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 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.
by Audrey Verreault | 8 April 2024
Published in Forest Ecology and Management 555(2): 121731. http://dx.doi.org/10.1016/j.foreco.2024.121731
Climate, soil, and competition factors jointly drive tree growth variability at local and regional scale. However, the comprehensive interaction of these factors and their combined effects on tree responses within their environment remains poorly explored in current research. Using a detailed forest inventory dataset in Québec, we examined tree growth of balsam fir (Abies balsamea Mill), black spruce (Picea mariana Mill), red maple (Acer rubrum L.), sugar maple (Acer saccharum Marshall), white birch (Betula papyrifera Marshall), and yellow birch (Betula alleghaniensis Britton), as a function of competition for light and space with neighboring trees, climate and soil-related variables. Interactions between all these variables were considered in a Bayesian model predicting tree growth. The amount of light received by trees was the main variables explaining tree growth except for coniferous tree species which was influenced mostly by climate variables. Among the studied species, only red maple and white birch exhibited increased growth under warmer conditions. Intraspecific competition had strong species-specific impacts, varying from negative effects for balsam fir, to positive for red maple and yellow birch. Interactions between climate, soil, and competition played a crucial role in shaping growth patterns, especially for sugar maple, and black spruce that strongly responded to a combination of climate and competition factors. In general, tree growth also increased with the soil cation-exchange capacity (CEC), especially when higher CEC is coupled with higher temperatures and precipitation, except for black spruce. While anticipated climate conditions in Quebec, even under the most optimistic scenarios, will have a strong negative impact on the tree growth of most tree species, management can mitigate this impact by promoting tree diversity with more complex stand structures.
by Marie-Claude Boileau | 27 March 2024
Published in Silva Fennica 58(2): 2309. https://doi.org/10.14214/sf.23029
Mechanical site preparation (MSP) is used prior to planting to control competing vegetation and enhance soil conditions, particularly in areas prone to paludification. Tree planting density can be adapted to the management context and objectives, as it influences yield and wood quality. However, the combined effects of MSP and planting density on understory vegetation composition, functional traits, and diversity remain uncertain. We thus conducted a study in the Clay Belt region of northwestern Quebec, Canada. After careful logging, the study area was divided into nine sites, each receiving one of three treatments: plowing, disc trenching, or no preparation. Sites were further divided into two, with black spruce (Picea mariana [Mill.] Britton, Sterns & Poggenb.) seedlings planted at either a low planting density of 1100 seedlings ha–1 or a high planting density of 2500 seedlings ha–1. After nine years, we assessed understory composition, diversity, key functional traits, sapling density and growth of planted trees. Careful logging alone led to a higher density of naturally established conifers compared to plowing or disc trenching. The interaction between planting density and MSP significantly influenced understory diversity and composition in plowed plots. Understory composition was affected by the soil C/N ratio, coniferous species, and deciduous species density. The growth of black spruce was notably enhanced with higher planting density in the plow treatment only. Neither planting density nor MSP alone affected tree height and diameter. Our results suggest that combining plowing with high-density planting can enhance stand growth and improve forest productivity. These findings guide future research on paludified forests.
by Claire Morin | 27 March 2024
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.
