by Audrey Verreault | 2 March 2023
Published in Canadian Journal of Forest Research 53: 134-150. https://doi.org/10.1139/cjfr-2022-0111
Individual tree recruitment is an important element needed to understand stand dynamics, as it influences both stand composition and productivity. Forest growth simulators usually include recruitment models. The quality of recruitment predictions can have long-term impacts on estimations of forest growth, ecosystem health and the commercial utility of managed forests. The main objective of this study was to develop a recruitment model for commercial-size trees (i.e., trees with a diameter at breast height > 9 cm) of 10 species groups using different dendrometric and environmental variables. The resulting model will be included in a growth simulator used to support forest management planning. We hypothesized that accounting for sapling density as a covariate would improve the recruitment model’s predictive performance. Using empirical data from periodically measured permanent sample plots (1982–2019) located throughout the managed mixed hardwood forests of Quebec, we constructed models with and without sapling-related covariates and compared them on the basis of cross-validation model performance statistics. Our results show that including sapling density significantly improved model performance. From this, we conclude that adding sapling density as a covariate can significantly improve a recruitment model’s predictive power for eastern mixed hardwood forests.
by Claire Morin | 27 February 2023
An aerial survey of moose in hunting Zone 17 showed a 35% decline since 2009. The number of moose was estimated at 1036 (±16%; α = 0.1), or a density of 0.52 moose/10 km2. Reduction in habitat quality over the past decade would not limit the growth in moose numbers. The low ratio of 27 males/100 females is unprecedented. The highly selective hunt conducted since 1996 has become unsustainable. However, the increase in the proportion of females increases the resilience potential of this population. Nevertheless, the low ratio of 30 calves/100 females indicates a recruitment problem in Zone 17. The increase in adult mortality is more likely to be caused by overharvesting by hunting than by wolf predation. Inadequate monitoring of the Indigenous harvesting would underestimate its effect on the moose population. Speculation on the causes of mortality limits interpretation of the proportions attributable to hunting and predation. The Zone 17 ecosystem would still be favourable to growing moose numbers in a context of sustainable hunting management.
by Marie-Claude Boileau | 2 February 2023
This brochure intended for trappers updates the brochure produced in 2014, which sought to reduce the impact on birds of prey of accidental trapping, especially golden eagles and bald eagles.
It makes recommendations on how to avoid accidentally trapping birds of prey in trapping implements, including an appropriate bait holder and the safe disposal of snares. This practical guide also indicates the procedure to follow when birds are captured.
by Audrey Verreault | 1 February 2023
Published in Forests 14: 280. https://doi.org/10.3390/f14020280
Northern hardwoods are susceptible to a wide range of defects that can reduce the amount of sound wood with desirable qualities, such as the clear sapwood of sugar maple trees. Yet, the rate at which trees decline in quality due to the development of such defects has never been quantified in northern hardwood forests due to a dearth of repeat inventories that record the appearance of defects over time. As a result, it remains uncertain whether, and how, selection management reduces the probability of decline in quality. In this study, we quantify the rate at which trees decline in quality due to the development of defects, and we test several hypotheses regarding the influence of selection management on quality. Our results show that (1) the probability of decline in quality increases as trees grow larger; (2) crown dieback also increases the probability of decline in quality; (3) the probability of decline in quality is slightly lower in managed stands than in unmanaged stands, and (4) the probability of decline in quality increases with the mean annual temperature of the site. Finally, we combined our estimates of the probability of decline in quality with previous estimates of the probability of mortality to assess the overall risk associated with retaining trees of different species, sizes, and vigour profiles. The resulting metric can inform efforts to improve the management of northern hardwood forests by providing an integrated estimate of the risk that the value of a tree will be reduced, or eliminated, due to mortality or decline in quality.
by Audrey Verreault | 14 December 2022
Published in Forest Ecology and Management 529: 120720. https://doi.org/10.1016/j.foreco.2022.120720
Northern hardwood forests include many degraded stands dominated by trees of low vigour due to past management. To facilitate the implementation of stand improvement, several classification systems have been developed to help tree markers visually assess tree vigour at time of harvest based on the presence of individual defects. Because very few studies have tried to empirically validate such systems, it remains uncertain whether many of these defects should be used to guide the tree marking process. In this study, we assess tree vigour using repeated measurements collected as part of long-term silvicultural trials conducted in 615 permanent plots throughout the northern hardwood forest of Quebec, Canada. We aimed to determine whether the defects that are commonly used for classification have a significant effect on both growth and survival over three decades, using 9,338 sugar maple and 1,316 yellow birch trees. We also conducted a retrospective analysis to quantify the rate at which vigorous trees develop defects. Our results confirmed that crown dieback is by far the best indicator of vigour for both sugar maple and yellow birch trees. Conversely, our results revealed that stem defects did not contribute much to explaining the variation in vigour, except for the presence of cankers and fungi, which had modest effects. Consequently, stem defects should not be used as the main indicators of tree vigour, and existing classification systems should be simplified by reducing the number of stem defects under consideration for this purpose. Lastly, our results showed that the rate that vigorous trees develop defects increased with increasing diameter, more so than the probability of surviving. Thus, assessing the risk of retaining large trees should not only be based on survival, but also on the risk of developing defects that reduce the growth and value of trees.
