by Audrey Verreault | 7 December 2023
Published in ZooKeys 927: 153-154. https://doi.org/10.3897/zookeys.927.52153
In a paper about the biodiversity of Microgastrinae (Hymenoptera: Braconidae) in Ottawa Canada (Fernandez-Triana et al. 2016) some figure captions are incorrect. That includes three cases where the species name shown does not correspond with the actual species being depicted in those figures. To correct those mistakes, we detail below the correct captions for the corresponding figures.
by Audrey Verreault | 4 December 2023
Published in Forest Ecology and Management 553: 121600. https://doi.org/10.1016/j.foreco.2023.121600
Soil scarification is a common soil mechanical preparation (MSP) method in forestry aimed to enhance the success of reforestation. However, by turning over and displacing the humus (forming a mound; M), and producing furrows of bare mineral soil (F), it is believed that this method has a substantial effect on soil C stocks. Here, we assessed the influence of this MSP on soil C stocks in two boreal lichen woodlands (LWs) in Québec, Canada, scarified ten and two years before sampling (2012 and 2020 sites, respectively). Carbon stocks averaged 11.8–15.4 kg C m−2 in the undisturbed section of the LWs (IF) with 9–15 % located in the vegetation, 36–42 % in the humus and 42–55 % in the mineral soil (0–30 cm). MSP caused a C concentration decline of ∼105 g C kg−1 in the displaced humus. Unexpectedly, this decrease was similar at both sites, suggesting that most C losses from this horizon occurred within two years. Higher C stock in the mineral horizons of the M than of the IF compartment at the 2012 site, suggests that a fraction of the C lost from the displaced humus may not have been released to the atmosphere but rather translocated to the underlying mineral soil. However, no such phenomenon was detected at the 2020 site, where a net C loss from the mineral soil was observed. Overall, the use of mass balance equations did not show evidence of net C losses at the scale of the whole profile in the disturbed sections of both LWs following MSP. This was partly due to site heterogeneity and a sampling bias, but also to mechanisms such as C translocation from the organic to the mineral soil horizons, and the replenishment of the soil C pool owing to natural regeneration occurring at the surface of the furrows. Overall, this study suggests that MSP may not have as strong an impact on soil C stocks as previously believed. Additionally, it highlights the challenges associated with estimating C changes in the soil following MSP and discusses ways to improve the assessment of C dynamics in such heterogeneous habitats.
by Audrey Verreault | 17 November 2023
Published in Forest Ecology and Management 552(2024): 121584. https://doi.org/10.1016/j.foreco.2023.121584
Regeneration failures in the closed-crown boreal forest, which lead to the creation of open lichen woodlands, are expected to increase with climate change due to a rise in burn rates. Past studies have shown that it was possible to restore the productivity of those stands through planting. Since most lichen woodland stands are remotely located, afforestation through planting can be prohibitive. Therefore, the objective of this research was to measure the afforestation efficiency of lichen woodlands through scarification and natural seeding after clear-cutting. Our results showed that clear-cutting, when combined with scarification, promoted seedling establishment more strongly than clear-cutting alone. Scarification was also necessary for creating suitable microsites for germination, which were essentially bare mineral soil and decomposed organic matter. Last, seedling growth was higher in lichen woodlands when logging and scarification were combined, but lower than their counterpart feather moss stands. We conclude that afforestation of lichen woodlands in the closed-crown boreal forest is possible through natural seeding following scarification and could be a cost-effective option compared to planting.
by Audrey Verreault | 23 October 2023
Published in Tree Genetics & Genomes 19(49). https://doi.org/10.1007/s11295-023-01625-7
Genetic parameters for growth, trunk quality, and susceptibility to frost and Sphaerulina musiva attack were estimated from 34 half-sib families of hybrid poplar from the crossing of non-native parents, Populus maximowiczii A. Henry, and Populus trichocarpa Torr. & Gray, 3 and 6 years after planting. The use of spatial analysis proved to be the best method for quantitative growth data. The proportion of the among-family variance to the total (phenotypic) variance as well as the high heritabilities of growth and susceptibility to frost and Spaherulina musiva showed a high potential for selection for these traits while the quality traits were under low genetic control. Some families showed gains for several traits, suggesting the possibility of developing a selection index to obtain superior families that show gain for not only growth but quality and adaptive traits as well. Type B correlations were high, suggesting that families responded in the same way regardless of the site. High type A correlation between growth traits at 3 and 6 years showed early selection potential, although these relationships should be confirmed with future measurements to evaluate this effect at maturity. These results can be integrated into the strategy for improving hybrid poplar parental populations and, in the longer term, will make it possible to optimize the selection of individuals with traits of interest for the operational deployment of hybrid poplar clones.
by Audrey Verreault | 12 October 2023
Published in Forest Ecology and Management 549: 121483. https://doi.org/10.1016/j.foreco.2023.121483
Forest management can enhance the ecosystem services forests provide, but it can also alter the capacity of forests to provide those services in the future. Ecosystem-based management has been widely implemented to mitigate the deterioration of forest ecosystems by reducing dissimilarities between managed and natural forests. Ecosystem-based management objectives generally aim to maintain community composition, stand structure, ecosystem functions and services. Heavy browsing pressure by ungulates at densities unrepresentative of past abundance could interfere with these objectives by chronically and selectively browsing tree regeneration following logging.
Using a browsing exclusion experiment, we investigated how the effects of different moose browsing pressures on tree regeneration could interfere with ecosystem management objectives in boreal forests of Quebec, Canada. Management objectives in this region include, among others, reaching targeted coniferous trees densities for commercial harvest, favouring the conservation of birches (Betula spp.) to maintain soil quality and conserving fruit-bearing trees due to their ecological significance for biodiversity. We used path analyses to differentiate direct and indirect effects of moose on seedling density and mixed models to investigate how browsing affected sapling recruitment and whether resulting densities are compatible with ecosystem management objectives.
By directly reducing the overall sapling density, moose browsing indirectly increased seedlings densities of all deciduous species. This indirect effect increased with browsing pressure and favoured raspberry cover, which was positively or negatively linked to seedling density, depending on tree species. Moderate and heavier browsing pressures reduced coniferous sapling density below the ecosystem management target. Moose suppressed birch saplings so that the minimal target of 50 birches ha−1 was not met under heavier browsing pressure. Sapling density of fruit-bearing trees was low under all browsing pressures when compared to exclosures.
Policy implications
Heavy moose browsing is preventing the achievement of ecosystem management objectives in our study area. Positive indirect effects on seedling densities suggest that reducing moose density could allow released seedlings to replenish the sapling layer, but we discuss why this would not guarantee reaching ecosystem management objectives. To help forest managers evaluate and respond to challenges posed by high ungulate densities, we suggest incorporating browsing inventories in national forest surveys to monitor this chronic disturbance and modulate decisions for forest ecosystem management.
