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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.)

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 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 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 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.)

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]

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]

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]

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]

Cedar-hemlock forests on Vancouver Island are primarily nitrogen limited and characterized by an understory dominated by the ericaceous shrub salal (Gaultheria shallon Pursh.). In 1984, an experiment was established on regenerating cedar-hemlock forests to determine the effects of nitrogen and phosphorus (N + P) fertilization and vegetation control on conifer growth. It was hypothesized that these treatments would not only stimulate tree growth, but also improve nutrient supply, stand productivity, and site quality. To test this hypothesis, tree height growth, canopy closure, salal biomass, foliar and forest floor N and P concentrations, and seedling growth on forest floor were measured 10-13 years after treatment. Both salal control and fertilization increased tree growth and canopy cover, and reduced salal biomass. However, only fertilized plots showed changes in site quality measurable 10-13 years following N + P application. Hemlock foliar P concentrations, forest floor total N and P levels, and hemlock height increments were higher in these plots. Forest floors from the fertilized plots also supported greater growth of conifer seedlings. These results suggest that sustained changes to site quality may be achieved with N + P fertilization of cedar-hemlock forests. [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.

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.

Describes the spatial and temporal patterns associated with canopy interception, throughfall and net forest water along a black spruce topo-sequence situated in northwestern Ontario. Detection of downward shifts in the potential of hydrogen ions for throughfall; Demographic profile of the study area; Modal conditions for three discrete vegetative communities.

Presents a study that examined the distribution and foraging behavior of northern waterthrushes in recently harvested and intact landscapes of Newfoundland. Method of the study; Results and discussion; Conclusion.

Presents information on a study which evaluated the role of certain substrates and litterfall on early conifer survivorship in southern boreal stands of Canada. Background on the study area; Materials and methods used; Results and discussion.

Presents information on a study which investigated the mass of turves of feathermoss beneath a black spruce canopy in the Canadian boreal forest. Background on the study area; Materials and methods used; Results and discussion.

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

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.