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Copyright of Canadian Journal of Forest Research 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 Canadian Journal of Forest Research 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 objective of this study was to characterize the effects of soil burn severity and initial tree composition on long-term forest floor dynamics and ecosystem biomass partitioning within the Picea mariana [Mill.] BSP-feathermoss bioclimatic domain of northwestern Quebec. Changes in forest floor organic matter and ecosystem biomass partitioning were evaluated along a 2,355-year chronosequence of extant stands. Dendroecological and paleoecological methods were used to determine the time since the last fire, the soil burn severity of the last fire (high vs. low severity), and the post-fire tree composition of each stand ( P. mariana vs. Pinus banksiana Lamb). In this paper, soil burn severity refers to the thickness of the organic matter layer accumulated above the mineral soil that was not burned by the last fire. In stands originating from high severity fires, the post-fire dominance by Pinus banksiana or P. mariana had little effect on the change in forest floor thickness and tree biomass. In contrast, stands established after low severity fires accumulated during the first century after fire 73% thicker forest floors and produced 50% less tree biomass than stands established after high severity fires. Standing tree biomass increased until approximately 100 years after high severity fires, and then decreased at a logarithmic rate in the millennial absence of fire. Forest floor thickness also showed a rapid initial accumulation rate, and continued to increase in the millennial absence of fire at a much slower rate. However, because forest floor density increased through time, the overall rate of increase in forest floor biomass (58 g m−2 y−1) remained constant for numerous centuries after fire (700 years). Although young stands (< 200 years) have more than 60% of ecosystem biomass locked-up in living biomass, older stands (> 200 years) sequester the majority (> 80%) of it in their forest floor. The results from this study illustrate that, under similar edaphic conditions, a single gradient related to time since disturbance is insufficient to account for the full spectrum of ecosystem biomass dynamics occurring in eastern boreal forests and highlights the importance of considering soil burn severity. Although fire severity induces diverging ecosystem biomass dynamics in the short term, the extended absence of fire brings about a convergence in terms of ecosystem biomass accumulation and partitioning. [ABSTRACT FROM AUTHOR]

Ecogeographic variation in black spruce clear wood properties was investigated for the two main vegetation types of the managed boreal forest of the province of Quebec, Canada. In total, 409 co-dominant and dominant trees from 82 mature stands were sampled. Basic wood density, modulus of elasticity and microfibril angle were measured using SilviScan. Mature fiber length was determined using a high-resolution Fiber Quality Analyzer. Wood growing in pure black spruce stands had longer mature fibers, a significantly denser wood with better mechanical characteristics than the wood growing in mixed stands with balsam fir. All wood properties were clearly influenced by radial growth and species composition. Given the limited number of sample plots for mapping purposes, a two-stage modeling approach was assessed to predict stand-level estimates of black spruce clear wood properties. This scaling-up method, based on field measurements and ring data from 3350 inventory plots, has improved the performance of all models. Stand-level models explained 47%, 57%, 63% and 63% of variance in wood density, modulus of elasticity, microfibril angle and mature fiber length respectively with estimated root mean square errors of 8.9 kg/m 3 , 0.52 GPa, 0.60° and 0.06 mm. An east-west gradient in black spruce clear wood properties was revealed as possibly the by-product of the change in relative proportions of both studied vegetation types across the study area. The results indicate that the black spruce wood from western regions of the managed boreal forest has a better potential for producing pulp and paper, lumber or engineered products due to its longer mature fibers and higher mechanical properties. [ABSTRACT FROM AUTHOR]

Simulates the theoretical behavior of the seasonal changes in backscattering signal in northern Quebec. Overview of the dielectric constant values of black spruce tree components used to run the forest canopy model for different seasons; Signal of wet and dry snow over open areas; Effects of the wet snow surface roughness.

Copyright of Canadian Journal of Forest Research 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 Canadian Journal of Forest Research 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 Canadian Journal of Forest Research 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.)

In the black-spruce clay-belt region of Western Québec, soil nutrients are limited due to paludification. Under paludified conditions, nutrient subsidies from decomposing surface coarse woody material (CWM) may be important particularly during the later stages of ecosystem development when deadwood from senescent trees has accumulated. For soil organisms, CWM can alter microclimatic conditions and resource availability. We compared abundance and species richness of oribatid mites below or adjacent to CWM across a chronosequence which spans ca. 700 years of stand development. We hypothesized that oribatid abundance and richness would be greater under the logs, particularly in later stages of forest development when logs may act as localized sources of carbon and nutrients in the paludified substrate. However, oribatid density was lower directly under CWM than adjacent to CWM but these differences were attenuated with time. We suggest that oribatids may be affected by soil compaction and also that such microarthropods are most likely feeding on recently fallen leaf litter, which may be rendered inaccessible by the presence of overlying CWM. This may also explain the progressive decline in oribatid density and diversity with time, which are presumably caused by decreases in litter availability due to self-thinning and Sphagnum growth. This is also supported by changes of different oribatid trophic groups, as litter feeders maintain different numbers relative to CWM with time while more generalist fungi feeders only show differences related to position in the beginning of the succession. [ABSTRACT FROM AUTHOR]

• Context: The Canadian forest industry is turning its attention towards the unmanaged areas at higher latitudes, where the forest resource is still poorly understood because of lack of accessibility. Despite a lower productivity in terms of volume, northern stands are expected to produce wood of higher quality, which may make these areas attractive for management and production. • Aims: This study aims to test the hypothesis that trees at high latitudes produce wood with better basic properties than trees at lower latitudes. • Methods: Growth and wood characteristics were assessed according to cambial age in 25 black spruce ( Picea mariana) trees from five sites located along an alti-latitudinal gradient in Quebec. • Results: Sites at higher latitudes and altitudes exhibited slower growth rates and lower stem volume. Wood density and mechanical properties were higher in the sites located at lower latitudes or altitudes. Fiber size had higher values in southern sites, but only at younger ages. Principal component analysis confirmed these results, with the northernmost site being the one where growth, density and mechanical properties were generally lowest. • Conclusion: The reduction in growth was not compensated by increases in the basic properties of wood. More extensive samplings are needed to validate the results at larger scale. [ABSTRACT FROM AUTHOR]

Logging in the boreal forest may benefit moose by increasing food availability. However, the influence of tree plantations on moose behavior, especially on moose spatial ecology, is poorly understood. We assessed the impacts of black spruce plantations on moose winter distribution at a landscape scale in the Bas-Saint-Laurent region (Québec, Canada). We used winter aerial surveys to examine relationships among plantation characteristics and other habitat variables known to affect moose distribution. The total area of plantations positively influenced moose abundance, but highly aggregated plantations resulted in fewer moose. Moose abundance was also positively associated with food availability and the density of edges between stands providing cover and stands offering high food availability, but moose abundance was negatively associated with road density. Although plantation characteristics were less influential than habitat variables related to foraging and predator avoidance, we demonstrate that the area of black spruce plantations and their configuration should be considered in moose management. We conclude that an integrated management strategy is needed to find a balance between overdeveloped road networks (needed to join homogeneously distributed plantations) and agglomerated plantations in order to mitigate impacts on moose winter distribution. © 2012 The Wildlife Society. [ABSTRACT FROM AUTHOR]

* Premise of the study: Treelines are temperature-sensitive ecotones that should be able to expand in response to global warming; however, they are also controlled by ecological constraints. These constraints can create bottlenecks for tree regeneration, hindering treeline advances. Near Kangiqsualujjuaq (Nunavik, subarctic Québec), previous studies suggested successful recruitment ofLarix laricina above the altitudinal treeline, while Picea mariana establishment remains scarce. We studied regeneration of both species to identify factors responsible for such contrasting responses. * Methods: We measured seeds and wings to evaluate species dispersal potential. We compared seed viability and tolerance to shrub leachates with germination trials. To evaluate seedbed preferences, we compared seedling occurrence on the different seedbeds with seedbed relative abundance in the field. * Key results: Seed germination was similar between L. laricina and P. mariana, whereas dispersal potential was higher for the latter. Germination of P. mariana seeds was more strongly inhibited by shrub leachates than were L. laricina seeds. In the field, we found only a few Picea seedlings, but numerous seedlings ofLarix had established disproportionally on several seedbeds. While Betula glandulosa, mosses, and Vaccinium uliginosim impeded Larix establishment, numerous seedlings were found on lichens, mineral soil, and liverworts. The low occurrence of suitable seedbeds for Picea, mainly mineral soil, could explain the seedling scarcity of this species. * Conclusions: This study highlighted that allelopathy and unsuitable seedbeds could contribute to regeneration failure of P. mariana in eastern Nunavik and emphasizes the need to consider ecological preferences of species before predicting treeline expansion under a warmer climate. [ABSTRACT FROM AUTHOR]

Copyright of Ecoscience (Ecoscience) is the property of Taylor & Francis Ltd 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 Canadian Journal of Forest Research 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 Canadian Journal of Forest Research 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 Canadian Journal of Forest Research 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.)

Context: To increase the wood supply to its industry, the government of Québec has allocated dead and sound wood (recently dead merchantable stems, DSW) to the wood supply chain in addition to the annual allowable cut of living trees. However, DSW is often criticized by sawmillers for its perceived poor quality and lower value. Aims: The objective of this study was to compare the lumber visual grade yield and value from live and recently dead merchantable trees in three different states of wood decomposition. Methods: In total, 162 black spruce trees [ Picea mariana (Mill.) BSP] were felled from three different sites comprising three different states of wood decomposition and three diameter classes. The state of decomposition of each standing tree was categorized following Hunter's classification (decay stages 1 & 2, 3 and 4) and the DSW classification developed by the Government of Québec. Results: Large trees (> 20 cm) of the Hunter 4 class have a lower value as a result of inferior quality. Conclusion: Considering the current economic difficulties facing the forest industry and the requirements of ecosystem-based management, we recommend leaving in the forest trees that have reached such a state of deterioration. [ABSTRACT FROM AUTHOR]

Processes governing tree interspecific interactions, such as facilitation and competition, may vary in strength over time. This study tried to unveil them by performing dendrometrical analyses on black spruce Picea mariana, trembling aspen Populus tremuloides and jack pine Pinus banksiana trees from pure and mixed mature boreal forest stands in the Clay Belt of northwestern Quebec and on the tills of northwestern Ontario. We cored 1430 trees and cut 120 for stem analysis across all stand composition types, tree species and study regions. Aspen annual growth rate was initially higher when mixed with conifers, but then progressively decreased over time compared to pure aspen stands, while jack pine growth rate did not differ with black spruce presence throughout all stages of stand development. When mixed with aspen, black spruce showed a contrary response to aspen, i.e. an initial loss in growth but a positive gain later. On the richer clay soil of the Quebec Clay Belt region, however, both aspen and spruce responses in mixed stands reversed between 37 and 54 years. Overall, our results demonstrate that interspecific interactions were present and tended to change with stand development and among species. Our results also suggest that the nature of interspecific interactions may differ with soil nutrient availability. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Forest Research 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.)

• Premise of the study: Climate warming might have resulted in altered initiation and termination dates of stem xylem growth in boreal stands. A systematic understanding of intra-annual xylem formation is thus needed for precise simulation of future growth in the context of sustainable forest management. • Methods: A recently developed novel microsampling approach was employed over two growing seasons (2005-2006) to investigate the intra-annual stem xylem formation of Picea mariana at three sites along a latitudinal gradient (approximately 47.5-50°N) in western Quebec, Canada. The critical timings of xylem cell formation were determined and compared among sites/ years. The relationships between xylem cell formation and meteorological variables were examined. • Key results: From south to north, the onset of xylem cell production was detected on 20 May (SD ±3) at Angliers, 24 May (SD ±3) at Chicobi and 24 May (SD+4) at Muskuchii in 2005, and on 12 May (SD ±4) at Angliers, 14 May (SD ±3) at Chicobi and 20 May (SD ±3) at Muskuchii in 2006, respectively. Xylem cell production at each respective site terminated on 11 August (SD ±4), 7 August (SD ±3), and 7 August (SD ±4) in 2005, and on 8 August (SD ±4), 4 August (SD ±4), and 4 August (SD ±4) in 2006, respectively. • Conclusion: Our study implies that despite the expected occurrence of earlier phenological development due to early spring climate warming, boreal trees like P. mariana might not be producing wider rings if cold temperatures occur later in the growing season in June to August. These results may challenge the view that boreal trees could be benefiting from spring warming to enhance growth. [ABSTRACT FROM AUTHOR]

In the next century, the boreal ecosystems are projected to experience greater rates of warming than most other regions of the world. As the boreal forest constitutes a reservoir of trees of huge ecological importance and only partially known economic potential, any possible climate-related change in plant growth and dynamics has to be promptly predicted and evaluated. A model for assessing xylem phenology in black spruce [ Picea mariana (Mill.) B.S.P.] using daily temperatures and thermal thresholds was defined and applied to predict changes in onset, ending and duration of xylem growth under different warming scenarios with temperatures rising by up to 3 °C. This was achieved by collecting and analyzing a dataset obtained from a 7-year monitoring of cambium phenology and wood formation on a weekly time-scale in trees growing in four sites at different latitudes and altitudes in the Saguenay-Lac-Saint-Jean region (Quebec, Canada). The onset of xylem growth occurred between mid-May and early June while the end ranged between mid-September and early October, resulting in a growing season of 101-141 days. The model predicted longer duration of xylem growth at higher temperatures, with an increase of 8-11 days/ °C, because of an earlier onset and later ending of growth. With an increase of 3 °C in the mean temperature during the year, the duration of xylem growth changed on average from 125 to 160 days. The predicted changes in cambial phenology could significantly affect future wood production of the boreal ecosystems. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Forest Research 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.)

Site index (SI) is commonly used in natural stands, even when their diameter distribution deviates from that of the monospecific, even-aged, fully stocked stands used to develop basic age–height relationships. Since deviations from basic age–height trajectories can be reflected in deviations of stand diameter distribution from a bell shape, we incorporated different diameter diversity indices into an age–height equation to help improve height predictions and determine which index is best related to stand dominant height. This procedure was performed using black spruce (Picea mariana (Mill.) BSP) stands from a large network of permanent sample plots established across the province of Quebec, Canada. The age–height model that minimized the Akaike’s information criterion used the Shannon evenness index (ESh) as an equation modifier accounting for the diameter diversity variable. The model showed that for stands established on relatively poor sites (SI = 9), no substantial differences in dominant height were found between two contrasting ESh values. For SI = 15, however, the larger ESh value increased the dominant height by as much as 1 m at 80 years. These results suggest that introduction of ESh into an age–height model can improve calculation of site index, particularly in regions characterized by the presence of numerous uneven-aged stands. L’indice de qualité de station (IQS) est souvent estimé pour des peuplements naturels, même si leur distribution de diamètres s’éloigne de celle des peuplements mono-spécifiques, de structure équienne, et de densité optimale qui sont utilisés pour mettre au point les relations âge–hauteur de référence. Puisque des déviations aux trajectoires âge–hauteur de référence peuvent se refléter dans des déviations de la distribution des diamètres des peuplements par rapport à une courbe normale, nous avons soumis différents indices de diversité diamétrale à une équation âge–hauteur dans le but d’améliorer la prédiction de la hauteur et de déterminer l’indice le mieux relié à la hauteur dominante des peuplements. Cette procédure a été appliquée à des peuplements d’épinette noire (Picea mariana (Mill.) BSP) à l’aide d’un vaste réseau de placettes échantillons permanentes établies dans la province de Québec, au Canada. Le modèle âge–hauteur qui a minimizé le « Akaike’s information criterion »utilisait l’indice de régularité de Shannon (ESh) comme modificateur d’équation relié à la diversité diamétrale. Dans le cas des peuplements établis sur des stations relativement pauvres (IQS = 9), ce modèle n’a pas produit de différences substantielles de hauteur dominante entre deux valeurs contrastées de ESh. Cependant, pour une valeur d’IQS égale à 15, la plus forte valeur de ESh a produit une augmentation de la hauteur dominante de 1 m à 80 ans. Ces résultats indiquent que l’introduction de ESh dans un modèle âge–hauteur peut améliorer l’estimation de l’IQS, particulièrement pour régions caractérisées par la présence de nombreux peuplements de structure inéquienne. [ABSTRACT FROM AUTHOR]

The coniferous boreal forest of northeastern North America is characterized by large and severe fire events and dominated by black spruce (Picea mariana), with scattered patches of balsam fir (Abies balsamea), a species otherwise predominant in the more southern mixedwood boreal forests, characterized by smaller and less severe fire events. Because balsam fir is a late-successional species ill-adapted to fire, this study aimed at determining if the scattered balsam-fir patches found in the coniferous forest were relics of a former fire regime characterized by less frequent and/or severe conflagrations. Fire and vegetation history were assessed for a coniferous forest site through analyses of charcoal, pollen and plant macroremains preserved in lake sediments, peat and hydromorphic forest soil. Pollen and macroremains analyses show that black spruce dominated the local vegetation since deglaciation (c. 8000 cal. yr BP). Balsam fir was abundant around the site during the warm and humid summers of the Hypsithermal (between c. 7000 and 3500 cal. yr BP), before gradually declining during the cool and dry Neoglacial, which was characterized by increased fire frequency and severity. Scattered balsam fir patches in the coniferous forest result from the fragmentation of formerly larger populations and are presently in disequilibrium with climate. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Forest Research 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.)

Previous studies conducted at the tree line in northwestern Québec suggested that the forest tundra was created over the last 3000 years by deforestation as a result of the combined action of forest fires and climatic cooling. Our objectives were to: (1) validate at a larger spatial scale the time frame of the last 3000 years; (2) verify if the opening process was more pronounced during particular time periods; and (3) confirm that fire was the triggering mechanism. Seventeen lakes from the forest tundra of northern Québec. Pollen records were analysed to determine the date of landscape opening, as interpreted by the time of decrease towards present-day values of the ratio of Picea pollen percentage to pollen percentage of the taxa typical of open forest tundra landscapes ( Betula, Ericaceae, Cyperaceae and Poaceae). Landscape opening in northern Québec started c. 3220 cal. bp(calibrated years before present) and was more pronounced between c. 2040 and 890 cal. bp. No spatial pattern was observed in the dates of landscape opening. The suggestion that landscape opening in the forest tundra occurred over the last 3000 years was validated at the scale of northern Québec. A period of more pronounced opening was identified between 2040 and 890 cal. bp and could be related to increased fire occurrence. Absence of a spatial pattern in the dates of landscape opening provides further confirmation that fire was the triggering mechanism. Des études antérieures menées à la limite des arbres dans le nord-ouest du Québec ont suggéré que la toundra forestière aurait été créée au cours des derniers 3000 ans par la déforestation résultant de l’action combinée des feux de forêt et d’un refroidissement climatique. Nos objectifs étaient de (1) valider à une échelle spatiale plus importante la période des derniers 3000 ans; (2) vérifier si le processus d’ouverture du paysage a été plus prononcéà certaines périodes; et (3) confirmer que le feu a été le mécanisme déclencheur. Dix-sept lacs de la toundra forestière du nord du Québec. Les enregistrements polliniques ont été analysés pour déterminer la date d’ouverture du paysage, telle qu’interprétée par le moment où survient une baisse marquée vers les valeurs actuelles du ratio du pourcentage de pollen de Picea sur le pourcentage de pollen de taxons typiques des milieux ouverts de la toundra forestière ( Betula, Ericaceae, Cyperaceae et Poaceae). L’ouverture du paysage dans le nord du Québec a débuté vers 3220 cal. BP et s’est exprimée de façon plus marquée entre 2040 et 890 BP cal. Aucun patron spatial n’a été observé dans les dates d’ouverture du paysage. La suggestion selon laquelle l’ouverture du paysage dans la toundra forestière aurait eu lieu au cours des derniers 3000 ans a été validée à l’échelle du Québec nordique. Une période plus marquée d’ouverture du paysage a été identifiée entre 2040 et 890 cal. BP et pourrait être reliée à des fréquences de feux plus élevées. L’absence de patron spatial dans les dates d’ouverture du paysage est une confirmation supplémentaire que le feu a été le mécanisme déclencheur. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Forest Research 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 Canadian Journal of Forest Research 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 Canadian Journal of Forest Research 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 Canadian Journal of Forest Research 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.)

Presents a study that examined whether computationally demanding competition indices outperform traditional indices in predicting mean basal area increment in a black spruce in northeastern Quebec. Background on black spruce; Materials and methods; Expectation on the competition indices used in the study.

Investigates the evolution pattern of the diameter structure of boreal black spruce stands originating from fire or logging in Quebec. Comparison of stands originating from fire and from logging; Impact of the widespread careful logging on the stands; Reconstitution of the dynamics of 40- to 90-year-old stands.

Giant circular patterns of low tree density in black spruce (Picea mariana) stands were investigated in the Abitibi region of Quebec. We used dendrochronological techniques to test the hypotheses that ring patterns of low tree density are caused either by radial changes in spruce mortality or productivity. Seven circles were sampled. We found no gradient in the age of spruce along circle radii suggesting that rings of low tree density do not expand radially, that is, they are not spatially dynamic entities. The results indicate, however, that spruce trees were less dense and productive within the rings due to excessive moisture in the soil. Measurements of surface elevation, thickness of the organic layer and elevation of the mineral substrate across the circles revealed that a depression in the mineral soil beneath the rings traps the surface water and this area of poor drainage seems to prevent the establishment of black spruce within the rings. The origin of the ring-shaped depressions was attributed to geological or geomorphological causes.Key words: black spruce, Picea mariana, mortality, productivity, rings, geomorphology.Des formations circulaires géantes caractérisées par une densité arborescente faible ont été étudiées dans des peuplements d'épinettes noires (Picea mariana) de l'Abitibi au Québec. Les hypothèses liées à un processus de mortalité radiale ou à une baisse de productivité dans l'anneau ont été documentées dans sept cercles à l'aide de techniques dendrochronologiques. L'absence d'un gradient d'âge des épinettes ne supporte pas une expansion radiale des anneaux. Par contre, les résultats indiquent que la productivité et la densité des épinettes sont plus faibles dans l'anneau à cause de l'humidité excessive du sol à cet endroit. Des relevés topographiques de la surface du sol, de l'épaisseur de la couche organique et de l'altitude du substrat minéral ont démontré l'existence d'une dépression dans le sol minéral sous l'anneau. Cette dépression, dans un environnement comme celui-ci où la nappe phréatique est près de la surface, piège les eaux de surface et maintient l'humidité excessive du sol prévenant ainsi l'établissement de l'épinette noire. Les anneaux sont donc statiques et l'origine de la dépression annulaire relève de causes géologiques ou géomorphologiques.Mots clés : épinette noire, Picea mariana, mortalité, productivité, anneau, géomorphologie. [ABSTRACT FROM AUTHOR]