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

Reports on the measured rates of decomposition at three sites representing the major mixedwood forest types of British Columbia: (i) boreal forests of white spruce (Picea glauca (Moench) Voss) and trembling aspen (Populus tremuloides Michx.), (ii) coastal forests of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and red alder (Alnus rubra Bong.), and (iii) a wet interior forest of Douglas-fir, paper birch (Betula papyrifera Marsh.), and lodgepole pine (Pinus contorta Doug. ex Loud.). Mass loss of litter of each species (both pure and in combination with the other species) that was measured in forests of each species to determine (i) if broadleaf litter decomposed faster than needle litter, (ii) if litter decomposed faster in broadleaf or mixedwood forests than in coniferous forests, and (iii) if mixing with broadleaf hastened decomposition of needle litter; Broadleaf litters that decomposed faster than needles during the first year but, thereafter, decomposed more slowly; Litter that tended to decompose faster in the broadleaf forests than in the coniferous forests; No evidence to indicate that the addition of broadleaf litter hastened decomposition of needle litter; Results that indicate that the mixing of needle litter with broadleaf litter is unlikely to hasten decomposition in mixedwood forests of British Columbia.

In 1996 we initiated a study to evaluate several techniques for measuring light under broadleaf canopies. Hourly average photosynthetic photon flux density and percent transmittance were measured 1 m above the ground at four points in each of three canopy densities created by a spacing experiment in a 35-year-old paper birch (Betula papyrifera Marsh.) dominated stand located near Prince George, B.C. At each point, fisheye photographs were taken and LAI-2000 plant canopy analyzer (LAI-2000), spherical densiometer, and competition index (Lorimer'sindex) measurements were made. Percent transmittance measurements onan overcast day (1-h average), transmittance measured over periods of 3 h or longer on a clear day, LAI-2000 diffuse noninterceptance measurements, and gap light index determined from fisheye photographs were strongly correlated with growing season percent transmittance (r2>= 0.96) as was competition index (r2 = 0.928). Concave spherical densiometer measurements and midday percent transmittance measurements on clear days were also well correlated with measured percent transmittance (r2>= 0.89). Estimates of understory light by the LITE model were strongly correlated with growing season percent transmittance. Correlations improved with increasing length of the period simulated (r2 = 0.755 for a point measurement on a clear day; r2 = 0.936 for an entire sunny day;and, r2 = 0.953 for the entire growing season). However, this version of the model underestimated percent transmittance in these spaced birch stands by 34-90%. [ABSTRACT FROM AUTHOR]

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In northern British Columbia and southern Yukon woodland, caribou forage extensively on terrestrial lichens, predominately mat-forming Cladina species in late-successional pine-lichen woodlands. Many of these stands are now reaching a point in their development where lichen abundance declines as feather-moss mats increase. We evaluated the response of forest floor plant communities in pine-lichen woodlands from the southern Yukon Lewes Marsh partial-cutting trial 8 years after harvesting. Photoplot results documented a major decline (>60% ± 5.6% SE) in the mean surface area of existing large clumps of C. mitis in control (unharvested) treatments, whereas the mean surface area of large C. mitis clumps declined by 28% (±15% SE) in the one-third basal-area removal and showed an increase of 13.5% (±25% SE) in the two-thirds basal-area removal. Line intercept transects documented no changes in overall stand-level lichen abundance between pre-harvest (2012) and post-harvest (2021) measurements, while feather-moss mats and dwarf shrubs showed declines and increases, respectively, in partial-cutting harvest plots. Stand thinning may provide a bridging strategy to extend the period of forage lichen availability in late-seral pine-lichen woodlands, an important consideration in landscapes where increasing severity and frequency of fires are changing the seral-state distribution of caribou habitat. [ABSTRACT FROM AUTHOR]

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Forestry is becoming more complex as a result of diverging societal demands. Indigenous Peoples' reconciliation and the challenges of climate change call for research that embraces transdisciplinarity, reciprocity, and problem-focused learning at the landscape scale. Both globally and in Canada, forestry and forest research are struggling to keep pace with this growing complexity. Place-based collaborative research and learning initiatives, described here as "learning landscapes," offer an under-explored approach to meeting diversifying goals for forest landscapes. We describe recent progress in Quesnel, British Columbia, where researchers and local institutions are engaging to strengthen resilience and innovation in the forest sector. We first define the concept of learning landscape in the context of transdisciplinary sustainability science, and then illustrate this approach using the case study of Quesnel. We describe a process of systems diagnosis, including asset mapping and analysis of potential forestry pathways through a "best bets" framework. We propose a Theory of Change as a way forward, outlining opportunities for government, industry, and communities in developing regional capacity for integrated management and high-value forest products. We reflect on the contributions of learning landscapes to knowledge generation, experiential learning, and institutional development, and discuss implications for steering decision-making in locally driven sustainability transitions. [ABSTRACT FROM AUTHOR]

As forest managers increasingly seek to implement partial-harvest silviculture systems in complex forests, more data are required on the potential development of the residual stand following treatment. In this study, we present 25-year data from a long-term silvicultural study of tree- and stand-level responses to differing levels of basal area following partial harvest in a complex spruce–fir forest in central British Columbia, Canada. Reducing stand basal area elicited stronger basal area increment response in fir than spruce; however, spruce productivity was overall higher than fir across all treatments. Smaller trees increased their size proportionally more than larger trees, and thinning resulted in increased recruitment of smaller trees into larger diameter classes. At the stand-level, basal area reductions to well below 20 m2/ha resulted in higher volume and basal area growth over the length of this study, and suggest that optimum stand-level growth may be achieved at lower basal areas than suggested in prior literature. We also found a positive relationship between stand-level residual basal area and mortality. In central British Columbia, stand structure, species composition, and growth rates in complex spruce–fir forests can be maintained through partial-harvest silviculture treatments. [ABSTRACT FROM AUTHOR]

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Provides information on the 4th International Workshop on Disturbance Dynamics in Boreal Forest held at the University of Northern British Columbia on August 9 to 12, 2002. Issues involving forest management discussed at the event; Keynote speakers who were present in the workshop; Discussion on the importance and role of disturbance in shaping boreal forest.

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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.)

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]

The Northern Secwepemc First Nations of central British Columbia are facing serious communication challenges in relation to the comanagement of natural resources in their traditional territories. For First Nations’ managers, communication by speaking and listening and by sharing stories continues to be important for maintaining traditional ecological knowledge and culture. However, in the dominant discourse currently used by management authorities, emphasis is placed on communication products represented in reading and writing, often in electronic format. This dichotomy is leading to communication crises, with traditional ecological knowledge being required to fit within a rigid technology of literacy. The hypothesis that the Northern Secwepemc First Nations are leading transformation initiatives toward sustainable management in their territories and that shared knowledge and responsibility emerges from new growth opportunities in crisis situations has been tested using the case study survey method for inquiry. Results indicate there is potential for transformation towards forest comanagement in Northern Secwepemc territories in times of crises; however, certain conditions such as adequate staffing, funding, and training must first exist at the site level of management for both provincial and Aboriginal managers, to make the best use of emergent opportunities for collaboration. Les Premières nations Northern Secwepemc dans le centre de la Colombie-Britannique font face à de sérieux défis de communication reliés à la cogestion des ressources naturelles dans leurs territoires ancestraux. Pour les gestionnaires des Premières nations, il est encore important de communiquer en parlant, en écoutant et en partageant des légendes pour conserver la culture et les connaissances écologiques traditionnelles. Cependant, dans le discours dominant couramment utilisé par ceux qui régissent l’aménagement, l’emphase est mis sur les produits de communication qui font appel à la lecture et à l’écriture, souvent sous la forme de documents électroniques. Cette dichotomie entraîne des problèmes de communication lorsque les connaissances écologiques traditionnelles doivent s’adapter à une technologie rigide fondée sur la lecture et l’écriture. L’hypothèse voulant que les Premières nations Northern Secwepemc soient en train d’évoluer vers l’aménagement durable dans leurs territoires et que le partage des connaissances et des responsabilités émerge à travers de nouvelles occasions de croissance, engendrées par des situations de crise, a été testée à l’aide de la méthode des cas comme outil d’enquête. Les résultats indiquent qu’une évolution vers la cogestion de la forêt dans les territoires des Northern Secwepemc pourrait survenir en période de crise. Cependant, certaines conditions, telles des effectifs, des fonds et un entraînement adéquats, doivent d’abord être remplies à l’échelon des gestionnaires sur le terrain, tant pour les gestionnaires provinciaux qu’aborigènes, afin de profiter au maximum des occasions de collaboration qui se présentent. [ABSTRACT FROM AUTHOR]

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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.)

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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]

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]

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]

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.

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.

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]

Discusses Holocene vegetation and natural disturbance in the Englemann Spruce-Subalpine Fir (ESSF) biogeoclimatic zone at Mount Kobau, British Columbia. Reconstruction of the vegetation and natural disturbance history of the Mount Kobau area, in the Engelmann spruce (Picea engelmannii Parry ex Engelm.) ? subalpine fir (Abies lasiocarpa (Hook.) Nutt.) ESSF forest, using pollen, plant macrofossils, and microscopic charcoal; Description of Holocene period of rapid warming; Increase of moisture during the mid-Holocene when fires may have occurred more widely and burned more severely; How open lodgepole pine (Pinus contorta Dougl. ex Loud.) parkland occupied the mountain summit; Cooling of the Late-Holocene which resulted in the establishment of modern ESSF forest; Confirmation of a broad three-stage regional climate pattern inferred by the vegetation of the Holocene; Under future anticipated climate change, the high-elevation, dry ESSF forests in southern British Columbia may be replaced by grasslands.