Publications

recovery kinetics of photochemical efficiency in winter stressed conifers: the effects of growth light environment, extent of the season and species.	evergreens undergo reductions in maximal photochemical efficiency (f(v)/f(m)) during winter due to increases in sustained thermal energy dissipation. upon removing winter stressed leaves to room temperature and low light, f(v)/f(m) recovers and can include both a rapid and a slow phase. the goal of this study was to determine whether the rapid component to recovery exists in winter stressed conifers at any point during the season in a seasonally extreme environment. additional goals were to comp ...	2013	22575048
a large herbivore triggers alternative successional trajectories in the boreal forest.	alternative successional trajectories (ast) may result in multiple climax states within an ecosystem when disturbances affect colonization history. in the boreal forest, ungulates have been proposed to drive ast because, under herbivore pressure, preferred species may go extinct and apparent competition may benefit browsing-resistant species. over a 15-year period following logging, we tested whether deer herbivory altered plant species composition and whether the competitive advantage of resist ...	2013	24597230
the action of antidiabetic plants of the canadian james bay cree traditional pharmacopeia on key enzymes of hepatic glucose homeostasis.	we determined the capacity of putative antidiabetic plants used by the eastern james bay cree (canada) to modulate key enzymes of gluconeogenesis and glycogen synthesis and key regulating kinases. glucose-6-phosphatase (g6pase) and glycogen synthase (gs) activities were assessed in cultured hepatocytes treated with crude extracts of seventeen plant species. phosphorylation of amp-dependent protein kinase (ampk), akt, and glycogen synthase kinase-3 (gsk-3) were probed by western blot. seven of th ...	2013	23864882
antioxidant potential of bark extracts from boreal forest conifers.	the bark of boreal forest conifers has been traditionally used by native americans to treat various ailments and diseases. some of these diseases involve reactive oxygen species (ros) that can be prevented by the consumption of antioxidants such as phenolic compounds that can be found in medicinal plants. in this study, ultrasonic assisted extraction has been performed under various solvent conditions (water:ethanol mixtures) on the bark of seven boreal forest conifers used by native americans i ...	2013	26784337
a molecular identification protocol for roots of boreal forest tree species.		2014	25383267
biogeographic variation in evergreen conifer needle longevity and impacts on boreal forest carbon cycle projections.	leaf life span is an important plant trait associated with interspecific variation in leaf, organismal, and ecosystem processes. we hypothesized that intraspecific variation in gymnosperm needle traits with latitude reflects both selection and acclimation for traits adaptive to the associated temperature and moisture gradient. this hypothesis was supported, because across 127 sites along a 2,160-km gradient in north america individuals of picea glauca, picea mariana, pinus banksiana, and abies b ...	2014	25225397
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 ...	2014	25422385
cloning and characterization of chitinases from interior spruce and lodgepole pine.	chitinases have been implicated in the defence of conifers against insects and pathogens. cdna for six chitinases were cloned from interior spruce (picea glauca x engelmannii) and four from lodgepole pine (pinus contorta). the cloned interior spruce chitinases were annotated class i pgechia1-1 and pgechia1-2, class ii pgechia2-1, class iv pgechia4-1, and class vii pgechia7-1 and pgechia7-2; lodgepole pine chitinases were annotated class i pcchia1-1, class iv pcchia4-1, and class vii pcchia7-1 an ...	2014	24564978
do offspring of insects feeding on defoliation-resistant trees have better biological performance when exposed to nutritionally-imbalanced food?	white spruce (picea glauca (moench) voss) trees that are resistant or susceptible to spruce budworm (choristoneura fumiferana (clem.)) attack were identified in a southern quebec plantation. due to high mortality-induced selective pressures imposed by resistant trees on spruce budworm larvae, insects that survive on resistant trees exhibited greater biological performance than those on susceptible trees. we tested the hypothesis that this better biological performance is maintained across genera ...	2015	26463069
expression of the β-glucosidase gene pgβglu-1 underpins natural resistance of white spruce against spruce budworm.	periodic outbreaks of spruce budworm (sbw) affect large areas of ecologically and economically important conifer forests in north america, causing tree mortality and reduced forest productivity. host resistance against sbw has been linked to growth phenology and the chemical composition of foliage, but the underlying molecular mechanisms and population variation are largely unknown. using a genomics approach, we discovered a β-glucosidase gene, pgβglu-1, whose expression levels and function unde ...	2015	25302566
spruce budworm (lepidoptera: tortricidae) oral secretions ii: chemistry.	as sessile organisms, plants have evolved different methods to defend against attacks and have adapted their defense measures to discriminate between mechanical damage and herbivory by insects. one of the ways that plant defenses are triggered is via elicitors from insect oral secretions (os). in this study, we investigated the ability of second-instar (l2) spruce budworm [sbw; choristoneura fumiferana (clemens)] to alter the volatile organic compounds (vocs) of four conifer species [abies balsa ...	2015	26454474
changes in hormone flux and signaling in white spruce (picea glauca) seeds during the transition from dormancy to germination in response to temperature cues.	seeds use environmental cues such as temperature to coordinate the timing of their germination, allowing plants to synchronize their life history with the seasons. winter chilling is of central importance to alleviate seed dormancy, but very little is known of how chilling responses are regulated in conifer seeds. white spruce (picea glauca) is an important conifer species of boreal forests in the north american taiga. the recent sequencing and assembly of the white spruce genome allows for comp ...	2015	26680643
links: scalable, alignment-free scaffolding of draft genomes with long reads.	owing to the complexity of the assembly problem, we do not yet have complete genome sequences. the difficulty in assembling reads into finished genomes is exacerbated by sequence repeats and the inability of short reads to capture sufficient genomic information to resolve those problematic regions. in this regard, established and emerging long read technologies show great promise, but their current associated higher error rates typically require computational base correction and/or additional bi ...	2015	26244089
fertility-dependent effects of ectomycorrhizal fungal communities on white spruce seedling nutrition.	ectomycorrhizal fungi (ecmf) typically colonize nursery seedlings, but nutritional and growth effects of these communities are only partly understood. to examine these effects, picea glauca seedlings collected from a tree nursery naturally colonized by three dominant ecmf were divided between fertilized and unfertilized treatments. after one growing season seedlings were harvested, ectomycorrhizas identified using dna sequencing, and seedlings analyzed for leaf nutrient concentration and content ...	2015	25904341
contrasting patterns of diterpene acid induction by red pine and white spruce to simulated bark beetle attack, and interspecific differences in sensitivity among fungal associates.	conifers possess a suite of physiochemical defenses that protect their subcortical tissues from bark beetle - fungal complexes. these defenses include rapid induction of terpenoids and phenolics at the site of attack. studies of the distribution, induction, and bioactivity of conifer terpenoids have focused heavily on monoterpenes. we assessed induction of diterpene acids in white spruce (picea glauca) and red pine (pinus resinosa) to fungal associates of two bark beetles, and the responses of f ...	2015	26003180
tree phyllosphere bacterial communities: exploring the magnitude of intra- and inter-individual variation among host species.	the diversity and composition of the microbial community of tree leaves (the phyllosphere) varies among trees and host species and along spatial, temporal, and environmental gradients. phyllosphere community variation within the canopy of an individual tree exists but the importance of this variation relative to among-tree and among-species variation is poorly understood. sampling techniques employed for phyllosphere studies include picking leaves from one canopy location to mixing randomly sele ...	2016	27635335
host species identity, site and time drive temperate tree phyllosphere bacterial community structure.	the increasing awareness of the role of phyllosphere microbial communities in plant health calls for a greater understanding of their structure and dynamics in natural ecosystems. since most knowledge of tree phyllosphere bacterial communities has been gathered in tropical forests, our goal was to characterize the community structure and assembly dynamics of phyllosphere epiphytic bacterial communities in temperate forests in quebec, canada. we targeted five dominant tree species: acer saccharum ...	2016	27316353
allometric exponents as a tool to study the influence of climate on the trade-off between primary and secondary growth in major north-eastern american tree species.	trees invest in both primary (e.g. height) and secondary (e.g. diameter) growth. the trade-off between these investments varies between species and changes with the tree growing environment. to better establish this trade-off, readily available allometric exponents relating height to diameter at breast height (γ(h,dbh)) and stem volume to diameter at breast height (α(v,dbh)) were simultaneously studied.	2016	26975315
characterization of light-dependent regulation of state transitions in gymnosperms.	the goal of this study was to characterize the light-dependent regulation of state transitions in gymnosperms. two species of conifer were examined: eastern white pine (pinus strobus l.) and white spruce [picea glauca (moench) voss], as well as the angiosperm pumpkin (cucurbita pepo l. subsp. pepo). both diurnal time courses in the field and manipulated light experiments in growth chambers were conducted. results from chlorophyll fluorescence analysis indicated that pumpkin was able to use a lar ...	2016	26802541
tree-ring isotopes reveal drought sensitivity in trees killed by spruce beetle outbreaks in south-central alaska.	increasing temperatures have resulted in reduced growth and increased tree mortality across large areas of western north american forests. we use tree-ring isotope chronologies (δ(13) c and δ(18) o) from live and dead trees from four locations in south-central alaska, usa, to test whether white spruce trees killed by recent spruce beetle (dendroctonus rufipennis kirby) outbreaks showed evidence of drought stress prior to death. trees that were killed were more sensitive to spring/summer temperat ...	2016	27755740
absence of net long-term successional facilitation by alder in a boreal alaska floodplain.	long-term experiments provide a way to test presumed causes of successional or environmentally driven vegetation changes. early-successional nitrogen (n)-fixing plants are widely thought to facilitate productivity and vegetation development on n-poor sites, thus accounting for observed vegetation patterns later in succession. we tested this facilitative impact on vegetation development in a 23-yr field experiment on an interior alaska (usa) floodplain. on three replicate early-successional silt ...	2016	27870053
modelling moose-forest interactions under different predation scenarios at isle royale national park, usa.	loss of top predators may contribute to high ungulate population densities and chronic over-browsing of forest ecosystems. however, spatial and temporal variability in the strength of interactions between predators and ungulates occurs over scales that are much shorter than the scales over which forest communities change, making it difficult to characterize trophic cascades in forest ecosystems. we applied the landis-ii forest succession model and a recently developed ungulate browsing extension ...	2017	28263421
insect herbivory (choristoneura fumiferana, tortricidea) underlies tree population structure (picea glauca, pinaceae).	variation in insect herbivory can lead to population structure in plant hosts as indicated by defence traits. in annual herbaceous, defence traits may vary between geographic areas but evidence of such patterns is lacking for long-lived species. this may result from the variety of selection pressures from herbivores, long distance gene flow, genome properties, and lack of research. we investigated the antagonistic interaction between white spruce (picea glauca) and spruce budworm (sbw, choriston ...	2017	28205578
spruce budworm feeding and oviposition are stimulated by monoterpenes in white spruce epicuticular waxes.	monoterpenes, source of the distinctive odor of conifers, are generally considered plant defensive compounds. however, they are also known to act as long-range insect attractants, as they are volatile and permeate forest airspaces. moreover, they are lipid soluble and can be absorbed into plant epicuticular waxes. we test their role in short-range host plant choice by both adult females and larvae of a folivorous forest pest (choristoneura fumiferana). we conducted laboratory assays testing the ...	2017	26463122