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Copyright of Canadian Journal of Earth 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 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.)

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]

We investigated interactions among harlequin ducks (Histrionicus histrionicus (L., 1758)), fish, and their shared aquatic insect prey. We measured flow variability, benthic aquatic prey abundance, fish presence, and breeding density of harlequins on eight rivers in the Southern Coast Mountain Range in British Columbia, Canada, in 2003 and 2004. Rivers with lower flow variability had higher abundance of aquatic insects. Densities of harlequins and fish presence on the rivers were both significantly and positively related to insect abundance, but path analysis revealed a strong negative correlation between them. We interpret this as an indirect interaction between harlequins and fish mediated by anti-predator behaviour of insects in the presence of fish, which reduces insect availability, rather than as a reduction in the abundance of aquatic insects through consumption by fishes. We hypothesize that the ongoing and widespread introduction of fish into historically fishless waters throughout North America may have contributed to the current low productivity and recruitment measured in populations of harlequins by reducing quality of breeding habitat. Nous étudions les interactions entre les arlequins plongeurs (Histrionicus histrionicus (L., 1758)), les poissons et les insectes aquatiques qu’ils utilisent conjointement comme proies. Nous avons mesuré la variabilité du débit, l’abondance des proies aquatiques benthiques, la présence de poissons et la densité des arlequins plongeurs en reproduction dans huit rivières de la chaîne de montagnes de la côte sud de la Colombie Britannique, Canada, en 2003 et 2004. Les rivières à débit moins variable ont de plus fortes abondances d’insectes aquatiques. Il y a une relation significative et positive entre les densités des arlequins plongeurs et la présence de poissons, d’une part, et l’abondance des insectes, d’autre part, mais une analyse des coefficients de direction montre une forte corrélation négative entre ces deux variables. Nous interprétons ce phénomène comme une interaction indirecte entre les arlequins plongeurs et les poissons qui s’explique par le comportement anti-prédateur des insectes en présence des poissons, ce qui réduit la disponibilité des insectes, plutôt que par une réduction de l’abondance des insectes aquatiques à cause de la consommation par les poissons. Nous posons l’hypothèse selon laquelle les introductions courantes et répandues de poissons dans des eaux historiquement sans poissons dans toute l’Amérique du Nord peuvent avoir contribué à la productivité et au recrutement faibles mesurés actuellement chez les populations d’arlequins plongeurs en réduisant la qualité des habitats de reproduction. [ABSTRACT FROM AUTHOR]

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 Geotechnical Journal 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 Earth 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 Earth 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 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 Earth 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 Earth 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 Journal of Environmental Engineering & Science 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 Earth 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 Earth 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 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 Earth 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 Earth 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 Earth 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 Earth 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 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.)

A white birch (Betula papyrifera Marsh.) overstory of a 30+ year old stand was thinned or completely removed, releasing an advance regeneration of subalpine fir (Abies lasiocarpa (Hook.) Nutt.). The overstory was clear-cut (T0), thinned to 600 (T600) or to 1200 (T1200) stems/ha, or left uncut (control). Three years after release, understory responses were best demonstrated by decreasing specific leaf area with increasing release level and by changes to height and radial growth increments. Clear-cutting the overstory stalled the height growth in fir for two seasons and radial growth at the tree base for one season. Compared with the control, the 3-year height increment was proportionally greatest in intermediate trees of T600, and this treatment produced the overall best response in height growth. Complete birch removal produced the best radial growth response despite the initial growth check. However, no release treatment significantly affected the whole tree variables (aboveground biomass, height, diameter at breast height (DBH), live crown ratio) within the studied time frame. Shoot silhouette ratios were lowest in the completely released understory trees, while they were similar to those of the controls in all partial-release treatments. Tree sturdiness (height/DBH ratio) was 80–90 in most treatments except T0, where it declined to below 80. Despite this improvement, large trees in T0 have been damaged by wind and snow.L'étage dominant composé de bouleau blanc (Betula papyrifera Marsh.) dans un peuplement de plus de 30 ans a été éclairci ou complètement enlevé pour dégager la régénération préexistante de sapin subalpin (Abies lasiocarpa (Hook.) Nutt.). L'étage dominant a été coupé à blanc (T0), éclairci à 600 (T600) ou à 1200 (T1200) tiges à l'hectare, ou laissé intact (témoin). Trois ans après le dégagement, la réaction du sous-étage était le mieux illustrée par la surface foliaire spécifique qui diminuait avec l'augmentation de l'intensité du dégagement et par les changements dans l'accroissement en hauteur et la croissance radiale. La coupe totale de l'étage dominant a arrêté la croissance en hauteur du sapin pendant deux saisons et la croissance radiale à la base de l'arbre pendant une saison. Comparativement au témoin, l'accroissement en hauteur après 3 ans a été le plus fort chez les arbres intermédiaires dans le traitement T600 et ce traitement a dans l'ensemble produit la meilleure réponse pour la croissance en hauteur. L'élimination complète du bouleau a produit la meilleure réponse pour la croissance radiale malgré la stagnation initiale de la croissance. Cependant, aucun traitement de dégagement n'a affecté les variables de l'arbre entier (biomasse épigée, hauteur, diamètre á hauteur de poitrine (DHP), rapport de cime verte) pendant la durée de l'étude. Le rapport de silhouette des pousses des arbres de sous-étage était le plus faible chez les arbres complètement dégagés alors qu'il était semblable à celui observé dans les parcelles témoin dans tous les traitements de dégagement partiel. La robustesse des arbres (rapport de la hauteur sur le DHP) a atteint 80–90 dans la plupart des traitements à l'exception du traitement T0 où la valeur a descendu au-dessous de 80. Malgré cette amélioration, les gros arbres ont été endommagés par le vent et la neige dans le traitement T0.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

Ten-year height data from 232 open-pollinated interior spruce families tested in five seed planning zones located in north-central interior British Columbia were used to investigate the extent and pattern of genotype by environment (G×E) interaction and to examine the validity of the seed planning zone delineation in this region. The G×E interaction in the entire region was both statistically and practically significant, with an estimated type b genetic correlation coefficient of 0.64. The detected geographic pattern of the G×E interaction indicates that the old delineation is overly conservative, and consolidating the five old zones into the two new zones is a valid decision. A procedure was developed to convert the expected genetic gain, with respect to the old zone, to the new zone when seed from a rogued local seed orchard is used for reforestation in the entire new zone. A similar procedure was also proposed to predict the breeding value of an individual that was only tested in the old zone of its origin with respect to the new zone. Given the detected amounts of the G×E interaction, and considering other factors, using three to five sites in each new zone for the second-generation progeny testing seems to be appropriate.L'auteur a étudié, chez l'épinette de l'intérieur, l'ampleur et l'allure de l'interaction génotype × environnement (G×E) ainsi que la validité de la délimitation des zones semencières de la région du centre nord de l'intérieur en Colombie-Britannique, à l'aide des données de hauteur à 10 ans de 232 descendances à pollinisation libre testées dans cinq zones semencières de la région. L'interaction G×E pour la région entière était significative, tant au plan statistique qu'à celui des incidences pratiques, avec un coefficient de corrélation génétique de type b de 0,64. Le patron de variation géographique de l'interaction G×E indique que l'ancienne délimitation est trop conservatrice, et que la fusion des cinq anciennes zones en deux nouvelles représente une solution valide. L'auteur a développé une procédure afin de convertir le gain génétique espéré dans le cadre de l'ancienne zone en fonction de la nouvelle zone, en assumant que les semences du verger à graines local éclairci sont utilisées pour l'ensemble du reboisement dans la nouvelle zone. Également, des procédures similaires ont été proposées pour prédire la valeur en croisement d'un individu en fonction de la nouvelle zone, alors qu'il n'avait été testé que dans son ancienne zone d'origine. Étant donnée l'ampleur observée de l'interaction G×E et en considérant d'autres facteurs, l'emploi de trois à cinq sites par nouvelle zone apparaît approprié pour l'évaluation des descendances de seconde génération.[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]

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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.

Focuses on the effects of nitrogen and boron fertilization on foliar boron nutrition and growth in two different lodgepole pine ecosystems in British Columbia. Factors that may suppress height development in the absence of deficiency symptoms; Continental climate characteristics of the study area; Implications of fertilization for first-year fascicle mass.

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.

Examines the cultural and nutritional importance of the red alga Porphyra abbottae Krishnamurthy and related species in the traditional food systems of the indigenous peoples of the Pacific Coast of Canada. Botany and ecology of P. abbottae; Summary of the traditional indigenous knowledge of the harvesting, processing and use of Porphyra; Applications and issues.

Presents the results of the computer modelling component of the cover instrumentation research program initiated by Placer Dome Canada in British Columbia. Objectives of the computer modelling; Functions of a vegetated soil cover; Processes which are controlling water fluxes.

The Upper Cretaceous Nanaimo Group of southwest British Columbia is a >4 km-thick succession consisting mostly of deep marine silicielastics deposited directly on the Insular Superterrane. As such, this succession has been the focus of several paleomagnetic, isotope geochemistry, paleontology, and sedimentology studies in attempts to elucidate the tectonic history and paleolatitude of the Insular Superterrane and associated entities during the critical time of Nanaimo Group deposition (ca. 90-65 Ma). However, disagreement as to whether deposition occurred into a single or multiple basins has led to confusion concerning the formal stratigraphy and formation names for the succession, and has resulted in problems with both local and regional correlations. The upper two-thirds of the succession is continuously and well exposed on Denman and Hornby islands and represents the best example of this part of the succession in the northern half of what we consider the single Nanaimo Basin. This area includes the previously only informally defined type areas for the Geoffrey and Spray formations, defined here formally for the first time with type sections and detailed descriptions. New interpretations of the geology of these islands demonstrate that previously interpreted major faults do not exist, resulting in stratigraphic and age controls that are both different and simpler than previously interpreted. The redefined stratigraphy of the northern part of the basin is remarkably similar to that of southern areas in both type and age, affirming both a single basin evolution and a single stratigraphic nomenclature. [ABSTRACT FROM AUTHOR]

Focuses on the scale of aggregative response of Harlequin Ducks to seasonally and locally superabundant prey at Pacifi herring spawning sites in the northern Strait of Georgia, British Columbia during 1995-2002. Average duration of stay at spawning sites; Percentage of the total population moving to spawning sites.

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.

Presents a study that examined the dunes and associated sand transport in a tidally influenced sand-bed channel in Fraser River, British Columbia. Methodology; Flow conditions and bed-form geometry; Dune migration and transport.

Presents a study that investigated the Greenschist-facies metamorphism of the Burgess Shale in British Columbia and its implications for models of fossil formation and preservation. Sampling and analytical methods; Minerological characteristics of the Burgess Shale; Interpretation of its petrological characteristics.

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]

In this study we investigated quantitative genetic variation in tracheid characteristics in two genetic tests of 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 88 half-sib families from the East Kootenay and Prince George regions. We have developed a technique for quantitative assessment of tracheid characteristics by measuring cross-sectional dimensions. We obtained cell size, wall thickness and their ratio in early-, transition-, and late-wood classes within a growth ring. Tracheid length and microfibril angle were measured in the transition wood. A number of tracheid characteristics showed significant genetic variation, but heritability, phenotypic, and genetic correlation estimates varied across test sites within and outside regions of origin of parental trees. Ring width was determined, both phenotypically and genetically, by the number of tracheids and to a lesser extent by the by their mean size. On average, rings with larger tracheids did not have significantly thicker walls. Wider rings had lower mean wall to tracheid size ratio. Faster growth did not result in shorter tracheids in the transition wood. Longer tracheids had lower micro fibril angle. There were no particular benefits from considering the anatomical component traits for breaking the negative genetic correlation between growth and wood density. [ABSTRACT FROM AUTHOR]

The Nicola horst exposes plutonic and amphibolite-grade metamorphic rocks and is surrounded by low-grade arc rocks of the Late Triassic Nicola Group. We present new geological mapping and U–Pb, Nd, and metamorphic data for the Nicola horst near Bob Lake, ~40 km south of Kamloops, British Columbia. The Bob Lake assemblage includes felsic to intermediate metavolcaniclastic rocks, metaconglomerate, schist, phyllite, and other rock types. From U–Pb zircon analysis, a felsic metaporphyry clast in metaconglomerate is 1.04 Ga old. The oldest detrital zircons in metaconglomerate and schist are also near 1 Ga. The Bob Lake assemblage was intruded by 230 Ma tonalite, 219 Ma diorite, and 64 Ma leucogranite and includes 161 Ma felsic porphyry and 157 Ma rhyodacite. Amphibolite-grade metamorphism and ductile flattening and stretching affected all rocks except crosscutting Paleocene granite and granodiorite. The high-grade rocks may be exposed as a result of latest Cretaceous – Eocene extensional ductile flow beneath a thin brittle upper crust. A thickness of ~20 km of juvenile crust beneath the proposed Quesnel terrane is inconsistent with the evidence of Proterozoic source rocks at surface. We infer that most of the crustal lithosphere in this part of the Intermontane Belt is continental, which does not preclude possibly thick arc rocks in other parts. The local thinness of the Nicola Group, however, is inconsistent with emplacement as a regional allochthon and thus with their inclusion in a Quesnel "terrane." The Nicola arc succession appears to have been built on the ancient continental margin.Le horst de Nicola présente des roches plutoniques et des roches métamorphiques au faciès des amphibolites et il est entouré de roches d'arc à faible intensité de métamorphisme du Groupe de Nicola (Trias tardif). Nous présentons une nouvelle cartographie géologique et de nouvelles données U–Pb, Nd et métamorphiques pour le horst de Nicola près du lac Bob, à ~ 40 km au sud de Kamloops, en Colombie-Britannique. L'assemblage de Bob Lake comprend des roches felsiques à métavolcanoclastiques intermédiaires, un métaconglomérat, un schiste, une phyllite et d'autres types de roches. À partir d'analyses U–Pb sur zircon, nous déterminons l'âge d'un fragment felsique métaporphyrique dans un métaconglomérat à 1,04 Ga. Les zircons détritiques les plus anciens dans le métaconglomérat et le schiste ont aussi un âge d'environ 1 Ga. L'assemblage de Bob Lake a été pénétré par une tonalite de 230 Ma, une diorite de 219 Ma et un leucogranite de 64 Ma; il comprend de plus un porphyre felsique de 161 Ma et une rhyodacite de 157 Ma. Du métamorphisme au grade des amphibolites et de l'aplatissement et de l'étirement ductiles ont affecté toutes les roches à l'exception du granite et du granodiorite, datant du Paléocène, qui les recoupent. L'affleurement des roches ayant un degré élevé de métamorphisme pourrait être le résultat d'un écoulement ductile d'extension (datant du Crétacé terminal – Éocène) sous une croûte supérieure mince et cassante. Une épaisseur d'environ 20 km de croûte juvénile sous le terrane proposé de Quesnel ne concorde pas avec les évidences de roches sources protérozoïques à la surface. Nous proposons que la plus grande partie de la lithosphère crustale dans cette partie de la ceinture du Plateau intérieur soit continentale, ce qui n'empêche pas la possibilité de grandes épaisseurs de roches d'arc dans d'autres parties. Toutefois, la minceur locale du Groupe de Nicola ne concorde pas avec une mise en place en tant qu'allochtone régional et donc avec l'inclusion de ces roches dans un « terrane » de Quesnel. La succession de l'arc de Nicola semble avoir été édifiée sur l'ancienne marge continentale.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]