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carrier herbal medicine: traditional and contemporary plant use.the carrier, an athapaskan-speaking people of northcentral british columbia, occupy the sub-boreal spruce forests of the central interior. this report, which is based on field study, documents some traditional and contemporary knowledge of the medicinal use of plants by the carrier people. important medicinal plants include: abies lasiocarpa, alnus incana, arctostaphylos uva-ursi, artemisia frigida, fragaria virginiana, juniperus communis, picea glauca, pinus contorta, populus tremuloides, rubus ...19968735452
exposure to dust, resin acids, and monoterpenes in softwood lumber mills.a study to assess exposure to potential respiratory hazards in a large lumber mill processing spruce (picea engelmannii and glauca), pine (pinus contorta), and fir (abies lasiocarpa) used a random sampling strategy to assess exposures for all jobs in the sawmill, planer mills, and yard. personal samples for inhalable particulate were collected to measure exposure to dust and resin acids (abietic acid and pimaric acid). to estimate wood dust exposure, rather than overall dust, the resin acid cont ...200010976682
interacting influence of light and size on aboveground biomass distribution in sub-boreal conifer saplings with contrasting shade tolerance.plant size often influences shade tolerance but relatively few studies have considered the functional response of taller plants to contrasting light environments. several boreal and sub-boreal abies, picea and pinus species were studied along a light (0-90% full sunlight) and size (30-400-cm high) gradient to examine the interactive influence of tree size and light availability on aboveground biomass distribution. sampling was conducted in two regions of canada: (a) british columbia, for abies l ...200515631985
controls of growth phenology vary in seedlings of three, co-occurring ecologically distinct northern conifers.the objective of this study was to investigate the effects of temperature and seed-source elevation on height-growth phenology of three co-occurring and ecologically distinct northern conifers (pinus contorta dougl. ex loud. var. latifolia (lodgepole pine), picea glauca (moench) voss x picea engelmannii parry ex engelm. (interior spruce) and abies lasiocarpa (hook.) nutt. (subalpine fir)). seed from populations of the three indigenous and co-occurring species was collected across an elevational ...200717472945
climate risk modelling of balsam woolly adelgid damage severity in subalpine fir stands of western north america.the balsam woolly adelgid (adelges piceae (ratzeburg) (homoptera: adelgidae)) (bwa) is a nonnative, invasive insect that threatens abies species throughout north america. it is well established in the pacific northwest, but continues to move eastward through idaho and into montana and potentially threatens subalpine fir to the south in the central and southern rocky mountains. we developed a climatic risk model and map that predicts bwa impacts to subalpine fir using a two-step process. using 30 ...201627780227
early-successional ectomycorrhizal fungi effectively support extracellular enzyme activities and seedling nitrogen accumulation in mature forests.after stand-replacing disturbance, regenerating conifer seedlings become colonized by different ectomycorrhizal fungi (emf) than the locally adapted emf communities present on seedlings in mature forests. we studied whether emf species that colonized subalpine fir (abies lasiocarpa) seedlings in clearcuts differed from those that colonized seedlings in adjacent mature forests with respect to mycorrhizoplane extracellular enzyme activities (eeas) and n status of the seedlings. we tested two alter ...201727900594
multiscale habitat relationships of snowshoe hares (lepus americanus) in the mixed conifer landscape of the northern rockies, usa: cross-scale effects of horizontal cover with implications for forest management.snowshoe hares (lepus americanus) are an ecologically important herbivore because they modify vegetation through browsing and serve as a prey resource for multiple predators. we implemented a multiscale approach to characterize habitat relationships for snowshoe hares across the mixed conifer landscape of the northern rocky mountains, usa. our objectives were to (1) assess the relationship between horizontal cover and snowshoe hares, (2) estimate how forest metrics vary across the gradient of sn ...201728070281
twenty years of ecosystem response after clearcutting and slashburning in conifer forests of central british columbia, canada.forests are being clearcut over extensive areas of western north america, but plant community response to harvesting and slashburning under varying climatic conditions in central british columbia, canada is still largely unknown. evaluation of resilience is hampered by the short history of logging, lack of long-term experiments and methodological limitations. to test the effect of clearcut logging, prescribed burning and reforestation on forest resilience, we recorded vascular plant cover repeat ...201728234960
epiphytic lichen diversity on dead and dying conifers under different levels of atmospheric pollution.based on literature data, epiphytic lichen abundance was comparably studied in montane woodlands on healthy versus dead or dying conifers of europe and north america in areas with different levels of atmospheric pollution. study sites comprised picea abies forests in the harz mountains and in the northern alps, germany, picea rubens-abies balsamea forests on whiteface mountain, adirondacks, new york, u.s.a. and picea engelmannii-abies lasiocarpa forests in the salish mountains, montana, u.s.a. d ...200515701398
integrating phylogeography and paleoecology to investigate the origin and dynamics of hybrid zones: insights from two widespread north american firs.secondary contact between closely related taxa routinely occurs during postglacial migrations. after initial contact, the location of hybrid zones may shift geographically or remain spatially stable over time in response to various selective pressures or neutral processes. studying the extent and direction of introgression using markers having contrasted levels of gene flow can help unravel the historical dynamics of hybrid zones. thanks to their contrasted maternal and paternal inheritance, res ...201525865063
eyeing emergence: modified treatments for terminating dormancy of conifer seeds.many seeds of coniferous species display a deep primary dormancy at maturity and require several weeks of pretreatment to produce seed populations that germinate in a vigorous and timely manner. facilitating an efficient transition from dormancy to germination by devising improved protocols for dormancy breakage is not only important to conifer seed research, aiding in the study of the dormancy process itself, but is also of interest and applicability to commercial forest nursery operations. in ...201121898249
conifer expansion reduces the competitive ability and herbivore defense of aspen by modifying light environment and soil chemistry.disturbance patterns strongly influence plant community structure. what remains less clear, particularly at a mechanistic level, is how changes in disturbance cycles alter successional outcomes in plant communities. there is evidence that fire suppression is resulting in longer fire return intervals in subalpine forests and that these lengthened intervals increase competitive interactions between aspen and conifer species. we conducted a field and greenhouse study to compare photosynthesis, grow ...201121602559
sapling leaf trait responses to light, tree height and soil nutrients for three conifer species of contrasting shade tolerance.we developed models to describe the responses of four commonly examined leaf traits (mass per area, weight, area and nitrogen (n) concentration) to gradients of light, soil nutrients and tree height in three conifer species of contrasting shade tolerance. our observational dataset from the sub-boreal spruce forests of british columbia included subalpine fir (abies lasioscarpa [hook.] nutt; high shade tolerance), interior spruce (picea glauca × picea engelmannii [moench] voss; intermediate shade ...201425422385
weather and climate controls over the seasonal carbon isotope dynamics of sugars from subalpine forest trees.we examined the environmental variables that influence the delta(13)c value of needle and phloem sugars in trees in a subalpine forest. we collected sugars from pinus contorta, picea engelmannii and abies lasiocarpa from 2006 to 2008. phloem and needle sugars were enriched in (13)c during the autumn, winter and early spring, but depleted during the growing season. we hypothesized that the late-winter and early-spring (13)c enrichment was due to the mobilization of carbon assimilated the previous ...201019843259
indirect and mitigated effects of pulsed resources on the population dynamics of a northern rodent.pulsed resources have significant effects on population and community dynamics in terrestrial ecosystems. mast seeding is an important resource pulse in deciduous forests; these boom and bust cycles of seed production generate strong lagged population responses by post-dispersal seed predators such as rodents, which then cascade through multiple trophic levels and regulate population dynamics of their predators and prey. however, similar interactions in another major pulsed system, coniferous fo ...201323461538
carbon balance of conifer seedlings at timberline: relative changes in uptake, storage, and utilization.low rates of growth for conifers at high elevations may relate to problems in acquiring or utilizing carbon. a traditional hypothesis for growth limits of trees at alpine treeline is that low photosynthesis (a) leads to insufficient supply of carbon for growth. alternatively, the sink-limitation hypothesis questions the importance of low a, and suggests that trees at treeline have abundant carbon for growth as a result of greater decreases in carbon use [respiration (r) and growth] than a at hig ...200818810499
use of temporal patterns in vapor pressure deficit to explain spatial autocorrelation dynamics in tree transpiration.to quantify the relationship between temporal and spatial variation in tree transpiration, we measured sap flow in 129 trees with constant-heat sap flow sensors in a subalpine forest in southern wyoming, usa. the forest stand was located along a soil water gradient from a stream side to near the top of a ridge. the stand was dominated by pinus contorta dougl. ex loud. with picea engelmannii parry ex engelm and abies lasiocarpa (hook.) nutt. present near the stream and scattered individuals of po ...200818244950
influences of secondary disturbances on lodgepole pine stand development in rocky mountain national park.although high-severity fire is the primary type of disturbance shaping the structure of lodgepole pine (pinus contorta) stands in the southern rocky mountains, many post-fire stands are also affected by blowdown, low-severity surface fires, and/or outbreaks of mountain pine beetle (mpb; dendroctonus ponderosae). the ecological effects of these secondary disturbances are poorly understood but are potentially important in the context of managing for ecological restoration and fire hazard mitigatio ...200717913129
influence of shoot structure on light interception and photosynthesis in conifers.the influence of shoot structure on net photosynthesis was evaluated under field conditions for the central rocky mountain (united states) conifers picea engelmannii (parry ex engelm.), abies lasiocarpa ([hook] nutt.), and pinus contorta (engelm.). in all species, the greater number of needles per unit stem length on sun shoots correlated with a smaller silhouette leaf area to total leaf area ratio (star). decreased star was due primarily to greater needle inclination toward the vertical, plus s ...198516664525
variability of cenococcum colonization and its ecophysiological significance for young conifers at alpine-treeline.* plants establishing in environments that are marginal for growth could be particularly sensitive to mycorrhizal associations. we investigated ectomycorrhizal colonization and its significance for young conifers growing at, or above, their normal limits for growth, in the alpine-treeline ecotone. * colonization of seedlings (<1 yr old) and juveniles (2- to 10-yr-old) of picea engelmannii and abies lasiocarpa by cenococcum geophilum was determined in a field study, and effects of cenococcum on p ...200515720698
physiographic, stand, and environmental effects on individual tree growth and growth efficiency in subalpine forests.annual volume growth of subalpine trees in the central rocky mountains was studied in relation to site and stand conditions. growth of individual trees was most strongly influenced by estimated potential absorbed radiation, which varied with physiographic conditions and tree leaf area. growth efficiency was estimated by the ratio of annual volume growth to potential radiation absorption by the crown. growth efficiency was higher in young lodgepole pine (pinus contorta var. latifolia engelm.) tha ...198614975841
importance of the method of leaf area measurement to the interpretation of gas exchange of complex shoots.net co(2) uptake in full sunlight, total leaf area (tla), projected leaf area of detached leaves (pla), and the silhouette area of attached leaves in their natural orientation to the sun at midday on june 1 (sla) were measured for sun shoots of six conifer species. among species, tla/sla ranged between 5.2 and 10.0 (x bar = 7.3), tla/pla ranged between 2.5 and 2.9 (x bar = 2.7) and pla/sla ranged between 2.0 and 3.7 (x bar = 2.2). these ratios were reflected in the ratios of net photosynthesis c ...199114972884
occurrence of ectomycorrhizal fungi on the forefront of retreating lyman glacier (washington, usa) in relation to time since deglaciation.glacier forefronts provide a unique system for studying primary succession of plants and fungi. we constructed a chronosequence of ectomycorrhizal fungus occurrence on the forefront of lyman glacier in the north cascades mountain range in washington, usa. the plant communities established on non-vegetated substrate as patchily distributed plant individuals and developed towards complex vegetation with a variety of ectomycorrhizal hosts, including salix commutata, s. phylicifolia, abies lasiocarp ...200211968946
fire severity unaffected by spruce beetle outbreak in spruce-fir forests in southwestern colorado.recent large and severe outbreaks of native bark beetles have raised concern among the general public and land managers about potential for amplified fire activity in western north america. to date, the majority of studies examining bark beetle outbreaks and subsequent fire severity in the u.s. rocky mountains have focused on outbreaks of mountain pine beetle (mpb; dendroctonus ponderosae) in lodgepole pine (pinus contorta) forests, but few studies, particularly field studies, have addressed the ...201627411244
stand composition, tree proximity and size have minimal effects on leaf function of coexisting aspen and subalpine fir.forest structural heterogeneity due to species composition, spatial relationships and tree size are widely studied patterns in forest systems, but their impacts on tree function are not as well documented. the objective of this study was to examine how stand composition, tree proximity relationships and tree size influence the leaf functional traits of aspen, an early successional species, and subalpine fir, a climax species. we measured foliar nutrients, nonstructural carbohydrates (aspen only) ...201627124496
gap locations influence the release of carbon, nitrogen and phosphorus in two shrub foliar litter in an alpine fir forest.gap formation favors the growth of understory plants and affects the decomposition process of plant debris inside and outside of gaps. little information is available regarding how bioelement release from shrub litter is affected by gap formation during critical periods. the release of carbon (c), nitrogen (n), and phosphorus (p) in the foliar litter of fargesia nitida and salix paraplesia in response to gap locations was determined in an alpine forest of the eastern qinghai-tibet plateau via a ...201626906762
forest gaps alter the total phenol dynamics in decomposing litter in an alpine fir forest.the total phenol content in decomposing litter not only acts as a crucial litter quality indicator, but is also closely related to litter humification due to its tight absorption to clay particles. however, limited attention has been focused on the total phenol dynamics in foliar litter in relation to forest gaps. here, the foliar litter of six representative tree species was incubated on the forest floor from the gap center to the closed canopy of an alpine minjiang fir (abies faxoniana) forest ...201626849120
carbon isotopic composition of forest soil respiration in the decade following bark beetle and stem girdling disturbances in the rocky mountains.bark beetle outbreaks are widespread in western north american forests, reducing primary productivity and transpiration, leading to forest mortality across large areas and altering ecosystem carbon cycling. here the carbon isotope composition (δ(13) c) of soil respiration (δj ) was monitored in the decade after disturbance for forests affected naturally by mountain pine beetle infestation and artificially by stem girdling. the seasonal mean δj changed along both chronosequences. we found (a) enr ...201626824577
engelmann spruce site index models: a comparison of model functions and parameterizations.engelmann spruce (picea engelmannii parry ex engelm.) is a high-elevation species found in western canada and western usa. as this species becomes increasingly targeted for harvesting, better height growth information is required for good management of this species. this project was initiated to fill this need. the objective of the project was threefold: develop a site index model for engelmann spruce; compare the fits and modelling and application issues between three model formulations and fou ...201525853472
deposition of mercury in forests along a montane elevation gradient.atmospheric mercury (hg) deposition varies along elevation gradients and is influenced by both orographic and biological factors. we quantified total hg deposition over a 2 year period at 24 forest sites at whiteface mountain, ny, usa, that ranged from 450 to 1450 m above sea level and covered three distinct forest types: deciduous/hardwood forest (14.1 μg/m2-yr), spruce/fir forest (33.8 μg/m2-yr), and stunted growth alpine/fir forest (44.0 μg/m2-yr). atmospheric hg deposition increased with ele ...201525822871
contrasting primary successional trajectories of fungi and bacteria in retreating glacier soils.early community assembly of soil microbial communities is essential for pedogenesis and development of organic legacies. we examined fungal and bacterial successions along a well-established temperate glacier forefront chronosequence representing ~70 years of deglaciation to determine community assembly. as microbial communities may be heavily structured by establishing vegetation, we included nonvegetated soils as well as soils from underneath four plant species with differing mycorrhizal ecolo ...201424112459
post-fire spatial patterns of soil nitrogen mineralization and microbial abundance.stand-replacing fires influence soil nitrogen availability and microbial community composition, which may in turn mediate post-fire successional dynamics and nutrient cycling. however, fires create patchiness at both local and landscape scales and do not result in consistent patterns of ecological dynamics. the objectives of this study were to (1) quantify the spatial structure of microbial communities in forest stands recently affected by stand-replacing fire and (2) determine whether microbial ...201223226324
temporal variation of nonstructural carbohydrates in montane conifers: similarities and differences among developmental stages, species and environmental conditions.nonstructural carbohydrates (nscs) are commonly used to assess the balance of carbon sources and sinks in plants. a notable application of this approach has been tests of hypotheses on carbon limitations of trees at their upper altitudinal limits, near the alpine. how nscs vary in time is not well known in conifers during their critical seedling stage, despite the importance of knowing the temporal variations of nscs to use snapshot measurements of nscs to assess carbon balance. we measured nscs ...200919203971
abundance and composition dynamics of soil ammonia-oxidizing archaea in an alpine fir forest on the eastern tibetan plateau of china.real-time qpcr and clone library sequencing targeting amoa genes were used to investigate the seasonal dynamics of an ammonia-oxidizing archaea (aoa) community in an alpine fir forest in western china. aoa were detected at all sampling dates, and there were significant variations in archaeal amoa gene copy numbers (7.63 × 10(5) to 8.35 × 10(8) per gram of dry soil) throughout the nongrowing season. compared with ammonia-oxidizing bacteria (aob), the aoa displayed a higher abundance on the majori ...201222494458
modeling whole-tree carbon assimilation rate using observed transpiration rates and needle sugar carbon isotope ratios.*understanding controls over plant-atmosphere co(2) exchange is important for quantifying carbon budgets across a range of spatial and temporal scales. in this study, we used a simple approach to estimate whole-tree co(2) assimilation rate (a(tree)) in a subalpine forest ecosystem. *we analysed the carbon isotope ratio (delta(13)c) of extracted needle sugars and combined it with the daytime leaf-to-air vapor pressure deficit to estimate tree water-use efficiency (wue). the estimated wue was then ...201020100209
tree species effects on ecosystem water-use efficiency in a high-elevation, subalpine forest.ecosystem water-use efficiency (ewue; the ratio of net ecosystem productivity to evapotranspiration rate) is a complex landscape-scale parameter controlled by both physical and biological processes occurring in soil and plants. leaf wue (lwue; the ratio of leaf co(2) assimilation rate to transpiration rate) is controlled at short time scales principally by leaf stomatal dynamics and this control varies among plant species. little is known about how leaf-scale variation in lwue influences landsca ...201019784850
diversity and species distribution of ectomycorrhizal fungi along productivity gradients of a southern boreal forest.coniferous forests with diverse ectomycorrhizal fungus (emf) communities are associated with nutrient-poor, acidic soils but there is some debate whether emf can be equally adapted to more productive, nitrogen-rich sites. we compared emf species distribution and diversity along a replicated productivity gradient in a southern boreal forest of british columbia (canada). roots from subalpine fir (abies lasiocarpa) saplings of the understory were sampled and emf species were identified by morphotyp ...200918941804
water use by whitebark pine and subalpine fir: potential consequences of fire exclusion in the northern rocky mountains.in subalpine forests of the northern rocky mountains, fire exclusion has contributed to large-scale shifts from early-successional whitebark pine (pinus albicaulis engelm.) to late-successional subalpine fir (abies lasiocarpa (hook.) nutt.), a species assumed to be more shade tolerant than whitebark pine and with leaf to sapwood area ratios (a(l):a(s)) over twice as high. potential consequences of high a(l):a(s) for subalpine fir include reduced light availability and, if hydraulic sufficiency i ...200111470657
xylem embolism in response to freeze-thaw cycles and water stress in ring-porous, diffuse-porous, and conifer species.vulnerability to xylem embolism by freeze-thaw cycles and water stress was quantified in ring-porous (quercus gambelii nutt.), diffuse-porous (populus tremuloides michx., betula occidentalis hook.), and conifer species (abies lasiocarpa nutt., juniperus scopulorum sarg.). embolism was measured by its reduction of xylem hydraulic conductivity; it was induced by xylem tension (water-stress response) and by a tension plus a freeze-thaw cycle (freeze response). conifers showed little (juniperus) or ...199216653035
importance of aerodynamic resistance to water use efficiency in three conifers under field conditions.the quantitative importance of aerodynamic resistance to h(2)o vapor and co(2) exchange was determined for shoots from saplings of three conifers (abies lasiocarpa [hook] nutt., pinus contorta dougl., juniperus communis l.) under natural conditions in the field. a combination of relatively low stomatal resistances (<300 seconds per centimeter) and low wind speeds (<30 centimeters per second) led to substantial contributions of the aerodynamic resistance (r(wv) (a)) to water use efficiency (wue = ...198016661128
[effects of gap in primitive subalpine fir forest on diversity of herb and shrub in tibet].effects of gap in primitive fir forest in southeast tibet on species diversity of herb and shrub were studied. the results showed that species composition, distribution and diversity in gap were different from those in non-gap. the improvement of illumination and other habitat conditions resulted in richer species of herb and shrub in gap. there were shade-tolerant and photophilic herb species and shrub species in gap, however, only shade-tolerant herb species and shrub species grew in non-gap. ...200415146621
nitrogen uptake and turnover in riparian woody vegetation.the nutrient balance of streams and adjacent riparian ecosystems may be modified by the elimination of anadromous fish runs and perhaps by forest fertilization. to better understand nitrogen (n) dynamics within stream and riparian ecosystems we fertilized two streams and their adjacent riparian corridors in central idaho. on each stream two nitrogen doses were applied to a swathe approximately 35 m wide centered on the stream. the fertilizer n was enriched in 15n to 18 per thousand. this enrichm ...200415133732
bacterial diversity associated with subalpine fir (abies lasiocarpa) ectomycorrhizae following wildfire and salvage-logging in central british columbia.to assess the effect of fire and salvage logging on the diversity of mycorrhizal-bacterial communities, bacteria associated with cenococcum, thelephora, tomentella, russulaceae, and e-strain ectomycorrhizae (ecm) of abies lasiocarpa seedlings were characterized using two approaches. first, bacteria were isolated and characterized by biolog, gas chromatography fatty acid methyl ester (gc-fame), and amplified 16s rdna restriction analysis (ardra). the bacterial communities retrieved from ecm from ...200212224560
dependence of winter water relations of mature high-elevation picea engelmannii and abies lasiocarpa on summer climate.water relations of engelmann spruce (picea engelmannii parry) and subalpine fir (abies lasiocarpa (hook.) nutt.) trees growing at an elevation of 3230 m on mt. evans, colorado, usa, were studied during the winters of 1995-1996 and 1996-1997. during both winters, current-year and 1-year-old shoots were collected weekly and their relative water contents (rwc) determined. measured meteorological parameters were used in a conifer winter water relations model, winwat, to simulate changes in shoot rwc ...200011269959
altitude trends in conifer leaf morphology and stable carbon isotope composition.the natural ratio of stable carbon isotopes (δ(13)c) was compared to leaf structural and chemical characteristics in evergreen conifers in the north-central rockies, united states. we sought a general model that would explain variation in δ(13)c across altitudinal gradients. because variation in δ(13)c is attributed to the shifts between supply and demand for carbon dioxide within the leaf, we measured structural and chemical variables related to supply and demand. we measured stomatal density, ...200028308741
photosynthesis, water relations and mortality in abies lasiocarpa seedlings during natural establishment.few studies have investigated the ecophysiology of natural seedling establishment in forest trees not associated with anthropogenic disturbance. photosynthesis and water relations measurements were made on one- through four-year-old seedlings of abies lasiocarpa nutt. (subalpine fir) establishing naturally in an understory environment. first (current)-year seedlings generally had only cotyledons, whereas most second-year seedlings had both cotyledons and primary leaves. mortality was high (> 60% ...199114972895
influence of krummholz mat microclimate on needle physiology and survival.microclimate and photosynthesis of krummholz mat growth forms of picea engelmanii (parry) and abies lasiocarpa [hook.] nutt. were investigated to determine structural features which may aid survival in alpine environments. the structure of krummholz mats was described in terms of the vertical distribution of leaf area index and leaf area density, which exceeded 50 m(-1) (based on total leaf surface area) near the canopy surface and approached zero below 30 cm from the surface in both species. ph ...198728311409
semiochemicals produced by western balsam bark beetle,dryocoetes confusus swaine (coleoptera: scolytidae).the most prominent beetle-produced volatiles identified in the abdominal extracts of maledryocoetes confusus swaine after they had bored for 24 hr in logs of subalpine fir,abies lasiocarpa (hook.) nutt. were:exo andendo-brevicomin,trans-verbenol, verbenone, myrtenol,trans-pinocarveol,cis- andtrans-p-menthen-7-ol, 3-caren-10-ol, and several monoterpenes and sesquiterpenes. myrtenol was the only conspicuous compound in extracts from males that had been exposed toa.lasiocarpa resin volatiles for 24 ...198724302049
winter water relations of a deciduous timberline conifer, larix lyallii parl.the degree of winter desiccation resistance exhibited by larix lyallii parl. was assessed by determination of water potential components and content of buds, xylem pressure potential (ψ xylem) of twigs and amount of damage through winter at timberline in the rocky mountains of canada. comparative measurements were made on sympatric evergreen tree species to evaluate differences in winter desiccation avoidance and tolerance between evergreen and deciduous trees. total (ψ) and osmotic plus matric ...198628311679
autumn stomatal closure in six conifer species of the central rocky mountains.environmental and water relations parameters during fall were monitored for six conifer tree species common to the central rocky mountains growing naturally at the same location (pinus contorta, pinus ponderosa, pinus flexilus, pseudotsuga menziesii, abies lasiocarpa, picea engelmannii). subsequent to what appeared to be the beginning of seasonal stomatal closure, leaf conductance to water vapor declined sharply following the onset of freezing air temperatures at night. a coincident rapid declin ...198428311019
abiotic factors limiting photosynthesis in abies lasiocarpa and picea engelmannii seedlings below and above the alpine timberline.most research on the occurrence and stability of alpine timberlines has focused on correlations between adult tree growth and mean temperatures rather than on specific mechanisms. timberline migration to higher altitude is dependent on new seedling establishment in the tree-line ecotone; however, reductions in photosynthetic carbon gain in establishing seedlings have previously been interpreted solely in terms of decreased seedling survival. our objective was to evaluate the impact of abiotic fa ...200414757577
tracheid diameter is the key trait determining the extent of freezing-induced embolism in conifers.we tested the hypotheses that freezing-induced embolism is related to conduit diameter, and that conifers and angiosperms with conduits of equivalent diameter will exhibit similar losses of hydraulic conductivity in response to freezing. we surveyed the freeze-thaw response of conifers with a broad range of tracheid diameters by subjecting wood segments (root, stem and trunk wood) to a freeze-thaw cycle at -0.5 mpa in a centrifuge. embolism increased as mean tracheid diameter exceeded 30 microm. ...200314532014
[characteristics and disturbance status of gaps in subalpine fir forest in southeast tibet].characteristics and disturbance status of gaps, including gap size, disturbance frequency, forming patterns of gaps, and quantity of the tree in gap, in subalpine fir forest in southeast tibet were studied. the results showed that expanded gaps accounted for 41.73% and canopy gaps accounted for 14.71% of land area in the forest. averagely, 0.82% and 0.29% of forest area were transformed into expanded and canopy gaps every year. the velocity of gap forming was 0.31 ind.hm-2.yr-1. the disturbance ...200212385202
determinants of exposure to inhalable particulate, wood dust, resin acids, and monoterpenes in a lumber mill environment.in a lumber mill in the northern inland region of british columbia, canada, we measured inhalable particulate, resin acid, and monoterpene exposures, and estimated wood dust exposures. potential determinants of exposure were documented concurrently, including weather conditions, tree species, wood conditions, jobs, tasks, equipment used, and certain control measures. over 220 personal samples were taken for each contaminant. geometric mean concentrations were 0.98 mg/m3 for inhalable particulate ...199910432869
diameter distribution of some subalpine fir stands in central british columbia.diameter distributions of subalpine fir (abies lasiocarpa (hook.) nutt.) in central british columbia were investigated. nine fire-originated, old-growth stands were selected with maximum tree age at breast height of about 300 years. the stage of stand development was determined by testing how well a negative exponential function matched the cumulative diameter distribution. as a comparison, the negative exponential function was also fitted on the frequency distributions. eight out of the nine di ...199624198033
structural scaling of light interception efficiency in picea engelmannii and abies lasiocarpa.sunlight interception efficiency was compared at the leaf, shoot, branch and crown levels for picea engelmannii (parry) and abies lasiocarpa ((hook.) nutt.), dominant tree species of the central rocky mountains, usa. the ratio of silhouette to total leaf area (star) was used to quantify the efficiency of direct-beam sunlight interception at each structural scale. total mean reductions in star from the leaf to the crown level were 0.39 to 0.06 in p. engelmannii and 0.46 to 0.02 in a. lasiocarpa. ...199414967624
deep undercooling of tissue water and winter hardiness limitations in timberline flora.deep undercooled tissue water, which froze near -40 c, was found in winter collected stem and leaf tissue of the dominant timberline tree species of the colorado rocky mountains, engelmann spruce (picea engelmannii (parry) engelm.) and subalpine fir (abies lasiocarpa (hook.) nutt.), and in numerous other woody species in and below the subalpine vegetation zone. previous work on numerous woody plants indicates that deep undercooling in xylem makes probable a -40 c winter hardiness limit in stem t ...198116661852
leaf conductance as a function of photosynthetic photon flux density and absolute humidity difference from leaf to air.for an entire season of stomatal activity, leaf or needle conductance was observed on four species, each in a different genus: engelmann spruce (picea engelmannii parry ex engelm.), subalpine fir (abies lasiocarpa [hook.] nutt.), lodgepole pine (pinus contorta var. latifolia engelm.), and aspen (populus tremuloides michx.). conductance in the natural environment was described for all species by photosynthetic photon flux density (ppfd) and absolute humidity difference from leaf to air (dah), as ...198216662336
evaluation of season, temperature, and water stress effects on stomata using a leaf conductance model.a model was developed earlier describing conductance for three conifers (picea engelmannii parry ex engelm., abies lasiocarpa [hook.] nutt., and pinus contorta var. latifolia engelm.) and one hardwood (populus tremuloides michx.) using only two terms, photosynthetic photon flux density (ppfd) and absolute humidity difference from leaf to air (dah). using residual analysis techniques (actual minus estimated conductance), it was determined that no seasonal or temperature effects existed that were ...198216662337
hydraulic compensation in northern rocky mountain conifers: does successional position and life history matter?as trees grow tall and the resistance of the hydraulic pathway increases, water supply to foliage may decrease forcing stomata to close and co2 uptake to decline. several structural (e.g. biomass allocation) and physiological adjustments, however, may partially or fully compensate for such hydraulic constraints and prevent limitations on co2 uptake and growth. the degree to which trees compensate for hydraulic constraints as they grow tall may depend on the costs and benefits associated with hyd ...200616639568
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