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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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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.)

This paper examines suspended sediment concentration and stream discharge during freshet in three small sub-boreal forest streams (<1.5 m in width) in the central interior of British Columbia for 1 year prior to (1996) and for 5 years following forest harvesting (1997-2001). Harvesting prescriptions in a 20-m strip beside one stream required complete removal of merchantable timber (>15 cm diameter at breast height (DBH) for pine and >20 cm for spruce), while all stems <30 cm DBH were retained beside a second stream. A third stream remained unharvested as a control. The two riparian treatments were prescribed to test the efficacy of current British Columbia legislation that allows for varying amounts of riparian retention as best management practices for the management of windthrow. Both treated watersheds were clear-cut harvested (approximately 55% removal) in January 1997, and in the following year, temporary access roads were deactivated, including two stream crossings in the low-retention watershed. An increase in peak snowmelt and total freshet discharge was first noted in the second spring following harvest in both treatments and remained above predicted in all subsequent years. Suspended sediment also increased during freshet following harvest but returned to levels at or below preharvest predictions within 3 years or less in the high-retention watershed. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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.

Presents a correction to the study 'An 1800-Year Record of the Spatial and Temporal Distribution of Fire From the West Coast of Vancouver Island, Canada,' by Daniel G. Gavin, Linda Brubaker and Kenneth P. Lertzman.

Laboratory experiments were conducted with the millipede Harpaphe haydeniana haydeniana Wood (Polydesmida: Xystodesmidae) to determine (i) its litter feeding preferences, (ii) rates of leaf litter consumption, (iii) feeding effects on available nitrogen, and (iv) functional microbial diversity. The millipede exhibited a preference for Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and, to a lesser extent, Sitka spruce (Picea sitchensis (Bong.) Carriere) litter compared withwestern hemlock (Tsuga heterophylla (Raf.) Sarg.) and western redcedar (Thuja plicata Donn ex D. Don) litter when given a choice. When only one litter type was provided, millipedes consumed considerably more western redcedar than Douglas-fir, Sitka spruce, or western hemlock. Among the six broadleaf species tested, paper birch (Betula papyrifera Marsh.), bigleaf maple (Acer macrophyllum Pursh), vine maple (Acer circinatum Pursh), and red alder (Alnus rubra Bong.) were consumed at much higher rates than swordfern (Polystichum munitum (Kaulf.) Presl.) or salal (Gaultheria shallon Pursh). Daily rates of conifer litter consumption ranged between 10 and 20% of the millipede's fresh biomass and may translate to 36% of the annual litter fall. Our results suggest that transformation of conifer litter into millipede frass can increase rates of litter decomposition and N mineralization, as well as influence microbial activity and diversity in coastal forests. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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]

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]

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

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

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

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

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

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

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

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

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

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.

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]

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

Investigates genetic variation in drought hardiness traits and their genetic correlations with growth potential and recovery traits in 39 full-sib families of coastal Douglas-fir in southwestern British Columbia. Method; Traits assessed; Findings; Conclusion that potential exists for identifying drought-hardy families at the seedling stage and using this information for deployment or breeding purposes; Suggestion that drought hardiness could be improved without negatively impacting growth potential.

Presents a study of Douglas-fir (Pseudotsuga menziesii var. menziesii (Mirb.) Franco) zygotic seedlings and seedlings produced through somatic embryogenesis on southern Vancouver Island, British Columbia. Comparison of the two stock types in a number of adaptive attributes evaluated during two growing seasons; Methods; Findings; Indication that somatic and zygotic seedlings had a similar pattern of physiological performance throughout two years of assessment.

Examines the vertical distributions of fine roots of western hemlock Tsuga heterophylla, western redcedar Thuja plicata Donn and salal Gaultheria shallon in Vancouver Island. Characterization of cedar, hemlock and salal roots in cedar-hemlock forests; Correlations of the roots with the nitrogen concentrations; Descriptions of the forest floor horizons.

Analyzes the structural pattern of roots in pure hemlock, pure redcedar and mixed-stands in British Columbia. Variations in the density of roots along the lateral gradient among stand types and root size classes; Potential of some forest sites to support mixed-species stands; Use of the vertical and horizontal distributions of root density in describing the root structural pattern.

Measures carbon dioxide fluxes from a five-year old vegetated clearcut in sub-boreal British Columbia using two different approaches. Share of conifer seedlings in overall carbon dioxide fluxes; Factors affecting divergence in the data; Main component of carbon dioxide fluxes.

Evaluates the validity of stream culvert discharge design of the Forest Practices Code of British Columbia. Analysis of annual maximum flows; Economic and environmental impact of flood; Estimation of return period of instantaneous peak flow.

Examines the growth and nutrition of hybrid poplars after fertilization in Vancouver Island, British Columbia. Use of readily soluble and controlled-release fertilizers in the study; Measurement of cutting diameters at planting; Analysis of multiyear repeated growth and nutrient measurements by analysis of covariance.

Evaluates the variation in trembling aspen productivity in British Columbia. Relationships between site index and environmental factors; Effect of topography on aspen growth; Soils associated with aspen stands.

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.

Examines the terpene levels in bark and wood samples of Sitka spruce in British Columbia. Use of artificial wounding to simulate attack by white pine weevil; Extraction of terpenes with hexane; Use of capillary gas chromatography; Number of bark terpenes with differences in sampling time.

Discusses the improvement of understanding of the role of soil invertebrates in the break-down of litter, cycling of nitrogen, and growth of seedlings in forests of British Columbia. Presence of millipedes in the microcosms of forest floor; Increase of inorganic nitrogen release in the presence of fauna; Rate of breakdown of forest litter.

Analyzes the quantitative framework for breeding and conservation of forest tree genetic resources in British Columbia. Relevance of the methods use in integrating breeding with conservation population Role of in- and ex-situ populations on forest tree gene resource management; Genetic conservation objectives of in situ-populations.

Examines the paleotemperature record from Picea engelmannii tree-line sites in Canadian Rockies, British Columbia. Differences in tree species modelling techniques, spatial coverage and seasonal temperatures; Development of temperature reconstruction for the Banff-Jasper region; Regional estimates of temperature.

Determines the effects of broadcast burning after clear-cutting on the diversity of ectomycorrhiza (ECM) on hybrid spruce seedlings in British Columbia. Abundance of Amphinema in planted seedlings from cut-burned and clear-cut sites; Relationship between mycorrhizal diversity and disturbance; Identification of fungal symbionts.

We have characterized canopy geometry and light transmission by the nine dominant conifer and broad-leaved tree species of the interior cedar-hemlock (ICH) forests of northern British Columbia. Our field data were used to parameterize a spatially explicit model of light transmission through mixed-species forests. That model, a component of the forest dynamics simulator SORTIE, was developed for eastern deciduous forests, and this paper presents a test of that model in a very different ecosystem. Our results show that individual crowns of the ICHforests intercepted much more light than species of eastern deciduous forests but that the canopy as a whole allowed greater light penetration, largely because of openings between the relatively narrow, conical crowns of the western conifers. Light transmission by individualcrowns was correlated with shade tolerance among the conifers (as ineastern deciduous species), but crown depth was not (in contrast with eastern species). Despite the fundamental differences in the natureof light transmission in the two ecosystems, the SORTIE light model developed for eastern deciduous forests was effective at predicting spatial variation in understory light levels in these western coniferous forests. The goodness of fit of such a simple model suggests that the most important factors regulating spatial variation in understorylight levels in these forests are simply the sizes and distribution of nearby trees, and the local sky brightness distribution. Discrete canopy gaps represent a special case in which a region of the canopy is not occupied by crowns. [ABSTRACT FROM AUTHOR]

On 14 April 1994, the British Columbia government announced a new stumpage formula that, at then-expected product prices, increased the average charge by about $12/m3 and more than doubled the rate at which stumpage fees change when lumber prices change. Most of the increased revenues are reinvested in the forest sector by a new organization, Forest Renewal British Columbia (FRBC), created specifically for that purpose. Using standard event-study methodologies, this paper documents the net effect of the fee increases and new policy direction on British Columbia forest products companies. After controlling for firm-specific risk and the decline in the Toronto Stock Exchange that occurred at about the same time, the new stumpage policy extracted about $1.0 billion from shareholders of the firms studied, andperhaps $2.4 billion from all licencees (an amount roughly equal to the capitalized after-tax cost of the higher fees). The impact on individual firms is highly correlated with the allowable annual cut (AAC) in replaceable licenses each holds, with an average impact of about$33.3/m3 of AAC. The market appears to have discounted both the good news about offsets in impending timber-supply reductions that the creation of FRBC implies and the reductions in earnings riskthat the new stumpage system provides. When added to the increased regulatory costs associated with the new provincial Forest Practice Code, the timber-fee increases appear to have fully depleted the value of holding British Columbia timber quotas. [ABSTRACT FROM AUTHOR]