by Audrey Verreault | 8 May 2023
Published in Forests 14(4): 802. http://doi.org/10.3390/f14040802
Despite new knowledge in recent years, our understanding of the phenology of wood formation for various species growing in different environments remains limited. To enhance our knowledge of the tree growth dynamics of boreal tree species, we investigated the average seasonal, monthly, daily, and diel patterns of tree growth and water status from 11 years of observations with the 15 min and 1.5 m resolved stem radial size variation data of 12 balsam fir (Abies balsamea (L.) Mill.) trees growing in a cold and humid boreal environment. Growth only occurred above an air temperature threshold of 9–10 C, and the maximal growth rate over the year (23–24 June) was synchronous with the maximal day length (20–21 June) and not with the maximal air temperature, which occurred on average about 2 weeks later (4–5 July). Tree growth was mostly restricted by air temperature and solar radiation under these cold and wet boreal conditions, but our results also highlight a turgor-driven growth mechanism. Diel dynamics reveal that tree growth is minimal during the day when the stem dehydrates, and higher past midnight when the stem is fully rehydrated. This pattern suggests that carbon assimilation through photosynthesis occurs primarily during the day, while energy production and carbon allocation to woody tissues occur primarily at night via cellular respiration. Overall, our results show that the temporal patterns of the growth and water status of balsam fir growing in cold and humid boreal environments are controlled by a set of environmental factors that influence various physiological processes and mechanisms, many of which still need to be documented.
by Audrey Verreault | 8 May 2023
Published in Soil Systems 7(2): 39. https://doi.org/10.3390/soilsystems7020039
The use of forest biomass to produce energy is increasingly viewed as a means to reduce fossil fuel consumption and mitigate global warming. However, the impact of such practices on soils in the long term is not well known. We revisited forest plots that were subjected to either whole-tree (WTH, n = 86) or stem-only (SOH, n = 110) harvesting 30 years ago in the boreal forest in Quebec, Canada. The objective of the present study was to find soil properties that could explain the lower soil C and N stocks at the sites subjected to WTH compared to SOH after 30 years. Compared to SOH, lower soil C and N stocks attributable to WTH occurred when soil particle content <20 m was below 30%. The theoretical separation of soil organic matter into two fractions according to soil particle content <20 m—a recalcitrant and a labile fraction—could explain the observed pattern of soil C and N differences between WTH and SOH. Imperfect or poor soil drainage conditions were also associated with lower soil C and N in WTH compared to SOH. Limiting additional biomass harvesting from these sites would help to preserve soil C and N from potential losses
by Audrey Verreault | 8 May 2023
Published in Canadian Journal Of Forest Research 53(4): 255-270. https://doi.org/10.1139/cjfr-2022-0256
Precommercial thinning could be a valuable tool for climate change adaptation, as it can promote stand diversity while increasing productivity. Softwood and hardwood stands are usually thinned following different methods, and we lack recommendations for application in mixedwood stands. We evaluated the effects of precommercial thinning on the growth and composition of balsam fir (Abies balsamea L.)–birch stands dominated by paper and yellow birch (Betula papyrifera Marsh. and Betula alleghaniensis Britt.), comparing methods and production objectives (systematic release-softwood, systematic releasemixedwood, crop-tree release-mixedwood, and crop-tree release-hardwood) in Québec (Canada). Precommercial thinning increased tree-level and stand-level growth, especially for both birches. Compared to the non-thinned control, thinning increased tree diameter at breast height annual increments by 60%–107%, with similar results among modalities. Thinning changed initial stand composition, but mixedwood production plots composition was similar to that of the control 15 years after treatment. Promoting diversity is often perceived to be made at the expense of wood production. Our results suggest that we can obtain both increased growth and maintain diversity. Precommercial thinning is currently suggested as an adaptation tool that can foster drought resistance. Based on our study, we suggest it could serve another purpose in climate-adapted forest management, that is, maintaining diversity and thus increasing resilience to disturbances.
by Claire Morin | 3 April 2023
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.
by Audrey Verreault | 24 March 2023
Published in Forests 14(3): 654. https://doi.org/10.3390/f14030654
The discharge of raw industrial wastewater (IWW) into ecosystems is a major environmental problem that adversely affects water quality, soil physicochemical properties, the food chain and, therefore, human health. Injection of treated IWW into irrigation and “fertigation” systems is an ecological, sustainable and economical approach for its appropriate disposal. Seedlings of two forest species (Salix alba, Casuarina glauca) were grown hydroponically and subjected to 25% diluted IWW and control (tap water) treatments for 35 days. Morphological and physiological traits were evaluated, including leaf symptoms, stem and root dry masses, leaf water potential, relative water content, chlorophyll content, photosystem II efficiency, hydrogen peroxide, thiobarbituric acid reactive substances, bioaccumulation and translocation factor estimates and removal efficiency for various heavy metals. Application of 25% IWW stress affected many aspects of plant morphology: chlorosis and necrosis in leaves, epinasty, leaf curling, early leaf senescence and root browning. In both species, the 25% IWW treatment reduced leaf, stem and root dry masses relative to controls. S. alba exhibited greater removal capacity for heavy metal ions and could be effective as a remediator of toxic-metal-polluted industrial effluent water
