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evaluation of a new battery of toxicity tests for boreal forest soils: assessment of the impact of hydrocarbons and salts.the ability to assess the toxic potential of soil contamination within boreal regions is currently limited to test species representative of arable lands. this study evaluated the use of six boreal plant (pinus banksiana, picea glauca, picea mariana, populus tremuloides, calamagrostis canadensis, and solidago canadensis) and four invertebrate (dendrodrilus rubidus, folsomia nivalis, proisotoma minuta, and oppia nitens) species, and compared their performance to a suite of standard agronomic soil ...201222228553
functional and expressional analyses of pmdam genes associated with endodormancy in japanese apricot (prunus mume).bud endodormancy in woody plants plays an important role in their perennial growth cycles. we previously identified a mads-box gene, prunus mume dormancy associated mads6 (pmdam6), expressed in the endodormant lateral buds of japanese apricot (p. mume) as a candidate for the dormancy-controlling gene. in this study, we demonstrated the growth inhibitory functions of pmdam6 by overexpressing it in transgenic poplar (populus tremula x tremuloides). transgenic poplar plants constitutively expressin ...201121795580
acute o(3) damage on first year coppice sprouts of aspen and maple sprouts in an open-air experiment.we studied the effect of high ozone (o(3)) concentration (110-490 nmol mol(-1)) on regenerating aspen (populus tremuloides) and maple (acer saccharum) trees at an open-air o(3) pollution experiment near rhinelander wi usa. this study is the first of its kind to examine the effects of acute o(3) exposure on aspen and maple sprouts after the parent trees, which were grown under elevated o(3) and/or co(2) for 12 years, were harvested. acute o(3) damage was not uniform within the crowns of aspen suc ...201121750809
high titer ethanol production from simultaneous enzymatic saccharification and fermentation of aspen at high solids: a comparison between sporl and dilute acid pretreatments.native aspen (populus tremuloides) was pretreated using sulfuric acid and sodium bisulfite (sporl) and dilute sulfuric acid alone (da). simultaneous enzymatic saccharification and fermentation (ssf) was conducted at 18% solids using commercial enzymes with cellulase loadings ranging from 6 to 15fpu/g glucan and saccharomyces cerevisiae y5. compared with da pretreatment, the sporl pretreatment reduced the energy required for wood chip size-reduction, and reduced mixing energy of the resultant sub ...201121824766
assisted migration to address climate change: recommendations for aspen reforestation in western canada.human-aided movement of species populations in large-scale reforestation programs could be a potent and cost-effective climate change adaptation strategy. such large-scale management interventions, however, tend to entail the risks of unintended consequences, and we propose that three conditions should be met before implementing assisted migration in reforestation programs: (1) evidence of a climate-related adaptational lag, (2) observed biological impacts, and (3) robust model projections to ta ...201121830704
The roles of hydraulic and carbon stress in a widespread climate-induced forest die-off.Forest ecosystems store approximately 45% of the carbon found in terrestrial ecosystems, but they are sensitive to climate-induced dieback. Forest die-off constitutes a large uncertainty in projections of climate impacts on terrestrial ecosystems, climate-ecosystem interactions, and carbon-cycle feedbacks. Current understanding of the physiological mechanisms mediating climate-induced forest mortality limits the ability to model or project these threshold events. We report here a direct and in s ...201122167807
accounting for density reduction and structural loss in standing dead trees: implications for forest biomass and carbon stock estimates in the united states.abstract: background: standing dead trees are one component of forest ecosystem dead wood carbon (c) pools, whose national stock is estimated by the u.s. as required by the united nations framework convention on climate change. historically, standing dead tree c has been estimated as a function of live tree growing stock volume in the u.s.'s national greenhouse gas inventory. initiated in 1998, the usda forest service's forest inventory and analysis program (responsible for compiling the nation ...201122115425
atmospheric change alters foliar quality of host trees and performance of two outbreak insect species.this study examined the independent and interactive effects of elevated carbon dioxide (co(2)) and ozone (o(3)) on the foliar quality of two deciduous trees species and the performance of two outbreak herbivore species. trembling aspen (populus tremuloides) and paper birch (betula papyrifera) were grown at the aspen face research site in northern wisconsin, usa, under four combinations of ambient and elevated co(2) and o(3). we measured the effects of elevated co(2) and o(3) on aspen and birch p ...201121971584
leaf respiratory acclimation to climate: comparisons among boreal and temperate tree species along a latitudinal transect.in common gardens along an ∼900 km latitudinal transect through wisconsin and illinois, u.s.a., tree species typical of boreal and temperate forests were compared with respect to the nature and magnitude of leaf respiratory acclimation to contrasting climates. the boreal representatives were trembling aspen (populus tremuloides michx.) and paper birch (betula papyrifera marsh.), while the temperate species were eastern cottonwood (populus deltoides bartr ex. marsh var. deltoides) and sweetgum (l ...201121990024
will changes in root-zone temperature in boreal spring affect recovery of photosynthesis in picea mariana and populus tremuloides in a future climate?future climate will alter the soil cover of mosses and snow depths in the boreal forests of eastern canada. in field manipulation experiments, we assessed the effects of varying moss and snow depths on the physiology of black spruce (picea -mariana (mill.) b.s.p.) and trembling aspen (populus tremuloides michx.) in the boreal black spruce forest of western québec. for 1 year, naturally regenerated 10-year-old spruce and aspen were grown with one of the following treatments: additional n fertiliz ...201122021010
fungal planet description sheets: 69-91.novel species of microfungi described in the present study include the following from australia: bagadiella victoriae and bagadiella koalae on eucalyptus spp., catenulostroma eucalyptorum on eucalyptus laevopinea, cercospora eremochloae on eremochloa bimaculata, devriesia queenslandica on scaevola taccada, diaporthe musigena on musa sp., diaporthe acaciigena on acacia retinodes, leptoxyphium kurandae on eucalyptus sp., neofusicoccum grevilleae on grevillea aurea, phytophthora fluvialis from wate ...201122025808
hebeloma crustuliniforme facilitates ammonium and nitrate assimilation in trembling aspen (populus tremuloides) seedlings.this study examined the role of ectomycorrhizal associations in nitrogen assimilation of populus tremuloides seedlings. seedlings were inoculated with hebeloma crustuliniforme and compared with non-inoculated plants. nitrogen-metabolizing enzymatic properties were also determined in h. crustuliniforme grown in sterile culture. the seedlings and fungal cultures were subjected to nitrogen treatments (including no₃⁻, nh₄⁺ and a combination of no₃⁻ + nh₄⁺) for 2 months to examine the effects on grow ...201122011965
climate change intensification of herbivore impacts on tree recruitment.altered species interactions are difficult to predict and yet may drive the response of ecological communities to climate change. we show that declining snowpack strengthens the impacts of a generalist herbivore, elk (cervus elaphus), on a common tree species. thick snowpack substantially reduces elk visitation to sites; aspen (populus tremuloides) shoots in these areas experience lower browsing rates, higher survival and enhanced recruitment. aspen inside herbivore exclosures have greatly incre ...201121976686
contrasting the morphology, anatomy and fungal colonization of new pioneer and fibrous roots.• not all roots born as first-order branches are the same and this has important consequences for overall function. we hypothesized that, compared with fibrous roots, pioneer roots are built to live longer at the expense of absorptive capacity. • we tested this hypothesis by investigating pioneer and fibrous roots in their first 14 d of life in the arbuscular mycorrhizal tree species: acer negundo, acer saccharum, juglans nigra, liriodendron tulipifera and populus tremuloides. root observations ...201121210817
perturbation of wood cellulose synthesis causes pleiotropic effects in transgenic aspen.genetic manipulation of cellulose biosynthesis in trees may provide novel insights into the growth and development of trees. to explore this possibility, the overexpression of an aspen secondary wall-associated cellulose synthase (ptdcesa8) gene was attempted in transgenic aspen (populus tremuloides l.) and unexpectedly resulted in silencing of the transgene as well as its endogenous counterparts. the main axis of the transgenic aspen plants quickly stopped growing, and weak branches adopted a w ...201121300756
effects of canopy-deposition interaction on h+ supply to soils in pinus banksiana and populus tremuloides ecosystems in the athabasca oil sands region in alberta, canada.soil acidification has been of concern in the oil sands region in alberta due to increased acid deposition. using the canopy budget model, and accounting for h(+) canopy leaching by organic acids, we determined sources and sinks of h+ in throughfall in jack pine (pinus banksiana) and trembling aspen (populus tremuloides) stands in two watersheds from 2006 to 2009. in pine stands, h+ deposition was greater in throughfall than in bulk precipitation while the opposite was true in aspen stands. the ...201121310518
ultra-structural organisation of cell wall polymers in normal and tension wood of aspen revealed by polarisation ftir microspectroscopy.polarisation fourier transform infra-red (ftir) microspectroscopy was used to characterize the organisation and orientation of wood polymers in normal wood and tension wood from hybrid aspen (populus tremula × populus tremuloides). it is shown that both xylan and lignin in normal wood are highly oriented in the fibre wall. their orientation is parallel with the cellulose microfibrils and hence in the direction of the fibre axis. in tension wood a similar orientation of lignin was found. however, ...201121340698
the influence of recent climate change on tree height growth differs with species and spatial environment.tree growth has been reported to increase in response to recent global climate change in controlled and semi-controlled experiments, but few studies have reported response of tree growth to increased temperature and atmospheric carbon dioxide (co2) concentration in natural environments. this study addresses how recent global climate change has affected height growth of trembling aspen (populus tremuloides michx) and black spruce (picea mariana mill b.s.) in their natural environments. we sampled ...201121358817
developmental contributions to phenotypic variation in functional leaf traits within quaking aspen clones.phenotypic variation in plant traits is strongly influenced by genetic and environmental factors. over the life span of trees, developmental factors may also strongly influence leaf phenotypes. the objective of this study was to fill gaps in our understanding of developmental influences on patterns of phenotypic trait variation among different-aged ramets within quaking aspen (populus tremuloides michx.) clones. we hypothesized that phenotypic variation in leaf functional traits is strongly infl ...201121389003
root-associated ectomycorrhizal fungi shared by various boreal forest seedlings naturally regenerating after a fire in interior alaska and correlation of different fungi with host growth responses.the role of common mycorrhizal networks (cmns) in postfire boreal forest successional trajectories is unknown. we investigated this issue by sampling a 50-m by 40-m area of naturally regenerating black spruce (picea mariana), trembling aspen (populus tremuloides), and paper birch (betula papyrifera) seedlings at various distances from alder (alnus viridis subsp. crispa), a nitrogen-fixing shrub, 5 years after wildfire in an alaskan interior boreal forest. shoot biomasses and stem diameters of 4- ...201121441343
root carbon reserve dynamics in aspen seedlings: does simulated drought induce reserve limitation?in a greenhouse study we quantified the gradual change of gas exchange, water relations and root reserves of aspen (populus tremuloides michx.) seedlings growing over a 3-month period of severe water stress. the aim of the study was to quantify the complex interrelationship between growth, water and gas exchange, and root carbon (c) dynamics. various growth, gas exchange and water relations variables in combination with root reserves were measured periodically on seedlings that had been exposed ...201121444372
surface tension phenomena in the xylem sap of three diffuse porous temperate tree species.in plant physiology models involving bubble nucleation, expansion or elimination, it is typically assumed that the surface tension of xylem sap is equal to that of pure water, though this has never been tested. in this study we collected xylem sap from branches of the tree species populus tremuloides, betula papyrifera and sorbus aucuparia over 3 months. we measured the instantaneous surface tension and followed changes over a period of 0.5-5 h using the pendant drop technique. in all thr ...201121470981
comparisons of sporl and dilute acid pretreatments for sugar and ethanol productions from aspen.this study reports comparative evaluations of sugar and ethanol production from a native aspen (populus tremuloides) between sulfite pretreatment to overcome recalcitrance of lignocellulose (sporl) and dilute acid (da) pretreatments. all aqueous pretreatments were carried out in a laboratory wood pulping digester using wood chips at 170°c with a liquid to oven dry (od) wood ratio (l/w) of 3:1 at two levels of acid charge on wood of 0.56 and 1.11%. sodium bisulfite charge on od wood was 0 for da ...201121485032
induction of a longer term component of isoprene release in darkened aspen leaves: origin and regulation under different environmental conditions.after darkening, isoprene emission continues for 20 to 30 min following biphasic kinetics. the initial dark release of isoprene (postillumination emission), for 200 to 300 s, occurs mainly at the expense of its immediate substrate, dimethylallyldiphosphate (dmadp), but the origin and controls of the secondary burst of isoprene release (dark-induced emission) between approximately 300 and 1,500 s, are not entirely understood. we used a fast-response gas-exchange system to characterize the control ...201121502186
using next generation transcriptome sequencing to predict an ectomycorrhizal metabolome.abstract: background: mycorrhizae, symbiotic interactions between soil fungi and tree roots, are ubiquitous in terrestrial ecosystems. the fungi contribute phosphorous, nitrogen and mobilized nutrients from organic matter in the soil and in return the fungus receives photosynthetically-derived carbohydrates. this union of plant and fungal metabolisms is the mycorrhizal metabolome. understanding this symbiotic relationship at a molecular level provides important contributions to the understanding ...201121569493
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
within-plant distribution of phenolic glycosides and extrafloral nectaries in trembling aspen (populus tremuloides; salicaceae).expression of foliar secondary compounds and extrafloral nectaries (efns) within the same leaves may be incompatible if secondary compounds repel beneficial insects that might otherwise be attracted to efns. this study examined the within-plant distributions of phenolic glycosides and efns in trembling aspen, populus tremuloides, and their relationships to herbivore damage. populus tremuloides expresses extrafloral nectaries (efns) on a subset of its leaves. we studied short and tall naturally o ...201021622422
comparisons of sporl and dilute acid pretreatments for sugar and ethanol productions from aspen.this study reports comparative evaluations of sugar and ethanol production from a native aspen (populus tremuloides) between sulfite pretreatment to overcome recalcitrance of lignocellulose (sporl) and dilute acid (da) pretreatments. all aqueous pretreatments were carried out in a laboratory wood pulping digester using wood chips at 170°c with a liquid to oven dry (od) wood ratio (l/w) of 3:1 at two levels of acid charge on wood of 0.56 and 1.11%. sodium bisulfite charge on od wood was 0 for da ...201021240938
analysis of a farquhar-von caemmerer-berry leaf-level photosynthetic rate model for populus tremuloides in the context of modeling and measurement limitations.the balance of mechanistic detail with mathematical simplicity contributes to the broad use of the farquhar, von caemmerer and berry (fvcb) photosynthetic rate model. here the fvcb model was coupled with a stomatal conductance model to form an [a,g(s)] model, and parameterized for mature populus tremuloides leaves under varying co(2) and temperature levels. data were selected to be within typical forest light, co(2) and temperature ranges, reducing artifacts associated with data collected at ext ...201019766365
diurnal changes in photosynthetic parameters of populus tremuloides, modulated by elevated concentrations of co2 and/or o3 and daily climatic variation.the diurnal changes in light-saturated photosynthesis (pn) under elevated co(2) and/or o(3) in relation to stomatal conductance (g(s)), water potential, intercellular [co(2)], leaf temperature and vapour-pressure difference between leaf and air (vpd(l)) were studied at the aspen face site. two aspen (populus tremuloides michx.) clones differing in their sensitivity to ozone were measured. the depression in pn was found after 10:00 h. the midday decline in pn corresponded with both decreased g(s) ...201019796856
elevated co2 response of photosynthesis depends on ozone concentration in aspen.the effect of elevated co(2) and o(3) on apparent quantum yield (varphi), maximum photosynthesis (p(max)), carboxylation efficiency (v(cmax)) and electron transport capacity (j(max)) at different canopy locations was studied in two aspen (populus tremuloides) clones of contrasting o(3) tolerance. local light climate at every leaf was characterized as fraction of above-canopy photosynthetic photon flux density (%ppfd). elevated co(2) alone did not affect varphi or p(max), and increased j(max) in ...201019854548
dna damage in populus tremuloides clones exposed to elevated o3.the effects of elevated concentrations of atmospheric tropospheric ozone (o(3)) on dna damage in five trembling aspen (populus tremuloides michx.) clones growing in a free-air enrichment experiment in the presence and absence of elevated concentrations of carbon dioxide (co(2)) were examined. growing season mean hourly o(3) concentrations were 36.3 and 47.3 ppb for ambient and elevated o(3) plots, respectively. the 4th highest daily maximum 8-h ambient and elevated o(3) concentrations were 79 an ...201019879681
direct amplification of dna from fresh and preserved ectomycorrhizal root tips.methods are described by which dna can be amplified directly from ectomycorrhizal root tip homogenates of a variety of plant species (picea mariana (black spruce), betula papyrifera (paper birch), populus tremuloides (trembling aspen) and alnus sp.(alder)), including root tips that have been preserved in rna later (ambion, austin, tx). in most cases for extracts and homogenates diluted 10-fold prior to pcr, and in all cases for 100-fold dilutions, direct amplification of dna from fresh root tip ...201019963016
inhibitor studies of leaf lamina hydraulic conductance in trembling aspen (populus tremuloides michx.) leaves.the present study investigated leaf water transport properties in trembling aspen (populus tremuloides) leaves. leaf lamina hydraulic conductance (k(lam)) and stomatal conductance (g(s)) were drastically suppressed by naf (a general metabolic inhibitor). in leaves treated with 0.2 mm hgcl(2) (an aquaporin blocker), k(lam) declined by 22% when the leaves were sampled in june but the decline was not significant when the leaves were sampled in august. the leaves sampled in june that transpired 30 m ...201020022867
design to monitor trend in abundance and presence of american beaver (castor canadensis) at the national forest scale.wildlife conservationists design monitoring programs to assess population dynamics, project future population states, and evaluate the impacts of management actions on populations. because agency mandates and conservation laws call for monitoring data to elicit management responses, it is imperative to design programs that match the administrative scale for which management decisions are made. we describe a program to monitor population trends in american beaver (castor canadensis) on the us dep ...201019396556
spring leaf flush in aspen (populus tremuloides) clones is altered by long-term growth at elevated carbon dioxide and elevated ozone concentration.early spring leaf out is important to the success of deciduous trees competing for light and space in dense forest plantation canopies. in this study, we investigated spring leaf flush and how long-term growth at elevated carbon dioxide concentration ([co(2)]) and elevated ozone concentration ([o(3)]) altered leaf area index development in a closed populus tremuloides (aspen) canopy. this work was done at the aspen face experiment where aspen clones have been grown since 1997 in conditions simul ...201019625117
thermal acclimation of photosynthesis: a comparison of boreal and temperate tree species along a latitudinal transect.common gardens were established along a approximately 900 km latitudinal transect to examine factors limiting geographical distributions of boreal and temperate tree species in eastern north america. boreal representatives were trembling aspen (populus tremuloides michx.) and paper birch (betula papyrifera marsh.), while temperate species were eastern cottonwood (populus deltoides bartr ex. marsh var. deltoides) and sweetgum (liquidambar styraciflua l.). the species were compared with respect to ...201020082671
solution-state 2d nmr of ball-milled plant cell wall gels in dmso-d(6)/pyridine-d(5).nmr fingerprinting of the components of finely divided plant cell walls swelled in dmso has been recently described. cell wall gels, produced directly in the nmr tube with perdeutero-dimethylsulfoxide, allowed the acquisition of well resolved/dispersed 2d (13)c-(1)h correlated solution-state nmr spectra of the entire array of wall polymers, without the need for component fractionation. that is, without actual solubilization, and without apparent structural modification beyond that inflicted by t ...201020090974
the impact of vessel size on vulnerability curves: data and models for within-species variability in saplings of aspen, populus tremuloides michx.the objective of this study was to quantify the relationship between vulnerability to cavitation and vessel diameter within a species. we measured vulnerability curves (vcs: percentage loss hydraulic conductivity versus tension) in aspen stems and measured vessel-size distributions. measurements were done on seed-grown, 4-month-old aspen (populus tremuloides michx) grown in a greenhouse. vcs of stem segments were measured using a centrifuge technique and by a staining technique that allowed a vc ...201020199629
changes in diurnal patterns within the populus transcriptome and metabolome in response to photoperiod variation.changes in seasonal photoperiod provides an important environmental signal that affects the timing of winter dormancy in perennial, deciduous, temperate tree species, such as hybrid aspen (populus tremula x populus tremuloides). in this species, growth cessation, cold acclimation and dormancy are induced in the autumn by the detection of day-length shortening that occurs at a given critical day length. important components in the detection of such day-length changes are photoreceptors and the ci ...201020302601
induction of phenolic glycosides by quaking aspen (populus tremuloides) leaves in relation to extrafloral nectaries and epidermal leaf mining.we studied the effect of epidermal leaf mining on the leaf chemistry of quaking aspen, populus tremuloides, during an outbreak of the aspen leaf miner, phyllocnistis populiella, in the boreal forest of interior alaska. phyllocnistis populiella feeds on the epidermal cells of p. tremuloides leaves. eleven days after the onset of leaf mining, concentrations of the phenolic glycosides tremulacin and salicortin were significantly higher in aspen leaves that had received natural levels of leaf mining ...201020354896
the speciation of water-soluble al and zn in the rhizosphere of forest soils.this study focuses on the relationships of dissolved al and zn speciation with microbial and chemical soil properties in the bulk and rhizosphere of forest soils. the soil components were sampled under populus tremuloides michx. at six sites located close to industrial facilities. total water-soluble (al(ws), zn(ws)) and reactive (al(r), zn(r)) al and zn concentrations measured in soil water extracts, speciation data modeled by wham 6, chemical properties (ph, doc, major cations and anions) and ...201020383395
impact of host tree on forest tent caterpillar performance and offspring overwintering mortality.one of the most damaging insect pests in deciduous forests of north america is the forest tent caterpillar, malacosoma disstria hübner. it can feed on a variety of plants, but trembling aspen (populus tremuloides michaux) is its preferred host and sugar maple (acer saccharum marshall) serves as a secondary one in the northern part of its distribution. because host plant characteristics influence insect performance and survival, we evaluated the impact of trembling aspen and sugar maple foliage o ...201020388280
targeted integration and removal of transgenes in hybrid aspen (populus tremula l. x p. tremuloides michx.) using site-specific recombination systems.two site-specific recombination systems, cre/lox and flp/frt, were tested for marker gene removal and targeted gene transfer in a model tree system. a hybrid aspen clone (populus tremula x populus tremuloides) was co-transformed with plasmids containing either the flp or the cre recombinase, both under control of a heat-inducible promoter (hsp, gmhsp17.5-e from soybean) flanked by the two recognition sites (frt or lox). molecular investigations of heat-shock treated cre or flp transgenic lines i ...201020398239
circadian clock components regulate entry and affect exit of seasonal dormancy as well as winter hardiness in populus trees.this study addresses the role of the circadian clock in the seasonal growth cycle of trees: growth cessation, bud set, freezing tolerance, and bud burst. populus tremula x populus tremuloides (ptt) late elongated hypocotyl1 (pttlhy1), pttlhy2, and timing of cab expression1 constitute regulatory clock components because down-regulation by rna interference of these genes leads to altered phase and period of clock-controlled gene expression as compared to the wild type. also, both rna interference ...201020530613
alteration of microbial communities colonizing leaf litter in a temperate woodland stream by growth of trees under conditions of elevated atmospheric co2.elevated atmospheric co(2) can cause increased carbon fixation and altered foliar chemical composition in a variety of plants, which has the potential to impact forested headwater streams because they are detritus-based ecosystems that rely on leaf litter as their primary source of organic carbon. fungi and bacteria play key roles in the entry of terrestrial carbon into aquatic food webs, as they decompose leaf litter and serve as a source of nutrition for invertebrate consumers. this study test ...201020543045
mass spectrometry-based sequencing of lignin oligomers.although the primary structure of proteins, nucleic acids, and carbohydrates can be readily determined, no sequencing method has been described yet for the second most abundant biopolymer on earth (i.e. lignin). within secondary-thickened plant cell walls, lignin forms an aromatic mesh arising from the combinatorial radical-radical coupling of monolignols and many other less abundant monomers. this polymerization process leads to a plethora of units and linkage types that affect the physicochemi ...201020554692
recovery of populus tremuloides seedlings following severe drought causing total leaf mortality and extreme stem embolism.in contrast with other native populus species in north america, populus tremuloides (aspen) can successfully establish itself in drought-prone areas, yet no comprehensive analysis has been performed on the ability of seedlings to withstand and recover from a severe drought resulting in complete leaf mortality. here, we subjected 4-month-old aspen seedlings grown in two contrasting soil media to a progressive drought until total leaf mortality, followed by a rewatering cycle. stomatal conductance ...201020618763
aging in a long-lived clonal tree.from bacteria to multicellular animals, most organisms exhibit declines in survivorship or reproductive performance with increasing age ("senescence"). evidence for senescence in clonal plants, however, is scant. during asexual growth, we expect that somatic mutations, which negatively impact sexual fitness, should accumulate and contribute to senescence, especially among long-lived clonal plants. we tested whether older clones of populus tremuloides (trembling aspen) from natural stands in brit ...201020808953
temperature response of isoprene emission in vivo reflects a combined effect of substrate limitations and isoprene synthase activity: a kinetic analysis.the responses of isoprene emission rate to temperature are characterized by complex time-dependent behaviors that are currently not entirely understood. to gain insight into the temperature dependencies of isoprene emission, we studied steady-state and transient responses of isoprene emission from hybrid aspen (populus tremula × populus tremuloides) leaves using a fast-response gas-exchange system coupled to a proton-transfer reaction mass spectrometer. a method based on postillumination isopren ...201020837700
defensive effects of extrafloral nectaries in quaking aspen differ with scale.the effects of plant defenses on herbivory can differ among spatial scales. this may be particularly common with indirect defenses, such as extrafloral nectaries (efns), that attract predatory arthropods and are dependent on predator distribution, abundance, and behavior. we tested the defensive effects of efns in quaking aspen (populus tremuloides michx.) against damage by a specialist herbivore, the aspen leaf miner (phyllocnistis populiella cham.), at the scale of individual leaves and entire ...201020931234
changes in composition and sugar release across the annual rings of populus wood and implications on recalcitrance.understanding structural characteristics that are responsible for biomass recalcitrance by identifying why it is more difficult for some plants, or portions of plants, to release their sugars would be extremely valuable in overcoming this barrier. with this in mind, this study investigated the recalcitrance of wood by considering the effects of aging in two populus tremuloides cross sections. by applying our novel small scale systems, including a multi-well pretreatment and enzymatic hydrolysis ...201020943384
are wolves saving yellowstone's aspen? a landscape-level test of a behaviorally mediated trophic cascade.behaviorally mediated trophic cascades (bmtcs) occur when the fear of predation among herbivores enhances plant productivity. based primarily on systems involving small-bodied predators, bmtcs have been proposed as both strong and ubiquitous in natural ecosystems. recently, however, synthetic work has suggested that the existence of bmtcs may be mediated by predator hunting mode, whereby passive (sit-and-wait) predators have much stronger effects than active (coursing) predators. one bmtc that h ...201020957967
altered leaf morphology, leaf resource dilution and defense chemistry induction in frost-defoliated aspen (populus tremuloides).in may 2007, a widespread frost event defoliated much of utah's high elevation aspen. about 5 weeks later, the frost-defoliated aspen produced a second leaf flush. the objective of this study was to characterize changes in leaf morphology and function in re-flush leaves following frost defoliation. leaf size and thickness, photosynthesis, carbohydrate and nutrient status, and defense chemistry (phenolic glycosides and condensed tannins) were measured in first and second flush leaves. the second ...200919671568
the influence of weather and fuel type on the fuel composition of the area burned by forest fires in ontario, 1996-2006.forest fires are influenced by weather, fuels, and topography, but the relative influence of these factors may vary in different forest types. compositional analysis can be used to assess the relative importance of fuels and weather in the boreal forest. do forest or wild land fires burn more flammable fuels preferentially or, because most large fires burn in extreme weather conditions, do fires burn fuels in the proportions they are available despite differences in flammability? in the canadian ...200919688931
take me to your leader: does early successional nonhost vegetation spatially inhibit pissodes strobi (coleoptera: curculionidae)?the spatial influences of host and nonhost trees and shrubs on the colonization patterns of white pine weevil pissodes strobi (peck) were studied within a stand of planted interior hybrid spruce [picea glauca (moench) voss x picea engelmannii (parry) ex engelm.]. planted spruce accounted for one third of all trees within the stand, whereas the remaining two thirds were comprised of early-successional nonhost vegetation, such as alder (alnus spp.), paper birch (betula papyrifera marsh.), black co ...200919689899
species-specific responses to atmospheric carbon dioxide and tropospheric ozone mediate changes in soil carbon.we repeatedly sampled the surface mineral soil (0-20 cm depth) in three northern temperate forest communities over an 11-year experimental fumigation to understand the effects of elevated carbon dioxide (co(2)) and/or elevated phyto-toxic ozone (o(3)) on soil carbon (c). after 11 years, there was no significant main effect of co(2) or o(3) on soil c. however, within the community containing only aspen (populus tremuloides michx.), elevated co(2) caused a significant decrease in soil c content. t ...200919754884
endomembrane system of aspen root cells plays a key role in defense against a common fungal root endophyte, cryptosporiopsis radicicola.the host-endophyte interaction between roots of aspen (populus tremuloides) and cryptosporiopsis radicicola was examined primarily by transmission electron microscopy. hyphae growing on the exterior of the inoculated roots had a thick, electron-dense, adhesive sheath. at hyphal contact and penetration, host epidermal cells exhibited a series of defense responses (viz. formation of papillae and partition walls, general wall thickening and walling-off of internal hyphae). in papilla formation, loo ...200919397190
the ectomycorrhizal morphotype pinirhiza sclerotia is formed by acephala macrosclerotiorum sp. nov., a close relative of phialocephala fortinii.relatively few ectomycorrhizal fungal species are known to form sclerotia. usually, sclerotia are initiated at the extraradical mycelium. in this study, we present anatomical and ultrastructural evidence for the formation of sclerotia directly in the hyphal mantle of the mycorrhizal morphotype pinirhiza sclerotia. a dark-pigmented fungal strain was isolated from pinirhiza sclerotia and identified by molecular tools as acephala macrosclerotiorum sp. nov., a close relative of phialocephala fortini ...200919415343
performance and secondary chemistry of two hybrid aspen (populus tremula l. x populus tremuloides michx.) clones in long-term elevated ozone exposure.the effects of moderately elevated ozone (ca. 35 ppb) on the growth and secondary chemistry of the leaves of two soil-grown finnish hybrid aspen (populus tremula l. x populus tremuloides michx.) clones with different ozone sensitivities were studied at an open-air exposure field in kuopio, finland. stomatal conductance, photosynthetic rate, and chlorophyll fluorescence were measured during the third growing season. foliar phenolic concentrations, ergosterol concentration of fine roots, and final ...200919462207
larval nutrition affects life history traits in a capital breeding moth.fitness depends not only on resource uptake but also on the allocation of these resources to various life history functions. this study explores the life-history consequences of larval diet in terms not only of larval performance but also of adult body composition and reproductive traits in the forest tent caterpillar (malacosoma disstria hübner). caterpillars were reared on their preferred tree host, trembling aspen (populus tremuloides), or on one of three artificial foods: high protein:low ca ...200919482996
impact of simulated herbivory on water relations of aspen (populus tremuloides) seedlings: the role of new tissue in the hydraulic conductivity recovery cycle.physiological mechanisms behind plant-herbivore interactions are commonly approached as input-output systems where the role of plant physiology is viewed as a black box. studies evaluating impacts of defoliation on plant physiology have mostly focused on changes in photosynthesis while the overall impact on plant water relations is largely unknown. stem hydraulic conductivity (k(h)), stem specific conductivity (k(s)), percent loss of hydraulic conductivity (plc), co(2) assimilation (a) and stoma ...200919603186
differences in leaf characteristics between ozone-sensitive and ozone-tolerant hybrid aspen (populus tremula x populus tremuloides) clones.the authors analyzed a suite of leaf characteristics that might help to explain the difference between ozone-sensitive and ozone-tolerant hybrid aspen (populus tremula l. x populus tremuloides michx.) clones. an open-field experiment comprising ambient ozone and 1.5x ambient ozone concentration (about 35 ppb) and two soil nitrogen regimes (60 and 140 kg n ha(-1) year(-1)) was conducted over two growing seasons on potted plants of eight hybrid aspen clones. four of the clones had previously been ...200919203932
rhizosphere carbon deposition, oxidative stress and nutritional changes in two poplar species exposed to aluminum.species and hybrids in the genus populus have become the focus of investigation for use in biofuels production and their capacity to sequester carbon (c) in the environment. the identification of species resistant to marginal edaphic sites may be important in both of these endeavors. plant growth, total dissolved organic carbon (toc) and low molecular weight organic acid (oa) production, antioxidative enzyme activities and mineral content were assessed in populus tremuloides l. and populus trich ...200919203961
senescence-related changes in nitrogen in fine roots: mass loss affects estimation.the fate of nitrogen (n) in senescing fine roots has broad implications for whole-plant n economies and ecosystem n cycling. studies to date have generally shown negligible changes in fine root n per unit root mass during senescence. however, unmeasured loss of mobile non-n constituents during senescence could lead to underestimates of fine root n loss. for n fertilized and unfertilized potted seedlings of populus tremuloides michx., acer rubrum l., acer saccharum marsh. and betula alleghaniensi ...200919203982
genetic mosaics of ecosystem functioning across aspen-dominated landscapes.genetic diversity is the foundation of all biodiversity, and the genetic variation within species is increasingly recognized as being important to ecosystem level processes. recent research demonstrates that plant genotype influences above- and belowground communities as well as basic ecosystem functions. however, the extent to which plant genotypes create spatial mosaics of genetically mediated ecosystem processes in natural forests is uncertain. we use populus tremuloides as a model system to ...200919214586
nonstomatal versus stomatal uptake of atmospheric mercury.atmospheric constituents may be deposited to and incorporated into plant leaves, with gases entering via stomata, and gas and particles being sorbed at the surface and in some cases traversing the cuticle, possibly reaching the epidermis. plants are known to be a sink for atmospheric mercury (hg), and the current paradigm is that uptake of gaseous elemental hg occurs by way of the stomata. four plant species, rudbeckia hirta, sorghastrum nutans, andropogon gerardii, and populus tremuloides, were ...200919350905
transcriptomic comparison in the leaves of two aspen genotypes having similar carbon assimilation rates but different partitioning patterns under elevated [co2].this study compared the leaf transcription profiles, physiological characteristics and primary metabolites of two populus tremuloides genotypes (clones 216 and 271) known to differ in their responses to long-term elevated [co2] (e[co2]) at the aspen free-air co2 enrichment site near rhinelander, wi, usa. the physiological responses of these clones were similar in terms of photosynthesis, stomatal conductance and leaf area index under e[co2], yet very different in terms of growth enhancement (0-1 ...200919383098
development of a combined sex pheromone-based monitoring system for malacosoma disstria (lepidoptera: lasoicampidae) and choristoneura conflictana (lepidoptera: tortricidae).sympatric insect species that do not share sex pheromone components but have a common host and overlapping adult flight periods are potential targets for the development of a combined sex pheromone-based monitoring tool. a system using a single synthetic pheromone blend in a single lure to bait a single trap to monitor two pests simultaneously represents a novel approach. in this study, a combined pheromone-based monitoring system was developed for two lepidopterous defoliators of trembling aspe ...200919389296
behavioral archives link the chemistry and clonal structure of trembling aspen to the food choice of north american porcupine.understanding the links among plant genotype, plant chemistry, and food selection by vertebrate herbivores is critical to assess the role of herbivores in the evolution of plant secondary chemistry. some specialized vertebrate herbivores have been shown to select plants differentially according to plant genotype, but examples from generalists, which constitute the vast majority of vertebrate herbivores, are few, especially in natural conditions. we examined the relationship between the north ame ...200919390868
postillumination isoprene emission: in vivo measurements of dimethylallyldiphosphate pool size and isoprene synthase kinetics in aspen leaves.the control of foliar isoprene emission is shared between the activity of isoprene synthase, the terminal enzyme catalyzing isoprene formation from dimethylallyldiphosphate (dmadp), and the pool size of dmadp. due to limited in vivo information of isoprene synthase kinetic characteristics and dmadp pool sizes, the relative importance of these controls is under debate. in this study, the phenomenon of postillumination isoprene release was employed to develop an in vivo method for estimation of th ...200919129417
glycosylation-mediated phenylpropanoid partitioning in populus tremuloides cell cultures.phenylpropanoid-derived phenolic glycosides (pgs) and condensed tannins (cts) comprise large, multi-purpose non-structural carbon sinks in populus. a negative correlation between pg and ct concentrations has been observed in several studies. however, the molecular mechanism underlying the relationship is not known.200920040108
leaf and canopy conductance in aspen and aspen-birch forests under free-air enrichment of carbon dioxide and ozone.increasing concentrations of atmospheric carbon dioxide (co2) and tropospheric ozone (o3) have the potential to affect tree physiology and structure, and hence forest feedbacks on climate. here, we investigated how elevated concentrations of co2 (+45%) and o3 (+35%), alone and in combination, affected conductance for mass transfer at the leaf and canopy levels in pure aspen (populus tremuloides michx.) and in mixed aspen and birch (betula papyrifera marsh.) forests in the free-air co2-o3 enrichm ...200919773339
phenolic compounds in ectomycorrhizal interaction of lignin modified silver birch.the monolignol biosynthetic pathway interconnects with the biosynthesis of other secondary phenolic metabolites, such as cinnamic acid derivatives, flavonoids and condensed tannins. the objective of this study is to evaluate whether genetic modification of the monolignol pathway in silver birch (betula pendula roth.) would alter the metabolism of these phenolic compounds and how such alterations, if exist, would affect the ectomycorrhizal symbiosis.200919788757
molecular and dendrochronological analysis of natural root grafting in populus tremuloides (salicaceae).trembling aspen (populus tremuloides) is a clonal tree species, which regenerates mostly through root suckering. in spite of vegetative propagation, aspen maintains high levels of clonal diversity. we hypothesized that the maintenance of clonal diversity in this species can be facilitated by integrating different clones through natural root grafts into aspen's communal root system. to verify this hypothesis, we analyzed root systems of three pure aspen stands where clones had been delineated wit ...200921628295
clonal dynamics in western north american aspen (populus tremuloides).clonality is a common phenomenon in plants, allowing genets to persist asexually for much longer periods of time than ramets. the relative frequency of sexual vs. asexual reproduction determines long-term dominance and persistence of clonal plants at the landscape scale. one of the most familiar and valued clonal plants in north america is aspen (populus tremuloides). previous researchers have suggested that aspen in xeric landscapes of the intermountain west represent genets of great chronologi ...200819140975
can clone size serve as a proxy for clone age? an exploration using microsatellite divergence in populus tremuloides.in long-lived clonal plants, the overall size of a clone is often used to estimate clone age. the size of a clone, however, might be largely determined by physical or biotic interactions, obscuring the relationship between clone size and age. here, we use the accumulation of mutations at 14 microsatellite loci to estimate clone age in trembling aspen (populus tremuloides) from southwestern canada. we show that the observed patterns of genetic divergence are consistent with a model of increasing ...200819140980
soil respiration, root biomass, and root turnover following long-term exposure of northern forests to elevated atmospheric co2 and tropospheric o3.the rhinelander free-air co(2) enrichment (face) experiment is designed to understand ecosystem response to elevated atmospheric carbon dioxide (+co(2)) and elevated tropospheric ozone (+o(3)). the objectives of this study were: to understand how soil respiration responded to the experimental treatments; to determine whether fine-root biomass was correlated to rates of soil respiration; and to measure rates of fine-root turnover in aspen (populus tremuloides) forests and determine whether root t ...200818643941
maximizing the liquid fuel yield in a biorefining process.biorefining strives to recover the maximum value from each fraction, at minimum energy cost. in order to seek an unbiased and thorough assessment of the alleged opportunity offered by biomass fuels, the direct conversion of various lignocellulosic biomass was studied: aspen pulp wood (populus tremuloides), aspen wood pretreated with dilute acid, aspen lignin, aspen logging residues, corn stalk, corn spathe, corn cob, corn stover, corn stover pellet, corn stover pretreated with dilute acid, and l ...200818781691
carbon gain and bud physiology in populus tremuloides and betula papyrifera grown under long-term exposure to elevated concentrations of co2 and o3.paper birch (betula papyrifera marsh.) and three trembling aspen clones (populus tremuloides michx.) were studied to determine if alterations in carbon gain in response to an elevated concentration of co(2) ([co(2)]) or o(3) ([o(3)]) or a combination of both affected bud size and carbohydrate composition in autumn, and early leaf development in the following spring. the trees were measured for gas exchange, leaf size, date of leaf abscission, size and biochemical characteristics of the overwinte ...200818055435
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
wood properties of trembling aspen and paper birch after 5 years of exposure to elevated concentrations of co(2) and o(3).we investigated the interactive effects of elevated concentrations of carbon dioxide ([co(2)]) and ozone ([o(3)]) on radial growth, wood chemistry and structure of five 5-year-old trembling aspen (populus tremuloides michx.) clones and the wood chemistry of paper birch (betula papyrifera marsh.). material for the study was collected from the aspen face (free-air co(2) enrichment) experiment in rhinelander, wi, where the saplings had been exposed to four treatments: control, elevated [co(2)] (560 ...200818316312
characterization of nonderivatized plant cell walls using high-resolution solution-state nmr spectroscopy.a recently described plant cell wall dissolution system has been modified to use perdeuterated solvents to allow direct in-nmr-tube dissolution and high-resolution solution-state nmr of the whole cell wall without derivatization. finely ground cell wall material dissolves in a solvent system containing dimethylsulfoxide-d(6) and 1-methylimidazole-d(6) in a ratio of 4:1 (v/v), keeping wood component structures mainly intact in their near-native state. two-dimensional nmr experiments, using gradie ...200818383438
dissecting the molecular basis of the regulation of wood formation by auxin in hybrid aspen.indole acetic acid (auxin) is a key regulator of wood formation, and an observed overlap between auxin concentration gradient and developing secondary xylem cells has led to the hypothesis that auxin regulates wood formation by acting as a morphogen. we dissected the role of auxin in wood formation by identifying the auxin-responsive transcriptome in wood-forming tissues and investigating alterations in wood formation in transgenic hybrid aspen plants (populus tremula x populus tremuloides) with ...200818424614
the lack of a systematic validation of reference genes: a serious pitfall undervalued in reverse transcription-polymerase chain reaction (rt-pcr) analysis in plants.reverse transcription-polymerase chain reaction (rt-pcr) approaches have been used in a large proportion of transcriptome analyses published to date. the accuracy of the results obtained by this method strongly depends on accurate transcript normalization using stably expressed genes, known as references. statistical algorithms have been developed recently to help validate reference genes, and most studies of gene expression in mammals, yeast and bacteria now include such validation. surprisingl ...200818433420
oxidation of ingested phenolics in the tree-feeding caterpillar orgyia leucostigma depends on foliar chemical composition.tannins are believed to function as antiherbivore defenses, in part, by acting as prooxidants. however, at the high ph found in the midguts of caterpillars, the oxidative activities of different types of tannins vary tremendously: ellagitannins >> galloyl glucoses > condensed tannins. ingested ascorbate is utilized by caterpillars to minimize phenolic oxidation in the midgut. thus, leaves that contain higher levels of reactive tannins and lower levels of ascorbate were hypothesized to produce hi ...200818473142
impact of epidermal leaf mining by the aspen leaf miner (phyllocnistis populiella) on the growth, physiology, and leaf longevity of quaking aspen.the aspen leaf miner, phyllocnistis populiella, feeds on the contents of epidermal cells on both top (adaxial) and bottom (abaxial) surfaces of quaking aspen leaves, leaving the photosynthetic tissue of the mesophyll intact. this type of feeding is taxonomically restricted to a small subset of leaf mining insects but can cause widespread plant damage during outbreaks. we studied the effect of epidermal mining on aspen growth and physiology during an outbreak of p. populiella in the boreal forest ...200818523809
isoprene emission rates under elevated co2 and o3 in two field-grown aspen clones differing in their sensitivity to o3.isoprene is the most important nonmethane hydrocarbon emitted by plants. the role of isoprene in the plant is not entirely understood but there is evidence that it might have a protective role against different oxidative stresses originating from heat shock and/or exposure to ozone (o(3)). thus, plants under stress conditions might benefit by constitutively high or by higher stress-induced isoprene emission rates. in this study, measurements are presented of isoprene emission from aspen (populus ...200818557875
auxin gradients are associated with polarity changes in trees.models of plant growth and development propose that changes in cell polarity are mediated by gradients of the plant hormone auxin. with use of gas chromatography-mass spectrometry, we measured the redistribution of endogenous auxin in stems of quaking aspen trees (populus tremuloides) after wounding. persistent (lasting at least 24 hours) auxin gradients were observed in the region of the cambium where cell polarity was changing. a computer model of the auxin redistribution shows agreement with ...200818566279
decay of aspen (populus tremuloides michx.) wood in moist and dry boreal, temperate, and tropical forest fragments.in this study, we set up a wood decomposition experiment to i) quantify the percent of mass remaining, decay constant and performance strength of aspen stakes (populus tremuloides) in dry and moist boreal (alaska and minnesota, usa), temperate (washington and idaho, usa), and tropical (puerto rico) forest types, and ii) determine the effects of fragmentation on wood decomposition rates as related to fragment size, forest age (and/or structure) and climate at the macro- and meso-scales. fragment ...200819205182
new exposure-based metric approach for evaluating o(3) risk to north american aspen forests.the united states and canada currently use exposure-based metrics to protect vegetation from o(3). using 5 years (1999-2003) of co-measured o(3), meteorology and growth response, we have developed exposure-based regression models that predict populus tremuloides growth change within the north american ambient air quality context. the models comprised growing season fourth-highest daily maximum 8-h average o(3) concentration, growing degree days, and wind speed. they had high statistical signific ...200717140714
interannual consistency in canopy stomatal conductance control of leaf water potential across seven tree species.we investigated interannual variability of canopy transpiration per unit ground area (e (c)) and per unit leaf area (e (l)) across seven tree species in northern wisconsin over two years. these species have previously been shown to be sufficient to upscale stand-level transpiration to the landscape level during one growing season. our objective was to test whether a simple plant hydraulic model could capture interannual variation in transpiration. three species, wetland balsam fir (abies balsame ...200717169902
plant growth, biomass partitioning and soil carbon formation in response to altered lignin biosynthesis in populus tremuloides.we conducted a glasshouse mesocosm study that combined (13)c isotope techniques with wild-type and transgenic aspen (populus tremuloides) in order to examine how altered lignin biosynthesis affects plant production and soil carbon formation. our transgenic aspen lines expressed low stem lignin concentration but normal cellulose concentration, low lignin stem concentration with high cellulose concentration or an increased stem syringyl to guaiacyl lignin ratio. large differences in stem lignin co ...200717286822
calcium nutrition has a significant influence on wood formation in poplar.to test the effects of calcium on wood formation, populus tremula x populus tremuloides clones were supplied with hoagland solution modified in its calcium contents. energy-dispersive x-ray analysis (edxa) revealed an increase in calcium in the phloem, the cambium and the xylem elongation zone with increasing ca(2+) supply in the nutrient solution. using light and electron microscopy, a strong impact was shown on the cambial and the elongation zones under calcium starvation. using fourier transf ...200717286823
identification of ptm5 protein interaction partners, a mads-box gene involved in aspen tree vegetative development.in a past article, our lab described the identification and characterization of a novel vegetative mads-box gene from quaking aspen trees, populus tremuloides mads-box 5 (ptm5). ptm5 was shown to be a member of the soc1/tm3 class of mads-box genes with a seasonal expression pattern specific to developing vascular tissues including the vascular cambium, the precursor to all woody branches, stems, and roots. since the proper function of mads-box proteins is dependent on specific interactions with ...200717331677
the glycine decarboxylase complex multienzyme family in populus.in plants, the glycine decarboxylase complex (gdc) cooperates with serine hydroxymethyltransferase (shmt) to mediate photorespiratory glycine-serine interconversion. gdc is also postulated to be an integral component of one-carbon (c1) metabolism in heterotrophic tissues, although molecular evidence in plants is scarce. an initial report of a xylem-specific isoform of gdc component h-protein, ptgdch1, in aspen (populus tremuloides michx.) provided molecular evidence consistent with an important ...200717355947
carbon isotope discrimination and water stress in trembling aspen following variable retention harvesting.variable retention harvesting (vrh) has been proposed as a silvicultural practice to maintain biodiversity and ecosystem integrity. no previous study has examined tree carbon isotope discrimination to provide insights into water stress that could lead to dieback and mortality of trees following vrh. we measured and compared the carbon isotope ratios (delta(13)c) in stem wood of trembling aspen (populus tremuloides michx.) before and after vrh. eight trees were sampled from isolated residual, edg ...200717403660
browse quality in quaking aspen (populus tremuloides): effects of genotype, nutrients, defoliation, and coppicing.the consequences of interactions among genetic, ontogenetic, and environmental factors for the quality of winter-dormant tissues as food for browsing herbivores is poorly understood. we conducted two sequential common garden studies to assess the impacts of intraspecific genetic variation, nutrient availability, prior defoliation, and ontogenetic stage on the chemical quality of winter-dormant tissue in quaking aspen (populus tremuloides michx.). in the first study, saplings of 12 aspen genotype ...200717404817
the seasonal activity and the effect of mechanical bending and wounding on the ptcomt promoter in betula pendula roth.in this study, 900-bp (signed as p including nucleotides -1 to -886) and partly deleted (signed as dp including nucleotides -1 to -414) comt (caffeate/5-hydroxyferulate o-methyltransferase) promoters from populus tremuloides michx. were fused to the gus reporter gene, and the tissue-specific expression patterns of the promoters were determined in betula pendula roth along the growing season, and as a response to mechanical bending and wounding. the main activity of the ptcomtp- and ptcomtdp-prom ...200717431633
high efficiency poplar transformation.with the completion of the poplar tree genome database, populus species have become one of the most useful model systems for the study of woody plant biology. populus tremuloides (quaking aspen) is the most wide-spread tree species in north america, and its rapid growth generates the most abundant wood-based biomass out of any other plant species. to study such beneficial traits, there is a need for easier and more efficient transformation procedures that will allow the study of large numbers of ...200717492451
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