Introduction: In eastern Canada, the boreal forest is associated with an important latitudinal shift in forest composition and structure, which occurs in the transition between the mixed southern boreal forest and the coniferous northern boreal forest. Along this transition, upland mixedwood stands with large deciduous trees (important for cavity-dependent vertebrate species) are gradually replaced by forests with smaller conifer trees, primarily black spruce (Picea mariana). Concomitantly, the availability of lowland forests flooded by the American beaver (Castor canadensis), which can provide adequate conditions for tree-cavity users, is also decreasing.

Methods: We hypothesized that this latitudinal gradient would bring important changes in the functional diversity and network structure of vertebrate cavity-using communities. Along this latitudinal gradient we used a nest web approach to analyze the structure and robustness of networks of cavity users in upland forests and in lowland forests flooded by beavers.

Results: Despite their low availability in the northern forest region, we found that mixedwood stands persisted throughout the boreal forest in being the main drivers of nest webs network structure of upland forests whereas old black spruce stands contribution was low. In lowland forests, beaver ponds harbored nest webs with a rich and complex structure in both forest regions. Species removal simulations revealed that across our latitudinal gradient upland and lowland forest nest webs responded differently. In upland forests, the removal of trembling aspen and the Pileated Woodpecker (Dryocopus pileatus) caused the highest proportions of secondary extinctions, showing low robustness of nest webs given that these two species were highly connected to the other species. Contrastingly, nest webs in beaver ponds were more robust mainly because excavator species used a higher diversity of tree species despite the removal of the Northern Flicker (Colaptes auratus) which induced numerous secondary extinctions. The Pileated Woodpecker remained the pivotal species across the two forest regions in upland forests whereas the Northern Flicker became the main large cavity provider in beaver ponds across the latitudinal gradient.

Discussion: We discuss how mixedwood forests and beaver ponds, which are key habitat types for the cavity-using vertebrate community across our latitudinal gradient, should be maintained and protected in landscapes under industrial timber harvesting.

Abstract Aim To determine the relationships between the functional trait composition of forest communities and environmental gradients across scales and biomes and the role of species relative abundances in these relationships. Location Global. Time period Recent. Major taxa studied Trees. Methods We integrated species abundance records from worldwide forest inventories and associated functional traits (wood density, specific leaf area and seed mass) to obtain a data set of 99,953 to 149,285 plots (depending on the trait) spanning all forested continents. We computed community-weighted and unweighted means of trait values for each plot and related them to three broad environmental gradients and their interactions (energy availability, precipitation and soil properties) at two scales (global and biomes). Results Our models explained up to 60% of the variance in trait distribution. At global scale, the energy gradient had the strongest influence on traits. However, within-biome models revealed different relationships among biomes. Notably, the functional composition of tropical forests was more influenced by precipitation and soil properties than energy availability, whereas temperate forests showed the opposite pattern. Depending on the trait studied, response to gradients was more variable and proportionally weaker in boreal forests. Community unweighted means were better predicted than weighted means for almost all models. Main conclusions Worldwide, trees require a large amount of energy (following latitude) to produce dense wood and seeds, while leaves with large surface to weight ratios are concentrated in temperate forests. However, patterns of functional composition within-biome differ from global patterns due to biome specificities such as the presence of conifers or unique combinations of climatic and soil properties. We recommend assessing the sensitivity of tree functional traits to environmental changes in their geographic context. Furthermore, at a given site, the distribution of tree functional traits appears to be driven more by species presence than species abundance.

The Canadian boreal forest biome has been subjected to a long history of management for wood production. Here, we examined the cumulative impacts of logging on older forests in terms of area, distribution and patch configuration in the managed forest zones of the

Deadwood is a key component for biodiversity and ecosystem services in boreal forests; however, the abundance of this critical element is declining worldwide. In natural forests, deadwood is produced by tree death due to physical disturbances, senescence, or pathogens. Timber harvesting, fire suppression, and salvage logging reduce deadwood abundance and diversity, and climate change is expected to bring further modifications. Although the effects of these changes are not yet fully understood, restoring a continuous supply of deadwood in boreal forest ecosystems is vital to reverse the negative trends in species richness and distribution. Increasing the availability of deadwood offers a path to building resilient forest ecosystems for the future.

Structural complexity generated by forest development processes and tree species compositional changes provide key habitat features for vertebrate communities that rely upon tree size and decay processes for foraging, denning or nesting. Complexity of forest structure in old stands could not only be key for harboring increased taxonomic species diversity but also greater functional diversity through more complexity in networks of tree cavity dependent species. Using a nest web approach that hierarchically links cavity-bearing trees with cavity formation agents (natural decay processes and avian excavators) and cavity users (non-excavator species), we compared network characteristics of nest webs along a time since fire gradient in a naturally disturbed boreal mixedwood forest landscape in eastern North America. Since 2003, twelve 24 to 40 ha plots ranging from 61 to more than 245 years after fire were surveyed at the Lake Duparquet Research and Teaching Forest in Abitibi, Quebec, Canada to detect active nesting, and denning cavities. We found that network complexity both in terms of number of vertebrate species and number of interactions among species, increased along the age gradient and was significantly higher in the older stands than predicted by chance. Whereas cavity-nesting communities in old forests used a higher diversity of tree species over a wide range of decay stages, trembling aspen remained a key cavity-bearing tree throughout the age gradient. Woodpeckers were the main cavity formation agents whereas less than 1% of cavities originated from natural decay. The structural development of older forests is thus a driver for functional diversity in cavity-using vertebrate communities through higher interaction richness in nest webs, among cavity-bearing trees, excavators and non-excavating users. The pivotal contribution of the entire gradient of old forest cover types to the overall complexity of nest webs in the boreal mixedwood zone is also a key for the resilience of the cavity-using vertebrate community to natural disturbances. We discuss how such resilience may be compromised by even-aged industrial timber harvesting with short rotations that shifts the age structure of boreal landscapes toward regenerating and young pole forests whereas old forest cover types become below their historical range of variability.

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.

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

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

Sustainable management of forest ecosystems requires the use of reliable and easy to implement biodiversity and naturalness indicators. Tree-related microhabitats (TreMs) can fulfill these roles as they harbor specialized species that directly or indirectly depend on them, and are generally more abundant and diverse in natural forests or forests unmanaged for several decades. The TreM concept is however still recent, implying the existence of many knowledge gaps that can challenge its robustness and applicability. To evaluate the current state of knowledge on TreMs, we conducted a systematic review followed by a bibliometric analysis of the literature identified. A total of 101 articles constituted the final corpus. Most of the articles (60.3%) were published in 2017 or after. TreM research presented a marked lack of geographical representativity, as the vast majority (68.3%) of the articles studied French, German or Italian forests. The main themes addressed by the literature were the value of TreMs as biodiversity indicators, the impact of forest management on TreMs and the factors at the tree- and stand-scales favoring TreMs occurrence. Old-growth and unmanaged forests played a key role as a “natural” forest reference for these previous themes, as TreMs were often much more abundant and diverse compared to managed forests. Arthropods were the main phylum studied for the theme of TreMs as biodiversity indicators. Other more diverse themes were identified, such as restoration, remote sensing, climate change and economy and there was a lack of research related to the social sciences. Overall, current research on TreMs has focused on assessing its robustness as an indicator of biodiversity and naturalness at the stand scale. The important geographical gap identified underscores the importance of expanding the use of the TreMs in other forest ecosystems of the world. The notable efforts made in recent years to standardize TreM studies are an important step in this direction. The novelty of the TreM concept can partially explain the thematic knowledge gaps. Our results nevertheless stress the high potential of TreMs for multidisciplinary research, and we discuss the benefits of expanding the use of TreMs on a larger spatial scale.

1. The vast majority of animal species display range fidelity, a space-use behaviour enhancing familiarity with local habitat features. While the fitness benefits of this behaviour have been demonstrated in a variety of taxa, some species or populations rather display infidelity, displacing their home range over time. Others, such as many ungulate species, show seasonal adjustments in their range fidelity to accommodate changes in the dominance of limiting factors or in the distribution of resources.
2. Few empirical studies have explored the adaptive value of seasonal adjustments in range fidelity. Using boreal populations of woodland caribou (Rangifer tarandus caribou) as a biological model, we evaluated how range fidelity impacted individual performance during two seasons where juvenile and adult survival are limited by different predation pressures.
3. Between 2004 and 2013, we monitored the survival, reproductive success, habitat selection and range fidelity of female caribou in the boreal forest of eastern Canada. Using resource selection functions, we assessed how seasonal range fidelity was linked to two fitness correlates: calf survival in summer and adult female survival in winter.
4. Females displayed season-specific space use tactics: they selected previously used areas during calving and summer, but tended to shift their winter range from 1 year to the next. During calving and summer, range fidelity yielded relatively high fitness benefits, as females that did not lose their calf displayed stronger fidelity than females that did. In winter, however, adult survival was negatively linked to range fidelity, as females that survived selected areas further away from their seasonal range of the previous year than females that died.
5. We provide one of the first evidences that making seasonal adjustments in range fidelity can be an adaptive behaviour influencing the spatial distribution of a threatened species. Assessing the seasonal nature of range fidelity tactics may improve our predictions of space use and associated fitness implications for species displaying this behaviour.

Background
Monitoring of fur-bearing species populations is relatively rare due to their low densities. In addition to catch data, trappers' experience provides information on the ecology and status of the harvested species. Fisher (Pekania pennanti) and American marten (Martes americana) are mustelids that are sensitive to forest management and therefore considered to be ecological indicators of forest health. Fisher populations have increased in eastern North America since the early 2000s and this could have resulted in a northeastern extension of the species' range and increased overlap with marten's range. Moreover, habitats of both species are subject to natural and anthropogenic disturbances. The objective of this study was to document the knowledge held by local trappers in the northern area of sympatry between fisher and marten to identify factors that could explain variation in populations of the two species and interactions between them.

Method
Forty-one semi-directed interviews with Indigenous and non-Indigenous trappers in the Abitibi-Témiscamingue region of western Quebec (Canada), at the northern limit of the overlapping ranges of the two mustelid species.

Results
Trappers highlighted the lack of exclusivity of marten and fisher to coniferous forests, although marten is more closely associated with them than is fisher. Fisher apparently also takes advantage of open environments, including agroforestry systems. Moreover, climate change increases the frequency of freeze-thaw events that cause the formation of an ice crust on the snow surface, which favors fisher movements.

Conclusion
The fisher was identified as a competitor and even a predator of the marten. Furthermore, the fisher is less affected than the marten by forest management, and it also seems to benefit from climate change to a greater extent.

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.

Context

Although logging has affected circumboreal forest dynamics for nearly a century, very few studies have reconstructed its influence on landscape structure at the subcontinental scale.

Objectives

This study aims to document spatiotemporal patterns of logging and fire since the introduction of logging in the early twentieth-century, and to evaluate the effects of these disturbances on landscape structure.

Methods

We used historical (1940–2009) logging and fire maps to document disturbance patterns across a 195,000-km2 boreal forest landscape of eastern Canada. We produced multitemporal (1970s–2010s) mosaics providing land cover status using Landsat imagery.

Results

Logging significantly increased the rate of disturbance (+74 %) in the study area. The area affected by logging increased linearly with time resulting in a significant rejuvenation of the landscape along the harvesting pattern (south–north progression). From 1940 to 2009, fire was the dominant disturbance and showed a more random spatial distribution than logging. The recent increase of fire influence and the expansion of the proportion of area classified as unproductive terrestrial land suggest that regeneration failures occurred.

Conclusions

This study reveals how logging has modified the disturbances dynamics, following the progression of the logging frontier. Future management practices should aim for a dispersed spatial distribution of harvests to generate landscape structures that are closer to natural conditions, in line with ecosystem-based management. The challenges of defining sustainable practices will remain complex with the predicted increase in fire frequency, since this factor, in combination with logging, can alter both the structure and potentially the resilience of boreal forest.

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.

Aim

In managed forest landscapes, the tolerance of species to contemporary alteration of forest cover is often assumed to reflect their resilience to natural disturbances. We tested this central tenet of ecosystem-based management by comparing the structure of forest bird assemblages among four regions with contrasting historical natural disturbance regimes.

Location

Canada's boreal and northern hardwood forests.

Methods

Using point count data from four study regions across Canada, we first determined the relative sensitivity of individual bird species to the contemporary reduction of old forest cover at stand and ‘landscape-context’ (1-km radius) scales with log-linear models. The richness of species most sensitive to loss of old forest (hereafter ‘sensitive species’) was then modelled as a function of landscape-scale changes in old forest cover. Differences in the rate of decline in the richness of sensitive species with contemporary cover of old forest were compared among regions using ANCOVA. We then compared broken-stick regression models with linear models to detect thresholds, if present, in this relationship in each region.

Results

Bird assemblages from regions with relatively infrequent natural disturbances hosted more species sensitive to contemporary reduction in old forest cover. Those species were also more abundant than in regions with frequent natural disturbances, and the rate of decline in their richness with the loss of old forest was steeper in regions with infrequent natural disturbances than in those where they were frequent. However, we did not detect thresholds in this rate of decline in any study region.

Main conclusions

Our findings are consistent with the contention that historical natural disturbance regimes shape the response of biota to contemporary landscape alterations through evolutionary adaptation. We argue that forest management conducted within the natural range of variability in stand and landscape structure specific to a region is likely to be ecologically sustainable.

1. Functional responses in habitat selection occur when individuals adjust their selection of habitat features as a function of the availability of those features. Functional responses in habitat selection are generally assumed to be fitness-rewarding tactics and are used to guide conservation actions. Fitness consequences of functional responses, however, have rarely been evaluated.

2. Eighty-three caribou were followed with GPS collars to establish the link between functional responses in habitat selection and adult female survival, a strong fitness correlate for caribou. We measured how caribou avoidance of mixed/deciduous stands and 6–20-year-old clearcuts varied with the proportion of 6–20-year-old clearcuts within their 100% minimal convex polygon (MCP), and if these functional responses were linked to survival. Mixed/deciduous stands and 6–20-year-old clearcuts are risky for caribou because they are selected by moose, thereby attracting wolves and increasing predation risk for caribou.

3. Caribou avoided mixed/deciduous stands, especially when 6–20-year-old clearcuts comprised a large proportion of their MCP, but this functional response did not differ between caribou that died and those that survived. When the proportion of 6–20-year-old clearcuts in the MCP was low, caribou generally had low odds of occurring near 6–20-year-old clearcuts. However, when the proportion of clearcuts in the MCP was relatively high, caribou that strongly increased their odds of being near 6–20-year-old clearcuts were generally those that died.

4. aSynthesis and applications. Assessing the fitness consequences of how animals respond to habitat disturbances is central to wildlife conservation. We demonstrate that distinct functional responses in habitat selection involve different mortality risks and that population dynamics should depend on the frequency of the different tactics observed within populations. Individuals that persistently select riskier areas should be important drivers of population decline. Caribou mortality could be reduced by decreasing the appeal of 6–20-year-old clearcuts for moose by removing deciduous vegetation through cleaning, which should reduce the selection of wolves for these stands. Removing deciduous vegetation should be especially effective in areas where those clearcuts comprise a large proportion of the landscape, because this is where a subset of the caribou population experiences high mortality rates by selecting 6–20-year-old clearcuts.

Snag degradation classification systems based on external morphological attributes are widely used in ecology but have rarely been related to elapsed time since death (TSD) or wood density. Furthermore, these classification systems rely on the overall aspect of snags, and the predictive ability of specific attributes has rarely been investigated. We examined which morphological attributes best predicted TSD and wood density in snags of four major boreal species in eastern North America: trembling aspen (Populus tremuloides Michx.), balsam fir (Abies balsamea [L.] Mill.), jack pine (Pinus banksiana Lamb.) and black spruce (Picea mariana [Mill.] BSP). We also investigated how a commonly used snag degradation classification system relates to TSD and wood density. Sampling was conducted in northwestern Quebec, Canada. For each species, 37–65 snags were sampled and TSD was determined using dendrochronology. Bark cover was the only morphological attribute common to models of all species and was the sole predictive variable of TSD in balsam fir. As for TSD, the combination of predictors for wood density was species- specific and wood penetrability was a common predictor in all species. Degradation stages provided rough approximations of TSD and wood density. This study shows that the degradation classification system used can be helpful when rough estimates are needed. However, species-specific models built according to significant morphological attributes do not represent more time- and resource-consuming field assessments and they provide more precise measurements of TSD and wood density.

La vitesse à laquelle le bois des arbres morts se décompose influence plusieurs processus écologiques. Les taux de décomposition des billes au sol ont été largement documentés, mais les taux de décomposition des chicots et les facteurs qui les influencent ont reçu beaucoup moins d’attention, particulièrement dans le cas des espèces boréales des forêts de l’est de l’Amérique du Nord. Dans cette étude, nous avons mesuré le taux de minéralisation (c.-à-d. la perte de densité du bois) des chicots de quatre espèces boréales : le peuplier faux-tremble (Populus tremuloides Michx.), le sapin baumier (Abies balsamea (L.) Mill.), le pin gris (Pinus banksiana Lamb.) et l’épinette noire (Picea mariana (Mill.) Britton, Sterns, Poggenb.). La densité du bois et les variables qui pouvaient influencer le taux de minéralisation (temps écoulé depuis la mort, âge, croissance radiale moyenne, diamètre à hauteur de poitrine, activité des cérambycidés et des scolytes) ont été mesurées sur des disques prélevés sur 207 chicots dans le nord-ouest du Québec, au Canada. Le taux de minéralisation différait significativement selon l’espèce d’arbre. Le taux de minéralisation du peuplier faux-tremble était plus élévé que ceux des conifères (k = 0,0274). Le pin gris occupait le deuxième rang (k = 0,0152), suivi du sapin baumier (k = 0,0123). L’épinette noire s’est révélée particulièrement résistante à la minéralisation (k = 0,0058) alors que la densité de son bois n’était pas significativement influencée par le temps écoulé depuis la mort durant la période à l’étude. Le temps écoulé depuis la mort et l’activité des cérambycidés étaient associés à une densité du bois plus faible chez le peuplier faux-tremble, le sapin baumier et le pin gris, alors que la croissance plus lente de l’épinette noire était associée à des taux de minéralisation plus lents.

Temporal patterns of tree mortality and snag dynamics after fire were investigated over 10 years in a permanent plot design established immediately after a wildfire in an eastern boreal forest landscape of north-western Quebec, Canada. Post-fire tree mortality, snag persistence, tree fall patterns and variables influencing snag dynamics were assessed in deciduous, mixed and coniferous stands that experienced low- and moderate-severity fires. Temporal patterns of tree mortality for the three species revealed that mortality was delayed through time. Most post-fire tree mortality occurred within 2 years following fire but continued until the end of the 10-year observation period. Jack pine was the most persistent snag species, followed by trembling aspen and black spruce. Factors influencing the persistence of snags were multi-scaled and generally species-specific. Fire severity was the only common factor influencing snag persistence among all species, with snags located in severely-burned stands being less susceptible to falling. Trembling aspen snag persistence increased with basal area and diameter. Salvage logging in the vicinity affected black spruce. Fall patterns also differed among species. Bypasses of the snag stage (i.e. when a living tree falls directly to the forest floor) as well as uprooting of snags were common.

Abstract: Partial cuts are increasingly proposed to maintain habitats for species negatively affected by clearcutting, even if their benefits on nonpasserine birds and large mammals are still poorly documented. Our main objective was to evaluate effects of commercial thinning (CT) on spruce grouse (Falcipennis canadensis L.), a game bird of the boreal forest. Because this species is known to be associated with a dense vegetation cover, we hypothesized that habitat use would be lower in treated sites. In spring 2006, we evaluated site occupancy in 94 forest stands (50 CT and 44 uncut stands) in Quebec by visiting each on three occasions during the breeding season (March–May). Additionally, during the molting period (May–July), we used radiotelemetry to monitor habitat use by 19 males. As compared with uncut stands, results show that a lower proportion of CTs were used in spring (39% versus 60%, after accounting for detection). During the molting period, CTs were also used less than expected according to their availability. The significant reduction of lateral and vertical forest cover in CT may explain these results. We conclude that even if CT is perceived beneficial for wildlife, it does not completely fulfill the needs of species associated with dense understory vegetation, such as spruce grouse.

Résumé : Les coupes partielles sont de plus en plus souvent proposées pour de maintenir l’habitat pour des espèces défavorisées par les coupes totales, et ce même si leurs avantages sont peu connus pour les grands mammifères et pour plusieurs autres groupes, à l’exception des passereaux. Notre principal objectif visait à évaluer l’influence de l’éclaircie commerciale (EC) sur l’habitat du tétras du Canada (Falcipennis canadensis L.), un gibier à plume des forêts boréales. En raison du fait que cette espèce est associée aux sites ayant un fort couvert végétal, nous avons émis l’hypothèse que l’utilisation des habitats serait moins élevée dans les sites traités. Au printemps 2006, l’occupation des sites a été évaluée dans 94 peuplements (50 EC et 44 peuplements non récoltés) au Québec. Chaque peuplement a été visité trois fois durant la période de reproduction (mars à mai). Durant la période de mue (mai à juillet), nous avons utilisé la télémétrie pour évaluer l’utilisation de l’habitat de 19 tétras mâles. Comparativement aux peuplements non récoltés, les résultats montrent qu’une plus faible proportion de sites ont été utilisés dans les EC au printemps (39 % versus 60 %, après avoir corrigé pour la détection). Durant la période de mue, les sites EC ont également été moins utilisés que ce qui était attendu compte tenu de leur disponibilité. La diminution importante du couvert forestier latéral et vertical dans les sites EC pourrait être à l’origine de ces résultats. Bien que comparativement aux coupes totales, l’EC puisse être perçue comme une mesure d’atténuation pour la faune, nous concluons qu’elle ne répond pas complètement aux besoins d’espèces associées aux milieux fermés ayant une végétation dense, telles que le tétras du Canada.

Fire severity can vary greatly within and among burns, even in the Canadian boreal forest where fire regimes consist mostly of stand-replacing fires. We investigated the effects of fire severity on the long-term occupancy of burns by (i) saproxylic insects and (ii) three wood-foraging birds. Based on observations made 6 to 11 years after fire in burned conifer forests that varied in fire severity in Quebec, Canada, our results indicate that low-severity portions of the burns likely provided snag conditions suitable for the long-term presence of deadwood-associated insects and birds. The black-backed woodpecker, a post-fire forest specialist, was still abundant 6 and 8 years after fire. This pattern was likely explained by the persistence of several saproxylic insect species that are associated with recently dead trees and by the positive effect of lower fire severity on the abundance of Arhopalus foveicollis, a cerambycid with a long life cycle in dead wood. The American three-toed woodpecker and the brown creeper, and their associated prey (Scolytinae beetles), were more abundant in burned stands of lower v. higher severity. We conclude that less severely burned snags and stands within high-severity burns may favour the long-term presence of trophic webs that involve saproxylic insects and wood-foraging birds in burned boreal forests.

Many studies have highlighted the importance of deadwood, whether standing (snags) or fallen, in boreal ecosystems dynamics. However, a dearth of literature exists regarding the persistence and degradation pathways of these structures in northeastern American boreal species.

Degradation pathways were examined in four tree species of the eastern boreal mixedwood and conifer forests of Canada: Trembling aspen (Populus tremuloides Michx.), balsam fir (Abies balsamea (L.) Mill.), jack pine (Pinus banksiana Lamb.) and black spruce (Picea mariana (Mill.) BSP). Sampling was conducted in unharvested forests of northwestern Que´ bec. Discs where collected on 363 snags and logs and dendrochronological analyses conducted to determine year of death by crossdating.

Survival curves were constructed for each species and degradation pathways were documented based on the shape of the relationship, lag time if applicable (time period from death to fall onset) and half-life (time required for half the stems to fall).

Most species survival curves exhibited a reverse sigmoid function. Trembling aspen, jack pine and to a lesser extent balsam fir presented significant lag times before initiation of a period with high fall rates. Black spruce experienced more snag losses during the first years following death. Jack pine was clearly the most persistent species due to snags high resistance to fall and stem breakage. Within the range of tree diameters in our study area, diameter per se did not significantly influence fall probability.

Differential degradation pathways of the four species translate individualistic responses that are related to species autecology. This has important implications for all ecological functions related to deadwood and should be considered when planning retention strategies of legacy trees in an ecosystem management perspective.

(c) 2009 Elsevier B.V. All rights reserved.

ABSTRACT

Extensive even-aged management of the boreal forest and its consequences on the loss of late-seral stages (>100 years) is raising concerns about the future of organisms associated with standing deadwood. The considerable reduction of deadwood not only at the stand but at the landscape level is considered to be one of the principal causes of biodiversity loss in managed forest ecosystems worldwide. Ecosystem-oriented management approaches propose a fundamental change in forestry practices whereby live and dead tree retention becomes an important consideration in forest harvesting. We use woodpecker assemblages and their association with standing deadwood for both nesting and foraging to emphasize the importance of the entire range of snag degradation stages for maintenance of key ecological processes in habitat remnants of managed landscapes. We argue that bridging foraging and nesting knowledge of woodpecker’s snag requirements can refine conservation objectives for deadwood retention in the boreal forest.

RÉSUMÉ

L’aménagement équien de la forêt boréale transforme le couvert forestier notamment en réduisant la proportion de forêts âgées (>100 ans). Cette diminution des forêts âgées s’accompagne d’une baisse considérable du bois mort à l’échelle des peuplements et des paysages, ce qui est considérée comme l’une des principales causes de perte de diversité biologique dans les forêts aménagées à l’échelle mondiale. Les approches écosystémiques proposent un changement fondamental en foresterie, soit que la rétention des arbres vivants et morts dans les forêts aménagées devient une considération importante en aménagement forestier. Dans cet article, nous utilisons les assemblages de pics et leurs relations avec le bois mort sur pied pour statuer sur l’importance de conserver le spectre complet de stades de dégradation du bois mort dans les habitats résiduels des territoires aménagés pour maintenir les fonctions écologiques des pics, un groupe d’espèces clés dans les forêts âgées. Nous considérons l’importance de faire les liens entre les besoins d’alimentation et de reproduction des pics pour raffiner les objectifs de conservation du bois mort en forêt boréale.

Abstract:

In the last 25 years, the number of published studies that refer to traditional ecological knowledge (TEK) has constantly increased, with now more than 200 papers published each year. The objective of this review was to determine how this knowledge is used in current forest management around the world, and how local communities are involved in forest management planning. Published papers from 1983 to 2005 relating to TEK were found using the ISI Web of Science database. Despite the growing amount of literature published on TEK, we found only 21 studies that specifically address forest management per se. In these studies, TEK integration took different paths: using traditional management rules as a framework (five studies), using value maps to adapt practices in time and space (three studies), or by a zoning process that divides the land into areas in which different land uses are emphasized (six studies). Some community involvements are “active” with co-management committees composed of stakeholders (including community members), each having a voice; some are “passive” with external managers using criteria and indicators previously developed from community values and objectives. Although important changes in mentality and firm political decisions are still required before more efficient partnership between TEK and western science is reached in forest management planning, our review showed that Canadian initiatives proposed promising processes that could ensure better TEK incorporation and improved community participation.

Résumé:

Au cours des 25 dernières années, la quantité d’études traitant des savoirs écologiques traditionnels (SET) a constamment augmenté, atteignant maintenant plus de 200 publications par an. L’objectif de cette revue de littérature était de déterminer comment ces connaissances sont utilisées aujourd’hui pour l’aménagement forestier à travers le monde, et comment les populations locales sont impliquées dans la planification de l’aménagement forestier. Tous les articles traitant des SET, publiés entre 1983 et 2005, ont été extraits à partir de la base de données ISI Web of Science.Malgré l’abondance de littérature publiée sur les SET, seulement 30 études abordaient spécifiquement l’aménagement forestier comme tel. Dans ces études, l’intégration du SET pouvait prendre différentes avenues : s’inspirer des règles ancestrales de gestion (cinq études), adapter les pratiques dans le temps et l’espace en fonction des valeurs à priorizer (trois études), ou en divisant le territoire en zones à vocations différentes basées sur l’utilisation des terres (six études). L’engagement des communautés pouvait être « actif », à travers des comités de co-gestion composés des différents utilisateurs de la forêt (incluant des membres de la communauté), chacun ayant une voix ; ou « passif » lorsque des aménagistes extérieurs utilisaient des critères et indicateurs développés à partir des valeurs et objectifs de la communauté. Cependant, d’importants changements de mentalité et des décisions politiques fermes seront encore nécessaires avant de voir une participation entière des communautés et une incorporation effective des SET et de la science occidentale dans la planification forestière. Il semble, par ailleurs, que plusieurs initiatives canadiennes présentent des processus prometteurs pour s’assurer de l’incorporation des savoirs traditionnels et pour instaurer une gestion participative.

2. In this study, mechanisms creating occurrence peaks of saprophagous wood-borers (Cerambycidae: Coleoptera) in standing dead aspen in the middle and late stages of decay were investigated by correlating insect occurrence with variations in substrate-related nutritional and physical parameters. Twenty-four snags at four decay stages were dissected from a mature stand in western Quebec, Canada. Wood samples were taken to measure levels of nitrogen, non-structural carbohydrates, phenols, wood density, water content and snag age.

3. Several nutritional and physical parameters varied significantly along the decay gradient and were correlated with insect occurrence, but all significant parameters were also strongly correlated with snag age and wood density. Model selection using Akaike’s second order information criteria was used to rank the different models; the model including snag age only performed best, with a wi of 0.873.

4. This importance of snag age gives support to a proposed hypothesis of host selection in which temporal autocorrelation in probability of insect occurrence explains peaks observed in the middle and late stages of decay. However, further studies will be needed to confirm the prevalence of such neutral mechanisms over active selection in the determination of host-use patterns in decaying aspen.

Abstract:

Several concepts are at the basis of forest ecosystem management, but a relative consensus exists around the idea of a forest management approach that is based on natural disturbances and forest dynamics. This type of approach aims to reproduce the main attributes of natural landscapes in order to maintain ecosystems within their natural range of variability and avoid creating an environment to which species are not adapted. By comparing attributes associated with natural fire regimes and current forest management, we were able to identify four major differences for the black spruce forest of the Clay Belt. The maintenance of older forests, the spatial extent of cutover areas, the maintenance of residuals within cutovers and disturbance severity on soils are major issues that should be addressed. Silvicultural strategies that mitigate differences between natural and managed forests are briefly discussed.

Résumé:

Plusieurs approches conceptuelles sont à l’origine de l’aménagement écosystémique, mais un certain consensus semble exister actuellement sur le fait qu’il doit viser à reproduire des paysages naturels, i.e., des territoires aménagés qui conservent les principaux attributs des forêts naturelles. En créant des paysages avec des attributs forestiers semblables à ceux des paysages naturels, on vise à maintenir l’écosystème à l’intérieur des limites de variabilité naturelle. Ainsi, les espèces ne risquent pas de se retrouver dans un environnement auquel elles n’ont jamais été confrontées historiquement. En comparant le régime naturel des feux et son impact sur la dynamique forestière avec l’aménagement forestier actuel nous avons pu identifier certains écarts importants. Le maintien de forêts surannées, la dispersion spatiale des aires de coupes, la préservation de forêts résiduelles dans les aires de coupes et la sévérité des perturbations au sol constituent des enjeux importants à prendre en considération dans l’aménagement écosystémique des forêts de la ceinture d’argile. Des stratégies sylvicoles permettant de décroître l’écart entre l’aménagement et la dynamique naturelle sont brièvement discutées. ©2007 NRC Canada

2 Research has led to contradictory conclusions about those hypotheses, especially for wood-feeding insects; however, recent studies suggest that both mechanisms may take place in a single taxon but at different scales.

3 We developed a field experiment to test the hypothesis that primary attraction occurs at larger scale and random landing at finer scale in wood-feeding insects. Landing rates, measured using sticky traps, were compared first between patches and then between individual trees according to their distance to a baited central tree.

4 Polynomial functions describing landing rate to distance relationships were compared with a function produced by a null model describing what should occur under the random landing hypothesis. Scolytidae and Cerambycidae (Coleoptera) responded to volatiles at the patch scale, supporting the primary attraction hypothesis, but the landing patterns of some groups at finer scale matched closely the predictions of our null model, giving support to the random landing hypothesis.

5 Our results show that the primary attraction and random landing hypotheses are not mutually exclusive and that prelanding use of host-produced volatile is scale-dependant. Scale considerations should thus be included in the study of prelanding host-selection of wood-feeding insects.

Questions: How do gap abundance and the spatial pattern of trees and snags change throughout stand development in Picea mariana forests? Does spatial pattern differ among site types and structural components of a forest?

Location: Boreal forests dominated by Picea mariana, northern Quebec and Ontario, Canada.

Methods: Data on the abundance, characteristics and spatial location of trees, snags and gaps were collected along 200 m transects at 91 sites along a chronosequence. Spatial analyses included 3TLQV, NLV and autocorrelation analysis. Nonparametric analyses were used to analyse trends with time and differences among structural components and site types.

Results: Gaps became more abundant, numerous and more evenly distributed with time. At distances of 1-4 m, tree cover, sapling density and snag density became more heterogeneous with time. Tree cover appeared to be more uniform for the 10- 33 m interval, although this was not significant. Patch size and variance at 1 m were greater for overstorey than for understorey tree cover. Snags were less spatially variable than trees at 1 m, but more so at intermediate distances (4 - 8 m). Few significant differences were found among site types.

Conclusions: During stand development in P. mariana forest, gaps formed by tree mortality are filled in slowly due to poor regeneration and growth, leading to greater gap abundance and clumping of trees and snags at fine scales. At broader scales, patchy regeneration is followed by homogenization of forest stands as trees become smaller with low productivity due to paludification.

Cet avis scientifique vise à éclairer le MRNF sur les conséquences possibles de la récolte de cette forêt résiduelle sur les populations animales dépendantes de ce type de forêt. En tenant compte de la revue des nouvelles connaissances acquises au cours des dix dernières années sur la faune boréale au Québec (tant sur la faune non-gibier que sur des espèces d’intérêt économique), nos principales recommandations sont 1) qu’un moratoire sur la récolte des habitats résiduels soit mis en place et qu’une analyse systématique de la proportion de forêts matures et âgées présentes dans les agglomérations de coupes soit menée; 2) qu’aucune récolte ne soit autorisée dans les habitats résiduels et qu’un statut de rétention permanente soit conféré à ces habitats par le MRNF dans l’éventualité où la forêt mature et âgée résiduelle représente moins de 20% (limite supérieure du pourcentage de forêts vertes résiduelles dans les feux) de la superficie du territoire aménagé.

Nous rappelons également que la disparition complète de forêts matures et âgées dans les aires de récolte peut conduire à l’extinction locale de plusieurs espèces et causer un préjudice économique aux entreprises qui sont actuellement engagées dans des processus volontaires de certification environnementale forestière. Nous concluons sur le fait que les normes d’interventions actuelles doivent évoluer en fonction des nouvelles connaissances acquises, ce qui est la base d’un aménagement évolutif « adaptive management », pour ainsi mieux s’arrimer aux critères d’aménagement durable des forêts, en particulier celui du maintien de la diversité biologique.

We investigated stand development along a chronosequence on organic, clay and sand sites in black spruce boreal forest in northwestern Quebec, Canada. Our objectiveswere: (1) to describe trends and stages of structural development following fire; (2) to compare trends and stages of development both in isolation from and in conjunction with species replacement. We tested the hypothesis that although trends in structural development are similar among site types, productivity and composition affect the timing of developmental stages. Data on live trees, snags and logs were collected at 91 sites. Trends with time since fire were analyzed using segmented piecewise linear regression. On organic sites, tree basal area and density increased continuously with time since fire, while deadwood abundance decreased and then increased. Live tree basal area, tree density and deadwood abundance generally followed expected S-, N- and U-shaped trends, respectively, on clay sites, but often with decreases in later stages due to paludification. Fewer trends were significant on sand sites, although tree basal area decreased likely due to a change in species composition. Older forests on all site types weremore structurally diverse. To estimate the timing of the stages of structural development, we introduce a newanalysis technique which uses the breakpoints of the piecewise regressions.On organic sites, only three stages of stand development were evident, whereas a four-stage stand development model was appropriate for both clay and sand sites.We found that local conditions affected not only the timing of developmental stages, but also the number of stages and the trends themselves.We attributed these differences to changes in species composition and productivity. We refine the theory of structural development by representing patterns in both live and deadwood as two-stage trends with two possible outcomes for each stage. Our new method of determining the timing of the developmental stages using empirical data can be used to develop management practices that emulate structural development in order to conserve biodiversity on a landscape scale. © 2005 Elsevier B.V. All rights reserved.

For thousands of years, fire has been the main stand-replacing disturbance in the boreal forest but is now being supplemented by logging over most of the biome's extant. Community response to such disturbances of different nature and severity has been extensively compared in plant, but rarely in animal communities. Effects of fire and logging on some groups, such as ground beetles, have been assessed but separately, in different regions and different time frames. In a single 250-km² spruce-dominated landscape in the province of Quebec, Canada, we sampled ground beetle assemblages from recently logged (n = 12), recently burned (n = 12) and control stands (n = 18) using pitfall traps. Our objective was to compare assemblages from recently disturbed areas of the same age and nested in the same matrix. Assemblages were not highly specific to single habitats, but diverged significantly between treatments in abundance and species dominance. Capture rates were highest in logged stands, and lowest in burned stands. Forest generalists, including Calathus ingratus Dejean and Pterostichus brevicornis (Kirby), dominated assemblages in logged stands. We suggest that the contrasting activity levels observed following these two types of disturbance and the dominance of forest generalist in logged stands may partly reflect initial mortality patterns caused by these disturbances, as fires as severe as the one sampled in this study generally result in a much higher mortality rate in soil invertebrates than logging. © 2005 Elsevier B.V. All rights reserved.

Au début de l’été, les conditions sèches et chaudes ont généré dans le nord du Québec une rafale d’incendies qui ont fait la manchette en raison de leur sévérité et de leur proximité aux secteurs habités. Les médias ont beaucoup insisté sur l’idée de catastrophe économique de ces événements pour les communautés locales qui dépendent fortement des ressources forestières. Une catastrophe qui, pour certains, vient s’ajouter à celle de la baisse des approvisionnements en bois résultant des recommandations de la Commission Coulombe. À l’inverse, pour d’autres, cette catastrophe offre une occasion d’atténuer les impacts économiques de la baisse annoncée de 20 % des approvisionnements de bois, car les plans spéciaux d’aménagement des bois brûlés ne seront pas assujettis à cette baisse.

Ground-dwelling spider (Araneae) assemblages were compared between recent clearcuts and burned black spruce (Picea mariana (Mill.) BSP) forests. Spiders were sampled using pitfall traps placed in 6 recently burned sites, 6 recently clear-cut sites, and 6 undisturbed sites in eastern Quebec, Canada. A total of 2935 individuals from 95 spider species were identified. Catch rates for hunting spiders were significantly higher in the clear-cut stands than in the burned stands, but between-stand species turnover of hunting spiders was twice as high in the burned stands as in the clear-cut stands. Web-building spiders had similar catch rates in the three stand types, but had the highest species turnover and gamma diversity in the undisturbed sites. Correspondence analysis showed that the composition of the spider assemblages varied among the three types of stands. Spider assemblages found in clearcuts were associated with environmental variables reflecting dry, open, disturbed forest floor, while assemblages found in burned stands were correlated with high percentages of shrub cover and dried moss–lichen substrate and deeper litter. We conclude that ground-living spider assemblages in boreal forest respond very differently to clearcuts and fires and we suggest modifications to present forestry practices to create disturbances that are more similar to wildfires.

Nous comparons la réaction des assemblages d'araignées (Araneae) qui vivent au sol à la suite de perturbations récentes dans la pessière noire (Picea mariana (Mill.) BSP). Les araignées ont été récoltées à l'aide de pièges-fosses dans six sites récemment coupés à blanc, six sites récemment brûlés et six sites non perturbés dans l'est du Québec, au Canada. Au total, 2935 individus représentant 95 espèces d'araignées ont été identifiés. Le taux de capture des araignées chasseresses était significativement plus élevé dans les peuplements coupés à blanc que dans les peuplements brûlés leur diversité bêta était deux fois plus élevée dans les sites brûlés que dans les sites coupés à blanc. Les araignées qui tissent des toiles avaient des taux de capture similaires dans les trois types de peuplements mais leur renouvellement en espèces et leur diversité gamma étaient les plus élevés dans les sites non perturbés. Une analyse de correspondance montre que la composition des assemblages d'araignées est caractéristique de chacun des traitements. Les assemblages d'araignées récoltées dans les sites coupés à blanc sont associés aux milieux secs et ouverts dont le sol est perturbé. Les assemblages d'araignées récoltées dans les sites brûlés sont associés à un pourcentage élevé de couvert arbustif, à un substrat composé de mousses et de lichens séchés et à une épaisse litière. Nous concluons que les assemblages d'araignées qui vivent au sol en forêt boréale réagissent très différemment à la coupe à blanc et aux incendies de forêt et nous suggérons des modifications aux pratiques forestières visant à créer des perturbations plus similaires à celles qui sont causées par les incendies de forêt. ©2005 NRC Canada

Au cours des dernières années, la demande accrue en matière ligneuse et sa raréfaction, l’expansion nordique de la coupe forestière, ainsi que la perception générale que les feux créent des désastres écologiques ont favorisé l’intensification de la coupe de récupération dans les forêts brûlées de l’écosystème boréal. En parallèle, des études récentes ont montré que ces forêts brûlées peuvent constituer des habitats importants pour plusieurs espèces animales et que la coupe de récupération intensive, en éliminant les chicots debout, entraîne plusieurs impacts sur la faune associée à cet habitat. Jusqu’à maintenant, la problématique des effets de la coupe de récupération sur la diversité biologique a été peu considérée dans l’aménagement des forêts brûlées. Cet article présente la problématique de la coupe de récupération pour la faune en forêt boréale. Nous utilisons la situation du Québec comme un exemple de l’aménagement actuel des forêts brûlées dans l’est de la forêt boréale. Nous décrivons l’état actuel de nos connaissances quant à l’utilisation de ces forêts par la faune et quant aux impacts de la coupe de récupération sur ces habitats. Nous concluons que la rétention de chicots à différentes échelles spatiales et temporelles, dans les forêts récemment brûlées soumises à la coupe de récupération, constitue une pratique sylvicole qui se doit d’être implantée afin de rencontrer les principes d’un aménagement forestier durable et le maintien de la biodiversité de la forêt boréale.

In recent years, the increase in wood demand, the reduction in the availability of timber resources and the northern expansion of timber harvesting, along with the general perception that wildfires create ecological disasters, have favoured an increase in salvage logging in burned boreal forests. Concurrently, pioneer studies have shown that these post-fire forests may represent important habitats for several wildlife species and that intensive salvage logging, by removing standing snags, has several impacts on wildlife. However, the effects of salvage logging on biodiversity have yet to be considered in post-fire management plans. We examine the issue of salvage logging for wildlife in the boreal forest, with particular reference to Québec as an example. We describe our current state of knowledge on the use of burned forests by some wildlife and on the impacts of salvage logging on these habitats. We conclude that snag retention at multiple spatial and temporal scales in recent burns, which will be salvage-logged, is a prescription that must be implemented to meet the principles of sustainable forest management and the maintenance of biodiversity in the boreal forest.

The host selection process of most phytophagous insects can be described as a sequence of behaviors leading from landscape-scale habitat location to host-plant scale, microsite selection. For the whitespotted sawyer, Monochamus scutellatus (Say), a fire-associated xylophagous cerambycid, host location and acceptance patterns have been relatively well described, whereas landscape-scale distribution patterns in recently disturbed areas have received virtually no attention. In a 5,097-ha recently burned black spruce forest of Quebec, Canada, we evaluated the variability of larval density of 569 trees in 114 plots, by using entry hole counts. This variability was then related to environmental variables ranging from tree- to landscape-scale. Both diameter at breast height (positive relationship) and fire severity (negative relationship) were significant at explaining larval density at tree scale. At larger scales, altitude had a negative effect on larval density, whereas plots having a higher percentage of unburned forest in a 500-m radius were more intensely colonized. The importance of the proximity of unburned stands could be linked to the feeding requirements of the adults, which should show preference for stands offering both egg-laying and feeding substrata, because several species of Monochamus have been shown to feed while being reproductively active. In our models, large-scale variables explained more variability in entry hole counts than did tree-scale variables. Thus, our results suggest that large-scale habitat location mechanisms may play an important role in the host selection process of the whitespotted sawyer.

We compared structure and composition at forest edges created by wildfire and clear-cutting in black spruce (Picea mariana (Mill.) BSP) dominated boreal forest in northwestern Quebec. Forest structure and plant species composition were sampled along transects perpendicular to eight 3- to 4-year-old fire edges and eight 2- to 5-year-old cut edges. Significance of edge influence was assessed by comparing mean values at different distances from the edge to the range of variation in interior forest. The influence of clearcut edges was minimal, generally extending only 5 m from the edge, and included greater log density and different species composition, compared with interior forest. At fire edges, prominent responses to edge creation included increased snag density and lower moss cover, compared with interior forest, extending up to 40 m into the forest. This initial structural change was likely due to partial burning extending into the forest. Overall, fire edges had more snags and a different species composition than cut edges. Our hypothesis that edge influence is more extensive at fire edges than at cut edges was supported for overstory and understory structure, but not for species composition. We suggest that there is a need for management to consider the cumulative effect of the loss of fire edges on the landscape.

Nous avons comparé la structure et la composition des bordures de feu et de coupe dans la forêt Boréale du Nord-Ouest du Québec dominée par l'épinette noire (Picea mariana (Mill.) BSP). La structure et la composition ont été échantillonnées le long de transects perpendiculaires à huit bordures de feu de 3 à 4 ans et à huit bordures de coupes totales de 2 à 5 ans. L'influence de la bordure a été évaluée en comparant les valeurs moyennes aux différentes distances de la bordure à l'étendue de la variation à l'intérieur de la forêt. L'influence de la bordure des coupes totales était minimale, s'étendant généralement jusqu'à seulement 5 m de la bordure. Ces changements comprenaient une augmentation de la densité des arbres morts au sol et une composition en espèces différente de celle observée à l'intérieur de la forêt. Aux bordures de feux, une densité accrue des chicots et une diminution de la couverture de mousses, comparativement à l'intérieur de la forêt, s'étendaient jusqu'à 40 m en forêt. Ces changements structuraux étaient probablement dus au brûlage partiel qui s'est étendu dans la forêt. De façon générale, les bordures de feu avaient plus de chicots et une composition différente d'espèces comparativement aux bordures de coupes. Notre hypothèse voulant que l'influence de la bordure soit plus grande pour les bordures de feu comparativement aux bordures de coupe est supportée pour la structure des étages supérieur et inférieur de la canopé mais non pour la composition des espèces. Puisque l'influence des bordures de coupe est limitée dans la pessière noire boréale, les aménagistes forestiers devraient davantage tenir compte des effets cumulatifs de la perte d'hétérogéneité structurale des bordures issues de feu dans les paysages aménagés.©2004 NRC Canada

Several insect groups have adapted to fire cycles in boreal forests, and can efficiently use new habitats created by fire. Our study aimed at producing a first characterization of post-fire Coleoptera assemblages of black spruce forests of eastern North America. For two years, we sampled Coleoptera using flight-interception traps in burned stands of contrasting age and structure in a 5097-ha wildfire and in neighbouring unburned mature stands. More than 40 species were exclusively captured in burned stands. Time elapsed since fire and proximity of unburned forests were the most significant parameters affecting Coleoptera assemblages. Stand age and structure had limited effects on assemblage structure; the Scolytid Polygraphus rufipennis Kirby was the only common species to clearly favor older stands. Fire-associated Coleoptera assemblages found in our study area were clearly distinct from those found in similar unburned stands; we should thus be conservative in our management approach concerning recently burned stands.

Contrary to what is observed in Fennoscandia, it seems to be widely accepted that small mammals do not exhibit multi-annual population cycles in the boreal forest of North America. However, in the last thirty years, irruptions of vole predators such as owls have been reported by ornithologists south of the North American boreal forest. While such southerly irruptions have been associated in Fennoscandia with periods of low abundance of small mammals within their usual distribution range, their possible cyclic nature and their relationships to fluctuations in vole densities at northern latitudes has not yet been demonstrated in North America. With information collected from existing databases, we examined the presence of cycles in small mammals and their main avian predators by using temporal autocorrelation analyses. Winter invasions of boreal owls (Aegolius funereus) were periodic, with a 4-yr cycle in Québec. Populations of one species of small mammal, the red-backed vole (Clethrionomys gapperi), fluctuated periodically in boreal forests of Québec (north to 48^°N). Boreal owls show invasion cycles which correspond to years of low density of red-backed voles, the main food item for this owl species. In addition, winter observations of northern hawk owls (Surnia ulula) and great gray owls (Strix nebulosa) south of their usual range increased in years of low density of red-backed voles. Our results suggest that a 4-yr population cycle exists in the eastern boreal forest of North America for voles and owls, which is very similar to the one observed in Fennoscandia.

Parce que le bois mort fait partie intégrante des forêts, une diversité d’organismes en dépendent pour compléter leur cycle vital : mammifères, oiseaux, amphibiens, insectes, plantes vasculaires, mousses, lichens, champignons, bactéries. L’aménagement forestier réduit la quantité et la qualité du bois mort et il conduit également à une raréfaction des gros chicots et des gros débris ligneux. La raréfaction du bois mort dans les forêts aménagées peut donc réduire la biodiversité ainsi que l’emprisonnement du carbone et la fertilité des sols. Nous proposons sept mesures complémentaires permettant le maintien d’un minimum de bois mort dans les forêts aménagées du Québec, tout en évitant le gaspillage et assurant la sécurité des travailleurs forestiers.

In recent years, studies of bird-habitat relationships undertaken in the context of habitat fragmentation have led to the widespread use of species categorisation according to their response to edge alongside mature forest patches (edge species, interior species, interior-edge generalist species). In other research contexts, especially in less fragmented landscapes dominated by a forested land base in various age classes, bird-habitat relationships are often described in relation to their use of various successional stages (early-successional species, mature forest species, generalist species). A simple comparison of these two commonly-used classifications schemes in a close geographical range for 60 species in eastern North America as well as for 36 species in north-western Europe clearly reveals that in these two particular biomes the two classifications are not independent. We believe that this association is not only a semantic issue and has important ecological consequences. For example, almost all edge species are associated with early-successional habitats when a wide range of forest age-classes are found in a given area. Accordingly, we suggest that most species considered to prefer edge habitats in agricultural landscapes are in fact only early-successional species that could not find shrubland conditions apart from the exposed edges of mature forest fragments. To be considered a true edge species, a given species should require the simultaneous availability of more than one habitat type and consequently should be classified as a habitat generalist in its use of successional stages. However, 28 out of 30 recognised edge species were considered habitat specialists in terms of successional status. Based on these results, we conclude that "real edge species" are probably quite rare and that we should make a difference between true edge species and species which in some landscapes, happen to find their habitat requirements on edges.

We studied the spatial and temporal response of three epiphytic lichens (Bryoria spp., Evernia mesomorpha Nyl., and Usnea spp.) to edge effects in conifer forests of northwestern Quebec. Lichen abundance and substrate variables were sampled at four distances (5, 25, 50, and 100 m) from the edge in 15 edge-interior transects in managed black spruce (Picea mariana (Mill.) BSP) forests. Responses to edge effects were assessed for short-term (1-3 years) and long-term (8 and 16-23 years) periods. We also assessed the effect of forest fragment size on lichen abundance in 27 forest fragments ranging in size from 0.03 ha to >4 ha. We found a significant effect of distance to edge on mass of E. mesomorpha and Usnea spp. Lichen mass was lower in the first 50 m of edge compared with the forest interior (100 m). Size of forest fragments had no significant effect in any of the three lichens. However, mass of Usnea spp. was low in the seven smallest (<0.5 ha) fragments. Our results suggest that the response of epiphytic lichens to edge conditions could be used by forest managers as an indicator in determining the size of remnant stands that should be left to increase the proportion of interior forest habitat in harvested forest landscapes. ©2003 NRC Canada

In Canada, there are still extensive tracts of boreal forest consisting of stands that have resulted from natural disturbances. The country's forests are a mosaic made up to a large extent of old-growth forest that is beyond commercial harvesting age, especially in the boreal forest of eastern Canada. As areas of boreal forest under management steadily expand, as demand for forest products continues to grow and as rotation periods become shorter in response to silvicultural practices, the forest cover will inevitably become younger, causing changes to the structure and composition of the mosaic of forest stands that will affect the aspect of entire landscapes. These changes may have an adverse impact on biological diversity. Forest birds are one group of living organisms that may respond quickly to the advent of younger forest landscapes, thereby acting as a biological indicator. In this paper, we discuss some of the problems that birds face as a result of the truncation of the age-class distribution of managed forest landscapes in eastern Canada's coniferous boreal forest, using data obtained from our research in the Clay Belt region of Quebec and Ontario. More specifically, we look at how birds respond to changes in forest structure and composition in terms of time since natural disturbances, and to variation in dead trees availability. We then consider the impact of the prospective rejuvenation of the forest cover in managed forest landscapes, and possible solutions aimed at mitigating that impact through new management strategies based on the maintenance of forest ecosystem diversity. The ability of these new management strategies to maintain the ecological integrity of bird communities provides an indication of their potential as tools for contributing to the maintenance of biological diversity in a broader sense.

Woodland caribou (Rangifer tarandus caribou) require a diversity of forested habitats over large areas and may thus be particularly affected by the large-scale changes in the composition and age-class distribution of forest landscapes induced by the northern expansion of forest management. In this study we examine habitat characteristics associated to the use of calving areas by woodland caribou females and calves at different spatial scales. Thirty females were captured and collared with Argos satellite transmitters that allowed to locate 14 calving areas. Field surveys were conducted at each of these areas to measure the landscape composition of forest cover types and local vegetation characteristics that are used for both forage conditions and protection cover. At the scale of the calving area, univariate comparisons of the amount of forest cover types between sites with and without calves showed that the presence of calves was associated to mature black spruce forest with a high percent cover of terrestrial lichens. Within calving grounds, univariate comparisons showed that vegetation features like ericaceans and terrestrial lichens, that are important food resources for lactating females, were more abundant in calving areas where females were seen with a calf in mid-July than in areas where females were seen alone. The protection of the vegetation cover against predators was however similar between calving areas with or with-out a calf. Logistic regression results also indicated that vegetation characteristics associated to forage conditions were pos-itively associated to calf presence on calving grounds. Our results suggest that foraging conditions should be given more attention in analyses on habitat requirements of woodland caribou.

Au Canada, la forêt boréale comporte encore des superficies importantes de peuplements issus de perturbations naturelles. Une forte proportion de la mosaïque forestière est constituée de vieilles forêts qui dépassent l’âge commercial d’exploitation forestière, notam-ment dans la forêt boréale de l’est du Canada. Avec l’importance grandissante des territoires aménagés en forêt boréale, les besoins toujours croissants pour la matière ligneuse et le recours à une sylviculture réduisant les périodes de rotation, des changements dans la structure et la composition des mosaïques de peuplements forestiers liés au rajeunissement du couvert forestier sont à anticiper à l’échelle des paysages. Ces changements peuvent causer des préjudices à la diversité biologique. L’avifaune représente l’un des groupes d’organismes qui peut répondre rapidement au rajeunissement des paysages forestiers et servir ainsi d’indicateur biologique. Dans cet article, nous exposons certains des problèmes auxquels est confrontée l’avifaune face au rajeunissement anticipé des mosaïques forestières aménagées de la forêt boréale résineuse de l’est du Canada à partir de nos travaux réalisés dans la région de la ceinture d’argile du Québec et de l’Ontario. Plus spécifiquement, nous examinons la réponse des oiseaux aux changements de structure et de composition des forêts en fonction du temps depuis les dernières perturbations dans des mosaïques forestières naturelles, ainsi qu’en rapport avec la varia-tion de la densité d’arbres morts disponibles dans ces écosystèmes. Nous discutons ensuite de l’effet du rajeunissement du couvert foresti-er qui est anticipé dans les mosaïques forestières aménagées de ces écosystèmes et des solutions envisageables pour atténuer cet effet au moyen des nouvelles stratégies d’aménagement fondées sur le maintien de la diversité des écosystèmes forestiers. La capacité de ces nouvelles stratégies d’aménagement à maintenir l’intégrité écologique des communautés d’oiseaux forestiers donne une indica-tion de leur potentiel à contribuer plus largement au maintien de la diversité biologique.

We studied snag use for foraging by Black-backed Woodpeckers (Picoides arcticus) one year after a fire in an eastern black spruce (Picea mariana) boreal forest in Quebec, Canada. We searched for signs of foraging (bark flaking and excavation holes) by Black-backed Woodpeckers on 6,536 snags sampled in 56 plots located in portions of the burned forest that had not been salvage logged. A logistic regression model was developed based on the presence or absence of foraging signs. Results showed that Black-backed Woodpeckers used larger snags that were less deteriorated by fire (qualified as high-quality snags). Direct field observations of individuals foraging on 119 snags also indicated that used snags corresponded to those of high predicted quality. Finally, we assessed the relationship between food availability and snag characteristics by measuring the density of wood-boring beetle larvae holes on 30 snags of different size and deterioration classes. High-quality snags contained higher prey densities (Vood-boring beetle holes) than smaller and more deteriorated snags. We recommend that forest blocks characterized by large and less deteriorated trees be preserved from salvage logging in recently burned boreal forests in northeastern North America.

Old-growth black spruce (Picea mariana) boreal forest in the Clay Belt region of Ontario and Quebec is an open forest with a low canopy, quite different from what many consider to be "old growth". Here, we provide an overview of the characteristics of old-growth black spruce forest for three different site types on organic, clay, and coarse deposits. Our objectives were (1) to identify the extent of older forests; (2) to describe the structure, composition, and diversity in different age classes; and (3) to identify key processes in old-growth black spruce forest. We sampled canopy composition, deadwood abundance, understorey composition, and nonvascular plant species in 91 forest stands along a chronosequence that extended from 20 to more than 250 years after fire. We used a peak in tree basal area, which occurred at 100 years on clay and coarse sites and at 200 years on organic sites, as a process-based means of defining the start of old-growth forest. Old-growth forests are extensive in the Clay Belt, covering 30–50% of the forested landscape. Black spruce was dominant on all organic sites, and in all older stands. Although there were fewer understorey species and none exclusive to old-growth, these forests were structurally diverse and had greater abundance of Sphagnum, epiphytic lichens, and ericaceous species. Paludification, a process characteristic of old-growth forest stands on clay deposits in this region, causes decreases in tree and deadwood abundance. Old-growth black spruce forests, therefore, lack the large trees and snags that are characteristic of other old-growth forests. Small-scale disturbances such as spruce budworm and windthrow are common, creating numerous gaps. Landscape and stand level management strategies could minimize structural changes caused by harvesting, but unmanaged forest in all stages of development must be preserved in order to conserve all the attributes of old-growth black spruce forest.

Fire reconstruction and forest inventory maps provided an opportunity to study changes in stand-level characteristics following fire using a data set comprised of all forest stands of fire origin in an area of over 10000 km². We assigned the date of the most recent fire occurrence to over 31000 forest stands in an ecoforestry database. We categorized stands on different substrates into age classes to investigate differences in canopy composition, cover and height, and incidence of secondary disturbance. Stands with over 75% Picea mariana (Mill.) BSP dominated all age classes on organic sites. On other substrates, there was a change in canopy composition from deciduous stands and stands dominated by Pinus banksiana Lamb. to Picea mariana stands after about 100 yr. This transition was later for xeric sites. After a peak in canopy cover and height at about 100 yr, there was a decrease in the area occupied by stands with dense, tall canopies. Structural development was slower on less productive sites. There was little incidence of spruce budworm outbreaks. Partial disturbance by windthrow coincided with canopy break-up at 3 00 yr, but appeared to have little effect on overall canopy structure in later stages. Structural diversity was independent of compositional diversity; on organic sites, stands with similar composition had different canopy structure. Diversity of stands with different composition and structure was greatest in the first 150 yr following fire. Maintaining stands in different stages of structural development on the landscape would serve to maintain regional biodiversity.

We sampled 22 black spruce (Picea mariana) - feathermoss (Pleurozium schreberi) sites (80 to >200 years) to describe and assess the diversity of bryophyte and lichen communities as a function of time since fire and site characteristics. Old growth had no more species than younger forests. We think that this result might be explained by the phenomenon of paludification, which is a major process in this region. Axis 1 of a nonmetric multidimensional scaling ordination (NMS) of terricolous species was interpreted as a paludification gradient. Mature forests were characterized by Pleurozium schreberi, Ptilium crista-castrensis, Polytrichum commune, and Dicranum polysetum, and older sites by a greater abundance of Sphagnum. Axis 1 of epiphytic species ordination (NMS) was interpreted as a gradient of time since the last fire. Abundance of Tuckermannopsis americana, Hypogymnia physodes, and Bryoria furcellata was greater in mature forests. In contrast, Mycoblastus sanguinarius, Bryoria trichodes, and Usnea spp. were more abundant in older forests. The abundance of epiphytic lichens increased with tree age, whereas their richness was higher in sites where trembling aspen (Populus tremuloides) and jack pine (Pinus banksiana) were present. Since species composition varied with time since the last fire, it is important to preserve the diversity of successional stages at the landscape level and the structural diversity at the stand level to maintain the bryophyte and lichen communities.©2002 NRC Canada

Fire reconstruction and forest inventory maps provided an opportunity to study changes in stand-level characteristics following fi re using a data set comprised of all forest stands of fi re origin in an area of over 10 000 km 2 . We assigned the date of the most recent fi re occurrence to over 31 000 forest stands in an ecoforestry database. We categorized stands on different substrates into age classes to investigate differences in canopy composition, cover and height, and incidence of secondary disturbance. Stands with over 75% Picea mariana (Mill.) BSP dominated all age classes on organic sites. On other substrates, there was a change in canopy composition from deciduous stands and stands dominated by Pinus banksiana Lamb. to Picea mariana stands after about 100 yr. This transition was later for xeric sites. After a peak in canopy cover and height at about 100 yr, there was a decrease in the area occupied by stands with dense, tall canopies. Structural development was slower on less productive sites. There was little incidence of spruce budworm outbreaks. Partial disturbance by windthrow coincided with canopy break-up at 100 yr, but appeared to have little effect on overall canopy structure in later stages. Structural diversity was independent of compositional diversity; on organic sites, stands with similar composition had differ-ent canopy structure. Diversity of stands with different composition and structure was greatest in the fi rst 150 yr following fi re. Maintaining stands in different stages of structural development on the landscape would serve to maintain regional biodiversity.

Bird community response to both landscape-scale and local (forest types) changes in forest cover was studied in three boreal mixed-wood forest landscapes modified by different types of disturbances: (1) a pre-industrial landscape where human settlement, agriculture, and logging activities date back to the early 1930s, (2) an industrial timber managed forest, and (3) a forest dominated by natural disturbances. Birds were sampled at 459 sampling stations distributed among the three landscapes. Local habitat and landscape characteristics of the context surrounding each sampling station (500-m and 1-km radius) were also computed. Bird communities were influenced by landscape-scale changes in forest cover. The higher proportion of early-successional habitats in both human-disturbed landscapes resulted in significantly higher abundance of early-successional bird species and generalists. The mean number of mature forest bird species was significantly lower in the industrial and pre-industrial landscapes than in the natural landscape. Landscape-scale conversion of mature forests from mixed-wood to deciduous cover in human-disturbed landscapes was the main cause of changes in mature forest bird communities. In these landscapes, the abundance of species associated with mixed and coniferous forest cover was lower, whereas species that preferred a deciduous cover were more abundant. Variation in bird community composition determined by the landscape context was as important as local habitat conditions, suggesting that predictions on the regional impact of forest management on songbirds with models solely based on local scale factors could be misleading. Patterns of bird species composition were related to several landscape composition variables (proportions of forest types), but not to configuration variables (e.g., interior habitat, amount of edge). Overall, our results indicated that the large-scale conversion of the southern portion of the boreal forest from a mined to a deciduous cover may be one of the most important threats to the integrity of bird communities in these forest mosaics. Negative effects of changes in bird communities could be attenuated if current forestry practices are modified toward maintaining forest types (deciduous, mixed-wood, and coniferous) at levels similar to those observed under natural disturbances.

Useful sampling guidelines have recently been provided to improve the precision of bird population parameter estimates from point count data. Less attention has been given, however, to the issue of accuracy or completeness of counts at each sampling point. While it may not be critical in studies that compare average counts among study plots, completeness of counts at the level of individual points may pose several problems in studies that assess relationships between response variables (species' occurrence or abundance) and explanatory variables (vegetation structure, size and isolation of the fragment, proportion of interior habitat) on a point by point basis. Reliability of models in such studies is greatly dependent on the accuracy of counts at each point. We examined how bias of incomplete counts could be minimised through refinements of the point-count method. Six forest types of the northeastern deciduous forest in Quebec (Canada) were intensively surveyed during an entire breeding season. Census performances of the point-count method for measuring species richness at individual points were assessed by resampling the original data set for a simulated census protocol of two visits at a point. Effects of daily variation, time of season, time of day, and count duration were tested. Census performances of counts conducted the same day were significantly poorer than counts from different days. Census performances were influenced by the time of season during which counts were conducted. When pooled across habitats, census performances for counts that combined visits at the beginning and at the end of the breeding season were significantly better than counts that were concentrated in either one of these periods. The 05:00 to 08:30 morning period yielded the best results for five of the six habitats. Census performances in open field were, however, significantly better during the first sampling period (04:30), suggesting that bird censuses in open habitats could be initiated before sunrise. Longer counts (25 and 20 min) greatly improved species richness estimates at a point. For studies that focus on comparisons at the scale of individual points, longer counts are preferable to short counts (15 and 10 min). We stress the importance of the scale (study plots or individual points) at which statistical analyses of point count data are conducted in the decision-making process of point count sampling procedures.