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The boreal forest is subject to various anthropogenic disturbances, including logging, mining, and hydroelectricity production and transport. These disturbances affect Indigenous communities and the culturally salient species they depend on for the practice of traditional and subsistence activities. Rhododendron groenlandicum (Oeder) Kron & Judd is one such species whose leaves are used to treat various ailments, due to their concentration in biologically active chemicals such as flavonoids. Our objective was to assess the effect of anthropogenic disturbances on the chemical properties of R. groenlandicum on the territories of three Indigenous communities. Leaf samples were collected near mines, under hydroelectric power lines, and in non-disturbed sites. Our results showed that variations in flavonoid concentration were mainly related to territory ([R.sup.2] = 0.43, P = 0.0005), while disturbance type had a smaller effect ([R.sup.2] = 0.18, P = 0.02). Samples from Nemaska, the northernmost territory with the most open forest stands, had higher concentrations of epicatechin (+23%, P = 0.03). Quercetin-3-glucoside concentrations were lower near mines (-19%, P = 0.01). The effects of disturbances on the chemical signature of R. groenlandicum are complex, and a complete assessment of the consequences of industrial activity on Indigenous landscape value must take into account other culturally salient species. Key words: Labrador tea, Indigenous people, anthropogenic disturbance, phenolic compounds, culturally salient species, Introduction The boreal forest is disturbed by various anthropogenic activities, which alter species composition, homogenize landscapes, and decrease biodiversity (Venier et al. 2014; Gauthier et al. 2015). In Canada, mining [...]

The natural disturbance-based management (NDBM) aims to maintain specific structural and compositional attributes of natural forests in managed stands. Operationally, NDBM relies on diversifying and adapting silvicultural practices, including partial harvesting (PC), to expand the range of options beyond that of simply clearcuts (CC). Established in 1998, the Sylviculture et Amenagement Forestier Ecosystemique (SAFE) project evaluates this potential in hardwood, mixedwood, and coniferous stands in northwestern Quebec, Canada. Our results confirmed a part of the NDBM objectives, i.e., PC allowed the maintenance of stands with mixed structure and composition, constituting an interesting complement to CC, which reset stand regeneration. However, PC did not accelerate the stand transition to later stages with less intensive harvesting or to earlier stages with more intensive harvesting. We essentially had an initial impact, delaying or stopping the stand evolution that dissipates over time and more quickly with less intensive harvesting. Furthermore, our results did not support the ability of PC to enhance the development of old-growth attributes like deadwood. Despite the 20-year horizon of this study, further field surveys will be required in the future to better understand the impact of different silvicultural treatments on forest productivity and biodiversity preservation throughout a forest rotation. Key words: natural disturbance-based management (NDBM), mixed stands, boreal forest, partial cuts, clearcuts, 1. Introduction Natural disturbance-based management (NDBM) has been widely advocated as a means to maintain healthy and resilient forest ecosystems by reducing differences between natural and managed landscapes throughout North [...]

The development of rare earth element (REE) production in Canada could generate significant economic benefits but also poses serious potential risks to the environment. Rare earth elements have been widely used in modern life and industries and are even indispensable in some crucial advanced technologies (e.g., permanent magnets). Increasing demand and the current United States - China trade tensions provide a commercial economic development opportunity for Canada, which has rich resources of REEs, to develop its own sector. However, environmental and health issues caused by REE production are challenges that Canada has to face given that significant environmental impacts have been reported elsewhere (e.g., China). Little literature is available on the potential environmental risks associated with the development of REE production in Canada. It is important to know what environmental issues, particularly those generated by REEs themselves, may happen in Canada in the future. Therefore, three major aspects are evaluated and summarized from multidisciplinary perspectives in this paper: (1) a general conceptual model of the transport of REEs as a group in the environment is established; (2) toxicity levels, biochemical mechanisms, and physiological effects of REEs on different organisms are reviewed, and case-studies from existing REE mining areas are briefly highlighted; and (3) considering specific environmental condition and risk factors, environmental risks that Canada may face in future REE developments are identified and discussed. This review concludes with macro-identification of potential environmental risks associated with the development of REE production in Canada considering both human and ecological health. We note that ingestion, inhalation, and dermal exposure for workers and surrounding residents (including potentially Indigenous communities) and subarctic and arctic climate conditions could increase the risks to human and ecological health in future REE production development in Canada. Finally, future research directions are proposed that could be applied to both Canadian and other geographical contexts. Key words: lanthanides, mining industry, emerging contaminants, ecological risks, boreal areas. Le developpement de la production de metaux du groupe des terres rares (MTR) au Canada pourrait generer des avantages economiques importants, mais il presente aussi des risques serieux pour l'environnement. Les metaux du groupe des terres rares ont ete largement utilises dans la vie moderne et les industries, et ils sont meme indispensables dans certaines technologies de pointe essentielles (par exemple, les aimants permanents). La demande croissante et les tensions commerciales actuelles entre les Etats-Unis et la Chine offrent des occasions de developpement economique commercial au Canada, qui dispose de riches ressources en MTR, pour developper son propre secteur. Cependant, les problemes d'environnement et de sante causes par la production de MTR constituent des defis auxquels le Canada doit faire face, puisque des impacts environnementaux importants ont ete rapportes ailleurs (par exemple en Chine). Il existe peu de documentation sur les risques environnementaux potentiels associes au developpement de la production de MTR au Canada. Il est important de savoir quels problemes environnementaux, en particulier ceux generes par les MTR eux-memes, pourraient survenir au Canada dans le futur. Par consequent, trois aspects majeurs sont evalues et resumes a partir de perspectives multidisciplinaires dans cet article : (1) un modele conceptuel general du transport des MTR en tant que groupe dans l'environnement est etabli; (2) les niveaux de toxicite, les mecanismes biochimiques et les effets physiologiques des MTR sur differents organismes sont examines, et des etudes de cas provenant de zones d'exploitation miniere des MTR existantes sont brievement mises en evidence; et (3) en tenant compte des conditions environnementales specifiques et des facteurs de risque, les risques environnementaux auxquels le Canada pourrait etre confronte dans les developpements futurs des MTR sont identifies et discutes. Cette synthese se termine par une macro-identification des risques environnementaux potentiels associes au developpement de la production de MTR au Canada, en tenant compte de la sante humaine et ecologique. Les auteurs notent que l'ingestion, l'inhalation et l'exposition cutanee chez les travailleurs et les residents avoisinants (y compris les communautes autochtones potentielles), ainsi que les conditions climatiques subarctiques et arctiques pourraient accroitre les risques pour la sante humaine et ecologique dans le developpement futur de la production de MTR au Canada. Enfin, des orientations de recherche futures sont proposees qui pourraient etre appliquees a la fois au contexte canadien et a d'autres contextes geographiques. [Traduit par la Redaction] Mots-cles: lanthanides, industrie miniere, contaminants emergents, risques ecologiques, regions boreales., 1. Introduction Increasing demand for rare earth elements (REEs) is stimulating an increasing number of production projects outside of China, which is currently the largest global REE producer. Several countries [...]

Although the mining industry provides minerals and metals to the global market and represents important economic opportunities, it also constitutes a major anthropogenic disturbance in the ecosystems where it takes place. However, little is known about its offsite impacts on plant communities. We assessed the frequency and the abundance of five common boreal understorey plant species (Coptis trifolia (L.) Salisb., Cornus canadensis L., Linnaea borealis L., Lysimachia borealis (Raf.) U.Manns & Anderb., and Maianthemum canadense Desf.) at different distances around six mines in Abitibi-Témiscamingue and Nord-du-Québec (Québec). Frequency and (or) abundance of Coptis trifolia and M. canadense decreased near mines, suggesting that they might be sensitive to the loss of forest cover, particle deposition, and soil contamination induced by mining. Conversely, the frequency and abundance of Cornus canadensis increased near active mines, which indicates its resilience to the stress caused by mines and its ability to exploit the niche space left by more sensitive species. No effects on Linnaea borealis and Lysimachia borealis were observed. Our study suggests the possible presence of offsite impacts of mines on plant communities. Further studies considering enigmatic impacts should be conducted in order to develop our understanding of the broader environmental footprint of mining activity. Key words: boreal forest, enigmatic impacts, offsite impacts, plant communities, stress. Bien que l'industrie minière fournisse des minéraux et des métaux pour le marché mondial et représente d'importantes occasions économiques, elle constitue aussi une perturbation anthropique majeure dans les écosystèmes où elle prend place. Toutefois, on sait peu de choses sur ses impacts hors site sur les communautés végétales. Les auteurs ont évalué la fréquence et l'abondance de cinq espèces de plantes de sous-bois boréales communes (Coptis trifolia (L.) Salisb., Cornus canadensis L., Linnaea borealis L., Lysimachia borealis (Raf.) U.Manns & Anderb., and Maianthemum canadense Desf.) à différentes distances autour de six mines en Abitibi-Témiscamingue et dans le Nord-du-Québec (Québec). Leurs résultats ont montré que Coptis trifolia et M. canadense étaient affectés négativement par la présence des mines, ce qui suggère qu'ils pourraient être sensibles à la perte du couvert forestier, au dépôt de particules et à la contamination du sol induits par l'exploitation minière. À l'inverse, Cornus canadensis a favorisé l'activité minière, ce qui indique sa résilience au stress causé par les mines et sa capacité à exploiter l'espace de niche laissé par les espèces plus sensibles. Aucun effet sur Linnaea borealis et Lysimachia borealis n'a été observé. Cette étude confirme l'existence d'impacts hors site des mines sur les communautés végétales. Des études supplémentaires portant sur les impacts non conventionnels devraient être réalisées afin de développer notre compréhension de l'empreinte environnementale plus large de l'activité minière. [Traduit par la Rédaction] Mots-clés : forêt boréale, impacts non conventionnels, impacts hors site, communautés végétales, stress., Introduction Although the mining industry provides minerals and metals to the global market and represents important economic opportunities, it also constitutes a major anthropogenic disturbance in the ecosystems where it [...]

The erosion of old-growth forests in boreal managed landscapes is a major issue currently faced by forest managers; however, resolving this problem requires accurate surveys. The intention of our study was to determine if historic operational aerial forest surveys accurately identified boreal old-growth forests in Quebec, Canada. We first compared stand successional stages (even-aged vs. old-growth) in two aerial surveys performed in 1968 (preindustrial aerial survey) and 2007 (modern aerial survey) on the same 2200 [km.sup.2] territory. Second, we evaluated the accuracy of the modern aerial survey by comparing its results with those of 74 field plots sampled in the study territory between 2014 and 2016. The two aerial surveys differed significantly; 80.8% of the undisturbed stands that were identified as 'old-growth' in the preindustrial survey were classified as 'even-aged' in the modern survey, and 60% of the stands identified as 'old-growth' by field sampling were also erroneously identified as 'even-aged' by the modern aerial survey. The scarcity of obvious old-growth attributes in boreal old-growth forests, as well as poorly adapted modern aerial survey criteria (i.e., criteria requiring high vertical stratification and significant changes in tree species composition along forest succession), were the main factors explaining these errors. It is therefore likely that most of Quebec's boreal old-growth forests are currently not recognized as such in forest inventories, challenging the efficacy of sustainable forest management policies. Key words: monitoring, ecosystem-based management, overmature, black spruce, sampling bias. L'erosion des superficies des vieilles forets boreales est actuellement l'un des enjeux majeurs de l'amenagement forestier; cependant, la resolution de ce probleme necessite des inventaires precises. Ainsi, l'objectif de cette etude etait de determiner si les precedents inventaires forestiers aeriens identifiaient correctement les vieilles forets dans les paysages boreaux du Quebec, au Canada. Nous avons compare les stades de succession (foret equienne ou vieille foret) de deux inventaires aeriens realises en 1968 (inventaire aerien preindustriel) et en 2007 (inventaire aerien moderne) sur un territoire de 2200 [km.sup.2]. Nous avons aussi compare les resultats de l'inventaire aerien moderne avec ceux obtenus a partir de 74 placettes de terrain echantillonnees entre 2014 et 2016. Les deux inventaires aeriens etaient tres incoherents : 80,8 % des peuplements non-perturbes identifies comme << vieilles forets >> par l'inventaire preindustriel etaient classes comme << equiennes >> par l'inventaire moderne et 60 % des placettes de terrain identifiees comme << vieilles forets >> etaient aussi classees << equiennes >> par l'inventaire aerien moderne. Le manque d'attributs de vieilles forets evidents ainsi que l'utilisation de criteres inadaptes (c.-a-d. necessitant une forte complexite verticale et d'importants changements de composition en especes arborescentes durant la succession forestiere) etaient les principaux elements expliquant ces erreurs. Il est ainsi possible que la majorite des vieilles forets boreales du Quebec ne soient pas identifiees comme telles, limitant l'efficacite des strategies de gestion durable. Mots-cles : inventaire, amenagement ecosystemique, suranne, epinette noire, biais d'echantillonnage., 1. Introduction Boreal old-growth forests, i.e., stands driven by gap dynamics, are defined by specific structural attributes as well as strong temporal continuity due to the absence of primary disturbances [...]

In the context of global changes that modify the distribution range of species, there is an urgent need to identify climate variables affecting species dispersal. We investigated patterns of aerial propagule release (sexual and asexual) of boreal bryophytes in response to weather. We present the first community-level study that examines the impact of weather on the phenology of bryophytes, and we divided it into phases. Bryophyte propagule rain was trapped in 2013 (summer and fall) and 2014 (spring and fall), and climatic variables were collated from the years 2012 to 2014. The phases of the phenology and the weather variables one season to two years preceding propagule release, which may influence the dispersal of propagules, were identified. Propagule release varies with weather conditions at the time of dispersal (direct effects), but is also associated with weather during the winter and summer one year preceding dispersal (indirect effects), which presumably influences survival, growth, and fertilization of the mother plant as well as propagule and sporophyte development. We suggest that propagule release is related to weather conditions occurring from one to several previous seasons, particularly humidity, temperature, and length (duration) of winter. Dividing the phenology into phases, we present an innovative method that should provide new insights into bryophyte dispersal dynamics in response to climate. Key words: boreal latitudes, climate, gametophyte, propagule release, phenology. Resume: Les changements globaux, modifiant les aires de distributions des especes, rendent opportun d'identifier les variables climatiques jouant sur les patrons de dispersion. Nous etudions les pluies de propagules aeriennes (unites sexuelles et asexuelles de dispersion) de bryophytes boreales en reponse au climat. Cette etude est la premiere effectuee a l'echelle de la communaute et ou le cycle phenologique des bryophytes est divise en phases. Les propagules furent interceptees en 2013 (ete et automne) et 2014 (printemps et automne), et les variables climatiques de la region compilees de 2012 a 2014. Les variables climatiques influencant chaque phase du cycle, une saison a deux ans avant la dispersion, furent identifiees pour determiner quelles phases et quelles variables impactent majoritairement le relargage des propagules. Ce relargage dependait de variables climatiques contemporaines a la dispersion (directes) et indirectes durant l'hiver et l'ete precedent (indirectes). Ces variables joueraient sur la survie/croissance de la plante mere, la fertilisation et le developpement des propagules et des sporophytes. Le relargage des propagules semble particulierement dependre de l'humidite, de la temperature et de la longueur de l'hiver des saisons en amont. En divisant leur cycle phenologique en phases nous fournissons ici une methode novatrice pour comprendre les relations entre la dispersion des bryophytes et le climat. Mots-cles : ecosystemes boreaux, conditions climatiques, phenologie, phenophases, relargage des propagules., Introduction How species diversity patterns are influenced by the impacts of environmental factors on the organisms' phenology and distribution has been investigated previously (Benson-Evans 1961; Dougherty et al. 1994; Xiao [...]

In the boreal forest, long-lasting canopy gaps are associated with lichens on dry sites and with Sphagnum spp. on wet sites. We hypothesize that ground-layer composition plays a role in maintaining gaps through its effects on fine root biomass (diameter [less than or equal to] 2 mm) and soil nutrient availability. Along gradients of canopy openness in both jack pine (Pinus banksiana Lamb.) lichen and black spruce (Picea mariana (Mill.) B.S.P.)--moss forests, the relationships between canopy closure, ground-layer composition, tree fine root biomass, and soil nutrients were analyzed and decomposed using path analysis. The effects of lichen and Sphagnum spp. removal on tree fine root biomass and soil nutrients were tested in situ. Although variations in pine fine root biomass were mainly explained by stand aboveground biomass, lichen removal locally increased fine root biomass by more than 50%, resin extractable soil potassium by 580%, and base cations by 180%. While Sphagnum cover was identified as a key driver of stand aboveground biomass reduction in paludified forest sites, its removal had no short-term effects on spruce fine root biomass and soil nutrients. Our results suggest that lichens, more than Sphagnum spp., affect tree growth via direct effects on soil nutrients. These two different patterns call for different silvicultural solutions to maintain productive stands. Key words: lichen, moss, Sphagnum spp., fine root, forest regeneration. En foret boreale, l'ouverture prolongee du couvert forestier favorise un couvert de lichens sur les stations xeriques et un couvert de sphaignes sur les stations hydriques a subhydriques. Nous posons l'hypothese que la composition de la strate des mousses et lichens joue un role dans le maintien de clairieres ouvertes par ses effets sur la biomasse de racines fines (diametre [less than or equal to] 2 mm) et la disponibilite des nutriments dans le sol. Nous avons analyse et decompose les relations entre l'ouverture de la canopee, la composition de la strate de vegetation basse, la biomasse de racines fines des arbres et les nutriments du sol a l'aide d'une analyse de pistes le long de gradients d'ouverture du couvert en pinede (Pinus banksiana Lamb.);! lichens et enpessiere (Picea mariana (Mill.) B.S.P.) a mousses. Les effets de l'enlevement des lichens etdes sphaignes sur la biomasse de racines fines des arbres et les nutriments du sol ont ete testes in situ. Quoique la variation de la biomasse de racines fines des pins ait ete principalement expliquee par la biomasse aerienne du peuplement, l'enlevement des lichens a localement augmente la biomasse de racines fines de plus de 50 %, ainsi que la disponibilite en potassium et en cations basiques extraits de resine de respectivement 580 % et 180 %. Bien que le couvert de sphaignes ait ete identifie comme un facteur cle de la reduction de la biomasse aerienne des peuplements etablis sur les stations forestieres paludifiees, son enlevement n'a pas eu d'effet a court terme sur la biomasse de racines fines des epinettes ni sur le contenu en nutriments du sol. Nos resultats indiquent que les lichens, plus que les sphaignes, influencent la croissance des arbres en ayant des effets directs sur les nutriments du sol. Le maintien de peuplements forestiers productifs sur ces deux types de station necessite des solutions sylvicoles differentes. Mots-cles: lichens, mousses, sphaignes, racines fines, regeneration forestiere., Introduction The ground layer (i.e., bryophyte and lichen layer) is an important component of the boreal forest biome (Cornelissen et al. 2007), whose composition largely influences ecosystem processes, including the [...]

Abstract: Canada's boreal biome is a mosaic of forests and peatlands. These ecosystems have developed dynamically, periodically affected by disturbance events of significant spatial extent and variable severity, reducing ecosystem [...]

Ecosystem-based management advocates that forestry disturbances should aim to emulate natural disturbances to mitigate the landscape-level impact of forest management. This study compares the impact of clear-cuts followed by a prescribed burn (CCPB) with clear-cuts alone (CC) and current careful logging practices (CLAAG: 'careful logging around advanced growth') on understory composition within black spruce (Picea mariana Miller (BSP)) paludified forest stands at the plot, site, and treatment levels using a functional-type approach. Vascular and nonvascular taxa showed significant differences in composition at the plot level among treatments. We found that pioneer taxa occurred mainly in CCPB sites, while late-successional taxa characterized CC sites. CLAAG sites had higher taxa richness than CCPB and CC sites, and we found that CCPB treatments were most likely to promote vascular taxa compositions that are more similar to those observed after natural disturbances. Additionally, the relative abundance of Sphagnum spp., responsible for paludification, was significantly reduced in sites treated by prescribed burning. This study therefore presents results suggesting that prescribed burning might represent a sustainable alternative to current harvesting techniques in the Clay Belt of eastern Canada that could help in preserving biodiversity (in terms of understory species assemblage) while maintaining or even enhancing forest productivity. Key words: boreal forest ecosystem, black spruce forest stands, prescribed fire, clear-cut, biodiversity, understory composition, conservation management, paludification. Les strategies d'amenagement forestier ecosystemique preconisent d'imiter les effets des perturbations naturelles pour attenuer l'impact de traitements sylvicoles a l'echelle du paysage. Cette etude compare les effets de coupe totale suivie de brulage dirige (CCPB) avec ceux de coupe totale (CC) et de pratique sylvicole appliquee limitant la perturbation du sol (CLAAG : << careful logging around advanced growth >>) sur la composition des especes de sous-bois, au sein de peuplements d'epinette noire (Picea mariana Miller (BSP)) touches par la paludification. Les analyses, effectuees a l'echelle de la placette, du site et du traitement ont permis via l'analyse des taxons et des types fonctionnels d'examiner les effets respectifs de chaque traitement. Des differences de composition significatives parmi les especes vasculaires et non-vasculaires ont ete observees a l'echelle de la placette selon le type de traitement considere. Nous avons constate que les especes pionnieres etaient associees aux sites CCPB tandis que les especes de fin de succession etaient caracteristiques des sites CC. Une richesse specifique plus elevee a ete observee parmi les sites CLAAG que dans les sites CCPB et CC. Nous avons par ailleurs trouve que les traitements CCPB etaient davantage enclin a promouvoir des patrons de composition d'especes vasculaires similaires a ceux observes apres des perturbations naturelles comme les feux de foret. Nous avons egalement constate une abondance relative plus faible des especes de sphaigne, responsible du phenomene de paludification, au sein des sites traites par brulage dirige. Les resultats de cette etude suggerent ainsi que le brulage dirige represente une alternative durable aux pratiques sylvicoles actuelles en permettant de conserver la biodiversite (en termes d'assemblages d'especes) et de maintenir voire d'augmenter la productivite des peuplements exploites. Mots-cles: ecosysteme forestier boreal, peuplements d'epinette noire, brulage dirige, coupe totale, biodiversite, composition des especes de sous-bois, gestion de la conservation, paludification., Introduction In boreal forests, stand-replacing wildfires are considered to be the primary disturbances that drive natural forest dynamics (Bergeron et al. 2001; Harvey et al. 2002, Bouchard et al. 2008; [...]

Native floras of oceanic islands are among the most threatened on Earth. For example, only 1% of intact dry-forest ecosystems remain on Reunion, harbouring numerous endangered native species. Alien species invasion is one of the more important threats facing these ecosystems, as it has been hypothesized that, over time, the abundance of alien species will increase more than that of native species. To explore this, we studied floristic changes over a 16 year period (1995-2011) in six dry-forest remnants. Species richness and abundance increased for both alien and native species over this period, but at a significantly higher rate for the abundance of invasive alien plants. Despite this, Jaccard's coefficient indicates a high level of similarity between the communities of 1995 and 2011. Also, the single site that benefited from invasive species management experienced the largest increase in native species, both in terms of specific richness and abundance. This study underlines the importance of permanent plots in studying the dynamics of invaded communities and in understanding plant succession. It also suggests a potential temporal persistence of island dry-forest communities, despite the expansion of alien species, and suggests the development of a new pathway in secondary succession where native and alien species coexist. Keywords: biological invasions, forest remnants, invasive alien species, semi-xerophytic forest. Les flores indigenes insulaires sont parmi les plus menacees du monde. A La Reunion par exemple, seulement 1 % des ecosystemes de foret semi-seche de basse altitude perdure alors que ces forets abritent de nombreuses especes endemiques et en danger d'extinction. Ces ecosystemes sont particulierement soumis aux invasions repetees par des especes exotiques; favorisant, au cours du temps, une augmentation des especes exotiques au detriment des especes indigenes. Nous testons cette hypothese via l'etude des changements floristiques sur une periode de 16 ans (de 1995 a 2011) dans les communautes vegetales de six fragments de foret semi-seche. La richesse specifique et l'abondance des especes exotiques et indigenes augmentent au cours de ces 16 annees mais avec un taux significativement plus important pour les especes exotiques envahissantes. Malgre ceci, l'indice de similarite de Jaccard indique un haut niveau de similarite entre les communautes de 1995 et de 2011. De plus, l'unique site beneficiant d'un programme de lutte contre les especes exotiques est aussi celui oU l'augmentation du nombre et de l'abondance des especes indigenes sont les plus importants. Cette etude souligne l'importance de recourir a des parcelles d'echantillonnages permanentes pour comprendre les dynamiques des communautes envahies et les successions vegetales. Elle indique aussi une potentielle persistance temporelle des communautes vegetales insulaires de foret semi-seche malgre l'expansion des especes exotiques. Pour finir, elle suggere de nouvelles voies de developpement dans la succession secondaire lorsque les especes indigenes et exotiques sont amenees a coexister. Mots-cles: invasions biologiques, fragments de foret, especes exotiques envahissantes, foret semi-xerophile., Introduction The decline and extinction of plants and animal species are indicators of ecosystem degradation (Menges 1990). The distribution range of regional and endemic species (specialist species with narrow niches) [...]

Modification of forest attributes and structural components like downed wood (DW) during forest harvest can lead to local species loss. Epixylic bryophytes have been proposed as good indicators of such changes. Unharvested control, variable canopy retention, and single pass harvest represent a gradient in forest harvest impact and can be used to test the response of epixylic bryophytes to different levels of environmental change. The objective of this study was to see if variable canopy retention attenuates environmental change associated with harvesting, consequently maintaining an epixylic community more similar to unharvested stands than single pass harvesting. Environmental conditions and DW characteristics were sampled on 225 DW pieces distributed in 45 permanent plots. Results showed that treatment affected epixylic richness through its impact on canopy openness and DW diameter and decomposition class. Fewer species were found in more open habitats and more species were found on bigger and more decomposed DW. Most epixylic species were more commonly found on the forest floor than on the DW. In conclusion, variable canopy retention harvest offered microclimatic conditions and DW availability and quality more suitable for epixylic species than single pass harvest, which was less suitable for epixylic species. Resume: La modification des attributs forestiers et des composantes structurales tel les debris ligneux grossiers (DLG) peut entrainer la perte locale d'especes associees. Les bryophytes epixyliques ont ete suggerees comme de bons indicateurs de ces changements. Un temoin non perturbe, une coupe a retention variable de canopee et une coupe totale constituent un gradient d'impact des activites forestieres et sont utilises pour observer la reponse des epixyliques aux niveaux de perturbation. L'objectif de cette etude est de voir si la retention variable de canopee attenue les changements micro environnementaux et la destruction des DLG associee avec la recolte maintenant ainsi une riche communaute d'epixyliques. Les resultats montrent que le traitement influence la richesse des epixyliques a travers son effet sur l'ouverture de la canopee, le diametre moyen et la classe de decomposition. Moins d'especes sont retrouvees dans les habitats ouverts et plus d'especes sont re-trouvees sur les gros DLG bien decomposes. La plupart des epixyliques sont plus communement retrouvees au sol que sur les DLG. La coupe totale est le traitement le moins propice a la colonisation par les epixyliques alors que la retention variable de canopee offre le microclimat et une disponibilite de DLG de qualite propice a la colonisation par les epixyliques., Introduction Forest harvest alters biodiversity by changing forest attributes and structural components like downed wood (DW) on which many organisms depend for food and shelter (Harmon et al. 1986). Modification [...]

Boreal forests have commonly been described as dominated by monospecific postfire stands that are reburnt well before other ecological process than those occurring immediately after fire can take place. Research undertaken over the last 30 years has given us a very different perspective of the complexity of Canadian boreal forests. Old-growth forests are common and their development is controlled by nonfire disturbances. Consequently, monospecific even-aged stands can develop towards more diversified uneven-aged stands with increasing time since fire. This complex disturbance regime, including both fire and nonfire disturbances, is partially responsible for a higher than expected biodiversity (e.g., understory) in these forests. The dominating forest management model in Canadian boreal forests, based on clear-cut harvesting and regeneration of short rotation even-aged stands, does not reflect the complexities of the disturbance-succession cycle observed in Canadian natural boreal forests. Key words: Boreal forest, succession, old growth, understory biodiversity, fire, secondary disturbances. Les forets boreales sont generalement considerees comme etant une large etendue de peuplements monospecifiques issus de feux qui vont rebruler bien avant que des processus ecologiques autres que ceux lies aux feux ne puissent avoir cours. Les recherches realisees au cours des 30 dernieres annees revelent une perspective tres differente. Les vieilles forets sont abondantes et elles sont souvent controlees par des regimes de perturbations autres que les feux. A mesure que le temps s'ecoule apres les feux, les peuplements equiennes et monospecifiques se transforment graduellement en peuplements plus diversifies et a structure inequienne. Ce regime de perturbations complexe qui inclut a la fois le feu et d'autres types de perturbations cree une biodiversite (ex., sous-bois) plus elevee que generalement attendue. Le modele d'amenagement actuellement preconise dans la foret boreale canadienne base sur la coupe totale, et la reconduction en rotation courte de peuplements monospecifiques equiennes, s'eloigne passablement de la complexite de la dynamique naturelle observee. Mots-cles : Foret boreale, succession, feu, biodiversite du sous-bois, forets anciennes, perturbations secondaires., Introduction The circumboreal forest accounts for about one quarter of the world's closed-canopy forested area, almost 1 billion hectares (Burton et al. 2010). Although heavily exploited for a long time [...]

: Machinery traffic restrictions during forest harvest have been adopted to minimize soil damage and protect tree regeneration. However, this practice is questioned for paludifying black spruce (Picea mariana (Mill.) BSP) stands in which severe soil disturbance by wildfire restores forest productivity. The objective of this study was to determine, 8 years after harvest, how soil disturbance created by clearcutting and careful logging affected black spruce natural regeneration and growth and how this effect varied by soil type. While regeneration density was higher following careful logging, stocking was not influenced by harvest method. Regenerating stands were taller following clearcutting despite potentially greater damages to preestablished regeneration. Compared with careful logging, clearcutting also resulted in reduced cover of Sphagnum spp. and ericaceous shrubs. Spruce stem density and stocking were both higher on organic and subhydric soils and lower on mesic soils. No significant interactions were observed between harvest method and soil type, indicating that the observation of taller black spruce stands and adequate stocking with clearcutting may be applicable to all soil types considered in this study. These results suggest that an adequate level of soil disturbance is an important part of forest regeneration, particularly in ecosystems where an autogenic reduction in productivity occurs. Resume: Afin de preserver les sols et la regeneration durant la recolte, la circulation de la machinerie forestiere est fre- quemment restreinte a des sentiers definis. Toutefois, cette pratique est remise en question dans les peuplements d'epinette noire (Picea mariana (Mill.) BSP) susceptibles a la paludification ou de severes perturbations des sols causees par le feu sont aptes a ameliorer la productivite des peuplements. L'objectif de cette etude etait de determiner comment la perturbation des sols causee lors de la coupe totale et la coupe de protection affectent la regeneration de l'epinette noire 8 ans apres la recolte, et comment cet effet est conditionne par le type de sol. Alors que la densite de regeneration de l'epinette noire etait superieure apres la coupe de protection, le coefficient de distribution n'etait pas influence par la methode de re- colte. Les peuplements d'epinette regeneres apres coupe totale etaient plus hauts en depit d'un potentiel de dommage plus grand a la regeneration preetablie. Comparee a la coupe de protection, la coupe totale a aussi resulte en une reduction de la couverture au sol de la sphaigne et des ericacees. La densite et le coefficient de distribution de l'epinette noire etaient superieurs sur les sols organiques et subhydriques et inferieurs sur les sols mesiques. Aucune interaction significative n'a ete observee entre la methode de recolte et le type de sol, indiquant qu'une plus grande hauteur des peuplements et un coefficient de distribution d'epinette adequat apres coupe totale pourrait etre applicable a toute la gamme de types de sol consideree dans cette etude. Ces resultats suggerent qu'un niveau de perturbation des sols suffisant lors des operations forestie res est necessaire, particulierement dans les ecosystemes ou des processus autogeniques reduisant la productivite s'operent., Introduction Black spruce (Picea mariana (Mill.) BSP) is one of the most wide-ranging and abundant conifers in North America (Burns and Honkala 1990) and sustains an important forest industry in [...]

Abstract: Boreal forest bryophyte communities are made up of distinct colonies of feathermosses that cover the forest floor. In some black spruce (Picea mariana (Mill.) BSP) boreal forests, Sphagnum spp. [...]