Personne :
Thiffault, Évelyne

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Structures organisationnelles
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Université Laval. Département des sciences du bois et de la forêt
Identifiant Canadiana

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Voici les éléments 1 - 8 sur 8
  • Publication
    Untapped volume of surplus forest growth as feedstock for bioenergy
    (Pergamon, 2018-12-08) Durocher, Claude; Achim, Alexis; Thiffault, Évelyne; Auty, David; Barrette, Julie
    In Canada, the annual allowable cut (AAC) sets the harvest limit of roundwood and aims to maintain the longterm productive capacity of the forest while taking into account other values such as biodiversity and needs of stakeholders. Current harvest levels in the province of Quebec, which feed an industrial network dominated by the production of lumber, panels and pulp, average only 55% of the AAC, which may cause a gradual depletion of the forest resource if stands that have the highest value are preferably selected. In this context, using surplus forest growth consisting of low quality trees and less desirable stands as bioenergy feedstock could help improve both silvicultural practices and wood value chain profitability. The aim of this study was to identify biophysical and socio-economic factors that affect the proportion of the AAC that is harvested in Quebec's 74 management units. Results from the analysis of AAC and harvesting data for the period 2008–2013 showed the harvested proportion of the AAC was particularly low for hardwood species, with the proportions for poplar, birch and maple ranging between 19 and 38%. The distance to the nearest pulp or particle board mill was confirmed as the prime factor determining the harvest/AAC ratio for deciduous species. For softwoods, the presence of deciduous stands in a given region affected the harvest/AAC ratio. Low quality hardwoods could be used as an important source of feedstock for the bioenergy sector. Developing a synergy between conventional and bioenergy products could facilitate the application of sound silvicultural practices and increase profitability along the entire wood value chain.
  • Publication
    Accès libre
    The changing culture of silviculture
    (London Milford, 2021-11-13) Achim, Alexis; Moreau, Guillaume; Coops, Nicholas C.; Axelson, Jodi N.; Barrette, Julie; Bédard, Steve; Byrne, Kenneth E.; Caspersen, John Peter; Dic, Adam R.; D’Orangeville, Loïc; Drolet, Guillaume; Eskelson, Bianca N.I.; Filipescu, Cosmin N.; Flamand-Hubert, Maude; Goodbody, Tristan R.H.; Griess, Verena C.; Hagerman, Shannon M.; Keys, Kevin; Lafleur, Benoit; Girona, Miguel Montoro; Morris, Dave M.; Nock, Charles A.; Pinno, Bradley D.; Raymond, Patricia; Roy, Vincent; Schneider, Robert; Soucy, Michel; Stewart, Bruce; Sylvain, Jean-Daniel; Taylor, Anthony R.; Thiffault, Évelyne; Thiffault, Nelson; Vepakomma, Udaya; White, Joanne C.
    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: reexamining 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.
  • Publication
    Dynamics of detrital carbon pools following harvesting of a humid eastern Canadian balsam fir boreal forest.
    (2018-12-15) Senez-Gagnon, Fanny; Paré, David.; Bergeron, Yves; Achim, Alexis; Thiffault, Évelyne
    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.
  • Publication
    Accès libre
    Naturalness assessment of forest management scenarios in Abies balsamea–Betula papyrifera forests
    (M D P I AG, 2020-05-25) Côté, Sylvie; Bélanger, Louis; Thiffault, Évelyne; Beauregard L., Robert; Margni, Manuele
    Research Highlights : This research provides an application of a model assessing the naturalness of the forest ecosystem to demonstrate its capacity to assess either the deterioration or the rehabilitation of the ecosystem through different forest management scenarios. Background and Objectives: The model allows the assessment of the quality of ecosystems at the landscape level based on the condition of the forest and the proportion of different forest management practices to precisely characterize a given strategy. The present work aims to: (1) verify the capacity of the Naturalness Assessment Model to perform bi-directional assessments, allowing not only the evaluation of the deterioration of naturalness characteristics, but also its improvement related to enhanced ecological management or restoration strategies; (2) identify forest management strategies prone to improving ecosystem quality; (3) analyze the model’s capacity to summarize the effect of different practices along a single alteration gradient. Materials and Methods: The Naturalness Assessment Model was adapted to the Abies balsamea–Betula papyrifera forest of Quebec (Canada), and a naturalness assessment of two sectors with different historical management strategies was performed. Fictive forest management scenarios were evaluated using different mixes of forestry practices. The sensitivity of the reference data set used for the naturalness assessment has been evaluated by comparing the results using data from old management plans with those based on Quebec’s reference state registry. Results: The model makes it possible to identify forest management strategies capable of improving ecosystem quality compared to the current situation. The model’s most sensitive variables are regeneration process, dead wood, closed forest and cover type. Conclusions: In the Abies balsamea–Betula papyrifera forest, scenarios with enhanced protection and inclusion of irregular shelterwood cuttings could play an important role in improving ecosystem quality. Conversely, scenarios with short rotation (50 years) could lead to further degradation of the ecosystem quality
  • Publication
    Accès libre
    Biogeochemistry of forest harvesting methods in the boreal zone of Quebec = : Biogéochimie des procédés de récolte forestière dans la zone boréale du Québec
    (2006) Thiffault, Évelyne; Paré, David.; Munson, Alison Dale; Bélanger, Nicolas
    L'intensité de la récolte forestière, définie par le niveau d'exportation de la biomasse des arbres hors du site, soulève plusieurs enjeux environnementaux, particulièrement par rapport au statut nutritionnel du sol et de la régénération après coupe. Des méthodes intensives telles la coupe par arbre entier (CAE) exportent plus de matière organique et d'éléments nutritifs que des méthodes moins intensives comme la coupe par tronc entier (CTE); on soupçonne donc la CAE de nuire à la nutrition des sols et des forêts. L'objectif de cette thèse était d'examiner, à l'aide de méthodes empiriques et de la simulation dynamique, les effets biogéochimiques de la CAE et de la CTE dans des peuplements boréaux du Québec représentant une gamme de caractéristiques de sol et de végétation. Les résultats empiriques ont montré que, 15-20 ans après la récolte, la CAE a réduit, par rapport à la CTE, la capacité du sol de stocker les cations basiques échangeables, et a réduit les concentrations de carbone organique dans les sols minéraux intrinsèquement pauvres en matière organique. La CTE a augmenté la quantité de Ca et Mg disponible pour la régénération, et a procuré un avantage nutritionnel par rapport à la CAE aux peuplements sur sols pauvres en Ca et/ou Mg élémentaires totaux. Cet avantage était plus évident pour le pin gris, une espèce possédant des attributs permettant une acquisition rapide des ressources. Toutefois, une étude de cas empirique dans des peuplements du Bouclier canadien a montré que, contrairement à notre hypothèse, la CTE ne reproduisait pas les effets biogéochimiques des feux de forêt : la coupe en soi a diminué la disponibilité des cations basiques et augmenté l'acidité du sol par rapport au feu, 15-20 ans après perturbation. Néanmoins, un exercice avec le modèle biogéochimique dynamique SAFE a suggéré que les perturbations forestières, anthropogéniques ou naturelles, influencent la disponibilité des cations basiques pour des périodes de une à cinq décennies, mais ne sont pas la principale force régissant la chimie du sol à long terme. Les tendances à long terme de l'acidification du sol et des réserves en cations basiques semblent être plus liées aux dépôts atmosphériques acides.
  • Publication
    Accès libre
    A conceptual model for forest naturalness assessment and application in Quebec’s boreal forest
    (M D P I AG, 2019-04-11) Côté, Sylvie; Bélanger, Louis; Thiffault, Évelyne; Beauregard L., Robert; Margni, Manuele
    Research Highlights: To inform eco-designers in green building conception, we propose a conceptual model for the assessment of the impact of using wood on the quality of ecosystems. Background and Objectives: The proposed model allows the assessment of the quality of ecosystems at the landscape level based on the condition of the forest and the proportion of different practices to characterize precisely the forest management strategy. The evaluation provides a numerical index, which corresponds to a suitable format to inform decision-making support tools, such as life cycle analysis. Materials and Methods: Based on the concept of naturalness, the methodology considers five naturalness characteristics (landscape context, forest composition, structure, dead wood, and regeneration process) and relies on forest inventory maps and data. An area within the boreal black spruce-feathermoss ecological domain of Quebec (Canada) was used as a case study for the development of the methodology, designed to be easily exportable. Results: In 2012, the test area had a near-natural class (naturalness index NI = 0.717). Simulation of different management strategies over 70 years shows that, considering 17.9% of strict protected areas, the naturalness index would have lost one to two classes of naturalness (out of five classes), depending on the strategy applied for the regeneration (0.206 ≤ ΔNI ≤ 0.413). Without the preservation of the protected areas, the management strategies would have further reduced the naturalness (0.274 ≤ ΔNI ≤ 0.492). Apart from exotic species plantation, the most sensitive variables are the percentage of area in irregular, old, and closed forests at time zero and the percentage of area in closed forests, late successional species groups, and modified wetlands after 70 years. Conclusions: Despite the necessity of further model and parameter validation, the use of the index makes it possible to combine the effects of different forestry management strategies and practices into one alteration gradient.
  • Publication
    Comparison of carbon balance and climate change mitigation potential of forest management strategies in the boreal forest of Quebec (Canada).
    (Institute of Chartered Foresters, 2019-03-04) Paradis, Laurence; Achim, Alexis; Thiffault, Évelyne
    Management of the world’s forests can play a role for climate change mitigation by increasing CO2 storage in vegetation biomass and harvested wood products, and by displacing CO2-intensive materials such as steel or concrete. This study aimed to determine how management of boreal forest stands could contribute to climate change mitigation in the context of ecosystem-based management. The study was based on the comparison of different strategies applied to a balsam fir-white birch stand in the Eastern boreal forest of Quebec (Canada). Five scenarios were simulated over a 199-year period at the stand level: a reference scenario involving clearcut at 50-year intervals, and four alternative scenarios clearcut with longer rotation length (70 and 80 years), partial cut, and a no harvest scenario. The study included an appropriate sensitivity analysis of the results. Overall, scenarios with longer clearcut rotations and, to a lesser extent, partial cut resulted in a higher potential to mitigate climate change. The substitution effect of wood products was revealed as a key aspect, suggesting that wood product manufacturing and utilization on the markets, and not only forest management, need to be carefully considered.
  • Publication
    A financial analysis of the potential of dead trees from the boreal forest of eastern Canada to serve as feedstock for wood pellet export.
    (2017-03-22) Pothier, David; De Grandpré, Louis; Achim, Alexis; Junginger, Martin; Thiffault, Évelyne; Barrette, Julie
    Global demand for forest biomass feedstock has increased drastically in recent years, mainly due to the implementation of policies and strategies for climate change mitigation and renewable energy production in many jurisdictions. The biomass from dead trees has been recognized by the International Panel on Climate Change (IPCC) as a promising source of forest biomass for bioenergy at the global scale both because of its wide scale availability and its potential to limit global warming. In eastern Canada, dead trees are not only very abundant but are also widely perceived by lumber and pulp and paper producers as contaminants in the wood supply chain with marginal profitability. The general aim of this study was to determine the conditions of profitability of an eastern Canada independent sawmill (i.e., unaffiliated with a pulp plant) to produce pellets destined for international export using either co-products or roundwood from dead trees as feedstock. We compared the yield and monetary value of dead trees at various sizes and degradation levels for the production of wood pellets, alone or in conjunction with the production of lumber, to current market conditions. Our results suggest that using dead trees for lumber and pellets is almost as profitable as using them for lumber and pulp, with a difference of about 1–12% depending on tree size. Dead trees from all classes of wood degradation could serve as an interesting feedstock for pellets because wood density was only slightly affected by wood degradation. Small dead trees (DBH < 15 cm) could serve for all scenarios, as the difference between revenues and costs remained generally minimal between them. Larger dead trees did not appear to represent a financially viable option under current market prices, unless suitable subsidies or other types of financial support are provided. The sustainability criteria applied by European consumers could therefore be a determining factor for the future importance of dead trees from eastern Canada as a source of feedstock for wood pellet production.