by Audrey Verreault | 26 March 2025
Canadian Journal of Forest Research 55: 1-12. https://doi.org/10.1139/cjfr-2024-0084
Beech bark disease is a major concern for northern hardwood forest management that affects most of the American beech range in North America. In infected stands, mitigating effects of the disease and promoting more resistant beech populations for natural regeneration relies heavily on our ability to identify high-risk trees and adapt tree marking for partial harvesting. We monitored several individual characteristics, including external signs of disease, on 871 beech trees in recently infected northern hardwood stands at the northern range limit of American beech in Canada, to assess their ability to predictmortality over an 8-year period. At the stand level, the mortality rate over the study period was 29.3%, while the uninfected rate was 16.6%. At the tree level, the diameter, the levels of Neonectria perithecia coverage on the stem, crown dieback, and the level of canker coverage on the bark had the greatest capacity to predict individual short-term mortality. Therefore, tree markers
should first select trees with a diameter > 20 cm that are affected by any sign or symptom of the disease, followed by smaller trees with >10% coverage of Neonectria perithecia or crown dieback >25%, and lastly, trees with >50% coverage of canker.
by Audrey Verreault | 26 March 2025
Canadian Journal of Forest Research 55: 1-14. https://doi.org/10.1139/cjfr-2024-0136
The wood of sugar maple trees (Acer saccharum Marsh.) is generally perceived as containing more defects, such as dark heartwood and wood rot, at the northern limit of its range compared to southern locations; however, assessments of these internal defects have primarily relied on direct observation, limiting the scope of analysis. To enable large-scale assessments, models are needed to estimate the internal quality of individual trees based on external defects. Accordingly, this study aimed to investigate the relationships between external and internal defects within sugar maple stems. Then, large-scale estimates of the importance of such defects were produced to understand the effects of site conditions and climate. Increment cores were sampled from 1108 trees across 108 plots. Results revealed that the probability of wood rot and the proportion of internal defects were associated with the presence of cracks and fungal fruiting bodies. Also, colder sites increased the probability of wood rot as well as the proportion of the stem affected by internal defects. Moreover, the western Balsam fir–Yellow birch subdomain had both the highest probability of wood rot and the greatest proportion of internal defects. Future studies should examine how this spatial distribution could evolve with climate change.
by Audrey Verreault | 26 March 2025
Forest Ecology and Management 585: 122655. https://doi.org/10.1016/j.foreco.2025.122655
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.
by Audrey Verreault | 26 March 2025
Forest Ecology and Management 581:122550. https://doi.org/10.1016/j.foreco.2025.122550
Climate change brings new constraints to which trees will have to adapt, including more frequent severe weather events due to climate anomalies. Black spruce and red spruce are phylogenetically close but adapted to different ecological conditions, and they form a natural hybrid zone where their natural distributions come into contact. Thus, they represent an interesting model to study the effect of introgressive hybridization in the context of climate change, given that interspecific gene flow could eventually affect their capacity to adapt where their natural distributions overlap. Using a common garden field test gathering 20-year-old progeny trees resulting from rigorous controlled crosses including previously verified genetic identity of the parents, growth patterns and wood density differences could be observed between species and between them and their F1 hybrids. A dendroecological analytical approach relying on wood cores was used and revealed similar wood responses to climatic variations between species, both through lifespan climate sensitivity and through episodic stress response indexes. They were however differentially expressed in early- and latewood between black spruce and red spruce, differences likely driven by diverging cambial phenology adaptations to different growing season lengths. F1 hybrids exhibited hybrid vigor for lifespan cumulative growth under the test site conditions but showed intermediate values for traits related to climate response. These results may assist the management of forest genetic resources and contribute to a better understanding of the dynamics of adaptation to climate in hybrid zones.
by Claire Morin | 19 March 2025
Order made under the Quebec Fishery Regulations (1990) which modifies the content of this Regulation with regard to the periods, quotas, fishing gear and methods and the length or weight limits for fish applicable to the sport fishing for an area or part of it.
