Forestry practices such as forest conservation, improved management, and afforestation offer important pathways for climate change mitigation through carbon sequestration. However, forests also influence the surface energy balance via changes in albedo, which can offset or enhance climate benefits depending on stand characteristics. Despite its importance, empirical data on how albedo dynamics evolves in plantation systems remain limited. This study evaluated surface albedo in hybrid poplar and white spruce plantations of varying ages and fertilization treatments in southern Quebec, using drone-mounted pyranometers. Measurements were conducted during the growing season, as well as under leaf-off and snow-covered conditions, to capture both structural and seasonal variability. Albedo remained below 0.3 during the growing season and was primarily controlled by stand development, with higher values observed in younger plantations and lower, more stable values in more mature plantations. Species effects emerged with canopy closure, as hybrid poplar exhibited higher albedo than white spruce at intermediate-to-late developmental stages. In contrast, fertilization had no consistent or persistent effect on albedo and was mainly associated with very early stages of plantation development. Leaf senescence did not lead to systematic increases in albedo, whereas snow cover exerted a dominant influence, substantially increasing surface reflectance. These results highlight the central role of canopy structure and surface conditions in controlling albedo dynamics in plantation systems. From a climate perspective, higher albedo in young plantations and under snow-covered conditions may contribute to radiative cooling, particularly in short-rotation systems such as hybrid poplar.

Transpiration phenology and stomatal regulation vary with tree species, and thus forest composition affects stand transpiration and its feedback to the atmosphere. To understand better this feedback to the atmosphere, transpiration and stomatal regulation were studied for three tree species: balsam fir, white spruce and paper birch in the boreal forest of eastern Canada. Sapflow was measured in six trees for each species using the Heat Pulse Velocity technique. From these sapflow measurements, total transpiration over the growing season and total conductance were calculated for each tree of the three species. Our results showed that the onset of transpiration occurred later in the deciduous species compared to both evergreen species. The deciduous species also had the highest total transpiration and largest hydro-active sapflow compared to the evergreen species. Our results validate those that have characterised deciduous hardwood species as having a shorter season of photosynthetic activity than evergreen conifers. An increased hydro-active sap flow may be an adaptation that allows paper birch to achieve optimal growth despite a shorter leaf-on season. Balsam fir had the smallest conductive area of all three species. Our results also showed that the deciduous trees exhibited a consistent strong stomatal regulation with increasing vapor pressure deficit. For the evergreen conifers, there was high intra-specific variation of total conductance, which could be due to spatial variability in soil moisture or canopy status. No general conclusion could be made for our studied coniferous species in respect to their stomatal regulation with increasing vapor pressure deficit. This study allows us to better understand transpiration phenology and stomatal regulation in paper birch. However, we recommend further research to identify environmental, physiological and anatomical drivers of transpiration for balsam fir and white spruce as well as other boreal species.

Reconciling carbon (C) sequestration with biodiversity conservation remains a key challenge for sustainable forest management, as C-biodiversity relationships vary across taxa and contexts. We evaluated how botanical composition, forest structure, C pools, and land use predict species richness of insects, birds, and bats across mature temperate forests in southern Qu & eacute;bec, Canada. Generalized linear models were fitted for insects and birds, while bat data were analyzed descriptively due to low and uneven richness. Botanical composition and forest structure were the most consistent predictors across groups. Insects responded strongly to vegetation structure and C allocation, with richness decreasing with shrub density and mineral soil C but increasing with the soil:above-ground C ratio and distance from infrastructure. Bird richness increased with herbaceous cover and wetland area, emphasizing the value of open and moist habitats. Across taxa, C pools acted as secondary but complementary predictors. Based on observational analyses, our results show that C-biodiversity relationships are compartment-specific and taxon-sensitive, and suggest that maintaining structural complexity, diverse vegetation strata, wetland habitats, and soil C pools may help align biodiversity conservation with C sequestration objectives in temperate forests.

Under climate change, some forest ecosystems appear to be transitioning into net source of carbon dioxide (CO2), raising questions about the future role of soil respiration rate (Rs), which depends on hydroclimatic conditions. Conversely, well-drained forest soils could become more significant sinks of methane (CH4) under warming. The main objective of this study was to assess the effects of artificial soil warming on Rs and CH4 fluxes in a sugar maple forest at the northern limit of Quebec temperate deciduous forests in eastern Canada, and to evaluate the effect of species composition on soil response to warming. We measured Rs and CH4 fluxes during the snow-free period of 2021 and 2022 in 32 plots distributed across three forest types, half of which were artificially heated by approximately 2 °C with heating cables. Forest soils were a very consistent sink for CH4 and it did not respond to artificial soil warming nor was it sensitive to variations in soil moisture, ionic activity in soil solution and forest types. However, we observed an increase in Rs in response to warming in the heated plots, but only up to a threshold of about 15 °C, beyond which Rs started to slow down in respect to the control plots. We also observed a weakening of the exponential relationship between Rs and soil temperature beyond this threshold. This trend varied across the forest types, with hardwood-beech stands being more sensitive to warming than mixedwoods and other hardwoods. This greater response of hardwood-beech stands to warming resulted in a more significant downshift of Rs, starting from a colder temperature threshold, around 10–12 °C. This study highlights a potential plateauing of Rs despite rising soil temperature, at least in eastern Canada’s temperate deciduous forest, but this trend could vary from one forest type to another.

Climate change is intensifying fire regimes in boreal forests, leading to ecological disruption and raising concerns about forest resilience and post-disturbance recovery. Altered fire dynamics creates novel opportunities for implementing adaptive silviculture for climate change, including assisted migration, the intentional movement and establishment of tree species or tree populations outside their current range of distribution to better match anticipated future climates. Here, we examine how the increasing frequency, severity, and spatial extent of Canadian boreal wildfires can serve as strategic windows for introducing climate-resilient tree species and genotypes. We review how fire influences the availability and suitability of post-fire sites for assisted migration, highlighting how fire-induced changes in soil abiotic and biotic properties may facilitate or hinder the establishment of relocated tree species. While fire can simplify site preparation, reduce biotic competition, and temporarily enhance soil nutrient availability, it may also degrade soil structure by consuming or altering soil organic matter and increasing soil susceptibility to erosion and disrupt essential mycorrhizal associations. We argue that assisted migration of tree species can be a proactive silvicultural tool when used in areas with regeneration failure or where future climate conditions are likely to exceed the tolerance limits of native species. Whilst scientific evidence remains limited on the regeneration success of migrated species and genotypes in post-fire environments, we argue for an integrated adaptation strategy that combines natural regeneration with targeted assisted migration interventions, guided by local site conditions, genetic considerations, and policy support, to build resilient boreal forests under changing disturbance regimes.

Temperate alley cropping systems (ACS) offer potential for both soil organic carbon (SOC) and tree-based C sequestration, but research is scarce. While SOC enhancement is recognized, C sequestration in tree biomass remains under-documented and species-dependent. Previous SOC studies are often limited by single-site designs and lack of agricultural controls. The general objective of this study was to evaluate C stocks in four ACS (50–104 trees ha−1; 9- to 19-year-old) established in southern Québec, Canada. SOC stocks were measured at three depths (0–20, 20–40 and 40–60 cm) with an increasing distance from the tree row (0, 2, 4, 8 m and at the centre of the cultivated alley) and compared with agricultural controls without trees. Allometric equations were used to estimate C stocks in above- and belowground tree biomass. Significant spatial variation in SOC stocks within the ACS was observed at the St-Télesphore and Baie-du-Febvre sites, but only in the surface layer (0–20 cm). At these sites, SOC stocks in the plots at all distances from the tree rows (except at 0 m at the St-Télesphore site and at 20 m at the Baie-du-Febvre site) were higher than in the controls. At Baie-du-Febvre, SOC stocks in the 0–20 cm layer were highest near the tree rows and gradually decreased with distance from the tree rows. The spatial distribution of SOC in the 20–40 cm layer at the St-Télesphore and Baie-du-Febvre sites followed a trend similar to that observed in the 0–20 cm layer, although statistical analyses yielded only marginally significant differences. SOC stocks in the ACS plots at Baie-du-Febvre (i.e., all distances combined) were higher than in the control plots, but only in the 0–20 cm layer, with an increase of + 0.51 Mg C ha−1 y−1. At the St-Paulin site, which was the only site cultivated with a permanent forage crop, SOC stocks in the 0–20 cm layer were significantly lower in the ACS plots than in the control plots (− 0.28 Mg C ha−1 y−1). At the four study sites, C accumulation rates in tree biomass varied from 0.14 to 0.49 Mg C ha−1 y−1. When both soil and tree C were considered, total accumulation in ACS relative to control plots varied from 0.01 to 2.0 Mg C ha−1 y−1. The results in this study suggest that ACS primarily influence C storage at the soil surface, at least during the first decade following tree establishment. The findings also highlight the greater potential of ACS to enhance soil C stocks in fields with annual cash crops compared to those with perennial forage crops.

Under climate change, some forest ecosystems appear to be transitioning into net source of carbon dioxide (CO2), raising questions about the future role of soil respiration rate (Rs), which depends on hydroclimatic conditions. The main objective of this study was to assess the effects of artificial warming on Rs in a sugar maple forest at the northern limit of Quebec temperate deciduous forests in eastern Canada, and to evaluate the effect of species composition on soil response to warming. We measured Rs during the snow-free period of 2021 and 2022 in 32 plots distributed across three forest types, half of which were artificially heated by approximately 2°C with heating cables. We observed an increase in Rs in response to warming in the heated plots, but only up to a threshold of about 15°C, beyond which Rs started to slow down in respect to the control plots. We also observed a weakening of the exponential relationship between Rs and soil temperature beyond this threshold. This trend varied across the forest types, with hardwood-beech stands being more sensitive to warming than mixedwoods and other hardwoods. This greater response of hardwood-beech stands to warming resulted in a more significant slowdown of Rs, starting from a colder temperature threshold, around 10–12°C. This study highlights a potential plateauing of Rs despite rising soil temperature, at least in eastern Canada’s temperate deciduous forest, but this trend could vary from one forest type to the another.

In the context of a changing climate and the increasing occurrences of extreme events, including droughts, field evidence, and models suggest that cases of forest decline and migration of tree species to more suitable climates will augment in the 21st century. In northeastern North America, an expansion of American beech at the expense of maples has been observed since the 1970s and has been associated to several causes. Through an analysis of time series leveraging thousands of data collected in a temperate forest in southern Quebec, Canada, dynamics of soil water potential were analyzed in interaction with soil temperature, meteorological variables and forest types, including hardwoods (mostly maple) with a large presence of beech trees (hardwood-beech stands), hardwoods (maple and birch) and mixedwoods (maple and fir). During flash drought events with a net precipitation deficit and water stress, the presence of beech led to a decrease in soil temperature and favored the maintenance of low soil water potential and faster restoration of water reserves compared to mixedwoods. Using machine learning-based approaches, distinct critical soil temperature thresholds in regard to water potential were identified for the various forest types, and the temporality in soil water regime changes was more favorable under hardwood-beech stands. The presence of beech appears to render greater resilience in regard to water stress in this forest. A greater capacity of beech to preserve and restore soil water not only offers an additional explanation for its establishment in hardwoods in the last decades, but greater water conservation in the presence of beech, assuming it remains in the landscape, could also help local plant species adapt to climate change and to the predicted increased water deficits, as well as species migrating northward to find more suitable environmental envelopes.

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.

Red oak is an important species within the North American landscape, with climate change projections indicating a potential northward shift in its distribution. However, understanding the factors influencing its regeneration success at the northern limit remains limited. Site conditions and seed provenance adaptability may play critical roles. To bridge this knowledge gap, we conducted a seed transfer study in two northern red oak stands in Quebec. We firstly investigated stand regeneration history through dendrochronological characterization. Then, we monitored the survival and growth of saplings for four red oak provenances across a south-to-north gradient in field and greenhouse settings, with varying soil nutrient levels due to fertilization, and with or without protection from large herbivores. Results indicated that stands have similar age structures with red oak establishment coinciding with the last major fire disturbance in the early 1920s. However, tree species composition and density differed, suggesting differences in fire disturbance regime or ecological succession status prior to fire. Site had the largest influence on red oak regeneration, with the highest tree density and soil water availability site exhibiting a 29% higher survival rate. Protection against large herbivores also significantly impacted red oak seedling performance, leading to a 16% higher survival rate. Germination, survival and growth also significantly differed between provenances. The local (northernmost) provenance exhibited the poorest overall performance with 28 to 42% lower germination, survival and growth rates, while the two southernmost provenances exhibited superior germination and sprout survival. An increase in soil nutrient availability was beneficial to red oak in the greenhouse, but only marginally benefited survival and growth in the field, suggesting that this factor is of less importance than other factors (e.g., water and light availability) for red oak early regeneration. The findings of this study suggest that silvicultural efforts to favor red oak should focus on site and provenance selection, and that water availability is currently limiting red oak regeneration success at acorn and early seedling life stages (i.e., 1 year old seedlings) near its northern distribution limit.

Developing land use strategies to optimize carbon sinks and improve carbon footprints involves proposing efficient nature-based solutions that industries and businesses can implement while considering financial and legislative constraints. The pulp and paper industry is associated with significant greenhouse gas (GHG) emissions, primarily due to the substantial carbon dioxide (CO2) footprint of its mills. Also, some forestry operations contribute to the release of carbon to the atmosphere in the form of CO2 and methane (CH4). Conversely, this industry could potentially be a significant ally in the fight against climate change by favoring forestry practices that reduce carbon emissions and increase its sequestration, namely, by adding value to industrial by-products (e.g., biosolids) instead of treating them as wastes and landfilling them. Notably, the pulp and paper industry has been seeking alternative uses of its by-products, such as fertilizers to maximize tree growth. In this paper, we identify opportunities and challenges that exist for the pulp and paper industry in regard to recycling industrial by-products to: 1) lower GHG emissions directly at the mill and 2) improve its GHG budget by increasing carbon sequestration in forests and plantations. We illustrate our analyses by describing a case study of a pulp and paper mill in southern Quebec, Canada, that uses its biosolids and other by-products as fertilizers. This case study highlights that this strategy could not only contribute to the reduction of GHGs but could also create added value and improve economic returns of forest operations.

Ongoing rapid climatic changes are expected to modify the structure, composition, and functioning of forest ecosystems. Studying the influence of such changes on biogeochemical processes is thus crucial for a fuller understanding of forest response to climate change. In a temperate forest of Quebec, Canada, we emulated climate change by warming the acidic, nutrient-poor, and dry soils of two mixedwoods by 3 to 4 °C using heating cables. Leaf-litter mass loss of the local red maple, sugar maple, large-tooth aspen, and American beech were monitored to assess the ability of these tree species to condition boreal soils in the context of their northward migration under climate change. We hypothesized that decomposition rates of all leaf-litter types would be decreased equally by warming due to a drying effect of the soil and its surface, which is detrimental to microbial biomass and activity. Our results suggest differences in decomposition rates between tree species as follows: sugar maple > red maple ≥ American beech = large-tooth aspen. There was no indication of a slower turnover in these marginal soils compared to other studies conducted on typical hardwood soils. Moreover, no difference in litter mass loss was detected between treatments, likely due to a drying effect of the soil warming treatment. Results imply that climate change has a marginal influence on leaf-litter dynamics of temperate tree species on soils that are typical of the boreal forest. However, some variables that could play an important role on litter decomposition in the context of climate change were not measured (e.g., plant phenology, understory composition and density, microbes) and thus, uncertainties remain. The soil drying effect by warming also needs to be further documented and modeled. The study year was characterized by significant periods of water stress but was not considered an exceptional year in that regard. It would be relevant to test for leaf-litter dynamics during dry and wet summers and verify again our initial hypothesis of decreased leaf-litter decomposition rates due to soil warming/drying.

The asbestos mining industry has deeply transformed the landscapes of southern Quebec, leaving behind about 800 million tonnes of tailings and waste rock (overburden) in large piles near former mining towns. Some environmental issues arising from these landscapes (e.g., wind and water erosion) have been successfully addressed by covering the piles by mixing by-products to create technosols, which are then seeded with grasses. Yet, no attempt at afforestation had been made thus far because these environments are thought to impose too many constraints on tree establishment and growth. We developed two experimental plantations at a decommissioned asbestos mine in southern Quebec, on waste rocks and on tailings, to test the performance of eight tree species/clones/provenances planted on two types of technosols. Both were constructed from mixtures of municipal biosolids and deinking sludge and configured in small windrows. Soil texture, apparent bulk density, element composition, including carbon, nitrogen and some metals, as well as soil temperature, water potential and volumetric water content were assessed, together with seedling survival and growth (diameter and height). Leaf specific surface area, nutrients, water use efficiency (δ13C) and gas exchange (i.e., net photosynthetic assimilation rate, Anet, and stomatal conductance to water vapour, gsw) were evaluated for three hybrid poplar clones (Populus spp.) during the third growing season. Hybrid poplar clones had significantly higher survival (87–94

Improved land stewardship is necessary for climate change mitigation. As such, actions are needed to increase carbon (C) sinks and reduce C emissions from land use activities. Residual materials with fertilizing capacity can be used to reconstruct severely degraded soils and recreate a sustainable vegetation cover, leading to reductions in atmospheric CO2 levels. We studied the temporal dynamics of CO2 sequestration potential in soils recon-structed with 1200 Mg ha-1 biosolids along a young chronosequence ranging from 0 to 7 years after initiating reclamation of a decommissioned asbestos mine in southern Que acute accent bec, Canada. We measured in situ soil CO2 fluxes, soil C pools and soil physicochemical properties. Since bacterial communities are highly responsive to soil physicochemical properties, we also analyzed both their diversity and community structure. The age since soil reclamation did not have a clear effect on soil properties, but it exerted greater control over soil C fluxes and soil bacterial community diversity and structure. Our results suggest large C fluxes to the atmosphere within the first year following soil reconstruction, but soils constitute a stable C pool thereafter.

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 µm 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.

Understanding the chemical composition of our planet's crust was one of the biggest questions of the 20th century. More than 100 years later, we are still far from understanding the global patterns in the bioavailability and spatial coupling of elements in topsoils worldwide, despite their importance for the productivity and functioning of terrestrial ecosystems. Here, we measured the bioavailability and coupling of thirteen macro‐ and micronutrients and phytotoxic elements in topsoils (3–8 cm) from a range of terrestrial ecosystems across all continents (∼10,000 observations) and in response to global change manipulations (∼5,000 observations). For this, we incubated between 1 and 4 pairs of anionic and cationic exchange membranes per site for a mean period of 53 days. The most bioavailable elements (Ca, Mg, and K) were also amongst the most abundant in the crust. Patterns of bioavailability were biome‐dependent and controlled by soil properties such as pH, organic matter content and texture, plant cover, and climate. However, global change simulations resulted in important alterations in the bioavailability of elements. Elements were highly coupled, and coupling was predictable by the atomic properties of elements, particularly mass, mass to charge ratio, and second ionization energy. Deviations from the predictable coupling‐atomic mass relationship were attributed to global change and agriculture. Our work illustrates the tight links between the bioavailability and coupling of topsoil elements and environmental context, human activities, and atomic properties of elements, thus deeply enhancing our integrated understanding of the biogeochemical connections that underlie the productivity and functioning of terrestrial ecosystems in a changing world.

Fertilization of hybrid poplar (HP) plantations with papermill by-products is a promising solution to improve soil fertility and nutrient availability, increase plantation productivity, and provide added value to these materials that would otherwise be incinerated or sent to the landfill. We assessed the growth and foliar nutrition of a HP clone (Populus ×canadensis × Populus maximowiczii) at six plantation sites aged 3–5 years in southern Quebec, Canada. Sites received a fertilization treatment consisting of a mixture of papermill biosolids (120 to 140 t·ha −1 , depending on site) and lime mud (10 to 15 t·ha −1 ) before being planted, or no fertilization (control). Tree growth was significantly improved by fertilization, with fertilized trees showing a mean annual height increment of 1.3 m (all-site mean; SD = 0.2), compared with 0.5 m (SD = 0.4) for unfertilized trees. Foliar calcium and magnesium increased following fertilization and levels met optimal thresholds at all sites, whereas nitrogen, phosphorous, and potassium concentrations also increased, but nutritional deficiencies remained for these elements at several sites. Our results confirm the benefits of fertilizing hybrid poplars with papermill by-products, but they also indicate that adjustments in application rates or type of by-products could be made to fully satisfy nutritional requirements and thus optimize tree growth.

In 2020, Quebec adopted a strategy to increase the quantity and quality of timber it produces. During a roundtable discussion held in the fall of 2021, experts in forestry and in related fields expressed their views on the new strategy and its implementation challenges. The main purpose of this article is to present the key observations from the roundtable. The observations addressed two themes: the general context in which the strategy was developed, and the context of its implementation on the ground. Although most of the panellists agreed on the relevance of such a strategy, particularly as regards to climate change mitigation and wealth creation, several questions remain. The challenge of harmonizing uses, regionalization, spatialization of management decisions, labour shortage, and uncertain ecosystem dynamics make it difficult to assess the strategy’s potential impact on the ground and its ability to achieve its targets.

En 2020, le Québec a adopté une stratégie nationale de production de bois (SNPB) afin d’augmenter la quantité et la qualité de la matière ligneuse produite. Au cours d’une table ronde tenue à l’automne 2021, des experts de la foresterie et de domaines connexes se sont prononcés sur cette nouvelle stratégie et sur les défis de mise en oeuvre qu’elle pose. L’objectif principal de cet article est de présenter les principaux constats émis au cours de cette table. Les constats ont été divisés en deux thématiques, soit le contexte général d’élaboration de cette stratégie et le contexte de sa mise en oeuvre en forêt. Bien que la plupart des panélistes s’entendent sur la pertinence de créer une telle stratégie, notamment en ce qui a trait à l’atténuation des changements climatiques et à la création de richesses, plusieurs interrogations persistent. Les défis d’harmonisation des usages, de régionalisation, de spatialisation des décisions d’aménagement, de manque de maind’oeuvre et de la dynamique incertaine des écosystèmes complexifient l’évaluation des retombées potentielles de la SNPB sur le terrain et sa capacité d’atteindre les cibles établies.