Forest Of Quebec Research Articles

Twenty-Eight Years of Changes in Landscape Heterogeneity of Mixedwood Boreal Forest Under Management in Quebec, Canada

ABSTRACTChanges in natural and anthropogenic disturbances in the mixedwood boreal forests of northwest Quebec have modified the landscape heterogeneity in terms of its composition and configuration. The aim of this study was to evaluate the heterogeneity (composition and configuration) of 78,000 km2 of mixedwood boreal forest landscape during recent decades (using Landsat imagery from 1985 to 2013) in areas affected by forest management. The classes Conifer, Mixed-Conifer, Mixed-Hardwood, and Hardwood were differentiated with an object-based classification (accuracy >80.2, Kappa coefficient >0.7). Also, 5 metrics (mean area, largest patch index, percentage the landscape of the core area, perimeter-area fractal dimension, and aggregation index) were calculated. This study showed that conifer-dominant cover dominates the mosaic and accounted for one third of the study area. Nevertheless, the conifer-dominant class showed the greatest decrease (reduction of 35% of its initial area at a rate of 1.7% per year). The metrics indicated that forest management in recent years produced a more heterogeneous landscape in 2013 unlike the landscape in 1985. The fire-influenced, old-growth conifer forests that previously dominated the landscape in northwestern Quebec were transformed by forestry practices into a more heterogeneous landscape.RÉSUMÉLes régimes des perturbations naturelles et anthropiques dans les forêts boréales mixtes du nord-ouest du Québec ont modifié l'hétérogénéité du paysage en termes de composition et de configuration. L'objectif de cette étude était d'évaluer l'hétérogénéité (composition et configuration) d'un territoire de 78,000 Km2 de la forêt boréale mixte aménagée au cours des dernières décennies en utilisant des images Landsat de 1985 à 2013. Les classes de couvertures forestières Résineux, Résineux mélangés, Feuillus mélangés et Feuillus ont été différenciées à l'aide d'une méthode de classification basée sur l'identification d'objets (précision >80.2, coefficient Kappa >0.7). En outre, cinq paramètres (superficie moyenne, indice de la taille de la plus grande parcelle, pourcentage du paysage de l'aire centrale, dimension fractale entre périmètre et surface et indice d'agrégation) ont été calculés. Les résultats de cette étude ont montré que la classe Résineux, domine la mosaïque et représente un tiers de la zone d'étude. Nonobstant, cette même classe a enregistré la plus forte diminution au cours de la période d'évaluation avec une réduction de 35% de sa superficie initiale au taux de 1,7% par an. Les paramètres indiquent que l'aménagement forestier au cours des dernières années a produit un paysage plus hétérogène en 2013, contrairement au paysage en 1985. Ces résultats indiquent que les forêts anciennes résineuses et influencées par le feu qui dominaient auparavant le paysage dans le nord-ouest du Québec ont été transformées par les pratiques forestières en un paysage plus hétérogène.

Boreal coniferous forest density leads to significant variations in soil physical and geochemical properties

Abstract. At the northernmost extent of the managed forest in Quebec, Canada, the boreal forest is currently undergoing an ecological transition between two forest ecosystems. Open lichen woodlands (LW) are spreading southward at the expense of more productive closed-canopy black spruce–moss forests (MF). The objective of this study was to investigate whether soil properties could distinguish MF from LW in the transition zone where both ecosystem types coexist. This study brings out clear evidence that differences in vegetation cover can lead to significant variations in soil physical and geochemical properties.Here, we showed that soil carbon, exchangeable cations, and iron and aluminium crystallinity vary between boreal closed-canopy forests and open lichen woodlands, likely attributed to variations in soil microclimatic conditions. All the soils studied were typical podzolic soil profiles evolved from glacial till deposits that shared a similar texture of the C layer. However, soil humus and the B layer varied in thickness and chemistry between the two forest ecosystems at the pedon scale. Multivariate analyses of variance were used to evaluate how soil properties could help distinguish the two types at the site scale. MF humus (FH horizons horizons composing the O layer) showed significantly higher concentrations of organic carbon and nitrogen and of the main exchangeable base cations (Ca, Mg) than LW soils. The B horizon of LW sites held higher concentrations of total Al and Fe oxides and particularly greater concentrations of inorganic amorphous Fe oxides than MF mineral soils, while showing a thinner B layer. Overall, our results show that MF store three times more organic carbon in their soils (B+FH horizons, roots apart) than LW. We suggest that variations in soil properties between MF and LW are linked to a cascade of events involving the impacts of natural disturbances such as wildfires on forest regeneration that determines the vegetation structure (stand density) and composition (ground cover type) and their subsequent consequences on soil environmental parameters (moisture, radiation rate, redox conditions, etc.). Our data underline significant differences in soil biogeochemistry under different forest ecosystems and reveal the importance of interactions in the soil–vegetation–climate system for the determination of soil composition.

Factors Affecting Abundance of Beaver Dams in Forested Landscapes

Beavers are ecosystem engineers that contribute to landscape heterogeneity in North American boreal forests. Despite the importance of beavers on landscapes, beaver distribution is still poorly understood, particularly at large spatial scales and in different ecoregions. The goal of our study was to determine the main environmental features affecting beaver dam abundance across ecoregions. We quantified the spatial distribution of beaver dams in Quebec forests using 257 systematically distributed provincial forestry maps, in which we sampled 1025 plots of 25 km2 in an area several orders of magnitude larger than in previous studies. The study area, covering over 300,000 km2, spanned over six ecoregions (Appalachians, Meridional Laurentians, Central Laurentians, Abitibi and James Bay Lowlands, Mistassini, and Anticosti Island). We constructed 17 candidate regression models using a negative binomial distribution with variables based on different hypotheses to explain beaver dam abundance. The mean stream gradient was the top variable influencing dam abundance, followed by the cover of non-forested land. However, there was substantial variability among ecoregions, as the models that included the random effect of hardwood cover and non-forested cover ranked higher than models without these variables. We conclude that such regional variation in factors affecting dam distribution patterns should be taken into account when establishing beaver management plans.

Xylogenesis in stems and roots after thinning in the boreal forest of Quebec, Canada.

The reduction of competition through thinning increases radial growth in the stem and roots of many conifer species. However, not much is known about the effect of thinning on the dynamics of wood formation and intra-annual development of the growth ring, especially in the roots, which are an essential part of the tree for stability and resource acquisition. The aim of this study was to evaluate the effect of an experimental thinning on the dynamics and phenology of xylogenesis in the stem and roots of black spruce and balsam fir. Experimental and control trees were selected in two mature even-aged stands, one black spruce (Picea mariana (Mill.) BSP) and one balsam fir (Abies balsamea (L.) Mill.). Wood microcores were collected weekly in the stem and roots from May to October for a period of 4 years. The onset and ending of each cell differentiation phase were computed, as well as growth rate and total cell production. Results show that thinning increased the cell production rate of stem and roots of black spruce and balsam fir. This higher daily growth rate caused an increase in the total number of cells produced by the cambium. The intensity of the treatment was sufficient to significantly increase light availability for residual trees, but insufficient to modify soil temperature and water content to a point at which a significant change in the timing or duration of xylogenesis would be induced. Thus, thinning increased cell production rate and total number of cells produced in both stem and roots, but did not result in a change in the phenology of wood formation that could lead to increased risks of frost damage in the spring or autumn.

Boreal small mammals show evidence of density-dependent patterns with area-sensitivity

In recent years, habitat amount in fragmented landscapes has been shown to positively influence population size, species occurrence, and species diversity. Quantifying how sensitive bioindicator species respond to the amount of habitat in disturbed landscapes (i.e. area-sensitivity) has become a growing research focus to provide robust guidelines for ecosystem-based management. In this study, we modelled the occurrence of North American boreal small mammals in relation with the total amount of forest surrounding remnant forest patches in disturbed landscapes while controlling for local habitat associations. Over the summers of 2013 and 2014, we conducted four trapping sessions in 60 sites located in old forest remnant patches of old forests in both wildfires and aggregated clearcuts, and in continuous old forest blocks within the black spruce forest of northwestern Quebec, Canada. American red squirrels (Tamiasciurus hudsonicus), southern red-backed voles (Myodes gapperi) and masked shrews (Sorex cinereus) represented 85.5% of our total captures. We measured the amount of habitat (percentage of forest cover) within 100 concentric buffers around each capture grid using digital forest cover maps. Buffers varied in radii from 50m to 5km. We quantified area-sensitivity using dynamic models of single-species occupancy to estimate the probabilities of initial site occupancy, site extinction and site colonisation of each species according to both local habitat variables and surrounding habitat amount. We found no associations between initial site occupancy, site colonisation, or site extinction with local habitat features, possibly in response to habitat structure similarity of our three site types. Species studied had different life histories in terms of population dynamics' and timing of juvenile dispersal, possibly explaining why each species had its individual response to the amount of habitat in the surrounding landscape. For the American red squirrel, we found no evidence of within-year area-sensitivity on initial site occupancy patterns, whereas negative area sensitivity on initial site occupancy between-years was observed for the southern red-backed vole. In contrast, we found positive area-sensitivity on between-years site colonisation for this latter species at small spatial scales. For masked shrews, we detected negative area-sensitivity on initial site occupancy within-year. As populations were sampled at low density, we suspect that the sparse distribution of individuals may influence area-sensitivity patterns. Future studies should consider area-sensitivity with regards to both spatial and temporal scales. We encourage long-term monitoring of animal populations at multiple spatial scales to investigate the underlying ecological mechanisms of positive and negative area-sensitivity.

Chemical composition and anti-herpes simplex virus type 1 (HSV-1) activity of extracts from Cornus canadensis

BackgroundMany plants of boreal forest of Quebec have been used by Native Americans to treat a variety of microbial infections. However, the antiviral activities of these plants have been seldom evaluated on cellular models to validate their in vitro efficiencies. In this study, Cornus canadensis L. (Cornaceae), a plant used in Native American traditional medicine to treat possible antiviral infections, has been selected for further examination.MethodsThe plant was extracted by decoction and infusion with water, water/ethanol 1:1 and ethanol to obtain extracts similar to those used by Native Americans. The effects of the extracts were tested on herpes simplex virus type-1 (HSV-1) using a plaque reduction assay. Moreover, bioassay-guided fractionation was achieved to isolate bioactive compounds.ResultsWater/ethanol 1:1 infusion of C. canadensis leaves were the most active extracts to inhibit virus absorption with EC50 of about 9 μg mL−1, whereas for direct mode, both extraction methods using water or water/ethanol 1:1 as solvent were relatively similar with EC50 ranging from 11 to 17 μg mL−1. The fractionation led to the identification of active fractions containing hydrolysable tannins. Tellimagrandin I was found the most active compound with an EC50 of 2.6 μM for the direct mode and 5.0 μM for the absorption mode.ConclusionAltogether, the results presented in this work support the antiviral activity of Cornus canadensis used in Native American traditional medicine.

Large-scale estimation of xylem phenology in black spruce through remote sensing

There is a growing need for understanding the timing of wood formation in relation to the dynamics of bud phenology at wide geographical scale. This study analysed the relationships between long-term chronologies of xylem growth and the timing of plant phenology detected by Normalized Difference Vegetation Index (NDVI) in five permanent stands across the latitudinal distribution of black spruce [Picea mariana (Mill.) BPS] in the boreal forest of Quebec, Canada. Xylogenesis was studied weekly from April to October for thirteen years (2002–2014) on anatomical sections derived by wood microcores. The timing of the growing season detected by remote sensing was extracted from MODerate resolution Imaging Spectroradiometer (MODIS) 250m 16-days NDVI data. The NDVI time-series were fitted using a double-logistic curve. Phenological chronologies from remote sensing and xylem phenology showed a latitudinal trend. The models correlating the data inferred from satellite sensors and the spring observations of xylem phenology were significant (p<0.0001). The length of NDVI growing season and the duration of xylogenesis showed a close correlation. This study demonstrated that the timing of xylem formation could be suitably estimated at wide geographical scale using remote sensing data. However, the inter-annual phenological variability remained unexplained, which might limit the application of the models only to the years considered by our chronologies.

Growth and wood quality of black spruce and balsam fir following careful logging around small merchantable stems (CLASS) in the boreal forest of Quebec, Canada

Careful logging around small merchantable stems (CLASS) is a partial cutting treatment in which 70–90 per cent of the merchantable volume of uneven-aged, irregular or multi-layered conifer stands is harvested. The decrease in stand density by means of partial cutting is known to induce an increase in residual stem growth, which could also influence wood properties. This research aims to evaluate the effect of CLASS on the growth and some wood quality parameters of black spruce (Picea mariana (Mill.) B.S.P.) and balsam fir (Abies balsamea (L.) Mill.) in the boreal forest of Quebec, Canada. Four uneven-aged black spruce-balsam fir stands were selected for the study and 15 black spruce and 15 balsam fir trees were sampled in each stand, distributed between a treated and a control area. Radial growth, latewood proportion, ring density, tracheid length and the moduli of elasticity and rupture were measured in each tree. A high proportion of residual stems significantly increased their radial growth after CLASS. No significant change was obtained for latewood proportion, average ring density, tracheid length or mechanical properties for black spruce. However, latewood proportion and ring density were significantly reduced in balsam fir after treatment, with no effect on modulus of elasticity or modulus of rupture. When looking at the wood properties comprehensively, a canonical discriminant analysis did not detect any significant difference between the wood properties before and after treatment for either species. This suggests that CLASS can stimulate the radial growth of residual stems with limited short-term effects on wood quality.

Effect of Tree Spacing on Tree Level Volume Growth, Morphology, and Wood Properties in a 25-Year-Old Pinus banksiana Plantation in the Boreal Forest of Quebec

The number of planted trees per hectare influences individual volume growth, which in turn can affect wood properties. The objective of this study was to assess the effect of six different plantation spacings of jack pine (Pinus banksiana Lamb.) 25 years following planting on tree growth, morphology, and wood properties. Stem analyses were performed to calculate annual and cumulative diameter, height, and volume growth. For morphological and wood property measurements several parameters were analyzed: diameter of the largest branch, live crown ratio, wood density, and the moduli of elasticity and rupture on small clear samples. The highest volume growth for individual trees was obtained in the 1111 trees/ha plantation, while the lowest was in the 4444 trees/ha plantation. Wood density and the moduli of elasticity and rupture did not change significantly between the six plantation spacings, but the largest branch diameter was significantly higher in the 1111 trees/ha (3.26 cm mean diameter) compared with the 4444 trees/ha spacing (2.03 cm mean diameter). Based on this study, a wide range of spacing induced little negative effect on the measured wood properties, except for the size of knots. Increasing the initial spacing of jack pine plantations appears to be a good choice if producing large, fast-growing stems is the primary goal, but lumber mechanical and visual properties could be decreased due to the larger branch diameter.

Predicting hardwood quality and its evolution over time in Quebec's forests

Predicting hardwood quality and its evolution over time in Quebec's forests

Comparative evaluation of three sampling methods to estimate detection probability of American red squirrels (Tamiasciurus hudsonicus)

Measuring changes in species distribution and understanding factors influencing site occupancy are recurring goals in wildlife studies. Imperfect detection of species hinders such studies, resulting in the underestimation of the number of sites occupied by the species of interest. American red squirrels (Tamiasciurus hudsonicus) are sampled traditionally with live-traps that require substantial resources to deploy and monitor. Here, we assessed whether auditory methods yield similar detection probabilities. We compared the detection probability of American red squirrels in boreal forest using point counts, playback counts, and live-trapping. Over the summer of 2014, we conducted three trapping sessions in 60 sites within black spruce forests of northwestern Quebec, Canada. We also conducted 10min point counts in the same sites, together with playback counts using recordings of American red squirrel alarm and territorial calls. Using dynamic occupancy models to analyse three primary periods, all composed of three secondary periods, we found that the detection probability of squirrels from point counts was as high as with live-trapping. Our results thus highlight the value of the point count method in measuring American red squirrel occupancy.

Fire is a stronger driver of forest composition than logging in the boreal forest of eastern Canada

AbstractAimsOur study aimed to: (1) document the preindustrial (1925) forest composition prior to extensive logging; (2) document the magnitude of changes from 1925 to 2005; and (3) identify the relative influence of logging and natural disturbances as drivers of the present‐day forest composition.LocationBoreal forest in central Quebec, eastern Canada.MethodsWe used a dense network of georeferenced historical (~1925) forest plots (n = 30 033) to document preindustrial forest composition. We evaluated the magnitude of changes with the present‐day using modern plots (1980s to 2000s). We reconstructed a long‐term, spatially explicit history of logging, spruce budworm outbreaks (Choristoneura fumiferana [Clem.], SBO), and fire using historical maps and field surveys.ResultsIn the preindustrial period, late successional coniferous taxa (Abies balsamea and Picea spp.) dominated the landscape, whereas early successional deciduous taxa (Betula spp. and Populus spp.) were confined to recently burned areas. In the present‐day landscape, large areas dominated by late successional coniferous taxa have been replaced by early successional deciduous taxa. Forest communities dominated by early successional deciduous taxa increased sharply throughout the study area. Logging has been a minor driver of these changes compared to fire and SBOs.ConclusionsThis study demonstrates the importance of documenting the long‐term history of both anthropogenic and natural disturbances in order to assess their relative contributions to the development of the present‐day forest ecosystems. Natural disturbances have remained the main drivers of forest composition during the 20th century, whereas logging played a less important role. In the current context of global change, long‐term experimental research is required to help forecast impacts of natural disturbances and forest management on boreal forest composition.

Tree phyllosphere bacterial communities: exploring the magnitude of intra- and inter-individual variation among host species.

BackgroundThe diversity and composition of the microbial community of tree leaves (the phyllosphere) varies among trees and host species and along spatial, temporal, and environmental gradients. Phyllosphere community variation within the canopy of an individual tree exists but the importance of this variation relative to among-tree and among-species variation is poorly understood. Sampling techniques employed for phyllosphere studies include picking leaves from one canopy location to mixing randomly selected leaves from throughout the canopy. In this context, our goal was to characterize the relative importance of intra-individual variation in phyllosphere communities across multiple species, and compare this variation to inter-individual and interspecific variation of phyllosphere epiphytic bacterial communities in a natural temperate forest in Quebec, Canada.MethodsWe targeted five dominant temperate forest tree species including angiosperms and gymnosperms: Acer saccharum, Acer rubrum, Betula papyrifera, Abies balsamea and Picea glauca. For one randomly selected tree of each species, we sampled microbial communities at six distinct canopy locations: bottom-canopy (1–2 m height), the four cardinal points of mid-canopy (2–4 m height), and the top-canopy (4–6 m height). We also collected bottom-canopy leaves from five additional trees from each species.ResultsBased on an analysis of bacterial community structure measured via Illumina sequencing of the bacterial 16S gene, we demonstrate that 65% of the intra-individual variation in leaf bacterial community structure could be attributed to the effect of inter-individual and inter-specific differences while the effect of canopy location was not significant. In comparison, host species identity explains 47% of inter-individual and inter-specific variation in leaf bacterial community structure followed by individual identity (32%) and canopy location (6%).DiscussionOur results suggest that individual samples from consistent positions within the tree canopy from multiple individuals per species can be used to accurately quantify variation in phyllosphere bacterial community structure. However, the considerable amount of intra-individual variation within a tree canopy ask for a better understanding of how changes in leaf characteristics and local abiotic conditions drive spatial variation in the phyllosphere microbiome.

Host species identity, site and time drive temperate tree phyllosphere bacterial community structure.

BackgroundThe increasing awareness of the role of phyllosphere microbial communities in plant health calls for a greater understanding of their structure and dynamics in natural ecosystems. Since most knowledge of tree phyllosphere bacterial communities has been gathered in tropical forests, our goal was to characterize the community structure and assembly dynamics of phyllosphere epiphytic bacterial communities in temperate forests in Quebec, Canada. We targeted five dominant tree species: Acer saccharum, Acer rubrum, Betula papyrifera, Abies balsamea, and Picea glauca. We collected 180 samples of phyllosphere communities on these species at four natural forest sites, three times during the growing season.ResultsHost functional traits (i.e., wood density, leaf nitrogen content) and climate variables (summer mean temperature and precipitation) were strongly correlated with community structure. We highlight three key findings: (1) temperate tree species share a “core microbiome”; (2) significant evolutionary associations exist between groups of bacteria and host species; and (3) a greater part of the variation in phyllosphere bacterial community assembly is explained by host species identity (27 %) and species-site interaction (14 %), than by site (11 %) or time (1 %).ConclusionsWe demonstrated that host species identity is a stronger driver of temperate tree phyllosphere bacterial communities than site or time. Our results suggest avenues for future studies on the influence of host functional traits on phyllosphere community functional biogeography across terrestrial biomes.Electronic supplementary materialThe online version of this article (doi:10.1186/s40168-016-0174-1) contains supplementary material, which is available to authorized users.

A landscape-level tool for assessing natural regeneration density of Picea mariana and Pinus banksiana following fire and salvage logging

We present a landscape-level operational natural regeneration assessment tool, created by linking a validated forest regeneration model with forest inventory maps. Using basal areas obtained from temporary plots and seedbed distributions from field data, seedling densities are simulated for pure Picea mariana (Mill.) and Pinus banksiana (Lamb.) stands under burned intact, and traditional first winter and delayed salvage scenarios. These stands are grouped by age-class, pre-fire stand cover, surficial deposit, and drainage. Following this classification scheme, simulated seedling densities are transferred onto forest inventory maps for the Lake Matagami lowland ecological region (6a) in the boreal forest of Quebec (used as a case study to illustrate the potential of the tool). The final output of the model is an estimate of seedlings/m2 following moderate to severe fire, and fire followed by 100% salvage in pure P. mariana and P. banksiana stands, however it is also capable of simulating partial salvage. Results are expressed as seedlings/ha, and illustrate that in our study area, only 35% of intact P. mariana and 6% of intact P. banksiana stands need to be planted following fire; however under the traditional 100% first winter salvage scenario, 100% of P. mariana and 74% of P. banksiana stands necessitate planting. If salvage logging is delayed until the second, third, or fourth winter following fire, planting will be required in 98%, 88%, and 66% of P. mariana, and 65%, 56%, and 56% of P. banksiana stands respectively. This type of tool allows managers and foresters to quickly assess reforestation needs following fire and salvage at the landscape level, and can be used to better plan the timing and location of salvage operations and subsequent silvicultural treatment application. In addition to being able to schedule operations faster, foresters will also be able to quickly identify regions where natural regeneration could be inadequate or excessive. Potential cost estimates of future interventions such as planting, aerial seeding, and pre-commercial thinning could be made. Foresters can also assess the current vulnerability of management units to fire and can identify regions at particular risk.

Aboveground carbon in Quebec forests: stock quantification at the provincial scale and assessment of temperature, precipitation and edaphic properties effects on the potential stand-level stocking.

Biological carbon sequestration by forest ecosystems plays an important role in the net balance of greenhouse gases, acting as a carbon sink for anthropogenic CO2 emissions. Nevertheless, relatively little is known about the abiotic environmental factors (including climate) that control carbon storage in temperate and boreal forests and consequently, about their potential response to climate changes. From a set of more than 94,000 forest inventory plots and a large set of spatial data on forest attributes interpreted from aerial photographs, we constructed a fine-resolution map (∼375 m) of the current carbon stock in aboveground live biomass in the 435,000 km2 of managed forests in Quebec, Canada. Our analysis resulted in an area-weighted average aboveground carbon stock for productive forestland of 37.6 Mg ha−1, which is lower than commonly reported values for similar environment. Models capable of predicting the influence of mean annual temperature, annual precipitation, and soil physical environment on maximum stand-level aboveground carbon stock (MSAC) were developed. These models were then used to project the future MSAC in response to climate change. Our results indicate that the MSAC was significantly related to both mean annual temperature and precipitation, or to the interaction of these variables, and suggest that Quebec’s managed forests MSAC may increase by 20% by 2041–2070 in response to climate change. Along with changes in climate, the natural disturbance regime and forest management practices will nevertheless largely drive future carbon stock at the landscape scale. Overall, our results allow accurate accounting of carbon stock in aboveground live tree biomass of Quebec’s forests, and provide a better understanding of possible feedbacks between climate change and carbon storage in temperate and boreal forests.

Modelling of hardwood forest in Quebec under dynamic disturbance regimes: a time‐inhomogeneous Markov chain approach

SummaryWe investigate the consequences of global warming scenarios in Quebec forests using an inhomogeneous Markov chain model. This allows us to unify predictions from climate change models and mechanistic models of forest disturbance and growth and allows predicting the potential impacts of climate change on Quebec forests. The model predicts changes in fire rate in Quebec hardwood forests as well as possible growth enhancements due to increasingand temperature.Our original method consists of three steps. (i) We estimate biomass transition matrices from forest inventories using the Bayesian method. (ii) We incorporate dynamic disturbance and forest growth scenarios, and (iii) we simulate transient dynamics and stationary states. This modelling approach allows for sensitivity analysis and quantitative assessment effects of variability of climate change scenarios.We have considered published climate change scenarios for Quebec and conducted simulations for the most extreme predictions (the smallest and largest predicted changes). None of the considered scenarios is able to counterbalance the currently observed trend of increasing biomass in the next 40 years. By the beginning of 2090, the extreme scenarios diverge within about ±5% mean biomass.Synthesis. In this work, we have developed an original modelling approach incorporating time‐ inhomogeneous effects within the Markov chain framework. We applied this approach to examine effects of climate change in Quebec's forests. The results demonstrate that the current trend of increase in forest biomass is robust with respect to a broad range of climate change scenarios. This study was not possible with previously employed homogeneous Markov chain models. The model can also be extended to include different harvesting methods and land‐use practices, enabling better long‐term management of Quebec's forest.

BorealFireSim: A GIS-based cellular automata model of wildfires for the boreal forest of Quebec in a climate change paradigm

Wildfires are the main cause of forest disturbance in the boreal forest of Canada. Climate change studies forecast important changes in fire cycles, such as increases in fire intensity, severity, and occurrence. The geographical information system (GIS) based cellular automata model, BorealFireSim, serves as a tool to identify future fire patterns in the boreal forest of Quebec, Canada. The model was calibrated using 1950–2010 climate data for the present baseline and forecasts of burning probability up to 2100 were calculated using two RCP scenarios of climate change. Results show that, with every scenario, the mean area burned will likely increase on a provincial scale, while some areas might expect decreases with a low emission scenario. Comparison with other models shows that areas forecasted to have an increase in fire likelihood, overlap with predicted areas of higher vegetation productivity. The results presented in this research aid identifying key areas for fire-dependent species in the near future.

Birch and conifer deadwood favour early establishment and shade tolerance in yellow birch juveniles growing in sugar maple dominated stands

Small-seeded tree species such as yellow birch (YB, Betula alleghaniensis Britt.) require deadwood or mineral soil for their establishment. Although much research has been done comparing YB germination on leaf litter vs. exposed mineral soil, less is known about deadwood as a seedbed and how different seedbeds affect YB early growth along light availability and size gradients. We examine how three common seedbeds (deadwood, moss cover on deadwood, and mineral soil) affected establishment and growth, biomass partitioning, and morphological traits of YB juveniles growing in the understory of temperate mixed deciduous and coniferous forests in southern Quebec. A total of 274 YB were sampled in four sugar maple (Acer saccharum Marsh.) dominated northern hardwood stands where selective cuts had been applied 6 and 15 years prior to sampling. Over 75% of the YB found on deadwood were on material of birch and conifer origin, although these species made less than 40% of the basal area. YB juveniles growing on deadwood showed traits that improve survival in shade such as reduced height growth for tall plants, higher efficiency in resource capture, and multilayered crowns. Our results demonstrate the importance of deadwood of birch and conifer origin in maintaining an abundant, natural, spatially well-distributed, and multistoried regeneration of YB.

Fine roots and ectomycorrhizal colonization in black spruce subjected to reductions in soil moisture

Growth and survival of boreal tree species depends on fungal symbionts, namely mycorrhizas. Owing to their rapid turnover, fine roots and their symbionts can be prompt and sensitive indicators of the effects of environmental changes on forest ecosystems. We investigated how a reduction in soil moisture influences the fine roots and ectomycorrhizas (ECM) of black spruce [Picea mariana (Mill.) BSP] after 3 years of rain exclusion in four mature stands of the boreal forest of Quebec, Canada. Rain was excluded with transparent plastic under-canopy covers installed during the growing seasons 2010–2012. Soil moisture was strongly affected by the treatment, with water content being reduced from 40% to 21% on average. As expected, the experimental trees showed a decrease in the proportion of vital root tips and ECM with respect to controls. The proportion of vital ECM was also globally reduced from 73.8% to 68.6%, but the effects of the treatment were only significant in two sites. The expected drier conditions due to current warming will likely influence the presence of mycorrhizas, with potential consequences on the root vitality of boreal tree species.