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The relationship between forest stand composition in southern interior British Columbia and fluorescent pseudomonad bacteria populations was investigated using seedling bioassays. The objectives of this study were to (i) compare the relative population sizes of fluorescent pseudomonads baited from soils in pure paper birch (Betula papyrifera Marsh.), pure Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), and mixed stands of the two species and (ii) determine if fluorescent pseudomonads from these soils have inhibitory effects against the root pathogen Armillaria ostoyae (Romagn.) Herink in vitro. Soil from birch stands supported four times more pseudomonads on seedling baits than soil from Douglas-fir stands, with the mixed stands intermediate. Soil from young stands yielded twice as many rhizosphere pseudomonads as soil from mature stands. Pseudomonad population size was positively correlated with percent cover and density of birch, and negatively correlated with basal area of Douglas-fir, percent cover of Douglas-fir, and carbon/nitrogen ratio of the soil. Greater than 50% of the fluorescent isolates reduced radial growth of A. ostoyae by more than 20% and greater than 90% reduced biomass of the fungus in dual culture tests. Cell-free bacterial culture filtrates added to the growth medium also reduced growth of A. ostoyae. This study provides evidence that paper birch provides a more favorable environment for fluorescent pseudomonads than Douglas-fir and suggests a mechanism by which paper birch can positively influence the susceptibility of managed forest stands to Armillaria root disease. [ABSTRACT FROM AUTHOR]

Forests are the locus of conflict in Canada, where the rights and interests of Indigenous peoples can collide with those of the province (Crown) and the forest industry. Efforts to achieve "forest justice" — or sufficient forest rights to meet the self-governance goals of Indigenous peoples, and in ways that ensure collective resilience — have typically been driven by the principle of reconciliation. In this paper, these "forest justice" efforts were examined through a tripartite justice theory, involving recognition, representation, and redistribution pathways. This paper documents that recognition involves Crown efforts to recognize Indigenous peoples' forest rights, including ownership, and access and use rights; representation includes improved participation in forest governance; and redistribution covers the allocation of timber harvesting rights and forest lands to Indigenous peoples. This study documents that the bulk of "forest justice" activity is focused on the redistribution of timber harvesting licences, the volume of which has doubled over the last two decades. These three paths to justice must all be pursued together to deliver "forest justice", and to move towards "reconciliation in the woods". Recommendations are offered to support forest justice in practice. [ABSTRACT FROM AUTHOR]

Traditionally, forest management has focused on forestry-related practices whereas other industries have been managed separately. Forest management requires the integration of all natural resource development activities, along with other anthropogenic and natural forest disturbances (e.g., climate change, pollution, wildfire, pest disturbance) to understand how human activities can change forested ecosystems. The term cumulative effects has been used to describe these attempts to integrate all disturbances to develop an understanding of past, current, and future impacts on environmental, social, and economic components of the system. In this review, we focus on the science required to understand the past, current, and future impacts of the cumulative effects of anthropogenic and natural disturbances on forested ecosystems or their components. We have primarily focused on the terrestrial system with an emphasis on northern forests in Canada. Our paper is not intended to be a comprehensive review of all cumulative effects science but a synthesis of the challenges and approaches currently being used. Central repositories were identified as an approach to deal with issues of availability of remotely sensed data on anthropogenic and natural disturbances. Data integration projects, open data, and well-designed large-scale data collection efforts are needed to provide sufficient data on environmental responses to cumulative effects. As well, large-scale integrated, modularized ecosystem models are needed to bring stressor and environmental response data together to explore responses to, and interactions between, multiple stressors to project these effects into the future and to identify future data collection needs. [ABSTRACT FROM AUTHOR]

Public advisory committees (PACs) are a dominant form of public participation in Canada's Crown forests, providing a venue in which members of the local public can engage and influence sustainable forest management decision-making. In this paper, we examine the experiences of Indigenous participants (relative to non-Indigenous participants) concerning the success of PAC processes. We focus on issues of fairness, equity, and inclusion of Indigenous voices along with an assessment of forest values diversity. Findings from surveys in 2004 and 2016 indicate statistically significant differences between Indigenous and non-Indigenous PAC members regarding their forest values and their evaluation of the success of PAC processes. This work draws attention to the relative experiences of survey participants and the identification of persistent challenges associated with public engagement over the last two decades. Policy recommendations include substantial changes to how we define and measure sustainable forest management in Canada. [ABSTRACT FROM AUTHOR]

Contemporary fire regimes of Canadian forests have been well documented based on forest fire records between the late 1950s to 1990s. Due to known limitations of fire datasets, an analysis of changes in fire-regime characteristics could not be easily undertaken. This paper presents fire-regime trends nationally and within two zonation systems, the homogeneous fire-regime zones and ecozones, for two time periods, 1959–2015 and 1980–2015. Nationally, trends in both area burned and number of large fires (≥200 ha) have increased significantly since 1959, which might be due to increases in lightning-caused fires. Human-caused fires, in contrast, have shown a decline. Results suggest that large fires have been getting larger over the last 57 years and that the fire season has been starting approximately one week earlier and ending one week later. At the regional level, trends in fire regimes are variable across the country, with fewer significant trends. Area burned, number of large fires, and lightning-caused fires are increasing in most of western Canada, whereas human-caused fires are either stable or declining throughout the country. Overall, Canadian forests appear to have been engaged in a trajectory towards more active fire regimes over the last half century. [ABSTRACT FROM AUTHOR]

Quebec's forests represent 20% of Canadian forests and 2% of the world forests. Over the entire planet, forests play a major role in habitat preservation and in supplying goods and services to the population. However, climate change will have an impact on the forest through inter alia increased droughts, forest fires, warmer weather, and infestations. In this paper, we analyze the economic impact of climate change on the forest industry in Quebec over a 40-year period using a recursive dynamic computable general equilibrium model. We find that the climate change effects will be relatively weak on most macroeconomic variables as agents adjust their behavior over time and factors are reallocated across sectors. We find that climate change could generate losses in gross domestic product of up to Can$300 million (0.12% of gross domestic product) at the end of a 40-year period for Quebec's economy. However, we find relatively more important effects within the sectors of the forest industry, with losses ranging from 3% to 7.5%. [ABSTRACT FROM AUTHOR]

The boreal zone and its ecosystems provide numerous provisioning, regulating, cultural, and supporting services. Because of its resources and its hydroelectric potential, Canada's boreal zone is important to the country's resource-based economy. The region presently occupied by Canada's boreal zone has experienced dramatic changes during the past 3 million years as the climate cooled and repeated glaciations affected both the biota and the landscape. For about the past 7000 years, climate, fire, insects, diseases, and their interactions have been the most important natural drivers of boreal ecosystem dynamics, including rejuvenation, biogeochemical cycling, maintenance of productivity, and landscape variability. Layered upon natural drivers are changes increasingly caused by people and development and those related to human-caused climate change. Effects of these agents vary spatially and temporally, and, as global population increases, the demands and impacts on ecosystems will likely increase. Understanding how humans directly affect terrestrial and aquatic ecosystems in Canada's boreal zone and how these effects and actions interact with natural disturbance agents is a prerequisite for informed and adaptive decisions about management of natural resources, while maintaining the economy and environment upon which humans depend. This paper reports on the genesis and present condition of the boreal zone and its ecosystems and sets the context for a detailed scientific investigation in subsequent papers published in this journal on several key aspects: carbon in boreal forests; climate change consequences, adaptation, and mitigation; nutrient and elemental cycling; protected areas; status, impacts, and risks of non-native species; factors affecting sustainable timber harvest levels; terrestrial and aquatic biodiversity; and water and wetland resources. [ABSTRACT FROM AUTHOR]

Despite its role as a keystone species, few studies have investigated the habitat requirements of the Yellow-bellied Sapsucker (Sphyrapicus varius (L., 1766)) in the northwestern part of its range, where the current forest harvesting rotation schedule and targets for reducing the prevalence of old and mixedwood stands may reduce the optimal habitat for this species. We studied nesting and foraging habitat requirements of nesting sapsuckers in a boreal mixedwood forest of northwestern Canada by collecting data on nesting sites and foraging substrates on twenty-four 16- to 56-ha plots distributed among four habitat types in 1998 and 2002. Nests (n = 68) were generally found in large (≥22 cm diameter at breast height) trembling aspen (Populus tremuloides Michx) that were alive but declining and that showed high incidence (81.1%) of heartwood rot infection (Phellinus tremulae (Bondarzev) Bondarzev & Borisov in Bondarzev). Nest-site use by sapsuckers was predicted mainly by the presence of external fungal conks and tree diameter. Among tree species used as foraging substrates, paper birch (Betula papyrifera Marsh.) (65.6%) and green alder (Alnus viridis (Vill.) Lam. & DC.) (21.3%) were used most frequently. The use of birch was strongly correlated with its availability. Mature forests had higher densities of nesting sites and foraging substrates than immature aspen stands. In addition to reconfirming the importance of mature mixedwood forests for Yellow-bellied Sapsuckers, our study also indicates that forest harvest rotations in northwestern Canada should exceed 90 years to promote the keystone role of this species. [ABSTRACT FROM AUTHOR]

There is an increasing demand for active public involvement in forestry decision making, but there are as yet few established models for achieving this in the new sustainable forest management (SFM) context. At the level of the working forest, the fields of forest sustainability assessment, public participation, decision support, and computer technology in spatial modelling and visualization need to be integrated. This paper presents the results of a literature review of public participation and decision-support methods, with emphasis on case study examples in participatory decision support. These suggest that emerging methods, such as public multicriteria analysis of alternative forest management scenarios and allied tools, may lend themselves to public processes addressing sustainability criteria and indicators. The paper develops a conceptual framework for participatory decision support to address the special needs of SFM in tactical planning at the landscape level. This framework consists of principles, process criteria, and preliminary guidelines for designing and evaluating SFM planning processes with community input. More well-documented studies are needed to develop comprehensive, engaging, open, and accountable processes that support informed decision making in forest management, and to strengthen guidance for managers. [ABSTRACT FROM AUTHOR]

The mountain pine beetle, Dendroctonus ponderosae Hopkins (Coleoptera, Curculionidae), a native insect of North America, periodically reaches population sizes that cause serious economic impact to the forest industry in western North America. The most recent outbreak in British Columbia (BC), Canada, which began in the late 1990s, is only now (2015) abating, after causing unprecedented tree mortality in lodgepole pine ( Pinus contorta Douglas ex. Loudon) forests. In this paper, we make use of permanent research plots to report on the condition of lodgepole pine forests in the Chilcotin Plateau of central BC, which underwent two fully documented mountain pine beetle outbreaks. In this region, the first outbreak started in the late 1970s and lasted until the mid-1980s; the second outbreak began in the early 2000s and ended in 2010. We measured the impacts of these outbreaks in terms of tree mortality and describe the characteristics of the legacies that remain following these outbreaks, including survivors in various canopy layers and levels of existing and new regeneration. We provide evidence in support of the existence of postdisturbance legacies that classify into five distinct stand structure types. Abundant regeneration and surviving intermediate canopy layers in most stands indicate that management actions to restock pine stands in this area will not likely be necessary. The information provided by this study is important for estimating future forest development and timber supply and for forest planning and 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]

As many insect outbreak reconstructions are typically based on targeted single-site sampling, researchers have often been limited in their ability to draw conclusions about regional trends as opposed to local trends in the data. The results of this paper demonstrate the value of a systematic sampling design when studying spatio-temporal processes that can vary greatly within large continuous areas of forest. Many single-site research programs have been conducted to reconstruct the history of larch sawfly (Pristiphora erichsonii Htg.) outbreaks in the eastern boreal region of North America. However, no such research has yet been conducted in the region of Labrador. In an attempt to illustrate the strength of a systematic gridded sampling protocol over a single-site study, we sampled a 12-site grid in western Labrador. Dominant and codominant species were sampled at each grid point, resulting in 24 master chronologies. Six eastern larch (Larix laricina (Du Roi) K. Koch) chronologies (host) and a regional black spruce (Picea mariana (Mill.) Britton, Sterns, Poggenb.) chronology (nonhost) were used to establish a host–nonhost analysis of past sawfly outbreaks on a regional scale. Both regional and localized larch sawfly outbreaks were identified, but in general, larch sawfly outbreaks in western Labrador appeared to be spatially synchronous and regional in scale. [ABSTRACT FROM AUTHOR]

The main objective of this paper is to evaluate whether future climate change would trigger an increase in the fire activity of the Waswanipi area, central Quebec. First, we used regression analyses to model the historical (1973–2002) link between weather conditions and fire activity. Then, we calculated Fire Weather Index system components using 1961–2100 daily weather variables from the Canadian Regional Climate Model for the A2 climate change scenario. We tested linear trends in 1961–2100 fire activity and calculated rates of change in fire activity between 1975–2005, 2030–2060, and 2070–2100. Our results suggest that the August fire risk would double (+110%) for 2100, while the May fire risk would slightly decrease (–20%), moving the fire season peak later in the season. Future climate change would trigger weather conditions more favourable to forest fires and a slight increase in regional fire activity (+7%). While considering this long-term increase, interannual variations of fire activity remain a major challenge for the development of sustainable forest management. [ABSTRACT FROM AUTHOR]

The boreal forest of higher latitudes constitutes a reservoir of trees of great ecological importance and unknown economic potential, but the stand dynamics in these regions still remain essentially unexplored. This paper examines the change in age and size structures during stand development on the northern border of the natural closed boreal forest in Quebec, Canada. Height, diameter, and age of trees were measured in 18 plots with stand ages between 77 and 340 years. The occurrence, size, and origin (layer or seed) of seedlings and saplings were assessed in subplots. Tree density ranged from 600 to 3750 trees·ha–1. Picea mariana (Mill.) BSP was the dominant species, mainly originating by layering. A cluster analysis segregated plots into even-aged and uneven-aged stands according to tree age, but size distribution of trees, saplings, and seedlings did not differ statistically between the two groups. Even-aged stands exhibited a 60% probability of assuming an uneven-aged structure between 120 and 200 years after stand initiation. At high latitudes, the closed boreal forest of P. mariana appears homogeneously sized, with similar distributions of diameter and height across all stages of stand development. [ABSTRACT FROM AUTHOR]

This paper uses survey information to examine several common assertions about the institutional prerequisites for successful profitability when a First Nation enters an economic enterprise either independently or in joint effort with an outside firm. In the winter of 2004–2005, we interviewed managers on both the First Nations and private sides of joint ventures and other business alliances in Canada, to determine what affected their recent profitability experience. We gathered information on the ages, sizes, and activities of the firms. We also gathered information about the firms’ management structures and relationship with the First Nation, and the characteristics of the government of the First Nation. With a sample size of 40 firms that responded, we found that several institutional characteristics affected profit positively: strong separation of management from band governance, participation in management planning, and the use of staggered terms in band council elections. We found that the likelihood of profitability decreased if the band had been in third party management as well as if there was formal participation of elders or hereditary chiefs in decision making. We offer interpretations of these results. Cet article utilise les données d’un sondage réalisé au cours de l’hiver 2004–2005 afin d’examiner plusieurs assertions courantes au sujet des préalables institutionnels requis pour atteindre la profitabilité des entreprises initiées par des Premières nations agissant seules ou en partenariat avec des acteurs privés. Nous avons interviewé des gestionnaires impliqués dans de tels partenariats d’affaires au Canada et provenant tant des Premières nations que du secteur privé. Nous voulions déterminer ce qui affectait la profitabilité qu’ils avaient connue récemment. Nous avons rassemblé de l’information sur l’âge, la taille et les activités des entreprises. Nous avons aussi recueilli des données sur la structure de gestion des entreprises, les relations avec les Premières nations et les caractéristiques de la gouvernance en vigueur dans les communautés d’accueil. Un échantillon, regroupant les quarante entreprises qui ont répondu, nous permet d’observer que plusieurs caractéristiques institutionnelles, comme la séparation claire entre la gestion des projets et la gouvernance des communautés, la participation dans la planification managériale et le recours à des mandats échelonnés lors des élections au conseil de bande, affectent positivement les profits. Nous avons aussi remarqué que les chances de profitabilité diminuent si les conseils de bandes jouent un rôle en tant que de tierce partie dans la gestion des entreprises et si les aînés ou les chefs héréditaires participent formellement au processus décisionnel. Nous tentons d’interpréter ces résultats. [ABSTRACT FROM AUTHOR]

The term “aboriginal forestry” is used increasingly to describe the evolving role of First Nations peoples in Canadian forestry over the last 30 years. This paper reviews a diversity of experiences and identifies issues that have important implications for governments, forest planners, and First Nations: a forestry regime that reflects the interests of governments and industry rather than those of First Nations; variable implementation of aboriginal rights in forestry practice; benefits and problems of economic partnerships; limitations on consultation, traditional knowledge, and comanagement in forestry; and finally, different forestry paradigms. Among these experiences and issues, we recognise different visions for the participation of First Nations peoples in Canadian forestry. At one end of the spectrum, “forestry excluding First Nations” is no longer accepted. The most common form may be “forestry by First Nations,” representing a role for First Nations within existing forestry regimes. Other options include “forestry for First Nations,” in which forest managers seek to incorporate aboriginal values and knowledge in management activities and “forestry with First Nations,” in which aboriginal peoples are equal partners in forest management. However, aboriginal forestry is better understood as a potential new form of forestry that uses knowledge and techniques drawn from both traditions and conventional forestry and is based on aboriginal rights, values, and institutions. Au Canada, le terme « foresterie autochtone »gagne en popularité pour décrire le rôle grandissant des Premières nations en foresterie au cours des trente dernières années. Cet article passe en revue de nombreuses expériences et identifie des enjeux aux conséquences importantes pour les gouvernements, les gestionnaires forestiers et les Premières nations. Un régime forestier qui reflète les intérêts des gouvernements et des industriels plutôt que ceux des Premières nations, la reconnaissance inégale des droits autochtones dans les pratiques forestières, les bénéfices et les problèmes associés aux partenariats d’affaires, les limites propres à la consultation, la place des savoirs traditionnels et de la cogestion en foresterie et enfin, la variété des paradigmes forestiers composent ces enjeux. Parmi ces expériences et enjeux, nous reconnaissons l’expression de différentes façons de concevoir la participation autochtone à la foresterie canadienne. À un bout du spectre, « une foresterie qui exclut les Premières nations »n’est plus une option acceptable. La vision la plus répandue est probablement celle d’« une foresterie par les Premières nations »signifiant que celles-ci ont un rôle à jouer dans les régimes forestiers existants. Une autre conception est celle de « la foresterie pour les Premières nations »lorsque les gestionnaires forestiers tentent d’intégrer des valeurs et des savoirs autochtones à leurs activités d’aménagement. Enfin, les situations où les autochtones sont partenaires à part entière dans l’aménagement de la forêt s’inscrivent sous la rubrique « la foresterie avec les Premières nations ». Cependant, la foresterie autochtone est mieux comprise lorsqu’elle implique la possibilité d’une nouvelle foresterie qui a recours à des savoirs et des techniques inspirés à la fois des traditions et de la foresterie conventionnelle et qui est fondée sur des droits, des valeurs et des institutions autochtones. [ABSTRACT FROM AUTHOR]

Light detection and ranging (lidar) is becoming an increasingly popular technology among scientists for the development of predictive models of forest biophysical variables. However, before this technology can be adopted with confidence for long-term monitoring applications in Canada, robust models must be developed that can be applied and validated over large and complex forested areas. This will require "scaling-up" from current models developed from high-density lidar data to low-density data collected at higher altitudes. This paper investigates the effect of lowering the average point spacing of discrete lidar returns on models of forest biophysical variables. Validation of results revealed that high-density models are well correlated with mean dominant height, basal area, crown closure, and average aboveground biomass (R2 = 0.84, 0.89, 0.60, and 0.91, respectively). Low-density models could not accurately predict crown closure (R2 = 0.36). However, they did provide slightly improved estimates for mean dominant height, basal area, and average aboveground biomass (R2 = 0.90, 0.91, and 0.92, respectively). Maps were generated and validated for the entire study area from the low-density models. The ability of low-density models to accurately map key biophysical variables is a positive indicator for the utility of lidar data for monitoring large forested areas. [ABSTRACT FROM AUTHOR]

The forest products sector is a major employer in much of rural Canada, and it is often assumed by policy makers that increased timber harvest is a viable means of rural economic development. Despite burgeoning research in the United States, relatively little attention has focused on the relationship between forest dependence and well-being in rural Canada. Especially lacking are macrocomparisons of regions and of forest sectors. This note presents an overview of the relationship between forest dependence and well-being in Canada. Analysis of 1996 Statistics Canada data revealed a great deal of variation in the effect of forest dependence on indicators of well-being (e.g., human capital, unemployment, income): some sectors had fairly positive outcomes (e.g., pulp and paper); others had more negative outcomes (e.g., logging). These relationships, however, vary a great deal by region, suggesting the need for more mid-range explanatory models that incorporate the particulars of place and sector. [ABSTRACT FROM AUTHOR]

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]