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Although many studies have focused on factors influencing treeline advance with climate change, less consideration has been given to potential changes in tree spatial pattern across the forest-tundra ecotone. We investigated trends in spatial pattern across the forest-tundra ecotone and geographical variation in the Yukon, Manitoba, and Labrador, Canada. Tree cover was measured in contiguous quadrats along transects up to 100 m long located in Forest, Ecotone, and Tundra sections across the forest-tundra transition. Spatial patterns were analyzed using new local variance to estimate patch size and wavelet analysis to determine the scale and amount of aggregation. Compared with the Forest, tree cover in the Ecotone was less aggregated at most sites, with fewer smaller patches of trees. We found evidence that shorter trees may be clumped at some sites, perhaps due to shelter from the wind, and we found little support for regular spacing that would indicate competition. With climate change, trees in the Ecotone will likely become more aggregated as patches enlarge and new patches establish. However, results were site-specific, varying with aspect and the presence of krummholz (stunted trees); therefore, strategies for adaptation of communities to climate change in Canada's subarctic forest would need to reflect these differences. Alors que plusieurs études ont mis l'accent sur les facteurs qui influencent la progression de la limite des arbres due aux changements climatiques, peu d'attention a été accordée aux changements potentiels du patron de répartition spatiale des arbres dans l'écotone entre la forêt et la toundra. Nous avons étudié les changements de la répartition spatiale dans l'écotone entre la forêt et la toundra de même que sa variation géographique au Yukon, au Manitoba et au Labrador, au Canada. Le couvert forestier a été mesuré dans des quadrats contigus établis le long de transects pouvant atteindre 100 m de longueur et situés dans les sections de forêt, d'écotone et de toundra dans la zone de transition entre la forêt et la toundra. Les patrons spatiaux ont été analysés avec les méthodes de la nouvelle variance locale pour estimer la taille des îlots de forêt et avec l'analyse par ondelettes pour déterminer l'échelle et le degré d'agrégation. Comparativement à la forêt, le couvert forestier de l'écotone était moins groupé dans la plupart des stations, ce qui s'est traduit par des îlots de forêt plus petits et moins nombreux. Nous avons trouvé des preuves que les petits arbres peuvent être regroupés dans certaines stations, probablement pour se protéger du vent, et nous avons trouvé peu de signes d'espacement régulier qui auraient indiqué la présence de compétition. Avec les changements climatiques, les arbres établis dans l'écotone se regrouperont probablement davantage par l'agrandissement des îlots et par l'établissement de nouveaux îlots. Cependant, ces résultats sont spécifiques aux stations puisqu'ils varient selon leur orientation et en fonction de la présence de krummholz (arbres prostrés). Ainsi, les stratégies d'adaptation des communautés aux changements climatiques dans la forêt subarctique canadienne devraient refléter ces différences. [ABSTRACT FROM AUTHOR]

Although the public advisory committee has become a very common tool for involving local people in forest management decisions, it does not necessarily broaden the base of public input and may simply replicate the challenges of access, representation, and capacity to participate that are found in wider society. As a category of social exclusion, this study explores why women are significantly underrepresented on forest management advisory committees in Canada and how these committees function as gendered units. Research involved 25 semistructured interviews with members (and former members) of two forest management advisory committees: Tembec in Manitoba and NewPage in Nova Scotia. The strongest evidence in our study suggests that these committees operate within male-dominated institutions and particular masculine norms that are simply taken for granted. Thus, social relations based on gender often go unacknowledged. Findings also showed that the lack of critical mass of women often limited the active participation of the small number of women involved in committee activities. Our empirical observations suggest that unless we attend to gender when involving communities in establishing strategies for forest management, we will reinforce gender disadvantage and exclusion and overrepresent industrial and utilitarian interests of forestry over other community and ecocentric values. Bien que les comités directeurs soient devenus des outils de participation du public auxquels on recourt de plus en plus afin d'inclure les populations locales dans le processus décisionnel en aménagement forestier, cela n'élargit pas nécessairement la contribution du public et peut simplement reproduire les défis qu'on retrouve à la grandeur de la société concernant l'accès, la représentation et la capacité à participer. Sous le thème de l'exclusion sociale, cette étude explore pourquoi les femmes sont fortement sous-représentées dans les comités directeurs en aménagement forestier au Canada et comment ces comités fonctionnent en tant qu'entités sexuées. La recherche s'appuie sur 25 entrevues semi-dirigées avec des membres (et ex-membres) de deux comités directeurs en aménagement forestier, soit ceux de Tembec au Manitoba et de NewPage en Nouvelle-Écosse. Le constat le plus manifeste de notre étude indique que ces comités fonctionnent dans le cadre d'institutions à prédominance masculine et où des normes masculines particulières sont tout simplement prises pour acquises. Ainsi, les relations sociales fondées sur le genre passent souvent inaperçues. Les résultats montrent aussi que l'absence de masse critique féminine limite souvent la participation active du petit groupe de femmes qui collaborent aux activités de ces comités. Nos observations empiriques indiquent que, faute de considérer le genre dans la contribution des communautés lors de l'établissement des stratégies d'aménagement, le désavantage envers les femmes et l'exclusion seront renforcés alors que les intérêts industriels et utilitaristes seront surreprésentés au détriment des autres communautés et des valeurs éco-centriques. [ABSTRACT FROM AUTHOR]

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We present the effects, 10 years after treatment, of different cutting intensities (removal of 0%, 35%, 50%, 65%, and 100% of basal area (BA)) on the response of residual trees in a 60-year-old mixed aspen–conifer stand in Quebec, Canada. While decennial mortality reached 170 stems·ha–1 under natural conditions (control, 24 m2·ha–1 BA), the removal of mature trembling aspen (Populus tremuloides Michx.) trees reduced hardwood losses to 125, 105, and 0 stems·ha–1, respectively, in the 35%, 50%, and 65% cuttings, without affecting losses of coniferous species (≤25 stems·ha–1). The growth response of conifers was generally higher than that of broad-leaved species. For hardwoods, the decennial gains in merchantable BA decreased with respect to the control (3.2 m2·ha–1), to 1.2 m2·ha–1 in the 35% cut and to 0.9 m2·ha–1 in the 50% cut, but increased under the 65% cut (2.5 m2·ha–1). For conifers, gains were proportional to removal in partial cuts (2.6–4.9 m2·ha–1) and lower in the control (1.7 m2·ha–1). As a whole, our results suggest that partial cutting may be an effective means of increasing growth of the softwood proportion occupying the intermediate and suppressed strata in a mixed aspen-dominated stand. Nous présentons les résultats de coupes de différentes intensités effectuées il y a 10 ans (prélèvements de 0, 35, 50, 65 et 100 % de la surface terrière (ST)) sur la réaction des tiges résiduelles d’un peuplement mixte de 60 ans, constitué de tremble et de conifères, au Québec, Canada. Alors que la mortalité décennale a atteint 170 tiges·ha–1 en conditions naturelles (témoin, 24 m2·ha–1 de ST), le prélèvement prioritaire du peuplier faux-tremble (Populus tremuloides Michx.) mature a permis de diminuer les pertes de feuillus à 125, 105 et 0 tiges·ha–1, respectivement dans les coupes à 35, 50 et 65 %, sans affecter les pertes de résineux (≤25 tiges·ha–1). La réaction de croissance des conifères a généralement été meilleure que celle des feuillus. Pour les feuillus, les gains décennaux en ST marchande ont diminué par rapport au témoin (3,2 m2·ha–1), à 1,2 m2·ha–1 dans la coupe à 35 % et à 0,9 m2·ha–1 dans la coupe à 50 %, pour remonter dans la coupe à 65 % (2,5 m2·ha–1). Pour les conifères, les gains ont été directement proportionnels au prélèvement dans les coupes partielles (2,6 à 4,9 m2·ha–1), et moins élevés dans le témoin (1,7 m2·ha–1). Dans l’ensemble, nos résultats indiquent que la coupe partielle peut être efficace pour augmenter la croissance de la fraction résineuse des étages intermédiaire et opprimé dans un peuplement mixte dominé par le tremble. [ABSTRACT FROM AUTHOR]

The effect of removing lodgepole pine (Pinus contorta Dougl. ex Loud.) and retaining Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) to reduce the risk of disturbance from mountain pine beetle (Dendroctonus ponderosae Hopk.) in mixed conifer stands in southern British Columbia, Canada, on population processes influencing outbreaks of western spruce budworm (Choristoneura occidentalis Free.) was evaluated in 10 paired (open vs. closed) field plots. Overall feeding damage to Douglas-fir was significantly, but only slightly, lower in open stands compared with closed stands. Although open plots tended to recruit more budworms, the losses resulting from the dispersal of spring-emerging budworms in search of feeding sites were significantly greater in open plots. The forest management benefits of these early season losses were mitigated, however, by more mortality of budworms from natural enemies, particularly diseases, in the closed plots during the budworm feeding period. These results are discussed in terms of compensating population processes and balancing objectives in forest pest management. In this case, selective harvesting of lodgepole pine as a mitigation strategy for the mountain pine beetle conserved the midterm timber supply potential represented by associated Douglas-fir even in the presence of an outbreak of the western spruce budworm. Dans les peuplements mélangés de conifères du sud de la Colombie-Britannique, au Canada, on élimine le pin tordu (Pinus contorta Dougl. ex Loud.) en conservant le douglas de Menzies (Pseudotsuga menziesii (Mirb.) Franco) pour réduire les risques de perturbation par le dendroctone du pin ponderosa (Dendroctonus ponderosae Hopk.). L’effet de cette pratique sur les processus démographiques qui influencent les épidémies de tordeuse occidentale de l’épinette (Choristoneura occidentalis Free.) a été évalué dans 10 paires (peuplements ouverts vs peuplements fermés) de parcelles sur le terrain. Globalement, les dommages subis par le douglas de Menzies à cause du broutement étaient, quoique légèrement, significativement plus faibles dans les peuplements ouverts que dans les peuplements fermés. Bien que les peuplements ouverts aient eu tendance à recruter plus de tordeuses, les pertes dues à la dispersion des tordeuses qui émergent au printemps à la recherche d’endroits pour se nourrir étaient plus élevées dans les peuplements ouverts. À la suite de ces pertes en début de saison, les bénéfices de l’aménagement forestier ont cependant été atténués par une plus forte mortalité des tordeuses causée par ses ennemis naturels, particulièrement les maladies, dans les peuplements fermés pendant la période de broutement de la tordeuse. La discussion porte sur la compensation des processus démographiques et l’équilibre entre les objectifs en lien avec le contrôle des ravageurs forestiers. Dans ce cas, la stratégie qui préconise la récolte sélective du pin tordu pour atténuer l’impact du dendroctone du pin ponderosa a permis de maintenir le potentiel d’approvisionnement en bois à mi-terme que constitue le douglas de Menzies associé au pin tordu, même en présence d’une épidémie de tordeuse occidentale de l’épinette. [ABSTRACT FROM AUTHOR]

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Copyright of Canadian Journal of Zoology 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.)

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 Botany 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 Fisheries & Aquatic Sciences 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.)

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 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.)

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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.)

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.)

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Copyright of Canadian Journal of Botany 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.)

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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.)

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.)

The effects of partial and clear-cut harvesting on forest floor physical, chemical, and biological properties, forest floor mesofauna, and nutrient cycling were investigated in conifer- and deciduous-dominated stands of Alberta's mixedwood boreal forest. Forest floor samples were collected 2.5 years after harvest from clearcuts, strip-cut corridors in a partial cut, green tree retention patches in a partial cut, and uncut control sites. Partial cuts showed intermediate decreases in annual litter input and NH[sub 4] -N between uncut and clear-cut sites of both the deciduous and conifer stands, as did microbial biomass, PO[sub 4] -P, mesofauna abundance (total, Acari, and Collembola), and fine root biomass in the conifer stands. In the deciduous stands, microbial biomass and fine root biomass in partial- and clear-cut treatments were not significantly different, but were significantly reduced compared with the uncut controls. Mesofauna abundance was reduced in the corridors of the partial-cut treatment compared with partial-cut patch, clear-cut, and uncut treatments. In both deciduous and conifer stands, NO[sub 3] -N was elevated in the partial-cut corridors and clearcuts compared with partial-cut patch and uncut treatments. Findings from this study show that negative impact to forest floor properties associated with clear-cut harvesting may be reduced in partial-cut harvesting systems.Les effets de la coupe à blanc et de la coupe partielle sur les propriétés physiques, chimiques et biologiques de la couverture morte, sur la mésofaune de la couverture morte et sur le recyclage des nutriments ont été étudiés dans des peuplements dominés soit par des conifères, soit par des feuillus, dans la forêt mixte boréale de l'Alberta. Des échantillons de la couverture morte ont été prélevés dans des sites coupés à blanc, dans les corridors de coupes partielles par bandes, dans les îlots de réserves de coupes partielles et dans des sites témoins non coupés deux ans et demi après la récolte. La coupe partielle a entraîné une diminution de l'apport annuel de litière et de N (NH[sub 4] ) intermédiaire entre les sites coupés à blanc et les sites non coupés dans les deux types de peuplements de même qu'une diminution de la biomasse microbienne, du P (PO[sub 4] ), de l'abondance de la mésofaune (totale, d'acariens et de collemboles) et de la biomasse des racines fines dans les peuplements résineux. Dans les peuplements feuillus, la biomasse microbienne et la biomasse de racines fines ne différaient pas significativement entre la coupe partielle et la coupe à blanc mais étaient significativement plus faibles que dans les sites témoins non coupés. L'abondance de la mésofaune dans les corridors de la coupe partielle était inférieure à celle observée dans la coupe partielle avec réserves, dans la coupe à blanc et dans les sites non coupés. Tant dans les peuplements résineux que feuillus, N (NO[sub 3] ) était plus élevé dans les corridors de la coupe partielle et dans la coupe à blanc que dans la coupe partielle avec réserves ou dans les sites non coupés. Les résultats de cette étude montrent que l'impact négatif de la coupe à blanc sur les propriétés de la couverture morte peut être minimisé avec des systèmes de coupe partielle.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

The 20-year successional development of understory vegetation was investigated in jack pine (Pinus banksiana Lamb.) and black spruce (Picea mariana (Mill.) BSP) plantations in northern Ontario, in relation to stand species composition, species diversity, and the rate of change in stands of different post-disturbance ages. Detrended correspondence analysis (DCA) ordination of plantation stands using species composition data from 1978 and 1998 indicated variation among stands in directions and rates of change in species composition over time. Rank correlations of environmental variables with the DCA axes suggested a light–moisture gradient along the first axis, driven by soil texture and overstory species, and a gradient representing time since disturbance and stand development along the second axis. Although overall beta diversity among stands remained constant over time, some convergence was found among a smaller group of stands, and divergence was noted between spruce and pine stands. Species composition also became more highly correlated with environmental variables through time. From 1978 to 1998, species richness increased in young, dry pine stands; decreased in older, dry pine stands; and decreased in young spruce stands. The understory vegetation in stands on mesic sites was more diverse than that on dry, sandy sites at both times. The rate of change in understory species composition slowed with time after disturbance, indicating an increasing stability in micro en vi ron men tal conditions as the influence of harvesting disturbance became weaker with time.Le développement sur une période de 20 ans de la succession de la végétation de sous-étage a été étudié dans des plantations de pin gris (Pinusbanksiana Lamb.) et d'épinette noire (Piceamariana (Mill.) BSP) situées dans le Nord de l'Ontario en lien avec la composition en espèces du peuplement, la diversité des espèces et le taux de changement dans des peuplements d'âge différent issus de perturbations. L'ordination des plantations par l'analyse de correspondance en utilisant les données de composition en espèces de 1978 et de 1998 indiquait une variation entre les peuplements dans la direction et le taux de changement dans la composition en espèces en fonction du temps. Les corrélations de rang des variables environnementales avec les axes associés à l'analyse de correspondance suggèrent l'ex istence d'un gradient de lumière et d'humidité le long du premier axe, déterminé par les espèces de l'étage dominant et la texture du sol, ainsi qu'un gradient représentant le développement du peuplement et le temps écoulé depuis la perturbation le long du deuxième axe. Bien que dans l'ensemble la diversité bêta parmi les peuplements soit demeurée constante dans le temps, une certaine convergence a été observée parmi un plus petit groupe de peuplements et une divergence a été notée entre les peuplements d'épinette et de pin. Avec le temps, la composition en espèce est également devenue plus étroitement corrélée avec les variables environnementales. De 1978 à 1998, la richesse en espèces a augmenté dans les jeunes peuplements secs de pin et a diminué dans les plus vieux peuplements secs de pin et les jeunes peuplements d'épinette. La végétation de sous-étage dans les peuplements sur des stations mésiques était plus diversifiée que sur les stations sèches et sableuses aux deux moments. Le taux de changement dans la composition en espèces de sous-étage a diminué avec le temps après la perturbation, reflétant la stabilité croissante des conditions en vironnementales à mesure que l'influence de la perturbation due à la récolte s'atténuait.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

Asymbiotic nitrogenase activity in coarse woody debris was measured using the acetylene reduction assay under ambient conditions in three different stand ages (5, 53, and 88 years old) of an unmanaged second-growth Tsuga heterophylla (Raf.) Sarg. – Abies amabilis (Dougl. ex Loud.) Dougl. ex J. Forbes forest type and a Thuja plicata Donn. ex D. Don – Tsuga heterophylla old-growth forest on northern Vancouver Island, British Columbia, Canada. Four different decay classes of coarse woody debris, different species in the early decay stages, and sapwood and heart wood were sampled separately. Mean nitrogenase activity ranged between 1.3 and 19.5 nmolC[sub 2] H[sub 4] ·d[sup –1] ·(g dry mass)[sup –1] , with an overall mean of 5.7. High variability of the activity rates between logs and within logs was observed in all four stands. Mean activity rates were, in most cases, significantly different between decay classes, with generally increasing nitrogenase activity with the progress of decay. Moisture content of the samples was a good predictor of nitrogenase activity and could explain differences between decay classes. Only minor differences in nitrogenase activity were found between the different stands. Estimates of nitrogen fixation ranged from 1.0 to 2.1 kg N·ha[sup –1] ·year[sup –1] , the magnitude of these values depending more on the mass of coarse woody debris substrate available for asymbiotic nitrogen-fixing bacteria (103–158 t·ha[sup –1] in this study) than on differences in nitrogenase activity rates. The measured nitrogenase activity and the resultant estimates of nitrogen fixation are among the highest values reported in the literature.L'activité non symbiotique de la nitrogénase dans les débris ligneux grossiers a été mesurée à l'aide du test de réduction de l'acétylène en conditions ambiantes dans trois peuplements d'âge différent (5, 53 et 88 ans) situés dans une forêt de seconde venue non aménagée de Tsugaheterophylla (Raf.) Sarg. et de Abiesamabilis (Dougl. ex Loud.) Dougl. ex J. Forbes ainsi que dans une forêt ancienne de Thujaplicata Donn. ex D. Don et de Tsugaheterophylla située au nord de l'île de Vancouver, en Colombie-Britannique, Canada. Quatre classes de décomposition des débris ligneux grossiers, différentes espèces aux stades initiaux de décomposition ainsi que le bois d'aubier et le bois de cœur ont été échantillonnés séparément. En moyenne, l'activité de la nitrogénase variait de 1,3 à 19,5 avec une moyenne globale de 5,7 nmol de C[sub 2] H[sub 4] ·j[sup –1] ·(g de masse sèche)[sup –1] . Le taux d'activité était très variable dans et entre les billes dans les quatre peuplements. Les taux moyens d'activité étaient dans la plupart des cas significativement différents entre les classes de décomposition et l'activité de la nitrogénase augmentait généralement avec le degré de décomposition. Le contenu en eau des échantillons était un bon prédicteur de l'activité de la nitrogénase et pouvait expliquer les différences entre les classes de décomposition. Seules des différences mineures dans l'activité de la nitrogénase ont été observées entre les différents peuplements. Les estimations de la fixation de l'azote variaient de 1,0 à 2,1 kg N·ha[sup –1] ·an[sup –1] . L'ampleur de ces valeurs dépendait plus de la masse de substrat disponible dans les débris ligneux grossiers pour les bactéries qui fixent l'azote de façon non symbiotique (103–158 t·ha[sup –1] dans cette étude) que des différences dans le taux d'activité de la nitrogénase. La mesure de l'activité de la nitrogénase et les estimations de la fixation de l'azote qui en résultent sont parmi les valeurs les plus élevées rapportées dans la littérature.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

Soluble organic N (SON) is recognized to be a source of N for plants, but the few studies of the effects of clear-cut harvesting on SON levels have reported inconsistent results. SON and soluble inorganic N (SIN) contents were measured in 1 mol/L KCl extracts of soil from forests and clearcuts in coastal cedar–hemlock forests near Port McNeill, B.C., and in high-elevation spruce–fir forests near Sicamous, B.C. To characterize the seedling root environment, sampling was confined to the top 20 cm of soil (consisting of forest floor at Port McNeill and forest floor plus mineral soil at Sicamous). Amino acid N and microbial N were determined on subsets of the samples. At both sites, SON content tended to be lower in clearcuts than in forests. Lower SON contents in clearcuts were caused by the removal of F-layer forest floor at Port McNeill and by reduced SON concentrations in the forest floor at Sicamous. Correlation analyses indicated close relationships between moisture content, SIN, SON, and microbial N. Changes in SON, SIN, and microbial N concentrations during buried bag incubations could not be explained simply by exchange among these three N pools. Free amino acid N accounted for 1–1.5% of the total SON content.L'azote (N) organique soluble est une source connue de N pour les plantes mais les quelques études qui portent sur les effets de la coupe à blanc sur les niveaux de N organique soluble rapportent des résultats inconsistants. Le contenu en N soluble organique et inorganique a été mesuré dans des extraits de sols au KCl (1 mol/L) provenant de forêts et de coupes à blanc dans des forêts côtières de thuya et de pruche près de Port McNeill et de forêts d'épinette et de sapin situées à haute altitude près de Sicamous, en Colombie-Britannique. Pour caractériser l'environnement du système racinaire des semis, l'échantillonnage a été limité aux premiers 20 cm de sol; ce qui correspond à la couverture morte à Port McNeill et à la couverture morte et au sol minéral à Sicamous. L'azote microbien et sous forme d'acides aminés a été mesuré sur des sous-ensembles des échantillons. Dans les deux stations, le contenu en N organique soluble avait tendance à être plus faible dans les coupes à blanc que dans les forêts. Le plus faible contenu en N organique soluble dans les coupes à blanc était dû à l'enlèvement de l'horizon F dans la couverture morte à Port McNeill et aux faibles concentrations de N organique soluble dans la couverture morte à Sicamous. Les analyses de corrélation indiquent qu'il y a une étroite relation entre le contenu en humidité, N inorganique soluble, N organique soluble et N microbien. Les changements dans la concentration de N organique soluble, de N inorganique soluble et de N microbien lors de tests d'incubation avec des sacs enfouis ne peuvent être expliqués simplement par les échanges entre ces trois pools de N. L'azote sous forme d'acides aminés représentait 1 à 1,5 % du contenu total de N organique soluble.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

The 6-year effects of differing levels of Sitka alder (Alnus viridus spp. sinuata (Regel) Á. Löve & D. Löve) retention (0, 500, 1000, and 2000 clumps/ha) on the development of retained alder and on the growth and foliar nutrition of 7-year-old naturally regenerated lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) were evaluated in a sub-boreal ecosystem in the central interior of British Columbia. Alder development was inversely related to alder retention density, with the largest height and crown width increments occurring at the lowest alder densities. Low to moderate levels of alder cover did not significantly inhibit the diameter or height growth of lodgepole pine. Even under high alder cover, growth was not reduced until alder cover exceeded 45%. Over the 6-year response period, lodgepole pine diameter and height increments under high alder cover were reduced by 10% and 12%, respectively, relative to the no-alder treatment. The effect of alder density on lodgepole pine foliar N was strongly linear, with the highest N levels measured in the high alder retention treatment. However, the positive impact of alder retention on foliar N resulted in probable imbalance of N relative to S and possibly P and K. Unless alleviated, nutritional imbalances may preclude reliable assessment of the competitive effects (i.e., light and soil resources) of alder density, if any, on lodgepole pine growth.Six ans après avoir conservé différentes densités d'aulne vert (Alnus viridus spp. sinuata (Regel) Á. Löve & D. Löve) (0, 500, 1000 ou 2000 bouquets/ha), les effets sur le développement des aulnes résiduels et sur la croissance et la nutrition foliaire de la régénération naturelle de pin lodgepole (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) âgée de 7 ans ont été évalués dans un écosystème sub-boréal situé dans le centre intérieur de la Colombie-Britannique. Le développement de l'aulne était inversement proportionnel à la densité de cette espèce; les plus forts accroissements en hauteur et en largeur de cime sont survenus aux plus faibles densités. Une couverture faible à modérée d'aulne n'a pas significativement inhibé la croissance en hauteur ou en diamètre du pin lodgepole. Même sous un fort couvert d'aulne, la croissance n'a pas été affectée tant que la couverture d'aulne ne dépassait pas 45 %. Sur la période de six ans, l'accroissement en diamètre et en hauteur du pin lodgepole sous couvert dense d'aulne a été réduit respectivement de 10 % et 12 % comparativement au traitement sans aulne. L'effet de la densité de l'aulne sur l'azote (N) foliaire du pin lodgepole était fortement linéaire et les concentrations les plus élevées de N ont été mesurées dans le traitement avec la plus grande quantité d'aulnes. Cependant, l'impact positif sur l'azote foliaire associé au maintien de l'aulne a probablement entraîné un déséquilibre de N relativement au soufre et possiblement au phosphore et au potassium. À moins d'y remédier, les déséquilibres nutritionnels peuvent empêcher d'évaluer adéquatement les effets potentiels dus à la compétition (p. ex. lumière et ressources du sol) de l'aulne sur la croissance du pin lodgepole.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

This study examined water temperature patterns and their physical controls for two small, clearing-heated streams in shaded reaches downstream of all forestry activity. Field observations were made during July-August 2000 in the central interior of British Columbia, Canada. For both reaches, downstream cooling of up to 4 Celsius had been observed during daytime over distances of ∼ 200 m. Radiative and convective exchanges of energy at heavily shaded sites on both reaches represented a net input of heat during most afternoons and therefore could not explain the observed cooling. In one stream, the greatest downstream cooling occurred when streamflow at the upstream site dropped below about 5 L · s[sup-1]. At those times, temperatures at the downstream site were controlled mainly by local inflow of groundwater, because the warmer water from upstream was lost by infiltration in the upper 150 m of the reach. Warming often occurred in the upper subreach, where cool groundwater did not interact with the channel. At the second stream, creek temperature patterns were comparatively stable. Energy balance estimates from one afternoon suggested that groundwater inflow caused about 40% of the ∼ 3 Celsius gross cooling effect in the daily maximum temperature, whereas bed heat conduction and hyporheic exchange caused about 60%. [ABSTRACT FROM AUTHOR]

Stream temperature impacts resulting from forest harvesting in riparian areas have been documented in a number of locations in North America. As part of the Stuart-Takla Fisheries-Forestry Interaction Project, we have investigated the influence of three variable-retention riparian harvesting prescriptions on temperatures in first-order streams in the interior sub-boreal forests of northern British Columbia. Prescriptions were designed to represent a range of possible harvesting options outlined by the Forest Practices Code of B.C., or associated best management practice guidelines. Five years after the completion of harvesting treatments, temperatures remained four to six degrees warmer, and diurnal temperature variation remained higher than in the control streams regardless of treatment. Initially, the high-retention treatment acted to mitigate the temperature effects of the harvesting, but 3 successive years of windthrow was antecedent to reduced canopy density and equivalent temperature impacts. We speculate that late autumn reversals in the impacts of forest harvesting also occur. Temperature impacts in this study remained within the tolerance limits of local biota. However, even modest temperature changes could alter insect production, egg incubation, fish rearing, migration timing, and susceptibility to disease, and the effects of large changes to daily temperature range are not well understood. [ABSTRACT FROM AUTHOR]

Site preparation alleviates the effects of pinegrass (Calamagrostis rubescens Buckl.) interference on conifers in British Columbia, but little is known about interference mechanisms and appropriate site preparation methods for steep slopes. In this study, lodgepole pine (Pinus contorta Dougl. ex Loud.) was planted in pinegrass controls and small (90 x 90 cm) and large (180 x 90 cm) patches where (i) only pinegrass was removed using glyphosate or (ii) both pinegrass and the forest floor were removed using an excavator. Treatments were replicated three times in east- and west-facing clearcuts and effects were followed for 9 years. Two-year pine survival was 78% in the control and >97% in large patches. All patch treatments improved pine growth, but it was greatest in large chemical patches during the initial 6 years and in both large patch treatments thereafter. Removal of the forest floor reduced foliar and soil nutrients, increased bulk density and soil water availability, decreased porosity and aggregate stability, and reduced ectomycorrhizal diversity and richness. These changes were not observed in chemical patches. All patch treatments increased soil temperatures and reduced frost relative to controls, but more so in large patches. Pinegrass can suppress early pine performance, and large chemical patches that retain the forest floor are best for relieving the multiple environmental stressors. [ABSTRACT FROM AUTHOR]

Headwater streams, varying in flow persistence from ephemeral to intermittent to perennial, provide the tightest coupling between water and land, yet they often receive the least protection during forest management. We described communities of aquatic insects in perennial, intermittent, and ephemeral channels surrounded by old-growth forest and 4- to 8-year-old clearcuts in Clayoquot Sound, British Columbia, to determine whether temporary streams have unique aquatic communities and to examine the short-term impacts of harvesting. We measured flow persistence, stream size, canopy cover, organic detritus, and algal biomass in 19 streams. We sampled aquatic invertebrates with a combination of emergence cages and kicknet samples. Temporary and old-growth streams had more organic detritus and a higher abundance of shredders. Perennial and clearcut streams had a higher abundance of some algal grazers, but not higher algal biomass. Insect richness was similar in intermittent and perennial streams of each seral stage but lower in ephemeral streams. Intermittent streams contained four taxa not found in the other stream classes; perennial and ephemeral streams had none. Communities of aquatic insects differed between streams surrounded by clearcuts and old growth, and varied with continuity of flow. [ABSTRACT FROM AUTHOR]

Much of the future timber supply in the Northern Hemisphere will come from boreal and sub-boreal forests, yet there has been little investigation of how aquatic communities in these regions would be affected by logging. We conducted an empirical, comparative study to investigate the effects of streamside clear-cut logging on benthic macroinvertebrates, algal standing stock, and in-stream physical and chemical habitats in the sub-boreal central interior region of British Columbia. We found that streams that flowed through old-growth forests (sites termed "not logged") did not differ from streams flowing through older logged forests (where the riparian zones were harvested 20-25 years before our sampling; sites termed "older logged") with respect to macroinvertebrate total density or biomass, feeding guild density or biomass, and chlorophyll a biomass. However, streams flowing through newly logged forests (where the riparian zones were harvested within 5 years of our sampling; sites termed "recently logged") had nearly twice the macroinvertebrate biomass as those in not logged or older logged sites and higher chlorophyll a biomass. There were no differences among the three stream categories in regard to structural aspects of the physical habitat (e.g., substrate composition, large organic debris density, dimensions of pools and riffles). Streamside logging in sub-boreal forests appears to enhance primary and secondary production, but this phenomenon may only be evident for the first two decades following logging. [ABSTRACT FROM AUTHOR]

Examines the ecological combining ability of three forest types in British Columbia and Alberta. Factors that are related to the stand volume of tree species; Effect of one species on the productivity of another species; Details of the forest policy in British Columbia; Analysis of vegetation and soil physics in British Columbia and Alberta.

Presents a study that examined postfire succession in forests where Pinus (P.) albicaulis is common in two areas in southern British Columbia. Influence of fire on structure and composition of individual plants as well as the pattern of forests on the landscape; Materials and methodology; Discussion on the patterns of fire disturbance and the successional trends reported for P. albicaulis forests.

Deals with a study which compared height growth and nutrition of second-growth plantations on imperfectly drained, lower productivity cedar-hemlock-salal forests with more productive ecosystems in north coastal British Columbia. Materials and methods; Results; Discussion.

Deals with a study which examined how forest structure and composition change with spatial variations in the fire cycle across a shore-hinterland gradient in the James Bay region of Quebec. Materials and methods; Results; Discussion.

Quantitative genetic variation in growth, latewood percentage, and wood density was investigated for British Columbia's interior spruce (the common name for white spruce, Picea glauca (Moench) Voss; Engelmann spruce, Picea engelmanni Parry ex Engelm.; and their hybrids). The study included 160 half-sib families from the East Kootenay and Prince George regions. At the time of sampling, progeny tests for those two regions were 20 and 22 years old, respectively. Univariate and multivariate restricted maximum likelihood (REML) estimates of genetic parameters were obtained. Estimates of genetic variances and heritabilities differed greatly across planting sites for the examined traits, especially after transplantation between the regions. Significant negative genetic correlation between overall growth and wood density was found for the East Kootenay progenies, while negative but nonsignificant genetic correlation between these traits was found for the Prince George progenies. Generally, there was no significant decrease in heritability for ring width and latewood percentage in successive growth rings. A general age trend for genetic correlation between those traits was not apparent, except that the correlation remained negative during the observed period. Our results show that it is not possible to select certain families as superior based on 1-year results because of the family by growing season interactions. Nevertheless, genetic age?age correlations for cumulative increments were high, having a decreasing trend with increasing difference in age. [ABSTRACT FROM AUTHOR]

Determines the contribution of old-growth and senescent forest stands regenerated through clear-cutting to the biodiversity of wet boreal fir stands in eastern Quebec because overmature stands are becoming scarce in that region. Comparisons of the structure and composition of nonvascular plant communities (mosses, hepatica, lichens, and saprophytic fungi) of old-growth forests with those of mature or senescent fir stands harvested 60 years ago; How the structural diversity of senescent second-growth fir stands becomes similar to that of old-growth stand because of mortality within the overstory; Findings suggest these structural characteristics favour the development of diversified nonvascular plant communities, especially wood-inhabiting species found on slightly decomposed woody debris and soil-inhabiting species that colonize disturbed soils.