bluuebunny/crossref_metadata_2025 huggingface dataset:
Mapping Quaternary paleovalleys and drift thickness using petrophysical logs, northeast British Columbia, Fontas map sheet, NTS 94IThis article is one of a selection of papers published in this Special Issue on the theme Geology of northeastern British Columbia and northwestern Alberta: diamonds, shallow gas, gravel, and glaciers.
Authors: Hickin Adrian S. , Kerr Ben , Turner Derek G. , Barchyn Tom E.
Published: June 2008

The relatively subdued topography of British Columbia’s northern interior plains does not reflect the irregular, buried bedrock surface. Many areas have been deeply incised by preglacial rivers that have subsequently filled with a succession of Quaternary sediments. In this study, oil and gas petrophysical logs, drill chip samples, water well logs, and surficial and bedrock outcrop maps were used to model the bedrock topography of the Fontas map sheet (NTS 94I). The modelled data produced several depressions that are interpreted to be paleovalleys incised into the soft Cretaceous shale of the Fort St. John Group. Understanding the geometry, thickness, and stratigraphy of the drift has considerable safety and resource management implications as artesian aquifers and natural gas were encountered in the drift during oil and gas well drilling. Four major paleovalleys are suggested. The most dominant paleovalley (Kotcho–Hoffard Paleovalley) is located south of the Etsho Plateau and trends west-southwest across the map area. A second depression occurs within the loop of the Hay River and may be a tributary of the Kotcho–Hoffard Paleovalley that links with the Rainbow Paleovalley in Alberta. A third paleovalley is mapped south of the Sahtaneh River (Kyklo Creek Paleovalley) and is either a tributary to, or crosscuts the Kotcho–Hoffard Paleovalley. The Niteal Creek Paleovalley is located between the Fontas and Sikanni Chief rivers. Its geometry is speculative as there are sparse data, but it may be a tributary of the Kotcho–Hoffard Paleovalley.
AMS-dated late Pleistocene taiga vole (Rodentia: Microtus xanthognathus) from northeast British Columbia, Canada: a cautionary lesson in chronologyThis article is one of a selection of papers published in this Special Issue on the themeGeology of northeastern British Columbia and northwestern Alberta: diamonds, shallow gas, gravel, and glaciers.
Authors: Hebda Richard J. , Burns James A. , Geertsema Marten , Jull A. J. Timothy
Published: June 2008

Dissected colluvial sediments on a Peace River terrace at Bear Flat, northeast British Columbia enclosed a late Pleistocene micromammalian faunule. The fossil remains, including a few loosely articulated skulls and mandibles, were dominated by taiga voles ( Microtus xanthognathus ). The Bear Flat site constitutes the second fossil occurrence in the region of this elusive species, which is unknown in British Columbia in historic times. The late Pleistocene age, determined by accelerator mass spectrometry directly on taiga vole bone collagen, is consistent with the ages of widespread taiga vole records peripheral to the Laurentide ice sheet in western, mid-western, and eastern North America. The presence of allo-chronous remains within a comprehensively dated sedimentary sequence provides a cautionary note about straightforward acceptance of relative stratigraphic dating.
Quaternary stratigraphy and glacial history of the Peace River valley, northeast British ColumbiaThis article is one of a selection of papers published in this Special Issue on the theme Geology of northeastern British Columbia and northwestern Alberta: diamonds, shallow gas, gravel, and glaciers.
Authors: Hartman Gregory M.D. , Clague John J.
Published: June 2008

Two Cordilleran and three Laurentide glacial advances are recorded in Quaternary sediments and landforms in the Peace River valley, northeast British Columbia. The advances are inferred from fluvial gravels, glaciolacustrine sediments, and tills within nested paleovalleys excavated during three interglaciations and from the distribution of granitoid clasts derived from the Canadian Shield. Till of the last (Late Wisconsinan) Laurentide glaciation occurs at the surface, except where it is overlain by postglacial sediments. The advance that deposited this till was the most extensive in the study area, and the only advance definitively recognized in western Alberta south of the study area. Late Wisconsinan Cordilleran till has not been found in the study area, but Cordilleran and Laurentide ice may have coalesced briefly during the last glaciation. Support for this supposition is provided by the inferred deflection of Laurentide flutings to the southeast by Cordilleran ice. The earliest Laurentide advance may have been the least extensive of the three Laurentide events recognized in the study area. Erratics attributed to this advance occur only east of the Halfway River – Beatton River drainage divide.
Quaternary stratigraphy of the Prophet River, northeastern British ColumbiaThis article is one of a selection of papers published in this Special Issue on the theme Geology of northeastern British Columbia and northwestern Alberta: diamonds, shallow gas, gravel, and glaciers.
Authors: Trommelen Michelle , Levson Vic
Published: June 2008

Exposures in the Prophet River valley in northeast British Columbia provide a unique glimpse into the Quaternary history of the northwest Canadian Boreal Plains. The region shows evidence of Late Wisconsinan Laurentide glaciation in the form of widespread till, containing abundant erratic clasts derived from the Canadian Shield. Vertical sections along the Prophet River expose non-glacial and advance glacial sediments below this till. Pre-Late Wisconsinan non-glacial or interglacial floodplain sediments are interbedded with fluvial gravels at many sites. Macrofossils within horizontally laminated organic-rich black clay and silt indicate deposition on the floodplain of the paleo-Prophet River within an oxbow lake. The climate during deposition is interpreted to be similar to present, supporting a dominantly spruce forest. Wood obtained from eight sites provided non-finite radiocarbon ages, and one sample provided an age of 49 300 ± 2000 BP, which is also considered non-finite. Glaciolacustrine clays and silts, deposited during impoundment of eastward-flowing drainage by the advance of the Laurentide Ice Sheet (LIS) in the Late Wisconsinan, overlie the non-glacial sediments throughout the valley. A blanket of clast-poor, clay-rich till up to 20 m thick, and deposited by the LIS, drapes the glaciolacustrine sediments. Since deglaciation, the Prophet River has incised the valley and formed fluvial terraces at different levels above the modern river.
The crustal structure of the southern Nain and Makkovik provinces of Labrador derived from refraction seismic data
Authors: Funck Thomas , Hansen Annette K. , Reid Ian D. , Louden Keith E.
Published: June 2008

Data from a refraction seismic profile parallel to the coast of Labrador (Canada) were used to determine the crustal structure across the boundary of the Nain and Makkovik provinces, and to look for evidence for an offshore continuation of the Mesoproterozoic Nain Plutonic Suite (NPS). Seven seismometers recorded airgun shots along the 283 km long line. P- and S-wave velocity models were developed from forward and inverse modeling of travel times. The velocity model distinguishes three distinct zones. In the Saglek block of the Nain Province, the crust is divided into three layers with P-wave velocities between 5.8 and 6.9 km/s. Farther to the south, upper crustal velocities increase to 6.3–6.5 km/s and the Poisson’s ratio increases from 0.24 to 0.27. This zone correlates with a gravity low that is interpreted to outline the offshore continuation of the NPS. The upper crustal velocities are intermediate between anorthositic and granitoid rock samples collected from the NPS. A lower crustal reflector is limited to the area underneath the NPS and may be related to dioritic magmas. Mid-crustal and lower crustal velocities do not vary along the line and no underplating was detected. Within the Makkovik Province, upper crustal velocities of 5.9–6.2 km/s may indicate a dioritic composition similar to the Island Harbour Bay plutonic suite. Moho depth varies between 28 and 36 km with the maximum beneath the NPS. The variations could not be linked to effects of the Makkovikian orogeny but are thought to relate to Mesozoic rifting in Labrador Sea.
An ornithischian dinosaur from the Sustut Basin, north-central British Columbia, Canada
Authors: Arbour Victoria M. , Graves Milton C.
Published: June 2008

Dinosaur bones were discovered in 1971 during uranium exploration in the Sustut Basin, northern British Columbia, Canada. These bones have more recently been prepared and described and represent an indeterminate cerapodan dinosaur. Although dinosaur bones have been reported from British Columbia before now, this specimen represents their earliest recorded discovery from the province. The bones were collected from loose blocks in a talus slope, near the intersection of Birdflat Creek and the Sustut River. They are encased in hard siltstone that shares characteristics with adjacent outcrops of the Upper Cretaceous Brothers Peak Formation. Bones collected include the right humerus, right radius, the distal portion of the right tibia and fibula, two right pedal phalanges, including two unguals, and several unidentifiable fragments.
High-resolution seismo-stratigraphy and sedimentological properties of late- and postglacial sediments in Lac Guillaume-Delisle Estuary and Nastapoka Sound, eastern Hudson Bay
Authors: Lavoie Caroline , Hill Philip R. , Allard Michel , St-Onge Guillaume , Lajeunesse Patrick
Published: June 2008

Lac Guillaume-Delisle Estuary and Nastapoka Sound are two sedimentary basins that recorded the late Quaternary deglaciation on the eastern coast of Hudson Bay. Acoustic profiles reveal an average sediments thickness of 15 m in the estuary and 6 m in the sound. These sediments reach 70 m thick in deep glacial troughs. Within the studied basins, four seismo-stratigraphic units overlying the acoustic basement were recognized. Unit 1 (subaqueous ice-contact and draped glaciomarine deposits associated with the Quebec–Labrador Ice Sector (QLIS) of the Laurentide Ice Sheet (LIS) and the Tyrrell Sea) records the presence of a short ice-marginal stillstand during glacial retreat. Unit 2 (paraglacial and postglacial fluvial-deltaic deposits) and unit 3 (postglacial silty deposits) result from erosion of emerged sediments and redeposition in response to changes in relative sea level (RSL). Finally, unit 4 is composed of deformed deposits associated with a mass wasting event. The stratigraphic sequence and the spatial distribution patterns of deposits show that Lac Guillaume-Delisle is a good model to explain the dynamics of the QLIS margin during and after successive ice stillstands, continuous RSL fall, river discharge (ablation on land), and its final ablation inland. Additionally, seven cores were sampled in the southeast part of the estuary. Geochemical (organic carbon and total nitrogen) and carbon isotopic contents, used as alternative proxy, indicate that the sampled sediments correspond to the postglacial estuarine deposits of unit 3. Allochthonous sources of carbon dominate the supply to the sediments where the environment is regularly flushed by fresh and marine waters.
Paleomagnetism and counterclockwise tectonic rotation of the Upper Oligocene Sooke Formation, southern Vancouver Island, British Columbia
Authors: Prothero Donald R. , Draus Elizabeth , Cockburn Thomas C. , Nesbitt Elizabeth A.
Published: June 2008

The age of the Sooke Formation on the southern coast of Vancouver Island, British Columbia, Canada, has long been controversial. Prior paleomagnetic studies have produced a puzzling counterclockwise tectonic rotation on the underlying Eocene volcanic basement rocks, and no conclusive results on the Sooke Formation itself. We took 21 samples in four sites in the fossiliferous portion of the Sooke Formation west of Sooke Bay from the mouth of Muir Creek to the mouth of Sandcut Creek. After both alternating field (AF) and thermal demagnetization, the Sooke Formation produces a single-component remanence, held largely in magnetite, which is entirely reversed and rotated counterclockwise by 35° ± 12°. This is consistent with earlier results and shows that the rotation is real and not due to tectonic tilting, since the Sooke Formation in this region has almost no dip. This rotational signature is also consistent with counterclockwise rotations obtained from the northeast tip of the Olympic Peninsula in the Port Townsend volcanics and the Eocene–Oligocene sediments of the Quimper Peninsula. The reversed magnetozone of the Sooke sections sampled is best correlated with Chron C6Cr (24.1–24.8 Ma) or latest Oligocene in age, based on the most recent work on the Liracassis apta Zone molluscan fauna, and also a number of unique marine mammals found in the same reversed magnetozone in Washington and Oregon.
The Middle Cambrian Mount Roosevelt Formation (new) of northeastern British Columbia: evidence for rifting and development of the Kechika Graben System
Authors: Post Ryan T. , Long Darrel G.F.
Published: June 2008

The eastern margin of the Kechika Graben in the vicinity of Muncho and Moose lakes, northeastern British Columbia, contains Middle Cambrian rift-related strata herein named the Mount Roosevelt Formation. The formation conformably overlies a quartzite package equivalent to the uppermost clastic unit of the informal late Early Cambrian Gataga group ( Bonnia – Olenellus zone) and is conformably overlain by a thick, unnamed carbonate sequence of Middle Cambrian age ( Plagiura – Poliella zone). The Mount Roosevelt Formation is subdivided into three members. The lowermost member is characterized by oöid-bearing siltstone and sandstone, interbedded with dolostone, limestone, and hematitic conglomerate. Conformably above this, the middle member is a thick sequence of polymict cobbly pebble conglomerate. The upper member includes karstified dolostone, calcareous-cemented conglomerate and sandstone, and limestone. Collectively the Mount Roosevelt Formation reflects alluvial fan delta progradation into a transgressive marine environment. Deposition occurred in an active fault-controlled basin, located on the eastern margin of the Kechika Graben adjacent to the Muskwa High. Basin initiation in the late Early Cambrian coincided with the reactivation of pre-existing regional faults. High rates of subsidence during the initial phase of extension were accommodated on these faults, which provided a locus for fan delta deposition. Continuing high rates of subsidence limited basinward fan delta development. Deposition of the formation ended with base-level transgression in the early Middle Cambrian that drowned the fan deltas and the adjacent Muskwa High and allowed development of the Kechika Trough above the older graben system.
Geology of northeast British Columbia and northwest Alberta: diamonds, shallow gas, gravel, and glaciersThis article introduces a selection of papers published in this Special Issue on the theme Geology of northeastern British Columbia and northwestern Alberta: diamonds, shallow gas, gravel, and glaciers.
Authors: Levson Vic
Published: June 2008

This special issue reports on some of the results of a multi-disciplinary research program conducted in the Boreal Plains of northwest Alberta and northeast British Columbia. Several innovative approaches to conducting geoscientific research in this remote drift-covered region are presented, including geochemical analysis of bentonites for evaluating kimberlite potential, the use of electromagnetic surveys for mapping buried aggregate deposits, and paleo-topographic mapping techniques to define buried channels. Results of the program include the discovery of several large aggregate deposits, the first kimberlite indicator minerals in northeast British Columbia, a significant sphalerite dispersal train in northwest Alberta, the first documented report of kimberlite-sourced bentonites, and numerous previously unknown interglacial sites. Together these papers provide a greatly enhanced understanding of the glacial history, Quaternary stratigraphy, and kimberlite geology of northwest Alberta and northeast British Columbia and provide an improved framework for resource exploration in the region.
Comanaging communication crises and opportunities between Northern Secwepemc First Nations and the province of British Columbia
Authors: Greskiw G. , Innes J.L.
Published: June 2008

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.
Predicting tree survival in Ontario sugar maple (Acer saccharum) forests based on crown condition
Authors: Tominaga Koji , Watmough Shaun A. , Aherne Julian
Published: June 2008

Decline index (indicator of crown condition) data from 102 forest plots (approximately 10 000 trees) during 1986–2004 were compiled to derive survival models for south-central Ontario, Canada. The dominant species was sugar maple ( Acer saccharum Marsh.) with approximately 75% occurrence (n = 7640). The predictor variables for sugar maple survivorship included the decline index of 1 or 2 years prior to the beginning of the modelled period and ecological region (Algoma, Georgian Bay, Huron–Ontario, and Upper St. Lawrence). The observed crown condition of sugar maple improved significantly over the study period; in contrast, short-term mortality rate did not improve. The risk of sugar maple mortality could be predicted from decline index data for a single year indicating that the risk of tree death increases with higher decline index values (declining crown condition). Moreover, using 2 years of decline index data indicated that the risk of tree death also increased with the length of consecutive time individual trees have higher decline index values. Trees in the Algoma region, which represent the northern limit of sugar maple distribution in Ontario, were significantly more likely to die than trees in Huron–Ontario region.
Root dynamics in sprouting tanoak forests of southwestern Oregon
Authors: Ahrens Glenn R. , Newton Michael
Published: June 2008

Root and shoot biomass were measured across an 8 year chronosequence in mature and regenerating stands of tanoak ( Lithocarpus densiflorus (Hook. & Arn.) Rehd.), following cutting and burning in mature tanoak forests. Tanoak stump sprouts rapidly replaced leaf biomass but did not maintain preexisting root systems. Rather, root biomass declined for several years, with the largest proportional decline in extra-fine roots. Four years after harvest, live root biomasses in diameter classes 0.25–2.00 and 0.25–5.00 mm were 25% and 30% of values in mature tanoak forests, respectively. The proportion of dead roots was strongly correlated with maximum summer soil temperature. Root/shoot ratios recovered to preharvest values by age 3–4 years, at which time the live biomass of fine roots and leaf biomass was approximately 30%–40% of values in mature forest. From age 4 to 8 years, stable root/shoot ratios were associated with a three- to four-fold reduction in growth rate of leaf biomass and a proportional increase in growth of fine roots. These findings support the general theory of a functional root–shoot balance in tanoak and suggest a possible role for soil temperature in postharvest root dynamics. Improved understanding of postdisturbance root and shoot dynamics in tanoak will help identify competitive interactions and priorities for vegetation management decisions in establishment of conifers following harvest of mixed conifer–hardwood forests of southwestern Oregon and northern California.
A biophysical process model of tree mortality in surface fires
Authors: Michaletz S. T. , Johnson E. A.
Published: June 2008

The mechanisms governing tree mortality in surface fires are poorly understood, owing in large part to the absence of a process-based framework for defining and evaluating these mechanisms. This paper begins the development of such a framework by deriving a first-order process model of tree mortality in surface fires (intensities less than approximately 2500 kW·m–1). A buoyant line-source plume model is used to drive heat transfer models of vascular cambium and vegetative bud necroses, which are linked to tree mortality using an allometrically-based sapwood area budget. Model predictions are illustrated for white spruce ( Picea glauca ), lodgepole pine ( Pinus contorta ), and trembling aspen ( Populus tremuloides ) and are compared with independent mortality data for Engelmann spruce ( Picea engelmannii Parry ex Engelm.) and Pinus contorta Dougl. Results help define first-order mortality mechanisms and suggest second-order mortality mechanisms that should be incorporated into future modeling efforts.
Male reproductive success and pedigree error in red spruce open-pollinated and polycross mating systems
Authors: Doerksen T. K. , Herbinger C. M.
Published: June 2008

Open-pollinated and polycross mating systems are widely used in forest genetics and breeding to quickly, simply, and inexpensively generate progenies assumed to be related as half-sibs (coefficient of relationship, r = 0.25) from a random mating population. However, nonrandom mating, such as unequal male reproductive success (RS) or selfing, can increase the genetic correlation among offspring, and thus, genetic variance and heritability are overestimated. Conversely, pedigree errors will cause additive genetic variance and heritability to be underestimated. Unequal male reproductive success and three types of potential pedigree errors (volunteers, mishandled maternal identities, and foreign pollen) were detected in operational open-pollinated and polycross red spruce ( Picea rubens Sarg.) progeny tests, through paternity testing using microsatellite (simple sequence repeat) DNA markers. The potential impact of unequal RS and pedigree errors on quantitative genetic parameters is discussed. Paternity and parentage analyses could be used to reconstruct the pedigree of any plantation consisting of sibships, where candidate parents (e.g., members of seed orchard) can be identified. This offers an alternative to traditional progeny testing for estimation of quantitative genetic parameters.
Fine root growth and mortality in different-aged ponderosa pine stands
Authors: Andersen Chris P. , Phillips Donald L. , Rygiewicz Paul T. , Storm Marjorie J.
Published: June 2008

Root minirhizotron tubes were installed at two sites around three different age classes of ponderosa pine ( Pinus ponderosa Dougl. ex Laws.) to follow patterns of fine root (≤2 mm diameter) dynamics during a 4 year study. Both sites were old-growth forests until 1978, when one site was clear-cut and allowed to regenerate naturally. The other site had both intermediate-aged trees (50–60 years) and old-growth trees (>250 years old). Estimates of fine root standing crop were greatest around young trees and least around intermediate-aged trees. Root production was highly synchronized in all age classes, showing a single peak in late May – early June each year. Root production and mortality were proportional to standing root crop (biomass), suggesting that allocation to new root growth was proportional to root density regardless of tree age. The turnover index (mortality/maximum standing crop) varied from 0.62 to 0.89·year–1, indicating root life spans in excess of 1 year. It appears that young ponderosa pine stands have greater rates of fine root production than older stands but lose more fine roots each year through mortality. The results indicate that soil carbon may accumulate faster in younger than in older stands.
Partial cutting reduces species richness of fungi on woody debris in oak-rich forests
Authors: Nordén Björn , Götmark Frank , Ryberg Martin , Paltto Heidi , Allmér Johan
Published: June 2008

Partial cutting is increasingly applied in European temperate oak-dominated forests for biofuel harvesting, and to counteract succession in protected stands. Effects on biodiversity of these measures need to be carefully evaluated, and species-rich but neglected taxa such as fungi should be considered. We studied the effects of partial cutting on fungal fruiting bodies on woody debris. In 21 closed canopy forests rich in large oaks in Sweden, on average 25%–30% of the basal area was cut. Fruiting bodies were counted and some were collected in treated and control plots before and after treatment. We found 334 basidiomycete and 47 ascomycete species. Species richness of basidiomycetes declined significantly more in treated plots (on average 26%) than in control plots (on average 13%) between seasons. Species richness of ascomycetes increased by 17% in control plots and decreased by 2% in treated plots. Total species richness was significantly reduced on fine woody debris (1–10 cm in diameter), but not on coarse woody debris (>10 cm). Overall species composition did not change significantly as a result of partial cutting, but red-listed species tended to decrease more in treated plots. We suggest that approximately 30% of the stands should not be thinned, and dead stems and fallen branches should not be removed, to favor saproxylic fungi and their associated fauna.
Competitive effects of woody and herbaceous vegetation in a young boreal mixedwood stand
Authors: Man Cosmin D. , Comeau Philip G. , Pitt Douglas G.
Published: June 2008

The influence of aspen ( Populus tremuloides Michx.) and herbaceous (forb and grass) vegetation on resource availability and white spruce ( Picea glauca (Moench) Voss) growth were examined as part of a long-term experiment established in 2002 near Whitecourt, Alberta, Canada. During the 2005 growing season, we examined the effects of herbicide treatments designed to control only woody (triclopyr ester) or both woody and herbaceous (glyphosate) vegetation on leaf area index (LAI) of both the woody and herbaceous components and relationships among LAI and light, soil moisture, air temperature, soil temperature, nitrogen availability, and spruce growth. Treatments reduced LAI and increased light, soil nitrogen availability, and white spruce growth. There were no apparent effects of the treatments on soil moisture in 2005. Both the woody and herb–grass layers appear to be competing for light and soil nitrogen in this young plantation. Controlling only woody vegetation resulted in an increase in herbaceous and total LAI (dominated by the grass Calamagrostis canadensis (Michx.) Beauv.). Spot treatment, involving control of vegetation within a 2 m radius of spruce seedlings while leaving 1 m of untreated ground between treated spots, may be a promising alternative to classical broadcast treatments for establishing spruce in a mixedwood stand. Spot treatments provided good growing conditions and reduced exposure of spruce seedlings to summer and winter frost injury during the first 3 years after planting.
Acceptabilité visuelle de coupes forestières pour la pessière noire : comparaison de la coupe à blanc traditionnelle et de différents types de rétention végétale chez divers groupes d’intérêt issus d’une région ressource forestière
Authors: Yelle Véronique , Bélanger Louis , Pâquet Josée
Published: June 2008

En pessière noire, le procédé de récolte habituel est celui de la coupe avec protection de la régénération et des sols (CPRS), un procédé de coupe totale. Socialement, ce type de pratique est mal perçu principalement pour ses impacts visuels. Toutefois, il existe pour les écosystèmes boréaux, d’autres procédés de récolte adaptés, issus de l’aménagement écosystémique. Cette étude présente une comparaison de l’acceptabilité visuelle des traitements sylvicoles permettant une plus grande rétention végétale par rapport à la CPRS (coupe avec protection de la haute régénération (CPHRS), coupe avec protection des petites tiges marchandes (CPPTM) et CPRS avec rétention de bouquets). Elle vérifie aussi si des différences dans les jugements d’acceptabilité existent selon l’appartenance à une région ressource forestière et à certains groupes d’intérêts, tels les environnementalistes, les amateurs de plein-air et d’intérêt général. Il en ressort que la qualité et la quantité de la régénération laissée après coupe influencent le jugement et que les traitements permettant de conserver une structure résiduelle parviennent à mitiger, partiellement, les impacts visuels des méthodes de coupe rase traditionnelles. Finalement, l’appartenance à une région forestière n’influence pas le jugement en ce qui a trait à l’acceptabilité visuelle des coupes. Les différences entre les groupes d’intérêts laissent plutôt croire que ce sont les connaissances reliées au milieu forestier qui influencent le plus le jugement.
Changes to preindustrial forest tree composition in central and northeastern Ontario, Canada
Authors: Pinto F. , Romaniuk S. , Ferguson M.
Published: June 2008

Preindustrial forest composition for >180 000 km2 throughout central and northeastern Ontario was recreated from Ontario Crown land survey notes (1816–1955) and compared with existing forest composition derived from current Forest Resource Inventories (1998–2009) in each of Site Regions 3E, 4E, and 5E. A validation analysis was performed using the Forest Resource Inventory data to test the assumption that sampling the land survey tree species composition along township boundaries is adequate in describing the composition of the whole forest. The majority of tree species in each of the three site regions validated successfully. A binary logistic regression model allowed birch genera to be classified at the species level to aid in the interpretation of survey notes. All analyses showed significant reductions in conifers (especially red pine ( Pinus resinosa Ait.), white pine ( Pinus strobus L.), and eastern larch ( Larix laricina (Du Roi) K. Koch)) and significant increases in maple ( Acer spp.), oak ( Quercus spp.), white birch ( Betula papyrifera Marsh.), and poplar ( Populus spp.).
Relative importance of different secondary successional pathways in an Alaskan boreal forest
Authors: Kurkowski Thomas A. , Mann Daniel H. , Rupp T. Scott , Verbyla David L.
Published: June 2008

Postfire succession in the Alaskan boreal forest follows several different pathways, the most common being self-replacement and species-dominance relay. In self-replacement, canopy-dominant tree species replace themselves as the postfire dominants. It implies a relatively unchanging forest composition through time maintained by trees segregated within their respective, ecophysiological niches on an environmentally complex landscape. In contrast, species-dominance relay involves the simultaneous, postfire establishment of multiple tree species, followed by later shifts in canopy dominance. It implies that stand compositions vary with time since last fire. The relative frequencies of these and other successional pathways are poorly understood, despite their importance in determining the species mosaic of the present forest and their varying, potential responses to climate changes. Here we assess the relative frequencies of different successional pathways by modeling the relationship between stand type, solar insolation, and altitude; by describing how stand age relates to species composition; and by inferring successional trajectories from stand understories. Results suggest that >70% of the study forest is the product of self-replacement, and tree distributions are controlled mainly by the spatial distribution of solar insolation and altitude, not by time since last fire. As climate warms over the coming decades, deciduous trees will invade cold sites formerly dominated by black spruce, and increased fire frequency will make species-dominance relay even rarer.
Interactions between drought and shade on growth and physiological traits in two Populus cathayana populations
Authors: Huang Xiaoxia , Yin Chunying , Duan Baoli , Li Chunyang
Published: June 2008

The morphological and physiological responses of two contrasting Populus cathayana Rehd. populations to three light regimes, full sunlight (control), 33% full sunlight (moderate shade), and 12% full sunlight (severe shade), were investigated under well-watered and drought conditions. The populations were from Hanyuan (relatively more annual rainfall and less annual solar radiation) and Ledu (less annual rainfall and more annual solar radiation) in western China. In both populations, drought-treated plants exhibited reduced growth, leaf relative water content, net photosynthesis, and maximal efficiency of photosystem II (PSII); increased levels of chlorophyll, carotenoid, abscisic acid, and carbon isotope composition; and a greater accumulation of malondialdehyde (MDA) than did well-watered plants. There was an apparent alleviation of drought effects by moderate shade, especially in the Hanyuan population, as indicated by the higher leaf relative water content, net photosynthesis, stomatal conductance, and maximal efficiency of PSII and the lower MDA content. On the other hand, an apparent aggravation of drought effects by severe shade was also observed, especially in the Ledu population, as indicated by the lower total biomass and net photosynthesis and the higher MDA content. Moreover, the Hanyuan population was more shade tolerant and drought sensitive than the Ledu population.
Basidiomycete decay fungi within stems of Nothofagus windfalls in a Southern Hemisphere beech forest
Authors: Hood I. A. , Beets P. N. , Gardner J. F. , Kimberley M. O. , Power M. W.P. , Ramsfield T. D.
Published: June 2008

Fungi were isolated to determine the predominant decomposer species active in the coarse woody debris in a beech forest in the central North Island of New Zealand. Basidiomycetes were obtained in 55% of 4569 isolation attempts from discs cut from six trees each of Nothofagus fusca (Hook. F.) Oerst. and Nothofagus menziesii (Hook. F.) Oerst. uprooted during a storm 24 years earlier. Percentage yields varied significantly among trees but not between tree species. However, for N. fusca, basidiomycetes were obtained less frequently from stems of greater mean diameter. In total, 96% of basidiomycete isolates were composed of 18 species, the most abundant being Armillaria novae-zelandiae (G. Stev.) Herink, mainly present in the outer 12 cm, and Ganoderma cf. applanatum sensu Wakef. and Cyclomyces tabacinus (Mont.) Pat., which penetrated more deeply. These fungi were distributed along the stems as somatically incompatible colonies reaching lengths of 11, 2, and 3 m for each species, respectively; those of G. cf. applanatum were separated by brown pseudosclerotial plates. Fruiting of these species was significantly associated with isolation of cultures and, for G. cf. applanatum and C. tabacinus, provided a reliable guide to stem colonization. Basidiomycete diversity in the Nothofagus stems was greater than in two podocarp species in an earlier study. Data from this investigation are being used to assess how decay fungi, together with other factors, influence rates of decomposition of indigenous coarse woody debris.
Occurrence, proportion, and vertical distribution of red heartwood in paper birch
Authors: Giroud Guillaume , Cloutier Alain , Alteyrac Jérôme
Published: June 2008

Normal paper birch ( Betula papyrifera Marsh.) wood has a clear and uniform color. However, some paper birch trees contain reddish-brown-, discolored wood known as red heartwood. Its occurrence, proportion, and vertical distribution were investigated. One hundred and fifty trees were randomly sampled from three stands located at the Montmorency Forest, 75 km north of Quebec City, Quebec, Canada. A subsample of 18 trees showing occurrence of red heartwood at stump height were felled, and 5 cm thick disks were cut at every 0.5 m of height. Red heartwood volume, proportion, and vertical distribution were determined from the disks. Trees with larger diameter at breast height and lower tree height had a higher probability of red heartwood occurrence. Red heartwood starts occurring in 40-year-old trees on average in the stands studied. The volume of red heartwood was positively correlated with tree age, and the proportion of red heartwood was positively related to tree age, and negatively related to the amount of sunlight on the live crown. Red heartwood proportion was 13.3% of the tree merchantable volume, mostly located under the live crown.
Adjustment of the age–height relationship for uneven-aged black spruce stands
Authors: Ouzennou Hakim , Pothier David , Raulier Frédéric
Published: June 2008

Site index (SI) is commonly used in natural stands, even when their diameter distribution deviates from that of the monospecific, even-aged, fully stocked stands used to develop basic age–height relationships. Since deviations from basic age–height trajectories can be reflected in deviations of stand diameter distribution from a bell shape, we incorporated different diameter diversity indices into an age–height equation to help improve height predictions and determine which index is best related to stand dominant height. This procedure was performed using black spruce ( Picea mariana (Mill.) BSP) stands from a large network of permanent sample plots established across the province of Quebec, Canada. The age–height model that minimized the Akaike’s information criterion used the Shannon evenness index (ESh) as an equation modifier accounting for the diameter diversity variable. The model showed that for stands established on relatively poor sites (SI = 9), no substantial differences in dominant height were found between two contrasting ESh values. For SI = 15, however, the larger ESh value increased the dominant height by as much as 1 m at 80 years. These results suggest that introduction of ESh into an age–height model can improve calculation of site index, particularly in regions characterized by the presence of numerous uneven-aged stands.
Future carbon storage in harvested wood products from Ontario’s Crown forests
Authors: Chen Jiaxin , Colombo Stephen J. , Ter-Mikaelian Michael T. , Heath Linda S.
Published: June 2008

This analysis quantifies projected carbon (C) storage in harvested wood products (HWP) from Ontario’s Crown forests. The large-scale forest C budget model, FORCARB-ON, was applied to estimate HWP C stock changes using the production approach defined by the Intergovernmental Panel on Climate Change. Harvested wood volume was converted to C mass and allocated to four HWP end-use categories: in use, landfill, energy, and emission. The redistribution of C over time among HWP end-use categories was calculated using a product age-based C-distribution matrix. Carbon emissions for harvest, transport, and manufacturing, as well as emission reductions from the use of wood in place of other construction materials and fossil fuels were not accounted for. Considering the wood harvested from Ontario Crown forests from 1951 to 2000 and the projected harvest from 2001 to 2100, C storage in HWP in use and in landfills is projected to increase by 3.6 Mt·year–1 during 2001–2100, with an additional 1.2 Mt·year–1 burned for energy. Annual additions of C projected for HWP far outweighs the annual increase of C storage in Ontario’s Crown forests managed for harvest, which is projected to increase by 0.1 Mt·year–1 during the same period. These projections indicate that regulated harvest in Ontario results in a steadily increasing C sink in HWP and forests. Uncertainties in HWP C estimation are also discussed.
Determinants of riparian fire severity in two Oregon fires, USA
Authors: Halofsky Jessica E. , Hibbs David E.
Published: June 2008

We sought to understand how vegetation indicators and local topographic factors interact to influence riparian fire severity in two recent fires in Oregon, USA. A stratified random sampling design was used to select points in a range of fire severity classes, forest stand ages, and stream sizes in each fire. At each point, plots were sampled in riparian areas and adjacent uplands. Fire severity was assessed in each plot, and measurements were made of factors that have been found to influence riparian fire severity. Understory fire severity (percent exposed mineral soil and bole char height) was significantly lower in riparian areas compared with adjacent uplands in both fires, suggesting a decoupling in understory fire effects in riparian areas versus uplands. However, overstory fire severity (percent crown scorch and percent basal area mortality) was similar in riparian areas and adjacent uplands in both fires. Fire severity in riparian areas was most strongly associated with upland fire severity. In addition, vegetation indicators, particularly those describing riparian fine fuel component and species composition, were strong predictors of riparian fire severity. Consistency in factors controlling fire severity in the two fires suggests that controls on riparian fire severity may be similar in other regions.
Absolute and relative changes in tree growth rates and changes to the stand diameter distribution of Pinus taeda as a result of midrotation fertilizer applications
Authors: Carlson Colleen A. , Burkhart Harold E. , Allen H. Lee , Fox Thomas R.
Published: June 2008

Silvicultural treatments have the potential to change the diameter distribution of a stand, which can alter the final product mix of the stand. Growth and yield models need to account for these changes in the diameter distribution to assess the economic viability of the silvicultural operations. We investigated how the diameter distribution of Pinus taeda L. stands changes as a result of midrotation fertilization. Data from 43 installations of a nitrogen and phosphorus midrotation fertilizer trial series established in the southeastern United States were used in the study. The results indicated that both the absolute growth response and the relative growth response of individual trees were greater among the larger trees. A three-parameter Weibull distribution fitted at each study site was used to investigate how the parameters of the distribution changed with time and treatment. The location and scale parameters of the Weibull distribution were both affected by fertilization. Stand variables, such as site index, age, stand density, and mean diameter at time of fertilization, also affected the location and scale parameters. The shape parameter was not affected by any of the treatments in this study.
Disproportionate bill length dimorphism and niche differentiation in wintering western sandpipers (Calidris mauri)
Authors: Stein R. W. , Fernández G. , de la Cueva H. , Elner R. W.
Published: June 2008

Western sandpipers ( Calidris mauri (Cabanis, 1857)) exhibit slight female-biased sexual size dimorphism (5%) but disproportionate bill length dimorphism (15.9%). We test two predictions of the niche differentiation hypothesis at two wintering sites in Mexico with uniform western sandpiper densities, and use sex ratio as an index of intersexual competition. First, to test whether bill length dimorphism is larger at sites where sex ratios are strongly male-biased, we develop a migrant-based null model to represent dimorphism (12%, based on the average of males and females) in the absence of competition. Relative to the null model, bill length dimorphism was significantly larger at the large site (Santa María: 13.4%) but not at the small site (Punta Banda: 12.7%). Second, we tested whether bill length dimorphism increases as sex ratio approaches 1:1. Although the sex-ratio difference between sites was only 5%, bill length dimorphism increased marginally in the predicted direction. Additional comparisons suggest a cline in bill length dimorphism that mirrors a latitudinal gradient in prey burial depth. While sexual size dimorphism in the western sandpiper likely derived from selection for different body size optima, intersexual competition for food on the wintering grounds appears to have promoted further divergence in bill length.
Robust flight performance of bumble bees with artificially induced wing wear
Authors: Haas C. A. , Cartar R. V.
Published: June 2008

We lack a mechanism that links wing wear with mortality in foraging social insects. This study tests the hypothesis that wing wear strongly degrades foraging flight performance, thereby providing a biomechanical explanation for the wing wear – mortality relationship. We examine the effect of simulated wing wear — wing area reduction and asymmetry — on the flight behaviour of bumble bee ( Bombus flavifrons Cresson, 1863) workers moving between vertically oriented flowers spaced 30 cm apart and arranged in a two-dimensional horizontal grid. Flight behaviour was measured in three dimensions as total flying distance, mean velocity, variability of velocity, maximum acceleration, maximum deceleration, percentage of time spent accelerating, and displacement from a straight line path between flowers. Loss of wing area had surprisingly little effect on flight behaviour. Viewed multivariately, bees with low asymmetry and low loss of mean area, or with high asymmetry and high loss of mean area, differed from the other three treatment groups. When bees were burdened with both high asymmetry and high loss of wing area, their between-flower flight path was less direct. Overall, flight behaviour of bumble bees was highly resilient to major changes in wing area and asymmetry in this simple foraging environment. The wing wear-associated causes of increased mortality remain elusive.
Sex-specific differences in diving behaviour of two sympatric Alcini species: thick-billed murres and razorbills
Authors: Paredes Rosana , Jones Ian L. , Boness Daryl J. , Tremblay Yann , Renner Martin
Published: June 2008

At the Gannet Islands, Labrador, sympatric thick-billed murres ( Uria lomvia (L., 1758)) and razorbills ( Alca torda L., 1758) are slightly sexually dimorphic and have similar intersexual differences in parental roles; females are the main meal providers and males are mostly involved in brooding and chick defence at the breeding site and at sea. The question is whether differences in parental roles influence the foraging behaviour patterns of males and females. Murre females foraged during twilight periods and dived shallower than males. In razorbills, although sex differences were not as clear, females also tended to dive shallower (<10 m) and more often at twilight. Males of both species foraged during daylight hours and tended to dive deeper than females. Females of both species had shorter dive bouts (i.e., duration of a series of dives) even though the number of bouts and dives per day were equal between sexes. In both species, female dives were mostly shallower W-shaped dives, likely for capturing crustaceans at twilight. In contrast, males performed mostly deeper U-shaped dives for capturing mid-water species (e.g., capelin, Mallotus villosus (Müller, 1776)). Altogether, our results show that the two sympatric auks had relatively similar intersexual segregation in feeding time, depth, and prey. Sex differences in nest attendance, driven by differences in parental roles, seem to explain these findings.