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Copyright of Environmental Reviews is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Environmental Reviews is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Environmental Reviews is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Environmental Reviews is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Environmental Reviews is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Environmental Reviews is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Environmental Reviews is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Environmental Reviews is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Environmental Reviews is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Douglas-fir forests of coastal British Columbia are within the most heavily modified forest ecosystem types in coastal BC and local land managers are developing new forestry practices to retain elements of old growth within the managed forest area. To determine how successful these practices are requires the selection and monitoring of appropriate attributes and knowledge on how they change with stand development. In this paper we summarize previously published results from an extensive data set on four Douglas-fir dominated sites located on eastern Vancouver Island. Data were collected as part of the Coastal Forest Chronosequences project which was addressing questions on (1) how does conversion to managed forests impact species and forest structural diversity and (2) how does this diversity recover in older second-growth stands. Each site contained four stands, a postharvest chronosequence: regeneration (R, 5–10 years), immature (I, 25–45 years), and maturing (M, 75–95 years) stands, and an old growth (O, >240 years) control stand. Over 20 attributes are summarized including structural attributes, and at three sites, detailed biodiversity and process attributes. All old-growth plots exceeded the minimum age criteria and some but not all of the minimum structural attribute criteria for old-growth Douglas-fir forests in the US Pacific Northwest, reflecting regional or site type differences. Most structural attributes showed their greatest change within the first 100 years, although older stands (M and O) still differed based on tree and snag sizes and tree mass or basal area. Most species abundance and richness attributes and process attributes clearly differentiated R from the forested stages but were of less value for differentiating among older (M and O) stands. Arboreal lichen abundance and species richness; the abundance of cryptogams, achlorophyllus plants, litter collembola, and specific species of fungi and carabids; litter fall and gap fraction were the exception, these attributes clearly differentiating M from O stands. In postharvest stands, the overall pattern of change with succession for most attributes, as inferred from the chronosequence, was confirmed to be very different from a previously published conceptual model for post-fire succession. Compared to the post-fire model, the greatest changes in the postharvest stands occurred early in stand development, associated with canopy closure. Although stand structural attributes can clearly be used to distinguish old-growth features in managed forest stands, none-the-less it is important to monitor and demonstrate, at least for a selection of nonstructural attributes, that forestry practices are effective in maintaining biodiversity and associated processes of old-growth forests in the managed forest area. Key words: old-growth forest, succession, Douglas-fir forest, criteria and indicators, biodiversity, managed forest.Les forêts de douglas comptent parmi les types d'écosystèmes forestiers les plus fortement modifiés dans les zones côtières de la Colombie-Britannique, et les aménagistes forestiers locaux mettent au point de nouvelles pratiques forestières pour conserver des éléments de forêt ancienne dans la forêt aménagée. Pour déterminer l'efficacité de ces pratiques, il faut bien choisir et surveiller des attributs de forêt ancienne, et savoir comment ils évoluent au cours du développement d'un peuplement. Dans cet article, nous résumons des résultats déjà publiés provenant d'une vaste base de données, sur quatre sites dominés par le douglas, dans l'est de l'île de Vancouver. Les données ont été recueillies dans le cadre du projet sur les chronoséquences des forêts côtières, lequel abordait notamment les questions suivantes : (1) Quel est l'effet de l'aménagement des forêts sur la diversité des espèces et sur la structure des forêts? (2) Comment cette diversité se rétablit-elle dans les peuplements plus âgés de seconde venue? Chaque site comprenait quatre peuplements constituant une chronoséquence post-récolte : un peuplement en régénération (R, de 5 à 10 ans), un peuplement immature (I, de 25 à 45 ans), un peuplement en cours de maturation (M, de 75 à 95 ans) et un peuplement ancien servant de témoin (O pour « old growth », plus de 240 ans). Nous résumons plus de 20 attributs, notamment des attributs structuraux et, pour trois sites, des attributs détaillés liés à la biodiversité et aux processus. Toutes les placettes d'étude dans les peuplements anciens satisfaisaient au critère d'âge et à certains des critères d'attributs structuraux établis pour les forêts anciennes de douglas, dans les États du nord-ouest des États-Unis donnant sur le Pacifique, ce qui reflète des différences régionales ou liées au type de site. Pour la plupart des attributs structuraux, le changement maximal se produit au cours des 100 premières années, quoique les stades M et O se distinguent toujours sur les plans de la taille des arbres et des chicots, ainsi que de la masse ou de la surface terrière des arbres. La plupart des attributs d'abondance et de richesse en espèces et des attributs de processus différenciaient clairement les peuplements R des autres, mais sont apparus moins utiles pour différencier les peuplements plus âgés (M et O). L'abondance et la richesse en espèces des lichens corticoles, l'abondance des cryptogames, des plantes sans chlorophylle, des collemboles de la litière et d'espèces particulières de champignons et de carabidés, ainsi que la chute de litière et la fraction de trouées faisaient exception : ces attributs différenciaient clairement les peuplements M et O. Dans les peuplements établis après une récolte, le patron général des changements successionnels pour la plupart des attributs, d'après la chronoséquence, s'est avéré très différent d'un modèle conceptuel de la succession après incendie, lequel a fait l'objet d'une publication. Par comparaison à ce modèle, les changements les plus importants dans les peuplements, après récolte, se produisent au début du développement des peuplements, en association avec la fermeture du couvert. Bien qu'il soit évident que des attributs structuraux des peuplements peuvent servir à distinguer des caractéristiques de forêt ancienne dans les peuplements aménagés, il est important de faire un suivi et de montrer, au moins pour certains attributs non structuraux, que les pratiques forestières permettent de maintenir la biodiversité et les processus connexes des forêts anciennes sur le territoire forestier aménagé. Mots clés : forêt ancienne, succession, forêts de douglas, critères et indicateurs, biodiversité, forêt aménagée. [Traduit par la rédaction] [ABSTRACT FROM AUTHOR]

Small lakes (<1 km2) are physically, chemically, and biologically linked to their watersheds through hydrologic, terrestrial, and aerial delivery of materials. Inputs affecting lake function and structure, such as nutrient, energy, sediment, and large wood subsidies, arrive at the lake on three spatial scales, that is, the lake watershed, lake-inflow streams, and lake riparian areas. Lakes are sinks in the waterscape and integrate cumulative inputs from the landscape. Lakes can, therefore, react to landscape disturbances such as forest harvesting. Forest harvesting and associated activities can induce changes in watershed water yields, inputs of organic and inorganic materials to lakes, and in lake temperatures and wind. These changes result in stressors that can alter the lake's physical habitat, water quality, and food webs. Here we review the reported impacts of forest harvesting on small, temperate zone lakes. The magnitude of the lake response to harvesting can depend on factors such as the proportion of the watershed harvested, the intensity of this harvesting, silvicultural practices and other activities, and road construction and density. Other additional factors include the proximity of the lake to harvesting and its impact on hydrological pathways connecting perturbed areas to stream and lake systems. The majority of surveyed studies reported short-term increases in nutrient and energy inputs, increased sedimentation due to harvesting, and increases in wind speeds, where about half reported increases in primary production or decreases in zooplankton biomass. Results on benthic macroinvertebrate, fish, and amphibians were less frequently reported and were geographically variable. Variation in the direction and magnitude of a lake's food web response is likely due to studies of lakes with differences in watershed characteristics and forestry activities that can affect the magnitude of the lake response (i.e., proportion of watershed harvesting, forestry operations methods, hydrological connections to the lake, and site-specific attributes). We also discuss watershed forestry management and the implementation of lakeshore riparian buffers in the context of reducing forestry impacts on lakes. Most studies have been short-term, and the long-term, cumulative effects of forest harvesting on lake ecosystems remain unclear. [ABSTRACT FROM AUTHOR]

Much of Canada's terrestrial biodiversity is supported by boreal forests. Natural resource development in boreal forests poses risks to this biodiversity. This paper reviews the scientific literature to assess the effects of natural resource development on terrestrial biodiversity in Canadian boreal forests. We address four questions: (1) To what extent have Canadian boreal forests changed due to natural resource development? (2) How has biodiversity responded to these changes? (3) Will the biodiversity of second-growth forests converge with that of primary boreal forests? (4) Are we losing species from boreal forests? We focus on trees, understory plants, insects, fungi, selected mammals, and songbirds because these groups have been most studied. We review more than 600 studies and found that changes in community composition are prevalent in response to large-scale conversion of forest types, changes in stand structures and age distributions, and altered landscape structure resulting from forest management and habitat loss associated with other developments such as oil and gas, hydroelectric, and mining. The southern boreal forest has been more highly impacted than the north due to more extensive forest management and the cumulative effects of multiple forms of development. There is abundant evidence that most species are not in danger of being extirpated from the boreal forest due to these anthropogenic changes. A few species, including woodland caribou ( Rangifer tarandus) and grizzly bear ( Ursus arctos), have, however, undergone long-term range contractions. Significant gaps in our ability to assess the effects of natural resource development on biodiversity in the boreal zone are the lack of long-term spatial and population data to monitor the impact of forest changes on ecosystems and species. [ABSTRACT FROM AUTHOR]

The article discusses the importance of unburnt patches (refugia) within the wildfire of Alberta for survival of organisms. Topics discussed include that the forests throughout Alberta experience wildfire as a naturally occurring disturbance that has dominated and molded the landscape, it defines the term refugia and its role in preserving the forest and the animal habitat of the forest; and presents an image showing examples of organisms using different refugia types and scales.

Climate change is affecting Canada's boreal zone, which includes most of the country's managed forests. The impacts of climate change in this zone are expected to be pervasive and will require adaptation of Canada's forest management system. This paper reviews potential climate change adaptation actions and strategies for the forest management system, considering current and projected climate change impacts and their related vulnerabilities. These impacts and vulnerabilities include regional increases in disturbance rates, regional changes in forest productivity, increased variability in timber supply, decreased socioeconomic resilience, and increased severity of safety and health issues for forest communities. Potential climate change adaptation actions of the forest management system are categorized as those that reduce nonclimatic stressors, those that reduce sensitivity to climate change, or those that maintain or enhance adaptive capacity in the biophysical and human subsystems of the forest management system. Efficient adaptation of the forest management system will revolve around the inclusion of risk management in planning processes, the selection of robust, diversified, and no-regret adaptation actions, and the adoption of an adaptive management framework. Monitoring is highlighted as a no-regret action that is central to the implementation of adaptive forest management. [ABSTRACT FROM AUTHOR]

Conservation efforts to sustain water resources and aquatic biodiversity in boreal watersheds will require reliable information on the recent status of various indicator species and an improved understanding of the risks to aquatic biodiversity posed by resource development activities. We reviewed the recent state of knowledge on the responses of aquatic biodiversity to forest management, pulp and paper mill effluents, hydroelectric impoundments, mining of minerals and metals, oil sands extractions, and peat mining and offer a prognosis for aquatic biodiversity under each of these environmental stressors. Despite the prevalence of natural resource development in Canada's largest forest ecosystem, there was a limited amount of published literature on the effects of many of the disturbance types on various indicators of aquatic biodiversity, making it difficult to produce a current and reliable status assessment. Across most of the boreal zone, there is a lack of coordinated, consistent data collection for many of the bioindicators and disturbance types discussed in this review. Forecasting the future state of aquatic biodiversity across the boreal zone is challenged by increasing natural resource development and its interactions with other stressors, especially climate change. The cumulative effects of multiple stressors coupled with resource development activities in boreal watersheds remain largely unknown. More importantly, the ecological thresholds for these cumulative effects (that is, the point at which aquatic ecosystems and their biodiversity cannot recover to a desired state within a reasonable time frame) are also unknown and remain gaps in our knowledge. The recent literature identifies a number of risks to aquatic biodiversity at local (tens of square kilometres) to regional (hundreds of square kilometres) scales associated with natural resource development. There are indications that many of these risks can be minimized by 'greener' technologies for resource development and reclamation, practical conservation planning and regulation, and increased stewardship in watershed management, although the effectiveness of many of these measures cannot yet be assessed from the published literature. [ABSTRACT FROM AUTHOR]

The article reports that linking instream wood recruitment to adjacent forest development in landscapes driven by stand-replacing disturbances like a conceptual model to inform riparian and stream management. Topics include the instream wood plays an important role in stream morphology and creation of fish habitat in conifer forests throughout the temperate zone, and the U.S. Pacific Northwest many streams currently have reduced amounts of instream wood due to past management activities.

The article reports that natural disturbances to inform implementation of ecological forestry in Nova Scotia, Canada. Topics include the core of ecological forestry is the idea that natural forest structure, the processes may be approximated by designing management practices that emulate natural disturbances, and the natural disturbance emulation depends on fundamental knowledge of disturbance characteristics.

Copyright of Environmental Reviews is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper synthesizes data extracted from the literature and data collected in various studies by the author on the quantity, characteristics, and functional importance of coarse woody debris (CWD) in the old-growth forests of British Columbia (B.C.). There is little agreement in the literature about the minimum diameter of CWD or the number of decay classes recognized. In western North America, five decay classes are commonly used, but recent studies suggest fewer decay classes are preferable. Comparisons among decay classes and biogeoclimatic zones and subzones in B.C. reveal that quantities and volumes are greatest (up to approximately 60 kg/m[sup 2] and approximately 1800 m[sup 3] /ha, respectively), and CWD persists the longest (sometimes in excess of 1000 years) in the Coastal Western Hemlock (CWH) biogeoclimatic zone. The quantity and ground cover of CWD increase with forest productivity. Persistence of CWD has varied from less than 100 to over 800 years in two coastal (CWH and Mountain Hemlock (MH)) and three interior (Interior Douglas-fir (IDF), Interior Cedar–Hemlock (ICH), and Engelmann Spruce – Subalpine Fir (ESSF)) biogeoclimatic zones. Trends in CWD quantity with forest age in managed coastal B.C. forests suggest a U-shaped curve, with greater quantities occurring in recent cutovers than in old-growth forests, and lowest quantities occurring in middle-aged forests. This may be the normal trend in CWD with forest age, with departures from this trend resulting from disturbance- or environment-specific factors. Relatively large amounts of data exist on the characteristics of CWD in the CWH, IDF, ICH, ESSF, and Boreal White and Black Spruce (BWBS) biogeoclimatic zones, but such data for the Coastal Douglas-fir, Sub-Boreal Pine–Spruce, Sub-Boreal Spruce (SBS), and Spruce–Willow–Birch biogeoclimatic zones appear relatively sparse. There have been few studies of the functional role of CWD in B.C. forests, but those studies that have been completed indicate that CWD is an important habitat component for some plant and animal species. A total of 169 plant species, including >95% of all lichens and liverworts, were found to grow on CWD in old-growth forests in the CWH, MH, IDF, ICH, and ESSF biogeoclimatic zones. One third of these species were restricted to CWD. Studies in several biogeoclimatic zones have found that CWD provided preferred habitat for and was associated with higher populations of some small animal species, such as shrews, some voles, and some salamanders, in old-growth forests, but the effects varied with species and biogeoclimatic zone. The nutrient cycling role of CWD is not yet well known, but it currently appears to be relatively insignificant in B.C. old-growth forests. Although it has been considered that CWD could increase mineral soil acidification and eluviation, no evidence for this was found in a study of the CWH, MH, IDF, ICH, ESSF, BWBS, and SBS biogeoclimatic zones. Future studies of the functional role of CWD should consider both scale (square metre vs. hectare) and temporal (changes in CWD with forest age) issues, as studies including these are sparse and both may be important. Key words: biogeoclimatic zones, British Columbia, coarse woody debris, old-growth forests.Cette communication résume les données tirées de la littérature et celles recueillies par l'auteur dans diverses études sur la quantité, les caractéristiques et l'importance fonctionnelle des débris ligneux grossiers (DLG) dans les forêts anciennes de la Colombie-Britannique (C.-B.). Dans la littérature, on ne s'entend pas sur le diamètre minimum des DLG, ou le nombre de classes de décomposition. Dans l'ouest de l'Amérique du Nord, on emploie le plus souvent cinq classes, mais des études récentes portent à croire qu'un nombre de classes inférieur serait préférable. Les comparaisons entre les classes de décomposition et les zones et sous-zones biogéoclimatiques de la C.-B. révèlent que les DLG sont plus abondants (pouvant atteindre environ 60 kg/m[sup 2] et 1800 m[sup 3] /ha) et persistent le plus longtemps (parfois pendant plus de 1000 ans) dans la zone biogéoclimatique cótière de la pruche de l'Ouest (CWH). L'abondance des DLG et la superficie de sol qu'ils couvrent augmentent avec la productivité de la forêt. La persistance des DLG varie de moins de 100 ans à plus de 800 ans dans cinq zones biogéoclimatiques : deux zones côtières (la CWH et la zone de la pruche subalpine (MH)) et trois zones intérieures (celle du douglas taxifolié de l'intérieur (IDF), celle des cèdres et des pruches de l'intérieur (ICH) et celle de l'épinette d'Engelmann et du sapin subalpin (ESSF)). Dans les forêts côtières aménagées de la C.-B., l'abondance des DLG en fonction de l'âge de la forêt suivrait une courbe en U, les débris étant plus abondants sur les parterres de coupe récents que dans les forêts anciennes, et moins abondants dans les forêts d'âge moyen. Cette relation entre les DLG et l'âge de la forêt est peut-être la tendance normale, et les écarts par rapport à celle-ci pourraient être le résultat de facteurs propres à chaque perturbation ou milieu. Il existe beaucoup de données sur les caractéristiques des DLG dans la CWH, la IDF, la ICH, la ESSF et la zone boréale des épinettes blanche et noire (BWBS), mais il en existe relativement peu pour la zone côtière du douglas taxifolié, la zone subboréale des pins et des épinettes, la zone subboréale de l'épinette (SBS) et la zone de l'épinette, du saule et du bouleau. Peu d'études ont été consacrées au rôle fonctionnel des DLG dans les forêts de la Colombie-Britannique, mais d'après celles qui ont été réalisées, les DLG constitueraient une composante importante de l'habitat de certaines espèces végétales et animales. On a recensé 169 espèces végétales poussant sur ces débris, dont plus de 95 % de tous les lichens et hépatiques, dans les forêts anciennes de la CWH, de la MH, de la IDF, de la ICH et de la ESSF. Le tiers de ces espèces ne poussent que sur les DLG. D'après des études effectuées dans plusieurs zones biogéoclimatiques, ces débris constituent l'habitat préféré de certains petits animaux présents dans les forêts anciennes, tels que les musaraignes, certains campagnols et certaines salamandres, et sont associés à de plus fortes populations de ces animaux, mais les effets varient selon l'espèce et la zone biogéoclimatique. Le rôle des DLG dans le recyclage des éléments nutritifs n'est pas bien connu, mais il semble qu'il soit relativement négligeable dans les forêts anciennes de la C.-B. Il a été avancé que les débris ligneux grossiers pourraient accroître l'acidification et le lessivage des sols minéraux, mais de tels effets n'ont pas été mis en évidence dans une étude de la zone CWH, de la MH, de la IDF, de la ICH, de la ESSF, de la BWBS et de la SBS. À l'avenir, les études sur le rôle fonctionnel des DLG devraient tenir compte des aspects liés à l'échelle (m[sup 2] ou ha) et temporels (modifications des DLG avec le vieillissement de la forêt) puisque les études impliquent ces paramètres potentiellement importants sont rares. Mots clés : zones biogéoclimatiques, Colombie-Britannique, débris ligneux grossiers, forêts anciennes. [Traduit par la rédaction] [ABSTRACT FROM AUTHOR]

Copyright of Environmental Reviews is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Environmental Reviews is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Environmental Reviews is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Environmental Reviews is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Environmental Reviews is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Environmental Reviews is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Environmental Reviews is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Environmental Reviews is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Environmental Reviews is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Environmental Reviews is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Describes the patterns and processes of North American boreal mixed woods (BMW) created by natural disturbances. Forest management implications related to stand development; Four stages of BMW stand development; Dependence of multiple pathways during BMW stand development on disturbances, neighbor effects and stand condition.

Mosses and hepatics (bryophytes) are the most diverse and abundant understorey vegetation within the Coastal Western Hemlock (CWH) and Interior Cedar–Hemlock (ICH) zones of British Columbia. This study intensively sampled bryophytes in 287 young- and old-growth stands in the CWH and ICH zones. Two major variables strongly influence the patterning of bryophyte diversity in these zones: stand age and habitat heterogeneity. Canonical correspondence analyses (CCA) identified these as the most important variables explaining stand–environment interactions. Alpha diversity is much greater in old-growth forests and beta diversity is high between young and old forests. Old-growth cedar–hemlock forests have between 60 (ICH) and 100% (CWH) more species than younger forests disturbed by wildfire in the ICH zones or logging in the CWH zones. Furthermore, a stand classification built on species composition partitioned species into stands of different ages and mesohabitat heterogeneity. Beta diversity was also partitioned between stands of different ages and habitat heterogeneity. This indicates that both young and old forests have a unique assemblage of species. Indicator analysis was used to choose a partial lists of species that are indicators of "old growthness". These old forests support a rich flora of hepatics and rare western North American endemics. High environmental continuity is associated with the most humid watersheds and cedar–hemlock forests within these watersheds have the highest bryophyte diversity. The establishment of rich communities of bryophytes in the moist cedar–hemlock forest has been occurring over the last 2000–7000 years, with the coastal rainforest much older than the inland rainforest. Large-scale disturbance, such as forestry, threatens the existence of these highly diverse communities. A better understanding of the patterning of bryophyte diversity will provide an opportunity to minimize the impact of forest operations on biodiversity. Bryophyte diversity in British Columbia cedar–hemlock forests will be sustained through ecosystem management of old-growth legacies (i.e., landscapes, stands, and their components) and preservation of areas of high diversity. Temporal and habitat variables are influential in the patterning of bryophyte diversity. Management plans that consider these variables will be better equipped to manage cedar–hemlock forests for maintaining biodiversity. Key words: biodiversity, bryophytes, cedar–hemlock, CWH, disturbance, ecosystem management, floristic habitat sampling, forest conservation, ICH, old growth, patterning of diversity, rare species, species richness.Les mousses et les hépatiques (bryophytes) représentent la végétation de sous-étage la plus diversifiée et abondante dans la zone côtière de la pruche de l'Ouest (CWH) et la zone à thuya et à pruche de l'Intérieur (ICH) en Colombie-Britannique. Cette étude a comporté un échantillonnage intensif des bryophytes dans 287 peuplements jeunes et anciens de ces deux zones. Deux variables y exercent une influence majeure sur le patron de répartition de la diversité des bryophytes : l'âge des peuplements et l'hétérogénéité des habitats. Des analyses canoniques des correspondances (ACC) ont indiqué qu'il s'agissait des plus importantes variables pour expliquer les interactions peuplement–environnement. La diversité alpha est beaucoup plus grande dans les forêts anciennes, et la diversité bêta est élevée entre les forêts jeunes et les forêts vieilles. Les forêts anciennes de thuya et de pruche comptent entre 60 % (ICH) et 100 % (CWH) plus d'espèces que les forêts plus jeunes perturbées par un incendie dans la zone ICH ou une récolte dans CWH. De plus, une classification des peuplements reposant sur la composition en espèces a fourni une répartition de la richesse en espèces entre peuplements ayant différentes caractéristiques d'âge et d'hétérogénéité des mesohabitats. La diversité bêta a aussi été répartie entre peuplements ayant différentes caractéristiques. Il ressort que la jeune forêt et la vieille forêt ont toutes deux un assemblage unique d'espèces. Une analyse a été effectuée pour établir une liste partielle d'espèces indicatrices d' « ancienneté ». Les vieilles forêts étudiées abritent une flore riche en hépatiques et en espèces endémiques rares de l'Ouest de l'Amérique du Nord. Une grande continuité de l'environnement est associée aux bassins versants les plus humides, et les forêts de thuya et de pruche de ces bassins renferment la plus forte diversité en bryophytes. L'établissement de riches communautés de bryophytes dans la forêt humide de thuya et de pruche se poursuit depuis des milliers d'années, de 2000 à 7000 ans, la forêt ombrophile côtière étant beaucoup plus âgée que la forêt ombrophile intérieure. Les perturbations de grande échelle, comme l'exploitation forestière, menacent l'existence de ces communautés de grande diversité. Une meilleure compréhension du patron de répartition de la diversité des bryophytes aidera à limiter l'impact des opérations forestières sur la biodiversité. La diversité des bryophytes dans les forêts de thuya et de pruche de la Colombie-Britannique pourra être maintenue en aménageant à l'échelle de l'écosystème les vestiges des forêts anciennes (c.-à-d. paysages, peuplements et leurs composantes) et en préservant des zones à forte diversité. Des variables temporelles et des variables de l'habitat influent sur le patron de répartition de la diversité des bryophytes. Les plans d'aménagement prenant en considération ces variables seront mieux en mesure d'assurer le maintien de la biodiversité des forêts de thuya et de pruche. Mots clés : aménagement écosystémique, biodiversité, bryophytes, conservation de la forêt, CWH, échantillonnage floristique de l'habitat, espèces rares, forêt ancienne, ICH, patron de répartition de la diversité, perturbation, pruche, richesse en espèces, thuya.[Traduit par la rédaction] [ABSTRACT FROM AUTHOR]

The Great Lakes forest region is a bioclimatic zone between the northern boreal forest and the eastern deciduous forest of North America. Relatively warm, dry conditions prevailed during the first half of the Holocene, at which time pines (Pinus spp.) and oaks (Quercus spp.) were more prominent than during the second half. The contemporary Great Lakes forest is dominated by sugar maple (Acer saccharum Marsh.) on optimum sites but almost 50 other tree species occur over the spectrum of sites and disturbance regimes encountered throughout the region. Although gap-phase regeneration typifies the undisturbed forest, wildfire and destructive windfall, due to downbursts, are not uncommon. The incidence of forest fire is lower than that in the boreal zone, and the incidence of windfall is lower than that of the deciduous forest to the south and east. Age-structure reconstruction points to the fire-related origin of many Pinus- and Quercus-dominated forests. Paleoecological and neoecological evidence indicates subsequent succession to dominance by either eastern hemlock (Tsuga canadensis (L.) Carr.) or to sugar maple. However, it seems that these shade-tolerant forests remain stable over millennia, even though they may occupy similar sites. Species composition changes only after catastrophic disruption and death of the original cohort. The old-growth stage has been identified by features linked to forest stand age, including a heterogeneous physiognomy, high biomass, high woody necromass, and high species diversity. Assessment of each feature along chronosequences of forests dominated by eastern white (Pinus strobus) and red pine (Pinus resinosa Ait.) yielded a more complicated picture. Productive sites led to forests of much taller stature and earlier canopy breakup than on poor sites. Standing woody biomass aggraded to 120–150 years and subsquently declined on all but the most productive sites, where it continued to increase with stand age. Snag volume tended to peak in the 90- to 125-year age range with subsequent decline. On the forest floor, coarse woody debris accumulated in a pattern similar to that of aboveground woody biomass. Plant species diversity was linked to the heterogeneity of substrata, much of which was attributed to woody necromass. These features persisted as legacies from stand growth before forest fire. Consequently, plant species diversity showed no correlation with postdisturbance stand age. The need to adopt a more dynamic view of the distribution and abundance of the Great Lakes forest flora is exemplified by the conservative understorey perennial, ground ginger (Asarum canadense L.) and cryptogamic epiphytes that indicate the continuity of old-growth forests with time. Key words: diversity, downbursts, fire, Holocene, necromass, old-growth criteria, pine chronosequence, site relations, succession.La région forestière des Grands Lacs est une zone bioclimatique située entre la forêt boréale et la forêt décidue de l'Est de l'Amérique du Nord. La première moitié de la période holocène y a été caractérisée par un climat relativement chaud et sec et par une plus grande dominance des pins et des chênes que durant la seconde moitié de l'Holocène. La forêt actuelle des Grands Lacs est dominée par l'érable à sucre (Acer saccharum Marsh.) dans les stations optimales, mais presque 50 autres essences sont présentes dans l'ensemble des stations et des régimes de perturbation de la région. Bien que la régénération par trouées caractérise la forêt non perturbée, les feux de forêt et les chablis (causés par des rafales descendantes) ne sont pas rares. La fréquence des feux de forêt est moins élevée que dans la zone boréale, tandis que la fréquence des chablis est moins élevée que dans les forêts décidues situées au sud et à l'est. La reconstitution de la structure d'âge semble indiquer que de nombreuses forêts dominées par les Pinus et les Quercus se sont établies à la suite d'un feu de forêt. Selon des données sur l'écologie actuelle et passée, la succession dans ces forêts mène ensuite à la dominance de la pruche (Tsuga canadensis (L.) Carr.) ou de l'érable à sucre. Il semble que ces forêts d'essences tolérantes à l'ombre restent stables durant des millénaires, même si elles peuvent occuper des stations semblables. La composition en essences ne change qu'à la suite d'une perturbation catastrophique qui tue la cohorte d'origine. Le stade de forêt ancienne a été identifié par des caractéristiques liées à l'âge du peuplement, notamment une physionomie hétérogène de la végétation, ainsi qu'une biomasse, une nécromasse ligneuse et une diversité spécifique élevées. L'évaluation de chaque caractéristique sur des chronoséquences de forêts dominées par les pins blanc (Pinus strobus) et rouge (Pinus resinosa Ait.), a montré une situation plus complexe. Dans les stations productives, les forêts présentent des arbres beaucoup plus grands et une ouverture du couvert plus hâtive que dans les stations peu productives. La biomasse ligneuse sur pied s'accumule pendant 120 à 150 ans, puis diminue dans toutes les stations sauf les plus productives, où elle continue d'augmenter avec l'âge du peuplement. Le volume total des chicots atteint généralement son maximum entre 90 et 125 ans, avant de diminuer. L'accumulation de débris ligneux grossiers sur le sol forestier suit la même évolution que la biomasse ligneuse aérienne. La diversité des espèces végétales est liée à l'hétérogénéité du substrat qui est en grande partie attribuable à la nécromasse ligneuse. Ces caractéristiques sont héritées de la croissance du peuplement avant un feu de forêt. Par conséquent, la diversité végétale ne présente aucune corrélation avec l'âge du peuplement établi à la suite d'un feu. Le gingembre sauvage (Asarum canadense L.), une vivace de sous-étage conservatrice, et des épiphytes cryptogames, qui indiquent la continuité des forêts anciennes dans le temps, illustrent le besoin d'adopter un point de vue qui tient davantage compte de l'aspect dynamique de la distribution et de l'abondance des espèces végétales de la forêt des Grands Lacs. Mots clés : diversité, rafales descendantes, feu, Holocène, nécromasse, critère de forêt ancienne, chronoséquence de pins, facteurs stationnels et succession. [Traduit par la rédaction] [ABSTRACT FROM AUTHOR]

Old-growth forests have been identified as a potentially important stage of stand development for maintaining biodiversity in the landscape, yet they have also been targeted by the forest industry in their drive to regulate the forest. We will attempt to propose a definition of old growth, applicable throughout the North American boreal forest, that takes into account the dynamic nature of forest development and that could be useful for management and conservation purposes. We define the start of the old-growth stage as occurring when the initial post-disturbance cohort begins dying off, concurrent with understorey stem recruitment into the canopy. We propose that species longevity and the regional fire cycle can be used to assess the extent of this phase in different regions. Using published data on fire history, we show that the amount of old growth expected to occur in western and central Canada is less than in eastern Canada, where most stands (in area) escape fire for periods longer than that necessary to incur substantial mortality of the initial cohort. At the stand level, we show that the old-growth stage is characterized by small-scale disturbances that engender gap dynamics. Until recently, this process had not been studied in the boreal forest. The old-growth index we present suggests that the relationship between time since the last major disturbance and old-growth status varies most in areas that have not been disturbed for long periods. Both management and conservation strategies have to take into account that old-growth forests are dynamic. To be effective, reserves should contain all stages of development and should be sufficiently large to encompass rare but large disturbances. The abundance of old growth in many boreal regions of North America also suggests that forest management strategies other than even-aged, fully regulated systems have to be developed. Key words: old growth, old-growth index, boreal forest, conservation, forest management, stand development.Les vieilles forêts ont été identifiées comme un stade potentiellement important de développement des peuplements pour le maintien de la biodiversité dans le paysage; elles ont cependant également été ciblées par l'industrie forestière dans ses activités d'aménagement. Les auteurs tentent de proposer une définition des vieilles forêts qui serait applicable à l'ensemble de la forêt boréale de l'Amérique du Nord et qui prendrait en compte la nature dynamique du développement du peuplement forestier tout en étant utile aux fins de l'aménagement et de la conservation. Les auteurs définissent le début du stade de vieille forêt comme le moment où la cohorte initiale post-perturbation commence à mourir, concurremment avec le recrutement de tiges du sous-étage dans la canopée. Pour évaluer l'importance de cette phase dans différentes régions, ils proposent d'utiliser la longévité des espèces et le cycle régional du feu. Avec l'historique des feux, ils démontrent que la quantité de vieilles forêts espérée dans le Canada central et de l'ouest est plus faible que dans l'est du Canada, où la plupart des peuplements (en superficie) échappent au feu pendant des périodes plus longues que celles qui sont nécessaires pour apporter une mortalité substantielle à la cohorte initiale. Au niveau du peuplement, les auteurs montrent que le stade de vieille forêt se caractérise par des perturbations à petite échelle qui engendrent une dynamique d'ouverture. Jusqu'à récemment, ce processus n'a pas été étudié en forêt boréale. L'index de vieille forêt présenté par les auteurs suggère que la relation entre le temps depuis la dernière perturbation majeure et le statut de vieille forêt varie le plus dans les régions qui n'ont pas été perturbées pendant de longues périodes. Les stratégies d'aménagement aussi bien que de conservation doivent prendre en compte le statut dynamique des vieilles forêts. Pour être efficaces, les réserves devraient contenir tous les stades de développement et devraient être suffisamment grandes pour inclure de rares mais vastes perturbations. L'abondance des vieilles forêts dans plusieurs régions boréales de l'Amérique du Nord suggère que des stratégies d'aménagement autre que les systèmes èquiennes visant la normalisation de la forêt doivent être développées. Mots clés : index de vieille forêt, vieille forêt, forêt boréale, conservation, aménagement forestier, stade de développement.[Traduit par la rédaction] [ABSTRACT FROM AUTHOR]