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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]

The discharge and stage measurements in a river system are characterized by a number of sources of uncertainty, which affects the accuracy of a rating curve established from measurements. This paper presents a fuzzy set theory based methodology for consideration of different sources of uncertainty in the stage and discharge measurements and their aggregation into a combined uncertainty. The uncertainty in individual measurements of stage and discharge is represented using triangular fuzzy numbers, and their spread is determined according to the International Organization for Standardization (ISO) standard 748 guidelines. The extension principle based fuzzy arithmetic is used for the aggregation of various uncertainties into overall stage-discharge measurement uncertainty. In addition, a fuzzified form of ISO 748 formulation is used for the calculation of combined uncertainty and comparison with the fuzzy aggregation method. The methodology developed in this paper is illustrated with a case study of the Thompson River near Spences Bridge in British Columbia, Canada. The results of the case study show that the selection of number of velocity measurement points on a vertical is the largest source of uncertainty in discharge measurement. An increase in the number of velocity measurement points provides the most effective reduction in the overall uncertainty. The next most important source of uncertainty for the case study location is the number of verticals used for velocity measurements. The study also shows that fuzzy set theory provides a suitable methodology for the uncertainty analysis of stage-discharge measurements. [ABSTRACT FROM AUTHOR]

The mountain pine beetle, Dendroctonus ponderosae Hopkins (Coleoptera, Curculionidae), a native insect of North America, periodically reaches population sizes that cause serious economic impact to the forest industry in western North America. The most recent outbreak in British Columbia (BC), Canada, which began in the late 1990s, is only now (2015) abating, after causing unprecedented tree mortality in lodgepole pine ( Pinus contorta Douglas ex. Loudon) forests. In this paper, we make use of permanent research plots to report on the condition of lodgepole pine forests in the Chilcotin Plateau of central BC, which underwent two fully documented mountain pine beetle outbreaks. In this region, the first outbreak started in the late 1970s and lasted until the mid-1980s; the second outbreak began in the early 2000s and ended in 2010. We measured the impacts of these outbreaks in terms of tree mortality and describe the characteristics of the legacies that remain following these outbreaks, including survivors in various canopy layers and levels of existing and new regeneration. We provide evidence in support of the existence of postdisturbance legacies that classify into five distinct stand structure types. Abundant regeneration and surviving intermediate canopy layers in most stands indicate that management actions to restock pine stands in this area will not likely be necessary. The information provided by this study is important for estimating future forest development and timber supply and for forest planning and management. [ABSTRACT FROM AUTHOR]

Harvest scheduling decisions are made in an uncertain environment, and current modeling techniques that consider uncertainty impose severe difficulties when solving real problems. In this paper we describe a robust optimization methodology that explicitly considers randomness in most of the model coefficients while keeping the model computationally tractable. We apply the method to schedule harvest decisions when both timber yield and demand of two products are uncertain. Since uncertain coefficients must be independent, uniform, and symmetrically distributed, we only address uncertainty attributable to estimate errors of forecast models. The methodology was applied to a 245 090 ha forest in British Columbia, Canada. We compared the change in harvest decisions and objective function when robust solutions are implemented relative to deterministic solutions. Although probability bounds can be used to a priori define the probability of constraint violations, they produce conservative solutions. We therefore tested the rates of constraint violations by simulation. While traditional deterministic decisions were always infeasible when uncertain data were simulated, robust decisions were much less sensitive to uncertainty and were, to a large extent, protected against the occurrence of infeasibilities. In exchange, reasonable reductions in the objective function were observed. [ABSTRACT FROM AUTHOR]

Holocene lateral moraines in the Coast Mountains of British Columbia are commonly composed of multiple drift units related to several glacier advances. In this paper, we document lateral moraine stratigraphy at Lillooet Glacier in the southern Coast Mountains. Five tills, separated by laterally extensive paleosols and layers of large woody debris, were found in three cross-sectional exposures through the northeast lateral moraine and two shallow gullies incised into its steep proximal face. Eighteen new radiocarbon ages constrain the timing of five separate advances of Lillooet Glacier: (1) prior to 3000 14C years BP; (2) ~3000 14C years BP; (3) ~2500 14C years BP; (4) ~1700 to 1400 14C years BP; and (5) during the Little Ice Age (LIA), after 470 14C years BP. The Lillooet Glacier chronology is broadly synchronous with other glacier records from the Coast Mountains. These records collectively demonstrate climate variability at higher frequencies during the late Holocene than is apparent from many paleoecological reconstructions. Reconstructions of glacier fluctuations are often hampered by poor preservation of landforms that predate the extensive LIA advances of the latest Holocene. Our results highlight the potential of lateral moraine stratigraphy for reconstructing these earlier events. [ABSTRACT FROM AUTHOR]

Treatments that reduce neighbour density are widely applied in the belief they will improve conifer growth in mixed forests. However, our understanding of stand composition and age effects on competition is poor. We used neighbourhood analysis for 748 target conifer trees to examine interspecific competition within 11-, 25-, and 50-year-old mixed, even-aged stands of paper birch (Betula papyrifera Marsh.), Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco), western redcedar (Thuja plicata Donn ex D. Don), and western larch (Larix occidentalis Nutt.) in southern interior British Columbia. Critical neighbourhood height and distance were identified where competition accounted for the greatest variation in target conifer diameter. Competition processes were emperically examined using relative height indices. We found that critical neighbourhood distance increased with stand age and was greater for larch than for cedar. Critical neighbourhood height was higher for cedar than for Douglas-fir or larch in the 11-year-old stands but lower in the older stands. The most important competitors in the 11-year-old stands were tall neighbours, whereas those in the older stands were short neighbours. We found asymmetrical relationships between target conifers and neighbours for all species and age-classes, indicating a resource preemption mode of competition. To be useful in developing prescriptions for competition management in mixed species stands, competition indices should consider neighbour identity and critical height for each target species. Assessment radius must also be sufficiently large to adequately characterize competition. [ABSTRACT FROM AUTHOR]

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]

To investigate the utility of short visits to seabird colonies to gauge nestling growth performance and diet, in four consecutive years from 1995 to 1998, the paper measures the nestling development and diet of rhinoceros auklets or cerorhinca monocerata at three colonies in British Columbia: Seabird Rocks, Triangle Island and SGaang Gwaii (Anthony Island).

The paper presents the results of laboratory triaxial compression tests to study the stiffness of very loose Fraser River sands. The stiffness has been shown to be very dependent on the time of confinement prior to shearing and the stress ratio at which the sample is aged. Higher stress ratios resulted in very low initial moduli with no ageing, but the moduli increased by several hundred percent during the first 1000 min of ageing. For ageing at a stress ratio of 1.0 (i.e., isotropic ageing), the initial moduli were higher than those for ageing at high stress ratios, but the stiffness increased by only about 60% during the first 1000 min of ageing. The rate of stiffness increase was approximately linear with the logarithm of time up to ageing times of 10 000 min (>1 week). Ageing at any stress ratio resulted in reduced contractive volumetric strain during subsequent shearing, reflecting a change in soil structure during ageing. The dℇ[sub v] /dℇ[sub a] ratio under triaxial compression loading decreased as the ageing stress ratio increased. The results suggest that close attention must be paid to the age of laboratory samples prepared to study the stress–strain response of sands at strains up to about 0.1%, particularly in studies on loose sand.Key words: sands, ageing, creep, modulus.Cet article présente les résultats d'un programme d'essais en laboratoire pour étudier la rigidité de sables très lâches du fleuve Fraser au moyen d'essais de compression triaxiale. On a montré que la rigidité était très dépendante du temps de confinement antérieur au cisaillement et du rapport des contraintes sous lequel l'échantillon a vieilli. Des rapports de contraintes plus élevés ont donné des modules initiaux très faibles sans vieillissement, mais les modules ont augmenté de plusieurs 100 % au cours des mille premières minutes de vieillissement. Sous un vieillissement isotrope, les modules initiaux étaient plus élevés que pour des rapports de contraintes plus élevés mais la rigidité a augmenté de seulement environ 60 % durant les 1000 premières minutes de vieillissement. La vitesse d'augmentation de la rigidité était approximativement linéaire en fonction du logarithme du temps jusqu'à des temps de vieillissement de 10 000 minutes (>1 semaine). Le vieillissement sous n'importe quel rapport de contraintes a donné des déformations volumétriques de contraction réduites durant le cisaillement subséquent, ce qui indiquait un changement dans la structure du sol durant le vieillissement. Le rapport dℇ[sub v] /dℇ[sub a] sous chargement triaxial en compression a diminué lorsque le rapport de contraintes de vieillissement augmentait. Les résultats suggèrent que l'on doit porter un attention particulière à l'âge des échantillons préparés en laboratoire pour étudier la réponse contrainte-déformation des sables jusqu'à des déformations de 0,1 %, particulièrement dans les études sur le sable lâche.Mots clés : sables, vieillissement, fluage, module.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

New bedrock mapping completed as part of the Nechako NATMAP Project indicates that the area between Babine and Takla lakes in central British Columbia is underlain by rocks of the Early Permian Asitka, Late Triassic Takla, and Early to Middle Jurassic Hazelton volcanic-arc assemblages of the Stikine Terrane. These are cut by large composite stocks of quartz diorite, granodiorite, and quartz monzonite previously mapped as the Late Triassic to Early Jurassic Topley intrusions. New U/Pb (n = 6) and laser [sup 40] Ar/[sup 39] Ar (n = 10) isotopic age dates reported in this paper suggest there are two distinct ages of plutons: the Topley intrusive suite with isotopic ages between 218 and 193 Ma; and, east of Babine Lake, the new Spike Peak intrusive suite with isotopic ages ranging from 179 to 166 Ma. West of the main plutonic belt is a thick volcanic succession of subaerial, porphyritic andesite flows, volcanic breccias, and rhyolitic ash-flow tuffs that have isotopic ages between 185 and 174 Ma. These rocks are assigned to the Saddle Hill Formation of the Hazelton Group. The plutonic roots of this proximal arc assemblage are most likely the coeval and compositionally similar plutons of the Spike Peak intrusive suite that have been unroofed in the area east of the Takla Fault. Major oxide and trace element data support the interpretation that the Topley and Spike Peak granitic rocks formed in a juvenile volcanic-arc environment and that magmatism is related to melts generated above a long-lived subduction zone of unknown orientation.Une nouvelle cartographie effectuée dans le cadre du projet NATMAP Nechako indique que la région entre les lacs Babine et Takla au centre de la Colombie-Britannique est recouverte de roches des assemblages d'arcs volcaniques du terrane de Stikine, soit Asitka du Permien précoce, Takla du Trias tardif et Hazelton du Jurassique précoce à moyen. Ces assemblages sont recoupés par des petits massifs intrusifs composites de diorite quartzique, de granodiorite et de monzonite quartzique qui avaient auparavant été cartographiés en tant que les intrusions Topley, du Trias tardif au Jurassique précoce. De nouvelles datations U-Pb (n = 6) et isotopes laser [sup 40] Ar/[sup 39] Ar (n = 10) présentées dans cet article suggèrent deux âges distincts de plutons, soit la suite intrusive de Topley avec des âges isotopiques entre 218 et 193 Ma et, à l'est du lac Babine, la nouvelle suite intrusive de Spike Peak dont les âges isotopiques varient de 179 à 166 Ma. À l'ouest de la ceinture plutonique principale se trouve une séquence volcanique épaisse d'écoulements subaériens d'andésite porphyrique, des brèches volcanique et des tufs d'écoulement de cendre rhyolitique dont les âges isotopiques varient entre 185 et 174 Ma. Ces roches sont assignées à la Formation de Saddle Hill du Groupe Hazelton. Les racines plutoniques de cet assemblage d'arc proximal sont fort probablement les plutons contemporains et à composition similaire de la suite intrusive de Spike Peak qui ont été décapés dans la région à l'est de la faille de Takla. Les données sur les principaux oxydes et les éléments traces corroborent l'interprétation que les roches granitiques de Topley et de Spike Peak se sont formées dans un environnement d'arc volcanique juvénile et que le magmatisme est relié aux fusions qui se sont produites au-dessus d'une ligne de subduction de longue durée mais dont l'orientation est inconnue.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

This paper synthesizes data extracted from the literature and data collected in various studies by the author on the quantity, characteristics, and functional importance of coarse woody debris (CWD) in the old-growth forests of British Columbia (B.C.). There is little agreement in the literature about the minimum diameter of CWD or the number of decay classes recognized. In western North America, five decay classes are commonly used, but recent studies suggest fewer decay classes are preferable. Comparisons among decay classes and biogeoclimatic zones and subzones in B.C. reveal that quantities and volumes are greatest (up to approximately 60 kg/m[sup 2] and approximately 1800 m[sup 3] /ha, respectively), and CWD persists the longest (sometimes in excess of 1000 years) in the Coastal Western Hemlock (CWH) biogeoclimatic zone. The quantity and ground cover of CWD increase with forest productivity. Persistence of CWD has varied from less than 100 to over 800 years in two coastal (CWH and Mountain Hemlock (MH)) and three interior (Interior Douglas-fir (IDF), Interior Cedar–Hemlock (ICH), and Engelmann Spruce – Subalpine Fir (ESSF)) biogeoclimatic zones. Trends in CWD quantity with forest age in managed coastal B.C. forests suggest a U-shaped curve, with greater quantities occurring in recent cutovers than in old-growth forests, and lowest quantities occurring in middle-aged forests. This may be the normal trend in CWD with forest age, with departures from this trend resulting from disturbance- or environment-specific factors. Relatively large amounts of data exist on the characteristics of CWD in the CWH, IDF, ICH, ESSF, and Boreal White and Black Spruce (BWBS) biogeoclimatic zones, but such data for the Coastal Douglas-fir, Sub-Boreal Pine–Spruce, Sub-Boreal Spruce (SBS), and Spruce–Willow–Birch biogeoclimatic zones appear relatively sparse. There have been few studies of the functional role of CWD in B.C. forests, but those studies that have been completed indicate that CWD is an important habitat component for some plant and animal species. A total of 169 plant species, including >95% of all lichens and liverworts, were found to grow on CWD in old-growth forests in the CWH, MH, IDF, ICH, and ESSF biogeoclimatic zones. One third of these species were restricted to CWD. Studies in several biogeoclimatic zones have found that CWD provided preferred habitat for and was associated with higher populations of some small animal species, such as shrews, some voles, and some salamanders, in old-growth forests, but the effects varied with species and biogeoclimatic zone. The nutrient cycling role of CWD is not yet well known, but it currently appears to be relatively insignificant in B.C. old-growth forests. Although it has been considered that CWD could increase mineral soil acidification and eluviation, no evidence for this was found in a study of the CWH, MH, IDF, ICH, ESSF, BWBS, and SBS biogeoclimatic zones. Future studies of the functional role of CWD should consider both scale (square metre vs. hectare) and temporal (changes in CWD with forest age) issues, as studies including these are sparse and both may be important. Key words: biogeoclimatic zones, British Columbia, coarse woody debris, old-growth forests.Cette communication résume les données tirées de la littérature et celles recueillies par l'auteur dans diverses études sur la quantité, les caractéristiques et l'importance fonctionnelle des débris ligneux grossiers (DLG) dans les forêts anciennes de la Colombie-Britannique (C.-B.). Dans la littérature, on ne s'entend pas sur le diamètre minimum des DLG, ou le nombre de classes de décomposition. Dans l'ouest de l'Amérique du Nord, on emploie le plus souvent cinq classes, mais des études récentes portent à croire qu'un nombre de classes inférieur serait préférable. Les comparaisons entre les classes de décomposition et les zones et sous-zones biogéoclimatiques de la C.-B. révèlent que les DLG sont plus abondants (pouvant atteindre environ 60 kg/m[sup 2] et 1800 m[sup 3] /ha) et persistent le plus longtemps (parfois pendant plus de 1000 ans) dans la zone biogéoclimatique cótière de la pruche de l'Ouest (CWH). L'abondance des DLG et la superficie de sol qu'ils couvrent augmentent avec la productivité de la forêt. La persistance des DLG varie de moins de 100 ans à plus de 800 ans dans cinq zones biogéoclimatiques : deux zones côtières (la CWH et la zone de la pruche subalpine (MH)) et trois zones intérieures (celle du douglas taxifolié de l'intérieur (IDF), celle des cèdres et des pruches de l'intérieur (ICH) et celle de l'épinette d'Engelmann et du sapin subalpin (ESSF)). Dans les forêts côtières aménagées de la C.-B., l'abondance des DLG en fonction de l'âge de la forêt suivrait une courbe en U, les débris étant plus abondants sur les parterres de coupe récents que dans les forêts anciennes, et moins abondants dans les forêts d'âge moyen. Cette relation entre les DLG et l'âge de la forêt est peut-être la tendance normale, et les écarts par rapport à celle-ci pourraient être le résultat de facteurs propres à chaque perturbation ou milieu. Il existe beaucoup de données sur les caractéristiques des DLG dans la CWH, la IDF, la ICH, la ESSF et la zone boréale des épinettes blanche et noire (BWBS), mais il en existe relativement peu pour la zone côtière du douglas taxifolié, la zone subboréale des pins et des épinettes, la zone subboréale de l'épinette (SBS) et la zone de l'épinette, du saule et du bouleau. Peu d'études ont été consacrées au rôle fonctionnel des DLG dans les forêts de la Colombie-Britannique, mais d'après celles qui ont été réalisées, les DLG constitueraient une composante importante de l'habitat de certaines espèces végétales et animales. On a recensé 169 espèces végétales poussant sur ces débris, dont plus de 95 % de tous les lichens et hépatiques, dans les forêts anciennes de la CWH, de la MH, de la IDF, de la ICH et de la ESSF. Le tiers de ces espèces ne poussent que sur les DLG. D'après des études effectuées dans plusieurs zones biogéoclimatiques, ces débris constituent l'habitat préféré de certains petits animaux présents dans les forêts anciennes, tels que les musaraignes, certains campagnols et certaines salamandres, et sont associés à de plus fortes populations de ces animaux, mais les effets varient selon l'espèce et la zone biogéoclimatique. Le rôle des DLG dans le recyclage des éléments nutritifs n'est pas bien connu, mais il semble qu'il soit relativement négligeable dans les forêts anciennes de la C.-B. Il a été avancé que les débris ligneux grossiers pourraient accroître l'acidification et le lessivage des sols minéraux, mais de tels effets n'ont pas été mis en évidence dans une étude de la zone CWH, de la MH, de la IDF, de la ICH, de la ESSF, de la BWBS et de la SBS. À l'avenir, les études sur le rôle fonctionnel des DLG devraient tenir compte des aspects liés à l'échelle (m[sup 2] ou ha) et temporels (modifications des DLG avec le vieillissement de la forêt) puisque les études impliquent ces paramètres potentiellement importants sont rares. Mots clés : zones biogéoclimatiques, Colombie-Britannique, débris ligneux grossiers, forêts anciennes. [Traduit par la rédaction] [ABSTRACT FROM AUTHOR]