Wetlands and predation in boreal ecosystems play essential roles throughout the breeding season for bird assemblages. We found a positive association of beaver activity and a negative influence of American red squirrels (Tamiasciurus hudsonicus) on bird assemblages. We used a multispecies hierarchical model to investigate whether bird communities differ between two major wetland habitats in boreal Canada: beaver ponds and peatland ponds. In addition to including variables such as forest cover and latitude, we adopted a structural equation model approach to estimate the occupancy of American red squirrels and its potential influence on bird communities. Using automated recording stations deployed at 50 ponds, we detected 96 bird species in 2018 and 2019. Bird species were grouped into four taxonomic guilds according to their habitat successional requirements: early successional species, late successional species, generalists, and wetland species. Beaver ponds harbored higher species richness, a pattern driven primarily by early successional species. The occupancy of almost a quarter of the species was lower in the presence of red squirrels. Late successional species responded positively to the cover of forest surrounding the pond. Our results highlight the value of considering acoustic data of red squirrels to quantify habitat quality in boreal forests. We conclude that beaver activity shapes bird assemblages through modification of their habitat, and that some bird guilds are associated negatively with the presence of American red squirrels.

Les milieux humides et la prédation dans les écosystèmes boréaux jouent des rôles essentiels tout au long de la saison de reproduction pour les assemblages d’oiseaux. Nous avons trouvé une association positive entre les assemblages d’oiseaux et l’activité des castors, mais une association négative entre les assemblages d’oiseaux et la présence des écureuils roux d’Amérique (Tamiasciurus hudsonicus). Nous avons utilisé un modèle hiérarchique multi-espèces pour étudier si les communautés d’oiseaux diffèrent entre deux importants types de milieux humides du Canada boréal: les étangs de castors et les étangs de tourbières. Au-delà de l’inclusion de variables telles que le couvert forestier et la latitude, nous avons adopté une approche de modèle d’équation structurelle pour estimer l’occupation de l’écureuil roux d’Amérique et son influence potentielle sur les communautés d’oiseaux. En utilisant des stations d’enregistrement automatisées déployées sur 50 étangs, nous avons détecté 96 espèces d’oiseaux en 2018 et 2019. Les espèces des oiseaux ont été regroupées en quatre guildes taxonomiques en fonction de leurs exigences en matière de succession de l’habitat: espèces de début de succession, espèces de fin de succession, généralistes et espèces des milieux humides. Les étangs de castors abritaient une plus grande richesse d’espèces et une composition d’espèces différente de celle des étangs de tourbières, une tendance principalement liée aux espèces de début de succession. L’occupation de près d’un quart des espèces était plus faible en présence de l’écureuil roux. Les espèces de fin de succession ont répondu positivement à la couverture de la forêt entourant l’étang. Nos résultats soulignent l’intérêt de considérer les données acoustiques de l’écureuil roux pour quantifier la qualité de l’habitat dans les forêts boréales. Nous concluons que l’activité des castors façonne les assemblages d’oiseaux en modifiant leur habitat et que certaines guildes d’oiseaux sont associées négativement à la présence de l’écureuil roux d’Amérique.

Interspecific interactions can mediate site occupancy of sympatric species and can be a key factor in habitat use patterns. American martens (Martes americana) and Fishers (Pekania pennanti) are two sympatric mesocarnivores in eastern North American forests. Due to their larger size, fishers have a competitive advantage over martens. We investigated site occupancy of martens and fishers in temperate deciduous forests of Québec, an environment modified by forest management and climate change. We formulated hypotheses on the spatial distribution of the studied species based on the knowledge of local trappers and on the scientific literature regarding forest cover composition, habitat fragmentation, and competitive relationships. We used a network of 49 camera traps monitored over two fall seasons to document site occupancy by both species. We used two-species site occupancy models to assess habitat use and the influence of fishers on martens at spatial grains of different sizes. None of the habitat variables that we considered explained site occupancy by fishers. Availability of dense old coniferous stands explained the spatial distribution of martens both at the home range grain size and at the landscape grain size. We identified the characteristics of habitat hotspots based on the knowledge of trappers, which highlighted the importance of stand composition, height, age, and canopy closure. The characteristics of habitat hotspots for martens in temperate deciduous forests refine the habitat suitability model for American martens that was originally developed for boreal forests of Québec.

Wetlands are essential for many animal and plant species. However, many of these ecosystems are being degraded. Wetland degradation affects the habitat of certain groups of species such as waterfowl, which use these environments at different stages of their life cycle. In this study, we assessed the quality of man-made wetlands, i.e., mine tailing ponds, in comparison to beaver ponds, which are natural wetlands used by waterfowl. We conducted repeated surveys of breeding waterfowl species present on 12 mining ponds and 38 beaver ponds in boreal western Quebec, Canada. We also conducted brood surveys and considered environmental variables at the sites that could affect their occupancy. Conditions at the mining ponds appear to be as favorable for the establishment of breeding waterfowl as those observed in beaver ponds. Using site occupancy models, we found that five out of the six species studied were as likely to occupy and breed in mining ponds as in beaver ponds: Mallard (Anas platyrhynchos), Ring-necked Duck (Aythya collaris), American Wigeon (Mareca americana), Green-winged Teal (Anas crecca), and Hooded Merganser (Lophodytes cucullatus). Both adults and broods of Common Goldeneye (Bucephala clangula) were more likely to use mining ponds than beaver ponds, but we did not find a direct relationship between goldeneye occupancy and environmental variables at our sites. Overall, the results of our study suggest that mining ponds have the potential to be managed for waterfowl and used by this group during the breeding season. However, further studies are required to assess the long-term effects of mining ponds on wildlife, particularly regarding contaminants such as heavy metals likely present at such sites.

Ecosystem-based management aims to preserve old-growth forest attributes using techniques mimicking natural disturbances. One such technique is irregular shelterwood logging, but its impacts on forest floor organisms are poorly known. Our objective was to quantify the effects of three different treatments of irregular shelterwood on population structure and the body condition of the eastern red-backed salamander (Plethodon cinereus) 5–6 years following harvesting. A total of 64 sites in western Québec were sampled using artificial refugia and quadrat searches. Large salamanders (>32 mm) were more abundant in the gap treatment than in strip, uniform, or control treatments. Small salamanders (≤32 mm) followed the same pattern, although the differences were marginal. For a given treatment, small salamanders were as abundant as large salamanders. Salamander body condition differed between the 2 years of sampling but did not differ among treatments, regardless of salamander size. We conclude that environmental conditions in irregular shelterwood treatments 5–6 years following harvesting support populations of small vertebrates on the forest floor.

Citizen science (CS) currently refers to the participation of non-scientist volunteers in any discipline of conventional scientific research. Over the last two decades, nature-based CS has flourished due to innovative technology, novel devices, and widespread digital platforms used to collect and classify species occurrence data. For scientists, CS offers a low-cost approach of collecting species occurrence information at large spatial scales that otherwise would be prohibitively expensive. We examined the trends and gaps linked to the use of CS as a source of data for species distribution models (SDMs), in order to propose guidelines and highlight solutions. We conducted a quantitative literature review of 207 peer-reviewed articles to measure how the representation of different taxa, regions, and data types have changed in SDM publications since the 2010s. Our review shows that the number of papers using CS for SDMs has increased at approximately double the rate of the overall number of SDM papers. However, disparities in taxonomic and geographic coverage remain in studies using CS. Western Europe and North America were the regions with the most coverage (73%). Papers on birds (49%) and mammals (19.3%) outnumbered other taxa. Among invertebrates, flying insects including Lepidoptera, Odonata and Hymenoptera received the most attention. Discrepancies between research interest and availability of data were as especially important for amphibians, reptiles and fishes. Compared to studies on animal taxa, papers on plants using CS data remain rare. Although the aims and scope of papers are diverse, species conservation remained the central theme of SDM using CS data. We present examples of the use of CS and highlight recommendations to motivate further research, such as combining multiple data sources and promoting local and traditional knowledge. We hope our findings will strengthen citizen-researchers partnerships to better inform SDMs, especially for less-studied taxa and regions. Researchers stand to benefit from the large quantity of data available from CS sources to improve global predictions of species distributions.

The boreal forest is considered to be a low productivity forest due to its cold climate and poorly drained soils promoting paludification. These factors create conditions favouring accumulation of undecomposed organic matter, which causes declining growth rates of forest stands, ultimately converting mature stands into peatlands. Under these conditions, careful logging is conducted during winter, which minimizes soil disturbance in northwestern Quebec boreal forest. This results in water table rise, increased light availability and paludification. Our main objective was to evaluate the short-term effect of partial harvesting as an alternative method to careful logging in winter to mitigate water table rise on black spruce (Picea mariana [Mill.] B.S.P.) stands. We quantified tree stem diameter variation and daily variation in water table depth in mature spruce stands before and after partial harvest (basal area reduction of 40%) and girdling (same basal area reduction with delayed mortality) during 2016 and 2017 growing seasons. Water table variation prior to and following silvicultural treatments did not differ one year after treatment. Daily stem diameter variation in black spruce did not differ between treatments and control. Furthermore, temperature exerted a positive effect on variation in water table and on stem diameter. These results suggest that partial harvest could be more effective than clearcutting to mitigate negative effects of a high water table while limiting paludification.

Since the mid?twentieth century, fisher populations (Pekania pennanti) increased in several eastern jurisdictions of North America, particularly in the northern part of the species’ range. Changes in fisher distribution have led to increased overlap with the southern portion of the range of American marten (Martes americana), whose populations may be locally declining. This overlap occurs particularly in habitats undergoing natural and anthropogenic modification. The objective of our study was to determine the respective effects of habitat changes and climatic conditions on fisher and marten populations in Quebec, Canada, based on trapper knowledge. We analyzed annual fisher and marten harvest (number of pelts sold/100?km2) between the 1984–1985 and 2014–2015 trapping seasons using linear mixed models. Fisher harvest increased with the increased abundance of mixed forests >12?m tall, resulting from decades of forest harvesting. Fisher harvest decreased with increasing spring rains, which can affect survival when rearing young. Marten harvest decreased with increasing winter rains, which lower thermoregulation capacity and hamper movements by creating an ice crust on the snowpack, reducing access to subnivean areas. Decline in marten harvest during the 30?year study period coincided with an increase in fisher harvest, suggesting possible interspecific competition. Results highlight that managers should strive to maintain mixedwood stands taller than 12?m to maintain high quality habitat for fishers. Our study confirms the importance of working with trappers to assess furbearing population trends in response to habitat changes and climatic conditions. © 2019 The Wildlife Society.

Sudden changes in habitat quality during the breeding season may mislead individuals when selecting their nesting site and result in population declines. In such cases, even semi-natural and extensive agricultural lands may become ecological traps. We examined how the availability of six open habitat types (i.e. agricultural lands, open forests, alder swamps, young forests, regeneration, and wetlands) could be affecting the habitat selection process, as well as the hatching and fledging successes of American kestrels (Falco sparverius). We hypothesized that natural open habitats are less disturbed by anthropogenic activities than extensive agricultural lands and thus represent higher quality habitats for kestrels. We also considered weather conditions during the breeding season as possible factors affecting hatching and fledging successes. We monitored 200 pairs of American kestrels during 11 years (2006–2016) within a network of 155 nest box stations and we characterized landscape composition metrics within 800?m radii from each nest box. We used generalized linear mixed models and multimodel inference to quantify the effects of landscape composition metrics on the probabilities of using nesting site, hatching success, and fledging success of American kestrels. We also tested the effects of weather conditions and clutch initiation date on hatching and fledging successes of kestrels. We found that the probability of nesting site use increased with the amount of agricultural lands. Hatching success decreased with the amount of agricultural lands, whereas the fledging success of kestrels did not vary with the amount of agricultural lands. Both the probabilities of hatching and of fledging increased with the area of young forests. There was no evidence of a weather effect on hatching success. However, the probability of fledging success increased with mean temperature during the raising period of nestlings. Although fledging success alone does not determine fitness or population dynamics, our results suggest that kestrels nesting in this region at the northern limit of their range may be caught in an ecological trap by extensive agricultural lands. Indeed, kestrels were attracted by meadows when selecting nesting habitat, but the hatching and early nestling periods coincided with hay harvesting which could reduce the hunting success of breeding adults and suddenly alter food availability. Although the causes of recent kestrel declines remain unclear, our results suggest that harvesting practices, even those related to extensive perennial agriculture, may have a negative effect on the breeding success of the species compared to areas dominated by young forests.

In temperate and boreal mixedwood forests of eastern North America, partial disturbances such as insect outbreaks and gap dynamics result in the development of irregular forest structures. From a forest ecosystem management perspective, management of these forests should therefore include silvicultural regimes that incorporate medium- to high-retention harvesting. We present 12-year results of a field experiment undertaken to evaluate the effects of variable retention harvesting on stand structure, recruitment, and mortality. Treatments were gap harvesting (GAP), diameter-limit harvesting (DL), careful logging (CL), and careful logging followed by scarification (CL + SCAR), and an unharvested control. Although post-harvest basal area in the GAP treatment was significantly lower than that of controls, it maintained a diameter distribution profile and densities of balsam fir regeneration similar to those of pre-harvest conditions. Lower retention treatments (DL, CL, and CL + SCAR) tended to favor regeneration of pioneer, shade-intolerant species. Except for black spruce (for which mortality was highest in DL), stem mortality was similar among harvesting treatments. From an ecosystem management perspective, this study suggests that gap harvesting can maintain, in the short term, forest stand composition and structure similar to unharvested forests, and could be used where management objectives include the maintenance of late successional forest conditions.

Litter decomposition is a major driver of carbon (C) and nitrogen (N) cycles in forest ecosystems and has major implications for C sequestration and nutrient availability. However, empirical information regarding long-term decomposition rates of foliage and wood remains rare. In this study, we assessed long-term C and N dynamics (12–13 years) during decomposition of foliage and wood for three boreal tree species, under a range of harvesting intensities and slash treatments. We used model selection based on the second-order Akaike’s Information Criterion to determine which decomposition model had the most support. The double-exponential model provided a good fit to C mass loss for foliage of trembling aspen, white spruce, and balsam fir, as well as aspen wood. These litters underwent a rapid initial phase of leaching and mineralisation, followed by a slow decomposition. In contrast, for spruce and fir wood, the single-exponential model had the most support. The long-term average decay rate of wood was faster than that of foliage for aspen, but not of conifers. However, we found no evidence that fir and spruce wood decomposed at slower rates than the recalcitrant fraction of their foliage. The critical C:N ratios, at which net N mineralisation began, were higher for wood than for foliage. Long-term decay rates following clear-cutting were either similar or faster than those observed in control stands, depending on litter material, tree species, and slash treatment. The critical C:N ratios were reached later and decreased for all conifer litters following stem-only clear-cutting, indicating increased N retention in harvested sites with high slash loads. Partial harvesting had weak effects on C and N dynamics of decaying litters. A comprehensive understanding of the long-term patterns and controls of C and N dynamics following forest disturbance would improve our ability to forecast the implications of forest harvesting for C sequestration and nutrient availability. © 2017 Springer Science+Business Media New York

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. © 2017, Society of Wetland Scientists.

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 50 m to 5 km. 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.

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 10 min 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.

Bryophytes and pteridophytes are important contributors to ecosystem services in boreal regions. Abiotic agents are considered their main dispersers, but recent studies suggest that biotic agents including invertebrates, birds and large mammals might also be efficient dispersal agents. Dispersal of cryptogams by ground-dwelling small mammals is often assumed to occur, but has yet to be demonstrated. In this study, we present the first evidence of boreal cryptogam species being dispersed by ground-dwelling small mammals. In 2013 and 2014, we recorded bryophyte cover and fern presence in 35 sites in black spruce forest. We also collected diaspores by brushing the fur of 99 ground-dwelling small mammals live-trapped in the same sites. Diaspores were then germinated on nutrient agar for six months. Viable diaspores of five bryophyte species and one fern species were successfully grown. No association was found between the cryptogam community sampled on site and the diaspore community grown on artificial substrate. Unlike abiotic agents that randomly disperse cryptogams, small mammals are more likely to transport diaspores to suitable substrates where microhabitat requirements for germination are met. Our results highlight the need to consider a broad spectrum of dispersal agents when focusing on the community dynamics of cryptogams.

Les cryptogames (bryophytes et ptéridophytes) représentent une composante fondamentale des régions boréales, et leur dispersion à moyenne et longue distances dépend principalement d’agents abiotiques. Des études récentes suggèrent pourtant l’importance d’agents biotiques tels que les invertébrés, les oiseaux et les grands mammifères comme vecteur de dispersion. La dispersion des cryptogames par les micromammifères est régulièrement admise mais n’a encore jamais été formellement examinée. Dans cette étude, nous présentons la première preuve tangible du transport des cryptogames boréaux par des micromammifères. Au cours des étés 2013 et 2014, nous avons estimé le couvert des bryophytes et la présence des fougères (communauté in situ) dans 35 sites en pessière noire à mousses. Nous avons brossé le pelage de 99 micromammifères de cinq espèces différentes capturés vivants dans les mêmes sites. Le matériel végétal collecté a été mis à germer durant six mois sur un gel nutritif d’agar. Nous avons observé la germination de cinq espèces de bryophytes et d’une espèce de fougère. Nous n’avons trouvé aucune association entre la communauté de cryptogames in situ présente dans les sites et la communauté germée sur un substrat artificiel. Contrairement à la dispersion aléatoire par des agents abiotiques, la dispersion par les micromammifères est plus susceptible de transporter les diaspores vers des substrats propices à leur germination. Nos résultats soulignent l’importance de considérer une vaste gamme d’agents de dispersion lors de l’étude des dynamiques des communautés de cryptogames.

Small rodents play a key role in forest ecosystems as common prey, but also as prevalent seed consumers and dispersers. Hence, there is a great interest in disentangling the factors involved in their population dynamics. We conducted an intensive 2-year field study to test the relative role of seasonality in seed abundance, shrub cover and wild boar interference on the population dynamics of wood mice, Apodemus sylvaticus, in a Mediterranean oak forest. Wood mice demographic parameters varied strongly with the seasonal variations in acorn availability on the ground. Mice survival and abundance dropped drastically during summer, the period of acorn scarcity, but rose again in autumn when acorn-fall began. Specifically, female abundance was associated with the temporal changes in acorn availability on the ground, but were randomly distributed in space whereas males showed a spatially aggregated pattern during the acorn-abundant seasons (autumn-winter). In contrast to studies conducted in sparse oak forests in drier environments, spatial variability in shrub cover and wild boar foraging activity did not affect directly the population dynamics of wood mice. This could be due to the presence of an abundant shrub layer and a closed canopy in our forest that enhance environmental conditions and provides shelter against predators and ungulates. Our study highlights that the relative importance of environmental factors and intraguild competition on rodent dynamics may be highly context-dependent, varying greatly among different sites. We suggest that the relationships between acorn dispersers and oaks are more reciprocal than previously considered.

Food insecurity is a growing concern for indigenous communities worldwide. While the risk of heavy metal contamination associated to wild food consumption has been extensively studied in the Arctic, data are scarce for the Boreal zone. This study addressed the concerns over possible heavy metal exposure through consumption of traditional food in four Anishnaabeg communities living in the Eastern North American boreal forest. Liver and meat samples were obtained from 196 snowshoe hares (Lepus americanus) trapped during winter 2012 across the traditional lands of the participating communities and within 56–156 km of a copper smelter. Interviews were conducted with 78 household heads to assess traditional food habits, focusing on snowshoe hare consumption. Concentrations in most meat and liver samples were below the detection limit for As, Co, Cr, Ni and Pb. Very few meat samples had detectable Cd and Hg concentrations, but liver samples had mean dry weight concentrations of 3.79 mg/kg and 0.15 mg/kg respectively. Distance and orientation from the smelter did not explain the variability between samples, but percent deciduous and mixed forest cover had a marginal negative effect on liver Cd, Cu and Zn concentrations. The estimated exposition risk from snowshoe hare consumption was low, although heavy consumers could slightly exceed recommended Hg doses. In accordance with the holistic perspective commonly adopted by indigenous people, the nutritional and sociocultural importance of traditional food must be considered in risk assessment. Traditional food plays a significant role in reducing and preventing serious health issues disproportionately affecting First Nations, such as obesity, diabetes, and cardiovascular diseases.

Mixed species stands present a number of opportunities and challenges to forest managers. Boreal mixedwood stands in eastern Canada are often characterized by a canopy of shade intolerant aspen (Populus tremuloides) with more shade tolerant conifers in the sub-canopy layers. Because the aspen and conifers often attain optimal merchantable sizes at different moments, there is an interest in developing silvicultural practices toremoval of aspen and favour accelerated growth of residual conifers. We tested three partial harvesting treatments in mixed aspen - white spruce (Picea glauca) stands in which different proportions of aspen (0, 50, 65 and 100% basal area) were removed. Ten years after treatments, 72 spruce stems destructively sampled for stem analysis. Using linear mixed effect models, we analyzed growth as a function of treatment intensity, time since treatment, social status, pre-treatment growth rate, and neighbourhood competition. Relative to control stands, radial and volume growth responses were detected only in the extreme treatment of 100% aspen removal. In relative terms, suppressed trees showed the greatest magnitude of cumulative growth increase. Growth response was proportional to pre-treatment growth rate and, among neighbouring trees, only coniferous neighbours had a negative effect on white spruce growth.

Natural forests likely will be unable to fulfill society's needs sustainably for wood fiber in the near future. In an attempt to meet increasing demands while protecting intact forests, producers have increasingly considered alternative sources of timber, such as intensively managed plantations. In regions that are economically dependent on forest harvesting, abandoned farm fields are often targeted for conversion to intensive coniferous plantations. These sites are generally in an early successional stage that is dominated by deciduous stands, which provide an important habitat type for several game species, including ruffed grouse (Bonasa umbellus). Therefore, conversion could represent a loss of habitat for this species and several others that are associated with early successional deciduous stages. We conducted grouse drumming surveys in northwestern Quebec, Canada, to evaluate the effects of transforming old fields into conifer plantations on ruffed grouse by comparing densities between two habitat types: abandoned farm fields (n = 22) and old fields converted to conifer plantations (n = 19). To correct any audibility bias between habitat types, we located all drumming males that were heard at each site. We then analyzed the number of individuals that were detected in the sites with repeated count models. Our results show that overall drumming males avoided plantations. Overhead cover increased drumming male densities in both habitat types wile lateral cover increased drumming grouse densities only in plantations. The density of deciduous stems and fruit bearing stems also had a tendency to increase drumming male abundance but their effects were marginal. Most ruffed grouse in abandoned farm fields used piles of woody debris on the ground as drumming structures rather than large logs or rock outcrops. Our results suggest that plantations do not have the vegetative cover and quantity of food stems necessary to support ruffed grouse densities during the drumming season and that conversion of abandoned farm fields to coniferous plantations may exert negative cascading effects for reproduction and population growth.

Irregular shelterwood cutting has been recently prescribed to improve the regeneration of semi-tolerant species such as yellow birch (Betula alleghaniensis B.), while also maintaining the complexity of natural mixed forests. However, its effects on forest dynamics are poorly known. In this study, we document the short-term effects of three irregular shelterwood cutting patterns on the establishment and composition of regeneration as well as on its use by snowshoe hare (Lepus americanus E.). Specifically, we compared uniform, gap, and strip cutting patterns with soil preparation, relative to uncut controls. We counted seedlings, browse, and hare pellets, and measured habitat characteristics after two growing seasons in micro-plots delimited in each of the shelterwood cutting patterns. The mixture of soil and humus resulting from scarification promoted yellow birch establishment. Yellow birch seedlings in gaps were more abundant than in controls, but their abundance was comparable to other irregular shelterwood patterns. All irregular shelterwood patterns promoted competition mainly by pin cherry (Prunus pensylvanica L.f.), beaked hazel (Corylus cornuta M.), and mountain maple (Acer spicatum Lam.). Snowshoe hare browse on yellow birch was low for all irregular shelterwood patterns. Moose browse pressure was higher than that from hare. We found no short-term impact of the snowshoe hare on yellow birch seedling establishment and survival. Snowshoe hare pellet counts suggested a preference for gaps. This result could be explained by increased food and protective cover from higher seedling and shrub densities in gaps than in other treatments. In the short-term, up to three years post-treatment, irregular shelterwood cutting helps to promote yellow birch regeneration, a semi-tolerant species, while maintaining habitat for snowshoe hare.

Differences in feeding ecology are now recognized as major determinants of inter-individual variations in contaminant profiles of free-ranging animals, but exceedingly little attention has been devoted to the role of habitat use. Marked inter-individual variations and high levels of polybrominated diphenyl ethers (PBDEs) (e.g., DecaBDE) have previously been documented in ring-billed gulls (Larus delawarensis) breeding in a colony near Montreal (QC, Canada). However, the environmental sources of these compounds, and thus the reasons causing these large inter-individual variations remain unidentified. In the present study, we used GPS-based telemetry (±5 to 10 m precision) to track ring-billed gulls from this colony to reconstruct their movements at the landscape level. We related habitat use of individual gulls (n=76) to plasma concentrations (ng/g ww) and relative contributions (percentages) to ?38PBDEs of major congeners in the internationally restricted PentaBDE and current-use DecaBDE mixtures. Male gulls that visited waste management facilities (WMFs; i.e., landfills, wastewater treatment plants and related facilities; 25% of all GPS-tracked males) exhibited greater DecaBDE (concentrations and percentages) and lower PentaBDE (percentages) relative to those that did not. In contrast, no such relationships were found in females. Moreover, in males, DecaBDE (concentrations and percentages) increased with percentages of time spent in WMFs (i.e., ~5% of total foraging time), while PentaBDE (percentages) decreased. No relationships between percentages of time spent in other habitats (i.e., urban areas, agriculture fields, and St. Lawrence River) were found in either sex. These findings suggest that animals breeding in the vicinity of WMFs as well as mobile species that only use these sites for short stopovers to forage, could be at risk of enhanced DecaBDE exposure.

Estimations of transition age (TA) and juvenile wood proportion (JWP) are important for wood industries due to their impact on end-product quality. However, the relationships between analytical determination of TA based on tracheid length (TL) and recognized thresholds for adequate end products have not yet been established. In this study, we used three different statistical models to estimate TA in white spruce (Picea glauca (Moench) Voss) based on TL radial variation. We compared the results with technological maturity. A two-millimeter threshold, previously suggested for good paper tear strength, was used. Tracheid length increased from pith to bark and from breast height to upper height. Juvenile wood (JW) was conical with the three models. At breast height, TA ranged from 11 to 27 years and JWP ranged from 15.3% to 47.5% across the three models. The linear mixed model produced more conservative estimates than the maximum-quadratic-linear (M_Q_L) model. Both the linear mixed model and the M_Q_L model produced more conservative TA estimates than the piecewise model. TA estimates by the MIXED model, and to a lesser extent by the M_Q_L model, were equivalent to those for real mature wood, whereas TA estimates by the piecewise model were considerably lower, falling into the transition wood area.

Le Québec offre un potentiel considérable pour le développement de l’industrie éolienne. Cette industrie peut être à l’origine de mortalités chez les rapaces et pourrait affecter certaines espèces vulnérables comme le faucon pèlerin. De 2008 à 2010, nous avons comparé l’utilisation de 5 types de milieux par 10 femelles nicheuses de faucon pèlerin dans le Québec méridional, afin de déterminer ceux à favoriser pour l’implantation de parcs éoliens. Les milieux les moins utilisés par les femelles étaient ceux considérés comme diminuant les risques de collision avec les éoliennes. Après l’envol des fauconneaux, les femelles parcouraient de plus grandes distances que lorsque les fauconneaux étaient confinés au nid. À cette période, 90 % des localisations télémétriques dans les cultures de maïs et de soya ont été enregistrées à l’intérieur d’un rayon de 8,3 km d’un nid, comparativement à un rayon de 15,9 km dans les autres cultures. Aussi, les femelles avaient moins de chances d’utiliser les cultures de maïs et de soya que les autres cultures et les milieux non propices pour la chasse. Nos résultats permettent de faire des recommandations quant à la localisation de projets éoliens, en termes de milieux à favoriser et de distances à respecter, afin de minimiser les risques de collision du faucon pèlerin.

With the increase in abandoned agricultural lands in Western Europe, knowledge on the successional pathways of newly developing forests becomes urgent. We evaluated the effect of time, soil type and dominant species type (shade tolerant or intolerant) on the development during succession of three stand attributes: above-ground biomass, stand height (HT) and stem density (SD). Additionally, we compared above-ground biomass (AGB) in natural and planted forests, using ten chronosequences (8 from the literature and 2 from this study). Both AGB and HT increased over time, whereas SD decreased. HT, SD and AGB differed among species types. For example, birch had greater HT than alder, willow and ash at a similar age and had higher SD than pine and oak at a similar age. However, birch showed lower AGB than pine. HT and AGB differed among soil types. They were higher in rich soil than in poor soils. Comparative analysis between chronosequences showed an effect of the regeneration method (natural regeneration vs plantation) on above-ground biomass. Planted sites had higher AGB than natural regeneration. Time, soil type, species and regeneration method influenced the mechanism of stand responses during secondary succession. These characteristics could be used to clarify the heterogeneity and potential productivity of such spontaneously growing temperate forest ecosystems.

Dynamic N-mixture models have been recently developed to estimate demographic parameters of unmarked individuals while accounting for imperfect detection. We propose an application of the Dail and Madsen (: Biometrics, 67, 577–587) dynamic N-mixture model in a manipulative experiment using a before-after control-impact design (BACI). Specifically, we tested the hypothesis of cavity limitation of a cavity specialist species, the northern flying squirrel, using nest box supplementation on half of 56 trapping sites. Our main purpose was to evaluate the impact of an increase in cavity availability on flying squirrel population dynamics in deciduous stands in northwestern Québec with the dynamic N-mixture model. We compared abundance estimates from this recent approach with those from classic capture–mark–recapture models and generalized linear models. We compared apparent survival estimates with those from Cormack–Jolly–Seber (CJS) models. Average recruitment rate was 6 individuals per site after 4 years. Nevertheless, we found no effect of cavity supplementation on apparent survival and recruitment rates of flying squirrels. Contrary to our expectations, initial abundance was not affected by conifer basal area (food availability) and was negatively affected by snag basal area (cavity availability). Northern flying squirrel population dynamics are not influenced by cavity availability at our deciduous sites. Consequently, we suggest that this species should not be considered an indicator of old forest attributes in our study area, especially in view of apparent wide population fluctuations across years. Abundance estimates from N-mixture models were similar to those from capture–mark–recapture models, although the latter had greater precision. Generalized linear mixed models produced lower abundance estimates, but revealed the same relationship between abundance and snag basal area. Apparent survival estimates from N-mixture models were higher and less precise than those from CJS models. However, N-mixture models can be particularly useful to evaluate management effects on animal populations, especially for species that are difficult to detect in situations where individuals cannot be uniquely identified. They also allow investigating the effects of covariates at the site level, when low recapture rates would require restricting classic CMR analyses to a subset of sites with the most captures.

The scientific community is increasingly aware that many amphibian and reptile species have experienced dramatic decreases in abundance and distribution, with at least 43% of amphibian species exhibiting population declines and 19% of all reptile species threatened with extinction since 2000. Species suffer from a suite of threats including habitat destruction, alteration and fragmentation, introduced species, over-exploitation, climate change, UV-B radiation, chemical contaminants, diseases and the synergisms among them. These worldwide threats are also present in northern landscapes and in Canada in particular where 20 amphibian and 37 reptile species are listed as at-risk by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). In fact, with more than 80° in longitude and 40° in latitude, Canada presents both a diversity of northern ecosystems and a range of threats to its herpetofauna at least equal to other countries. The physical scale of Canada, its varied climate, its economic realities, and the legislative differences among levels of government and their respective mandates have long challenged traditional approaches to conservation. However, science and stewardship are leading forces in the conservation of emblematic species at risk in Canada and can serve to inform best practices elsewhere. Recent advances in data analysis and management have transformed our understanding of populations in northern landscapes. Canadian amphibians and reptiles, most of which are cold-adapted species at the northern edge of their distribution, can serve as case studies to improve modeling of population dynamics, create cogent, science-based policies, and prevent further declines of these taxa.

We explore the possibility of predicting wood fiber attributes across Newfoundland for two commercial species: black spruce (Picea mariana (Mill.) B.S.P.) and balsam fir (Abies balsamea (L.) Mill.). Estimates of key fiber attributes (including wood density, coarseness, fiber length, and modulus of elasticity) were derived from measurements of wood cores taken from sample plots representing a wide structural gradient of forest stands. Candidate models for predicting fiber attributes at plot and landscape scales were developed using an information-theoretical approach and compared based on Akaike’s information criterion. The most influential variables were stand age and the presence of precommercial thinning. Other significant explanatory variables included those that characterize vegetation structure (mean diameter at breast height, dominant height), climate (annual precipitation, mean temperature of the growing season), and geography (elevation, latitude) depending on the species and fiber attribute being modeled. At the plot level, model inference gave root mean square errors of 5.3–11.9% for all attributes. At the landscape level, prediction errors were similar (5.4–12.1%), with the added benefit of being suitable for mapping fiber attributes across the landscape. The results obtained demonstrate the potential for predicting and mapping fiber attributes over a large region of boreal forest in Newfoundland, Canada.

Invasive plants can substantially modify wetland structure and animal distribution patterns. In eastern North America, a Eurasian haplotype of the common reed (Phragmites australis, haplotype M) is invading wetlands. We studied the invasion of common reed in freshwater wetlands of an urbanized landscape and its effects on the distribution of amphibians at different life stages. Specifically, we hypothesized that the probability of reed invasion would be greatest in wetlands near anthropic disturbances. We predicted that the probability of desiccation at sampling stations increases with reed cover. Furthermore, we expected that wetlands invaded by common reed would have lower amphibian abundances, apparent survival, and rates of recruitment. We conducted trapping surveys to compare anuran assemblages of tadpoles, juveniles, and adults in 50 wetlands during two field seasons. The probability of reed invasion in wetlands increased with the cover of heavily-managed areas within 1,000 m and the distance to the nearest forest, but decreased with the length of roads within 1,000 m. The probability of station desiccation increased with reed cover. We found no evidence of a negative effect of reed presence on anuran population parameters, at any life stage. Landscape variables, such as the percent cover of forest or heavily-managed areas within a given radius from each wetland, influenced the abundance or the apparent survival of juvenile frogs and the abundance of ranid tadpoles. Our results show that amphibian patterns depend more strongly on the structure of the landscape surrounding wetlands than on exotic reed invasion in wetlands. © 2013 Springer Science+Business Media Dordrecht.

Synchronous production of large seed crops, or mast years (MYs), is a common feature of many Fagus species, which is closely linked to the dynamics of forest ecosystems, including regeneration of canopy trees and changes in animal population densities. To better understand its climatic controls and check for the presence of long-term temporal trends in MY frequencies, we reconstructed MY record of the European beech (Fagus sylvatica L.) for the southern Swedish province of Halland over 1753–2006. We used superimposed epoch analysis (SEA) to relate MY (a) to summer temperature fields over the European subcontinent and (b) to the patterns of 500 mb geopotential heights over the 35–75°N. For the MY reconstruction, we used newly developed regional beech ring-width chronology (1753–2006), an available summer temperature reconstruction, and a discontinuous historical MY record. A Monte Carlo experiment allowed identification of the thresholds in both growth and summer temperature anomalies, indicative of historical MYs, which were verified by dividing data into temporally independent calibration and verification sub-periods.

MYs were strongly associated with both the 500 mb height anomalies and average summer temperatures during two years preceding a MY: a mast year (t) followed a cold summer two years (t-2) prior to the mast year and a warm summer one year prior (t-1) to the mast year. During t-2 years, the geographical pattern of 500 mb height anomalies exhibited a strong height depression in the region centered in the Northern Sea and extending toward eastern North America and statistically significant (p < 0.05) temperature anomalies covering predominantly southern Scandinavia (area below 60 N) and British Isles. A year immediately preceding a mast year (t-1) was characterized by a strong regional high pressure anomaly centered in southern Scandinavia with significant temperature anomalies extended mostly over southern Scandinavia and Germany.

The long-term mean MY return interval was 6.3 years, with 50 and 90% probabilities of MY occurrence corresponding to 6 and 15 years, respectively. Periods with intervals significantly shorter than the long-term mean were observed around 1820–1860 and 1990–2006 (means – 3.9 and 3.2 years, respectively). However, the difference in return intervals between two sub-periods themselves was not significant.

Geographically large and temporally rapid changes in atmospheric circulation among years, responsible for summer temperature conditions in the Northern Europe, are likely primary environmental drivers of masting phenomenon. However, decadal and centurial variability in MY intervals is difficult to relate directly to temperature variability, suggesting the presence of conditions “canceling” would-be MYs. Long-term MY reconstruction demonstrates high variability of reproductive behavior in European beech and indicates that a period with shorter MY intervals at the end of 20th may be not unique in a multi-century perspective.

The abundance of eastern white pine (Pinus strobus L.) has been significantly reduced across its distribution range over the past few centuries. The species’ regeneration dynamics is well documented in the centre of its range, but is poorly understood at the northern limit of continuous distribution. To address this knowledge gap, we quantified natural white pine regeneration in unmanaged mature stands, identified the most important variables influencing it, and evaluated the impact of damaging agents, namely white pine blister rust (Cronartium ribicola J.C. Fisch.), white pine weevil (Pissodes strobi Peck), and herbivory. We also quantified the influence of remnant stands and residual trees on the spatial distribution of regeneration in logged sites. The results reveal continuous but low recruitment in mature stands. The basal area of balsam fir (Abies balsamea (L.) Miller) had a strong negative effect on white pine regeneration. Regeneration was more abundant than expected on moister substrates, including moss, decaying wood and organic matter. White pine regeneration was noted in recently logged areas, where distance from remnant stands had a significant effect on the abundance of white pine regeneration. The northern limit of continuous distribution holds potential for white pine restoration, for example by preserving remnant white pine stands that can provide seed sources for natural regeneration in a shelterwood cut system, or in adjacent clearcut areas. This study illustrates that different management strategies should be used near northern range limits, where effects of site conditions and disturbance agents are different than in the center of a species’ range.

Exotic species contribute to aquatic habitat degradation. In the context of declining amphibian populations, the introduction of alien species has been the subject of numerous studies but few have been dedicated to exotic plants. We hypothesized that the establishment of the exotic common reed (Phragmites australis) in North America would lengthen larval anuran development and decrease the survival rate by modifying habitat structure, changing water characteristics, and decreasing food availability. We tested these hypotheses by studying the larval development of the wood frog (Lithobates sylvaticus) during an experiment in field enclosures. Within each enclosure, we created habitats with three different reed densities (zero, medium, and high). Tadpoles were placed in the enclosures and were followed for six weeks up to metamorphosis, during which we monitored water quality and phytoplankton composition. At the end of the experiment, tadpoles at medium and high reed densities developed more slowly than under the control. However, tadpole survival was similar across treatments. For a given developmental stage, total body length did not differ among treatments. Phytoplankton abundance varied with reed density, and groups known to be consumed by tadpoles were negatively influenced by reed density. We found no impact of reed density on pH, total phenolic concentration, or conductivity. Our results suggest that common reed establishment can influence amphibians with rapid development such as wood frogs. Though larval survival rates were similar across treatments, slower development under high reed densities implies a longer exposure to the risk of the pond drying out and to predators. © 2013 Copyright Taylor and Francis Group, LLC.

Intensive agriculture, as is typical of corn and soybean production, may be responsible for declines in the abundance and diversity of farmland birds. In Quebec, the transition to intensive crops is evidenced by marked increases of corn and soybean fields. From 2008 to 2010, we used satellite telemetry to study use of corn (Zea mays) and soybean (Glycine max) fields, other farmlands, wetlands, urban areas, and other habitats by 10 female Peregrine Falcons (Falco peregrinus) of the anatum–tundrius complex, a taxon of “special concern” in Canada. We monitored females during the nesting season, from hatching of eggs to independence of young, but before the young dispersed away from the nest site. Adult females were less likely to use corn and soybean fields than the “other farmlands” and “other habitats” categories during the nestling stage and the first month after young fledged. Once young fledged, other farmlands and urban areas were more likely to be used than the “other habitats” category when females were hunting in the areas that were farthest from the nest. The expansion of corn and soybean fields in the Quebec agricultural landscape has occurred to the detriment of other crops and may contribute to the decline in quality of hunting habitat of Peregrine Falcons and other avian top predators.

Le déclin des volumes de débris ligneux grossiers (DLG) en décomposition, causé par l'aménagement forestier et un intérêt grandissant pour le développement des biocarburants, risque de compromettre la pérennité d'un large éventail d'organismes tels que les micromammifères. Dans cette étude, nous avons quantifié les effets des DLG dégradés sur la dynamique d'occupation des petits rongeurs et des musaraignes et ce, dans les forêts boréales aménagées et non-aménagées. Les probabilités d'occupation initiale, de colonisation, d'extinction locale et de cooccurrence de cinq espèces de micromammifères boréaux ont été modélisées. Les campagnols à dos roux de Gapper (Myodes gapperi Vigor) et les campagnols-lemmings de Cooper (Synaptomys cooperi Baird) avaient une plus grande probabilité d'occuper les sites comportant un grand volume de DLG dégradés tôt en été. La probabilité d'extinction locale des souris sylvestres (Peromyscus maniculatus Wagner) a légèrement diminuée en fonction du volume des DLG dégradés dans les sites perturbés. La probabilité de cooccurrence des campagnols à dos roux de Gapper et des campagnols des champs (Microtus pennsylvanicus Ord) était plus forte dans les vieilles forêts non-perturbées de même que dans les sites coupés caractérisés par un grand volume de DLG dégradés. Le couvert offert par les DLG dégradés a été bénéfique pour deux des espèces de micromammifères pendant la reproduction hâtive en début d'été et plus tard en été pour les souris sylvestres. Finalement, nous avons trouvé qu'en plus d'une surface terrière élevée, le volume de DLG dégradés a le potentiel de favoriser la diversité locale des petits rongeurs.

Dead wood such as stumps and logs found on the forest floor is a key structural element that is used by a broad spectrum of organisms and contributes to soil nutrient cycling. The complexity of the forest floor in the boreal forest is largely dependent on coarse woody debris (CWD), but actual forestry practices may compromise the future recruitment of this resource. The main goal of our study was to determine the effects of CWD on small mammals in stands of varying green-tree retention levels. Since small mammals are associated with microhabitat components at multiple spatial scales, our secondary goal was to assess the effects of scale on small mammal relationship with CWD. Five trapping sessions were conducted in the boreal forest of western Québec, Canada during the summers of 2009 and 2010 in four managed forest blocks. Each block was composed of 12 independent trapping grids equally distributed in three treatments: clearcuts (0% green-tree retention), partial cuts (30% green-tree retention) and controls (undisturbed). We live-trapped small rodents and used pitfall traps for shrews in trapping sub-grids (fine-scale; 50 m) nested in larger grids (stand-scale; 300 m). Southern red-backed vole (Myodes gapperi) and deer mouse (Peromyscus maniculatus) abundances were positively associated with sites with high volumes of well decayed CWD in all treatments, at the fine-scale. Southern bog lemming (Synaptomys cooperi) abundance was positively associated with well decayed CWD, at both scales, but mainly in clearcut areas. Masked shrew (Sorex cinereus) abundance increased with high volumes of well decayed CWD in clearcuts but only at the stand-scale. In contrast, meadow voles were more abundant in sites with high volumes of well decayed CWD in controls than in sites with small volumes at the stand-scale. Patches of partial cuts with high volumes of well decayed CWD were characterized by high abundances of red-backed voles and this clearly indicates that volume and decay of CWD are important drivers that can mitigate the impacts of tree removal. We found different scale-dependent responses of small mammals to volumes of well decayed CWD, which indicates that associations were found at the individual as well as at the population level.

Abstract: Natural forests will likely be unable to sustainably fulfill society needs for wood fibers and intensively managed plantations could be an alternative source of timber in the future. Abandoned farm fields are often targeted for conversion, as they are already disturbed sites; however, they also represent high-quality habitat for species such as snowshoe hares (Lepus americanus Erxleben 1777), a keystone mammal in the boreal forest. We evaluated the effect of converting abandoned farm fields (n = 22) to conifer plantations (n = 19) on habitat use by snowshoe hares, using pellet counts and snow-tracking surveys. Both survey techniques yielded similar results: winter habitat use by hares is mostly affected by vegetation cover rather than habitat type. In the short term, plantations do not offer less protective cover than the one found in abandoned farm fields. However, upon reaching a certain height (≥7 m), plantations are mechanically pruned and lose their protective quality. Promoting silvicultural techniques that maintain lateral cover beyond a critical threshold (70%) could preserve the quality of hare habitat for an extended proportion of rotation time of the plantation.

Résumé : Il est vraisemblable que les forêts naturelles ne puissent pas combler de façon durable les besoins de la société pour les fibres de bois et que des plantations intensives servent alors de sources de replacement de bois dans le futur. Les champs de ferme abandonnés sont souvent visés pour la conversion en plantation, car ce sont des sites déjà perturbés; ils représentent toutefois un habitat de grande qualité pour des espèces comme le lièvre d’Amérique (Lepus americanus Erxleben, 1777), un mammifère clé de la forêt boréale. Nous avons évalué l’effet de la conversion de champs de ferme abandonnés (n = 22) en plantations de conifères (n = 19) sur l’utilisation de l’habitat par le lièvre d’Amérique en utilisant le décompte de fèces et les inventaires de pistes sur la neige. Les deux techniques d’inventaire donnent des résultats similaires : l’utilisation de l’habitat en hiver par les lièvres est plus affectée par le couvert protecteur que par le type d’habitat. À court terme, les plantations n’offrent pas moins de couvert protecteur que les champs de ferme abandonnés. Cependant, lorsqu’elles ont atteint une certaine taille (≥7 m), les plantations sont émondées mécaniquement et perdent leur propriété protectrice. La promotion de techniques de sylviculture qui laisseraient la couverture latérale au-delà d’un seuil critique (70 %) pourrait préserver la qualité de l’habitat du lièvre pendant une portion étendue de la période de rotation de la plantation.

En forêt boréale québécoise, l’aménagement forestier écosystémique tend à s’inspirer de la dynamique naturelle des écosystèmes afin de réduire les écarts entre les forêts aménagées et les forêts non aménagées. La variabilité dans la taille, la sévérité et la fréquence des feux de forêts créent une mosaïque paysagère hétérogène formée de peuplements d’âges, de composition et de structures différentes. Au sein des superficies brûlées, certaines parcelles rescapées, les îlots résiduels, jouent un rôle prépondérant dans le fonctionnement à long terme de ces milieux perturbés en assurant le maintien d’habitat pour de nombreuses espèces et en contribuant à la recolonisation de la matrice brûlée. Les coupes à rétention variable sont des traitements sylvicoles intéressants qui permettent de produire des îlots forestiers dans les secteurs de coupe. Afin de définir les lignes directrices nécessaires aux aménagistes pour émuler de tels îlots résiduels, la caractérisation de la structure, du fonctionnement et de la dynamique de ces véritables « Arches de Noé » naturelles a été réalisée par le biais de différentes études regroupées sous le projet ILOTS.

Jack pine specimens were examined for longitudinal and radial variations in selected wood quality parameters. Wood density and ring width of cross-sections were measured systematically from pith to bark along the merchantable stem using X-ray densitometry. Effects of cambial age and stem height were analyzed using a linear mixed model with two levels of nesting. A strong interaction between the two factors was found in corewood. Tree individual variation increased with cambial age for all studied wood properties and was larger in earlywood than in latewood. Radial patterns in the studied parameters closely approximated published ones in the lower stem but lessened considerably with increasing stem height. By contrast, longitudinal patterns reversed with cambial age in earlywood. High coordination was found between longitudinal patterns in corewood and radial patterns in the stem base, indicating a similar maturation pattern in the apical meristem and cambia. However, with increasing cambial age, this high coordination disappeared rapidly.