We evaluated geographic variations in mean fire return intervals and postfire forest succession within a 66 497 km2 land area located in the eastern Quebec boreal forest. Fire return intervals were calculated using a time since last fire map for 1800–2000, and forest dynamics were studied by superimposing 3204 forest inventory plots onto the fire map. Mean fire return interval proved significantly shorter in the western part of the study area, at 270 years, compared with the eastern part, where it was probably more than 500 years. The two main tree species in the study area were balsam fir ( Abies balsamea (L.) P. Mill.) and black spruce ( Picea mariana (Mill.) BSP). Balsam fir abundance increased progressively as a function of time since fire, whereas black spruce abundance increased during the first 90 years after fire and then declined. Balsam fir was significantly more abundant in the southeastern portion of the study area, which we attribute to the combined limitations imposed by temperature along the north–south axis and by fire along the east–west axis. Large forest patches (i.e., ≥200 km2) dominated by early successional tree species, within a matrix of irregular black spruce – balsam fir mixtures, are an important feature of preindustrial forest landscapes in this region.

We present the 5-year combined effects of different cutting intensities (removal of 0, 35, 50, 65, and 100% of basal area) and scarification on available light, soil temperature, and regeneration dynamics in a mixed aspenconifer stand in Quebec, Canada. Compared with the control, the 35% cut did not change transmitted light to the understory (<20% of full light), while the 50, 65, and 100% cuttings transmitted 30, 48, and 90% of full light, respectively, during the first summer. Trembling aspen (Populus tremuloides Michx.) suckering increased with percent basal area removal (p < 0.001). After 5 years, the 35 and 50% cuttings limited growth and survival of suckers (<1000 stems/ha, of which 5% are >1 m high), but the 65 and 100% cuttings favoured their development (8000 and 11 000 stems/ha, respectively, of which 29 and 38%, respectively, are >2 m high). Balsam fir (Abies balsamea (L.) Mill.) responded well to canopy opening alone with a maximal recruitment (31 000 seedlings/ha) in the 50% cut. Spruces (white spruce, Picea glauca (Moench) Voss, and red spruce, Picea rubens Sarg.) establish following scarification only, with a better response in the 65% cut (32 000 seedlings/ha) than in the 50 (15 000), 35 (10 000), and 0% (8000) cuttings. Résumé :Nous présentons les résultats de 5 ans des effets combinés de différentes intensités de coupe (prélèvements de 0, 35, 50, 65 et 100 % de la surface terrière) et du scarifiage sur la lumière disponible, la température du sol et la dynamique de la régénération dans un peuplement mélangé de trembles et conifères situé au Québec, Canada. La coupe à 35 % n'a pas changé la lumière transmise sous couvert (<20 % de la pleine lumière) par rapport au témoin, alors que les coupes à 50, 65 et 100 % ont transmis 30, 48 et 90 % de la pleine lumière durant le premier été. Le drageonnement du peuplier faux-tremble (Populus tremuloides Michx.) a augmenté avec le pourcentage de la surface terrière prélevée (p < 0,001). Après 5 ans, les coupes à 35 et 50 % ont limité la croissance et la survie des drageons (<1000 tiges/ha, dont 5 % >1 m), alors que les coupes à 65 et 100 % ont favorisé leur développement (respectivement, 8000 et 11 000 tiges/ha, dont, respectivement, 29 et 38 % >2 m). Le sapin baumier (Abies balsamea (L.) Mill.) a bien réagi à la seule ouverture du couvert avec une régénération maximale (31 000 semis/ha) dans la coupe à 50 %. Les épinettes (épinette blanche, Picea glauca (Moench) Voss, et épinette rouge, Picea rubens Sarg.) ne se sont établies qu'à la suite du scarifiage, avec un meilleur résultat dans la coupe à 65 % (32 000 semis/ha) que dans les coupes à 50 (15 000), 35 (10 000) et 0 % (8000). Prévost and Pothier 15

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Aim Using total species richness to characterize biodiversity may mask multiple response patterns of species. We propose a null model analysis of species cooccurrence-based classification to identify sets of species that may have similar (within-groups) and distinct (between groups) response patterns to their environment. The classification should also provide an explicit framework for selecting indicator species with characteristic co-occurrence patterns to predict overall species richness.Location Cô te-Nord, Québec, Canada. MethodsWe combined null-model of species co-occurrence and cluster analysis to identify species groups within diverse assemblages of ground-dwelling and flying beetles of stands in a boreal forest mosaic; we then examined their cooccurrence and response patterns to habitat characteristics. Best subset regressions were used to select indicator species of richness within each group, from which indicators of total species richness were selected. ResultsThe identified species groups appeared to display contrasting cooccurrence and response patterns to at least one of the stand-level habitat characteristics. Among flying beetles, for example, richness increased with standlevel heterogeneity for two groups and decreased for two other groups, but the relationship was non-significant for the total richness. We identified 28 indicator species that explained > 80% (validated by bootstrap analysis) of the variation in total species richness. Predictive performance of indicators was higher than when their co-occurrence were reshuffled, even under a highly constrained null model, indicating that co-occurrence patterns contributed to their predictive performance.Main conclusions Co-occurrence-based classification appears as a promising and effective tool for deconstructing biodiversity into species groups which reflect their ecological commonalities and differences, thus reducing the risk of making faulty inferences about the causes underlying overall diversity patterns. The method provides an explicit framework for selecting indicator species representing different species groups that may reflect the multiple responses of species co-occurring with them. Indicator species can be effective for predicting overall species richness.

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Understanding how large herbivores shape plant diversity patterns is an important challenge in community ecology, especially because many ungulate populations in the northern hemisphere have recently expanded. Because species within plant communities can exhibit strong interactions (e.g., competition, facilitation), selective foraging by large herbivores is likely not only to affect the abundance of palatable species, but also to induce cascading effects across entire plant communities. To investigate these possibilities, we first tested the effects of deer browsing and soil disturbance on herbaceous plant diversity patterns in boreal forest, using standard analyses of variance. Second, we evaluated direct and indirect effects of deer browsing and soil disturbance on the small-scale richness of herbaceous taxa using a multilevel path analysis approach. The first set of analyses showed that deer browsing and soil disturbance influenced herb richness. Path analyses revealed that deer browsing and soil disturbance influenced richness via complex chains of interactions, involving dominant (i.e., the most abundant) browsing-tolerant (DBT) taxa and white birch (Betula papyrifera), a species highly preferred by white-tailed deer (Odocoileus virginianus). We found no evidence that an increase of white birch in fenced quadrats was the direct cause of a decrease in herb richness. However, we found strong evidence that a higher abundance of DBT taxa (i.e., graminoids and Circium arvense), both in fenced and unfenced quadrats, increased herb layer richness. We propose an empirical model in which competitive interactions between white birch and DBT taxa regulate the strength of facilitative relationships between the abundance of DBT taxa and herb richness. In this model, deer browsing and the intensity of soil disturbance initiate a complex chain of cascading effects in boreal plant communities by controlling the abundance of white birch.

We evaluated spruce budworm (Choristoneura fumiferana (Clem.)) outbreak effects in nine study areas (60-86 ha each) located in the boreal forest of eastern Quebec (Canada). In each area, spruce budworm outbreak effects were measured from vegetation plots, dominant canopy and understory tree age structures, retrospective analysis of aerial photographs, defoliation records, and host tree growth reductions (dendrochronology). Large-scale synchronous outbreaks were detected across the region around the years 1880 , 1915 , 1950 , and 1980 to what was expected for a region where host species (balsam fir (Abies balsamea (L.) Mill.), Picea spp.) content is relatively high, these spruce budworm outbreaks seemed to have a relatively minor influence on stand dynamics, with the exception of the most recent outbreak (1980). This outbreak resulted in major stand mortality in the southern part of the region and favored the establishment of extensive tracts of young even-aged stands with few residual mature trees. This very abrupt increase in outbreak severity compared with earlier outbreaks, perhaps due to climatic or random factors, suggests that historical trends in successive outbreak severity should be extrapolated very cautiously and that the study of several outbreak cycles is needed to establish a range of natural variability that can be used to develop an ecosystem forest management strategy.Résumé : Nous avons évalué les effets des épidémies de tordeuse des bourgeons de l'épinette (Choristoneura fumiferana (Clem.)) dans neuf aires d'étude (de 60-86 ha chaque) situées dans la forêt boréale de l'est du Québec, au Canada. Dans chaque aire d'étude, les effets des épidémies de tordeuse des bourgeons de l'épinette ont été mesurés à partir de placettes de végétation, de la structure d'âge des arbres de la canopée dominante et du sous-bois, d'une analyse rétrospective de photographies aériennes, de relevés de défoliation et des réductions de croissance des arbres hôtes (dendrochronologie). Des épidémies synchrones ont été détectées sur l'ensemble de la région autour des années 1880, 1915, 1950 et 1980. Contrairement à ce qui était anticipé dans une région où les espèces hôtes (sapin baumier (Abies balsamea (L.) Mill.), Picea spp.) sont relativement abondantes, ces épidémies de tordeuse des bourgeons de l'épinette semblent avoir eu un impact relativement limité sur la dynamique des peuplements, à l'exception de l'épidémie la plus récente (1980). Cette épidémie a causé une forte mortalité dans les peuplements situés dans la partie sud de la région et a favorisé l'établissement, sur de vastes étendues, de jeunes peuplements équiennes contenant peu d'arbres matures résiduels. La hausse très abrupte de l'intensité de cette épidémie comparativement aux épidémies précédentes est probablement attribuable à des facteurs climatiques ou aléatoires et indique que les tendances historiques de l'intensité des épidémies successives devraient être extrapolées avec beaucoup de prudence. Ce résultat indique aussi qu'il faut étudier plusieurs cy...

Abstract. Heavy browsing pressure from large ungulates is a multicontinent phenomenon that causes regeneration failure of many palatable tree species and induces important socioeconomic and ecological impacts in forest ecosystems. The development of forest management practices that address adequately this issue, however, remains scarce and challenging because (1) large herbivores are both a resource and a source of disturbance; (2) the management of forests and ungulate populations remains largely disconnected in practice; and (3) we still lack a good understanding of the role of critical factors, especially deer densities, vegetation attributes, and their interactions, on the magnitude of browsing damages on forest regeneration. We bring new insights into these challenging issues by critically reviewing the current methods used by managers and conservationists to mitigate deer impacts on forest regeneration, emphasizing the spatial scale at which these methods are undertaken. Specifically, we review management actions at multiple scales on both deer populations (e.g., hunting) and vegetation (e.g., silvicultural treatments) that are common to most deer-forest systems and, for that reason, deserve priority investigation. We identify strengths and limitations of current management actions and highlight the main research gaps. Based on this review, we propose a new integrated management scheme that explicitly addresses: (1) the integration and prioritization of management actions, (2) the development of adaptive management plans, and (3) the participation of stakeholders. Conflicting demands by different stakeholders have challenged the effectiveness of management strategies in deer-forest systems. To reverse this situation, we advocate for a shift of paradigm and the development of integrated strategies that (1) bridge the gap between management actions and the design of in situ experiments and (2) coordinate actions at multiple spatial scales on both deer populations and forests. We propose a new framework informed by key objectives and grounded in the adaptive management paradigm to support this transition, and suggest a research agenda for the next decade(s).