience of forests to multiple stressors, developing technological workflows and infrastructures to allow for continuous forest inventory updating frameworks, and implementing bold, innovative silvicultural trials in consultation with the relevant communities where a range of adaptive silvicultural strategies are tested. In this holistic perspective, silviculture can be defined as the science of observing forest condition and anticipating its development to apply tending and regeneration treatments adapted to a multiplicity of desired outcomes in rapidly changing realities.}

Forest management strongly influences the carbon (C) budget of boreal forests and their potential to mitigating greenhouse gas emissions. A better quantification of the net changes of carbon pools with time since harvesting is necessary to guide the development of climate-friendly forest management practices. The objective of this study was to assess the evolution of forest C pools, with a special focus on detrital biomass, in an 80-year post-harvesting chronosequence consisting of 36 very homogenous stem-only harvested plots from a humid boreal balsam fir forest of eastern Canada. Dead wood C stocks comprised of snags, stumps, downed woody debris and buried wood averaged 37?Mg?C?ha?1 and evolved according to an upward-facing «boomerang» shape pattern throughout the chronosequence (rapid decrease in the first years followed by a constant increase until the end of the time horizon). In contrast, soil C stocks (FH and mineral) averaged 156?Mg?C?ha?1 and remain constant through time. Stand C sequestration increased rapidly in the early stages up to age 50 when it reached about 250?Mg?C?ha?1, and then continued to accumulate at a slower rate. The temporal trends observed in C pools suggest that C originating from aboveground dead wood (snags, stumps, downed woody debris) is either leaving the system (respired or leached) or transferred into buried wood, and does not appear to influence the C stocks of the fine fraction of the organic and mineral soil horizons. However, the ultimate fate of dead wood C is still poorly understood and further research is needed in this field. We recommend fixing the length of harvest rotation at a minimum of 50?years for this ecosystem to allow the build-up of its dead wood capital, and to promote dead wood retention on site. We also recommend including buried wood in carbon inventories as this pool represents an important share of the detrital C stock in these humid boreal forests.

Strategies for increasing the mobilization of forest biomass supply chains for bioenergy production require continuous assessments of the spatial and temporal availability of biomass feedstock. Using remote sensing products at a 250-m pixel resolution, estimates of theoretical biomass availability from harvest residues and fire-killed trees were computed by combining Canada-wide maps of forest attributes (2001) and of yearly (2002–2011) fires and harvests. At the national scale, biomass availability was estimated at 47 ± 18 M ODT year?1 from fire-killed trees and at 14 ± 2 M ODT year?1 from harvest residues. Mean biomass densities in burned and harvested pixels were estimated at 34 ± 3.0 ODT ha?1 and at 24 ± 1.2 ODT ha?1, respectively. Mean biomass densities also varied dramatically among ecozones, from 14 ODT ha?1 to 206 ODT ha?1 and from 6 ODT ha?1 to 63 ODT ha?1 for burned and harvested pixels, respectively. Spatial averaging with a 100-km radius window shows distinct hotspots of biomass availability across Canada. The largest hotspots from fire-killed trees reached 3.6 M ODT year?1 in the Boreal Shield and the Boreal Plains ecozones of northern Alberta and Saskatchewan, where fires are large and frequent. The largest hotspots from harvest residues reached 1.2 M ODT year?1 in the Montane Cordillera ecozone of British Columbia. The use of spatially explicit remote sensing products yields estimates of theoretical biomass availability that are methodologically consistent across Canada. Future development should include validations with on-the-ground forest inventories as well as the factoring in of environmental, technical and economic considerations to implement operational biomass supply chains.

In the Lower Athabasca region of Alberta (Canada), surface mining for bitumen from oil sands creates highly disturbed environments, which need to be restored, after mine closing, to equivalent land capability in terms of biodiversity and ecosystem services. We demonstrate a method to characterize ecosystem diversity and conditions using biophysical indicators of the Lower Athabasca meant for informing land reclamation planning and monitoring by identifying and creating a typology of the main assemblages of topography, soil and forest vegetation at the watershed, landform and ecosite scales, and analysing the relationships among land units of various scales. Our results showed that watersheds could be classified into distinct groups with specific features, even for a region with a generally flat or gently rolling topography, with slope, surficial deposits and aspect as key drivers of differences. Despite the subtle topography, the moisture regime, which is linked to large-scale cycles that are dependent on the surrounding matrix, was of primary importance for driving vegetation assemblages. There was no unique and homogeneous association between topography and vegetation; the specific landforms each displayed a range of ecosites, and the same ecosites were found in different landforms. This suggests that landscapes cannot be defined in a qualitative manner but rather with quantitative indicators that express the proportion occupied by each class of ecological units within the coarser units, therefore requiring during land reclamation that sufficient care is given to create heterogeneity within a given landform in terms of soil texture and drainage so that a mosaic of ecosite conditions is created.

We studied three hybrid poplar plantations in Quebec (Canada) established on sites with varying soil and environmental characteristics to investigate the effects of logging residues on the water potential, carbon isotope ratio and foliar nutrients of planted trees. On each site, four treatments representing different residue loads, as well as treatments aimed at manipulating specific factors of the environment (Herbicide, Geotextile) were applied to test their effects on seedling water potential, carbon isotope ratio and foliar nutrients. Along with analyses of variance, we used structural equation modelling to infer causal relationships of logging residues on height, basal diameter and foliar nutrition of trees through their effects on soil temperature, soil water content and competing vegetation cover. Logging residues decreased soil temperature at all sites and woody plants cover at one site out of three. Height, basal diameter and unit leaf mass were strongly related to each other. Foliar ?13C, N concentration and unit leaf mass increased with decreasing cover of woody plants suggesting an important role of competition for resources. Overall, logging residues had no direct influence on hybrid poplar dimensions after two growing seasons: their effects on the microenvironment of this resource demanding tree species were either cancelling out each other, or were not significant enough to have a significant impact on the growth drivers measured. For example, presence of logging residues might reduce soil temperature, impeding overall seedling performance. Our study highlights the fact that any given silvicultural method aimed at manipulating logging residues has a complex influence involving the interaction of multiple environmental drivers and that the net effect on tree productivity will depend on species and site specific conditions.

We quantified the effects of different loads of forest logging residues on the microenvironment (soil temperature, soil volumetric water content, competing vegetation cover, and available nutrients) of planted hybrid poplars one year after planting, and assessed the corresponding seedling growth until the third growing season. In four experimental plantations across Quebec (Canada), we used a factorial design of four residue loads that were applied at the tree-level over three planted species: hybrid poplars ( Populus spp.), black spruce ( Picea mariana (Mill.) BSP), and either jack pine ( Pinus banksiana Lamb.) or white spruce ( Picea glauca (Moench) Voss), depending upon the site. Logging residues linearly decreased competing vegetation cover on two of four sites and reduced fluctuations in soil temperature on all sites. Logging residues also decreased summer soil temperatures at all sites through a negative quadratic effect. On one site, the frequency of freeze-thaw cycles increased under logging residues, while logging residues increased soil water content on another site, for certain measurement events. Logging residues did not affect available nutrients. Seedlings showed no consistent growth response to logging residues for three years after planting, except for a beneficial effect of logging residues on hybrid poplar growth on one site. Because logging residues affected seedling microclimate and competing vegetation, their maintenance and on-site spatial arrangement on site could be used to manipulate the growing conditions for planted trees.

Experimental research on beetle responses to removal of logging residues following clearcut harvesting in the boreal balsam fir forest of Quebec revealed several abundant rove beetle (Staphylinidae) species potentially important for long-term monitoring. To understand the trophic affiliations of these species in forest ecosystems, it was necessary to analyze their gut contents. We used microscopic and molecular (DNA) methods to identify the gut contents of the following rove beetles: Atheta capsularis Klimaszewski, Atheta klagesi Bernhauer, Oxypoda grandipennis (Casey), Bryophacis smetanai Campbell, Ischnosoma longicorne (Mäklin), Mycetoporus montanus Luze, Tachinus frigidus Erichson, Tachinus fumipennis (Say), Tachinus quebecensis Robert, and Pseudopsis subulata Herman. We found no apparent arthropod fragments within the guts; however, a number of fungi were identified by DNA sequences, including filamentous fungi and budding yeasts [Ascomycota: Candida derodonti Suh & Blackwell (accession number FJ623605), Candida mesenterica (Geiger) Diddens & Lodder (accession number FM178362), Candida railenensis Ramirez and Gonzáles (accession number JX455763), Candida sophie-reginae Ramirez & González (accession number HQ652073), Candida sp. (accession number AY498864), Pichia delftensis Beech (accession number AY923246), Pichia membranifaciens Hansen (accession number JQ26345), Pichia misumaiensis Y. Sasaki and Tak. Yoshida ex Kurtzman 2000 (accession number U73581), Pichia sp. (accession number AM261630), Cladosporium sp. (accession number KF367501), Acremoniumpsammosporum W. Gams (accession number GU566287), Alternaria sp. (accession number GU584946), Aspergillus versicolor Bubak (accession number AJ937750), and Aspergillusamstelodami (L. Mangin) Thom and Church (accession number HQ728257)]. In addition, two species of bacteria [Bradyrhizobium japonicum (Kirchner) Jordan (accession number BA000040) and Serratia marcescens Bizio accession number CP003942] were found in the guts. These results not only provide evidence of the consumer-resource relations of these beetles but also clarify the relationship between rove beetles, woody debris and fungi. Predominance of yeast-feeding by abundant rove beetles suggests that it may play an important role in their dietary requirements.

Increased interest in biomass harvesting for bioenergetic applications has raised questions regarding the potential ecological consequences on forest biodiversity. Here we evaluate the initial changes in the abundance, species richness and community composition of rove (Staphylinidae) and ground beetles (Carabidae), immediately following 1) stem-only harvesting (SOH), in which logging debris (i.e., tree tops and branches) are retained on site, and 2) whole-tree harvesting (WTH), in which stems, tops and branches are removed in mature balsam fir stands in Quebec, Canada. Beetles were collected throughout the summer of 2011, one year following harvesting, using pitfall traps. Overall catch rates were greater in uncut forest (Control) than either stem-only or whole-tree harvested sites. Catch rates in WTH were greater than SOH sites. Uncut stands were characterized primarily by five species: Atheta capsularis, Atheta klagesi, Atheta strigosula, Tachinus fumipennis/frigidus complex (Staphylinidae) and to a lesser extent to Pterostichus punctatissimus(Carabidae). Increased catch rates in WTH sites, where post-harvest biomass was less, were attributable to increased catches of rove beetles Pseudopsis subulata, Quedius labradorensis and to a lesser extent Gabrius brevipennis. We were able to characterize differences in beetle assemblages between harvested and non-harvested plots as well as differences between whole tree (WTH) and stem only (SOH) harvested sites where logging residues had been removed or left following harvest. However, the overall assemblage response was largely a recapitulation of the responses of several abundant species.

Abstract:

A renewed interest in the intensive harvesting of forest biomass as a source of bioenergy in North America raises concerns about the impacts that this practice may have on the maintenance of forest soil productivity. In Canada, such concerns were first voiced in the 1970s, and studies were launched to investigate and predict the impact of intensive forest biomass removal on site productivity. Most of these studies focused on static nutrient budgets. In Canada and around the world, more detailed process models were also developed to study carbon, nitrogen and base cation cycles under different forest harvesting intensities. However, the validity of modelling results is still constrained by our lack of knowledge on the capacity of ecosystems to supply nutrients. A few sets of field trials have been established in Canada to gather empirical data on the impact of biomass removal on soil nutrient reserves as well as on tree nutrition and growth. Although still fairly recent, these field trials, along with the older ones established in other countries with similar site conditions and climates, provide opportunities to refine our understanding of the resilience of ecosystem processes and of the impacts of intensive biomass removal on ecosystem functions. Although numerous knowledge gaps and questions remain, some jurisdictions around the world have nevertheless issued policy directives and developed guidelines for biomass harvesting. As described by the concept of adaptive forest management, ecological monitoring of harvesting operations, scientific field testing and modelling can all interact to produce better knowledge that could then help improve policy directives.

Résumé:

L’intérêt renouvelé pour la récolte intensive de biomasse forestière comme source de bioénergie en Amérique du Nord soulève des inquiétudes quant aux impacts de cette pratique sur le maintien de la productivité des sols. Au Canada, ces inquiétudes ont été émises pour la première fois dans les années 1970 et des travaux de recherche ont été entrepris pour étudier et prédire les effets de la récolte de biomasse sur la productivité des sites. La plupart de ces études étaient basées sur des budgets nutritionnels statiques. Au Canada et ailleurs dans le monde, des modèles plus détaillés incluant la description des processus écologiques ont aussi été développés pour étudier les cycles du carbone, de l’azote et des cations basiques sous différentes intensités de récolte. Cependant, la validité des résultats de modélisation est toujours contrainte par notre connaissance limitée de la capacité des écosystèmes à fournir des éléments nutritifs. Quelques dispositifs expérimentaux ont été établis au Canada pour recueillir des données empiriques sur l’impact de la récolte de biomasse sur les réserves nutritionnelles du sol ainsi que sur la croissance et la nutrition des arbres. Bien que relativement récents, ces dispositifs, ainsi que des dispositifs plus anciens installés dans d’autres pays aux conditions de site et de climat semblables à celles du Canada, nous offrent l’opportunité de raffiner notre compréhension de la résilience des processus écologiques et des impacts de la récolte de biomasse sur le fonctionnement des écosystèmes. Bien que les incertitudes et les questions restent nombreuses, certaines juridictions dans le monde ont tout de même fourni un cadre politique et développé des lignes directrices pour la récolte de biomasse. Tel que décrit par le concept d’aménagement forestier adaptatif, le suivi écologique des opérations de récolte, les études sur le terrain et la modélisation peuvent interagir afin d’améliorer les connaissances scientifiques qui pourront par la suite être utilisées de façon à ajuster le cadre politique.