by Marie-Claude Boileau | 3 July 2024
Published in Forest Ecology and Management 566: 122084. https://doi.org/10.1016/j.foreco.2024.122084
Clear-cutting is used by foresters worldwide to harvest timber from forest ecosystems. Clear-cutting of cool–wet boreal forests in late successional stages can maintain successional trajectories pointed toward the composition of a late successional stages. However, clear-cutting of warm–dry boreal forests in late successional stages can trigger reversion of successional trajectories back toward forests of earlier stages because early-successional shade-intolerant species are more abundant than in cool–wet boreal forests, a process that is referred to as a successional setback. Such successional setbacks can generate sustainability issues by extending the expected time to compositional recovery after clear-cutting. This can lead to an overestimation of allowable cuts of economically important late-successional species and subsequently to a temporary forest composition conversion if the occurrence of successional setbacks remains unassessed. Temperate forests in late successional stages are warmer and drier than boreal forests and consequently include more early-successional shade-intolerant species susceptible to encroach clear-cut areas. Even if current ecological knowledge suggests that temperate forests could be susceptible to post-clearcut successional setbacks, a comprehensive assessment has yet to be undertaken. The objective of the present study was to assess whether clear-cutting has triggered successional setbacks in temperate forests. Therefore, we studied post-clearcut successional trajectories by using forest inventory data covering the entire temperate forest of the province of Qu´ebec, eastern Canada (209 000 km2). Clear-cutting triggered successional setbacks in both ecological regions forming the temperate forest. After clear-cutting, successional trajectories of trees pointed toward the composition of an early successional stage. To address this sustainable management issue in a comprehensive manner with clear-cutting, foresters could use partial cut approaches.
by Audrey Verreault | 30 April 2024
Published in Evolutionary Applications 17(4): e13689. https://doi.org/10.1111/eva.13689
Arctic and subarctic ecosystems are rapidly transforming due to global warming, emphasizing the need to understand the genetic diversity and adaptive strategies of northern plant species for effective conservation. This study focuses on Betula glandulosa, a native North American tundra shrub known as dwarf birch, which demonstrates an apparent capacity to adapt to changing climate conditions. To address the taxonomic challenges associated with shrub birches and logistical complexities of sampling in the northernmost areas where species’ ranges overlap, we adopted a multicriteria approach. Incorporating molecular data, ploidy level assessment and leaf morphology, we aimed to distinguish B. glandulosa individuals from other shrub birch species sampled. Our results revealed three distinct species and their hybrids within the 537 collected samples, suggesting the existence of a shrub birch syngameon, a reproductive network of interconnected species. Additionally, we identified two discrete genetic clusters within the core species, B. glandulosa, that likely correspond to two different glacial lineages. A comparison between the nuclear and chloroplast SNP data emphasizes a long history of gene exchange between different birch species and genetic clusters. Furthermore, our results highlight the significance of incorporating interfertile congeneric species in conservation strategies and underscores the need for a holistic approach to conservation in the context of climate change, considering the complex dynamics of species interactions. While further research will be needed to describe this shrub birches syngameon and its constituents, this study is a first step in recognizing its existence and disseminating awareness among ecologists and conservation practitioners. This biological phenomenon, which offers evolutionary flexibility and resilience beyond what its constituent species can achieve individually, may have significant ecological implications.
by Audrey Verreault | 19 April 2024
Published in Frontiers in Forests and Global Change 7: 1368590. https://doi.org/10.3389/ffgc.2024.1368590
Forest ecosystems have a major role in sequestering atmospheric CO2 and as such, their resilience is of upmost importance. In the boreal forest, trees grow only during a short period when air temperature is favourable. During winter, trees have specific mechanisms to survive in the cold air temperature. In order to understand the response of trees to a changing climate, this study assessed the influence of environmental variables on three phases of tree radial variation (i.e., growth, shrinkage and expansion) during three periods of the year (i.e., growing season, freeze–thaw period, and winter). The three phases were extracted from stem radial variation measured for as much as 11 years on 12 balsam fir [Abies balsamea (L.) Mill.] trees located in a cold and humid boreal forest of eastern Canada. The random forest algorithm was used to model each phase during each period. Our results show that tree growth increased with high precipitation and high relative humidity. Stem shrinkage was affected mostly by solar radiation, precipitation and vapour pressure deficit during the growing season and was likely caused by tree transpiration. During both the freeze–thaw and winter season periods, stem shrinkage increased with decreasing air temperature. During the growing season, stem expansion was related to 1-day-lag solar radiation and 1-day-lag vapour pressure deficit, which are the same variables associated with shrinkage the preceding day. Stem expansion increased with increasing air temperature and relative humidity during the freeze–thaw and winter season periods, respectively. This study shows that sink-driven tree growth is promoted mostly under humid conditions while antecedent dry and warm conditions are required during the growing season for trees to assimilate carbon through photosynthesis.
by Claire Morin | 12 April 2024
Afin d’assurer la conservation et la mise en valeur du saumon atlantique dans une perspective de développement durable, le ministère de l’Environnement, de la Lutte contre les changements climatiques, de la Faune et des Parcs (MELCCFP) effectue un suivi rigoureux de l’abondance et de l’exploitation du saumon atlantique dans la province. Ce document fournit la synthèse des données d’abondance des saumons atlantiques adultes et des activités de pêche associées à cette espèce au Québec de 1984 à 2023. L’année 2023 se caractérise par une baisse de 24 % des montaisons totales, comparativement à la moyenne quinquennale. Les montaisons de madeleineaux ont été de 65 % inférieurs à la moyenne et les retours de rédibermarins inférieurs de 3 %. D’autre part, la récolte de petits saumons à la pêche sportive a été de 51 % inférieure à la moyenne quinquennale et la récolte des grands saumons a diminué de 10 %. Ces résultats sont en partie dus aux faibles retours de petits saumons dans nos rivières et aux mesures réglementaires qui en ont découlé, ainsi qu’aux mesures appliquées depuis 2016 pour assurer la protection des grands saumons. Le nombre de remises à l’eau déclarées a, quant à lui, augmenté de 5 %. La fréquentation des rivières à saumon s’est chiffrée à 70 938 jours-pêche en 2023, ce qui est égal à la moyenne des cinq dernières années (0 %).
by Audrey Verreault | 12 April 2024
Published in Canadian Journal of Forest Research. https://doi.org/10.1139/cjfr-2023-0224
Forest plantations play an increasingly important role in meeting global demand for wood. They usually have higher yield than naturally regenerated forests. Thus, plantations can support economically viable wood production, enable forest conservation elsewere, help mitigate climate change by contributing to carbon sequestration and increase forest resilience and resistance to biotic and abiotic stressors. If yield of plantations is not as high as anticipated, then their use could generate important sustainability issues. There are still major gaps in our understanding of the factors that influence yield, even with respect to black spruce, white spruce, and jack pine, three of the most commonly planted tree species in northeastern North America. Our objective was to evaluate the yield of forest plantations of these species over a 416 000 km2 region that was representative of northeastern North American forests. Contrary to our prediction, realized yield of operational plantations was consistently lower than anticipated. Site index and competition both played a significant role in determining the yield of plantations. In the context of uncertain realized yield of operational plantations, we emphasize the necessity of relying on adaptive management to determine harvest levels that are compatible with sustainable management objectives.
