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induction of anti-timothy pollen reaginic antibodies and their cross-reactivity in the rat.anti-timothy pollen reaginic antibody produced in rats cross-reacted with a large number of grass pollen antigens (orchard, june grass, perennial rye grass, velvet, meadow fescue, red top and broncho grass), but did not react with bermuda, brome and johnson grass.1977911069
diagnostic performance characteristics of the standard phadebas rast, modified rast, and pharmacia cap system versus skin testing.results from three in vitro assays for allergen-specific ige, the standard phadebas radioallergosorbent test (phrast), modified rast (mrast), and the new pharmacia cap system (cap) were compared with skin prick testing (spt) results in 104 patients with allergic rhinitis and/or asthma and 24 nonatopic controls. five allergens were evaluated: cat, dermatophagoides pteronyssinus, alternaria, june grass, and short ragweed. using spt results as the reference standard, the phrast had the lowest sensi ...19911958005
effect of forage species and season on nutrient digestion and supply in grazing cattle.1. a total of twenty friesian steers were grazed on pure swards of either perennial ryegrass (lolium perenne cv. melle) or white clover (trifolium repens cv. blanca) from may to late august to examine the effect of forage species and season on nutrient digestion and supply. within each forage species, two daily allowances of forage (i.e. 30 and 60 g dry matter (dm)/kg live weight) were given, and nutrient flow into the small intestine was measured on thirteen separate occasions (viz. seven grass ...19863676197
a computerized micro-elisa assay for allergen-specific ige antibodies.a computer-normalized micro-elisa assay employing horseradish peroxidase and polystyrene microtiter plates (ip assay) for allergen-specific ige antibodies is described. the specificity of the assay was confirmed by heat inactivation and multiple absorption experiments. individual allergen blanks were used to account for the variability in the nonspecific binding among various allergens. the results obtained in milliunits of absorbance were normalized by a computer protocol using four reference s ...19846372431
comparison of soil bacterial communities in rhizospheres of three plant species and the interspaces in an arid grassland.soil bacteria are important contributors to primary productivity and nutrient cycling in arid land ecosystems, and their populations may be greatly affected by changes in environmental conditions. in parallel studies, the composition of the total bacterial community and of members of the acidobacterium division were assessed in arid grassland soils using terminal restriction fragment length polymorphism (trf, also known as t-rflp) analysis of 16s rrna genes amplified from soil dna. bacterial com ...200211916705
impact of grazing intensity during drought in an arizona grassland.the ecological benefits of changing cattle grazing practices in the western united states remain controversial, due in part to a lack of experimentation. in 1997 we initiated an experimental study of two rangeland alternatives, cattle removal and high-impact grazing, and compared grassland community responses with those with more conventional, moderate grazing practices. the study was conducted in a high-elevation, semiarid grassland near flagstaff, arizona (u.s.a.). we conducted annual plant su ...200717298514
prevalence of pollen sensitization in younger children who have asthma.it is commonly believed that young children are incapable of pollen sensitization; therefore, skin testing usually is not performed to these allergens. the purpose of this study was to identify the frequency of positive skin tests to outdoor allergens among younger children who have asthma. patients who have asthma, aged 6 months to 10 years, were evaluated for pollen sensitization over a 10-year period. skin-prick testing was performed to relevant individual aeroallergens including trees, grass ...200718201429
genomic organization of ribosomal rna genes in bromus (poaceae).restriction site maps of the rdna genes of nine bromus species are described. the rdna repeat units ranged from 8.2 to 11.1 kbp in length. intraspecific length variation was observed in the bamhi digestions in three of the nine species. restriction site variation was observed mainly in the intergenic spacer (igs) but was also detected in the coding region. a unique kpni site was present in the igs of bromus tectorum and bromus sericeus (subgenus stenobromus); in addition, b. sericeus contained a ...199618469887
effect of between and on row distance of first development, tillering, yield and yield components in wheat cultivars (triticum sp.).this study was carried out at the university of ankara, faculty of agriculture, haymana research and application farm, haymana county, ankara, turkey during 1987/1990 with the aim of to determine the effect of between and on row distances (b(rd) and o(rd), respectively) on the first development, tillering, yield and yield components in wheat cultivars (triticum sp.). five wheat cultivars (bezostaja-i, gerek 79, haymana 79; triticum aestivum l., cakmak 79 and kunduru 1149; triticum durum desf.) w ...200719093497
changes in plant communities along soil pollution gradients: responses of leaf antioxidant enzyme activities and phytochelatin contents.this work describes an ecological and ecotoxicological study of polluted wasteland plant communities in a former coke-factory located in homécourt (france). ecological analyses were performed along two transects to investigate changes in plant community structure through species richness (s), biological diversity (h') and evenness (j). five species (arrhenatherum elatius, bromus tectorum, euphorbia cyparissias, hypericum perforatum and tanacetum vulgare) were then selected to assess cellular res ...200919692108
use of biosolids to enhance rangeland forage quality.biosolids land application was demonstrated to be a potentially cost-effective means for restoring forage productivity and enhancing soil-moisture-holding capacity on disturbed rangelands. by land-applying aerobically digested, anaerobically digested, composted, and lime-stabilized biosolids on rangeland test plots at rates of up to 20 times (20x) the estimated nitrogen-based agronomic rate, forage yields were found to increase from 132.8 kg/ha (118.2 lb/ac) (control plots) to 1182.3 kg/ha (1052 ...201020480767
native perennial grasses show evolutionary response to bromus tectorum (cheatgrass) invasion.invasive species can change selective pressures on native plants by altering biotic and abiotic conditions in invaded habitats. although invasions can lead to native species extirpation, they may also induce rapid evolutionary changes in remnant native plants. we investigated whether adult plants of five native perennial grasses exhibited trait shifts consistent with evolution in response to invasion by the introduced annual grass bromus tectorum l. (cheatgrass), and asked how much variation the ...201121479185
ecological genetics of the bromus tectorum (poaceae)-ustilago bullata (ustilaginaceae) pathosystem: a role for frequency-dependent selection?• premise of the study: evolutionary processes that maintain genetic diversity in plants are likely to include selection imposed by pathogens. negative frequency-dependent selection is a mechanism for maintenance of resistance polymorphism in plant-pathogen interactions. we explored whether such selection operates in the bromus tectorum-ustilago bullata pathosystem. gene-for-gene relationships between resistance and avirulence loci have been demonstrated for this pathosystem. • methods: we used ...201021616883
plutonium uptake and behavior in vegetation of the desert southwest: a preliminary assessment.eight species of desert vegetation and associated soils were collected from the nevada national security site (n2s2) and analyzed for 238pu and 239 + 240pu concentrations. amongst the plant species sampled were: atmospheric elemental accumulators (moss and lichen), the very slow growing, long-lived creosote bush and the rapidly growing, short-lived cheatgrass brome. the diversity of growth strategies provided insight into the geochemical behavior and bio-availability of pu at the n2s2. the highe ...201121796316
correlation between molecular markers and adaptively significant genetic variation in bromus tectorum (poaceae), an inbreedingannual grass.single sequence repeat (ssr) and amplified fragment length polymorphic (aflp) molecular marker genotypes in cheatgrass (bromus tectorum) were compared to published data on phenotypic variation in seed dormancy, vernalization requirement, and resistance to the pathogen ustilago bullata. several features of cheatgrass facilitated this study: it is a recent invader in the western united states, has considerable phenotypic polymorphism, and is an obligate self-pollinator. forty self-pollinating line ...200421653434
introduced annual grass increases regional fire activity across the arid western usa (1980-2009).non-native, invasive grasses have been linked to altered grass-fire cycles worldwide. although a few studies have quantified resulting changes in fire activity at local scales, and many have speculated about larger scales, regional alterations to fire regimes remain poorly documented. we assessed the influence of large-scale bromus tectorum (hereafter cheatgrass) invasion on fire size, duration, spread rate, and interannual variability in comparison to other prominent land cover classes across t ...201223504729
global change effects on bromus tectorum l. (poaceae) at its high-elevation range margin.global change is likely to affect invasive species distribution, especially at range margins. in the eastern sierra nevada, california, usa, the invasive annual grass, bromus tectorum, is patchily distributed and its impacts have been minimal compared with other areas of the intermountain west. we used a series of in situ field manipulations to determine how b. tectorum might respond to changing climatic conditions and increased nitrogen deposition at the high-elevation edge of its invaded range ...201223504728
lack of host specialization on winter annual grasses in the fungal seed bank pathogen pyrenophora semeniperda.generalist plant pathogens may have wide host ranges, but many exhibit varying degrees of host specialization, with multiple pathogen races that have narrower host ranges. these races are often genetically distinct, with each race causing highest disease incidence on its host of origin. we examined host specialization in the seed pathogen pyrenophora semeniperda by reciprocally inoculating pathogen strains from bromus tectorum and from four other winter annual grass weeds (bromus diandrus, bromu ...201626950931
the population biology of bromus tectorum in forests: distinguishing the opportunity for dispersal from environmental restriction.with increasing elevation and corresponding changes in the macroclimate, forest zones in the intermountain region of western north america are often dominated in turn by pinus ponderosa, pseudotsuga menziesii, abies grandis, an thuja plicata. bromus tectorum (cheatgrass), and introduced annual grass now abundant in the region's steppe, is uncommon in mature stands representative of these forest zones. in order to determine whether b. tectorum is largely excluded from these forests by insufficien ...199028312969
the use of stable carbon isotope analysis in rooting studies.stable carbon isotope analysis was evaluated as a means of predicting the relative proportions of c3 and c4 root phytomass in species mixtures. the following mixtures of c3 and c4 species were used: 1) big bluestem (andropogon gerardii)/cheatgrass (bromus tectorum), 2) little bluestem (schizachyrium scoparium)/cheatgrass, and 3) sorghum (sorghum bicolor)/sunflower (helianthus annuus). there was a significant correlation (p<0.01) between % c4 phytomass and stable carbon isotope values for each of ...198528311309
effects of carbohydrate and nitrogen supplementation on fermentation of cheatgrass () in a dual-flow continuous culture system.cheatgrass (cg; ), an introduced winter annual grass, is an aggressive invader of the sagebrush community in the western united states. because of its greater flammability, mature cg constitutes a fire hazard leading to repeated wildfires. one fuel-reduction strategy is livestock grazing. the objective of this study was to evaluate the effects of urea, molasses, or a combination of urea and molasses supplementation of a cg-based diet on digestibility, microbial fermentation, bacterial protein sy ...201728380537
wildfire, climate, and invasive grass interactions negatively impact an indicator species by reshaping sagebrush ecosystems.iconic sagebrush ecosystems of the american west are threatened by larger and more frequent wildfires that can kill sagebrush and facilitate invasion by annual grasses, creating a cycle that alters sagebrush ecosystem recovery post disturbance. thwarting this accelerated grass-fire cycle is at the forefront of current national conservation efforts, yet its impacts on wildlife populations inhabiting these ecosystems have not been quantified rigorously. within a bayesian framework, we modeled 30 y ...201627791084
prefire grazing by cattle increases postfire resistance to exotic annual grass (bromus tectorum) invasion and dominance for decades.fire, herbivory and their interaction influence plant community dynamics. however, little is known about the influence of prefire herbivory on postfire plant community response, particularly long-term resistance to postfire exotic plant invasion in areas that historically experienced limited large herbivore pressure and infrequent, periodic fires.we investigated the long-term postfire effects of prefire herbivory by cattle, an exotic herbivore, in artemisia (sagebrush) plant communities in the n ...201627103990
annual grass invasion in sagebrush steppe: the relative importance of climate, soil properties and biotic interactions.the invasion by winter-annual grasses (ags) such as bromus tectorum into sagebrush steppe throughout the western usa is a classic example of a biological invasion with multiple, interacting climate, soil and biotic factors driving the invasion, although few studies have examined all components together. across a 6000-km(2) area of the northern great basin, we conducted a field assessment of 100 climate, soil, and biotic (functional group abundances, diversity) factors at each of 90 sites that sp ...201626920900
relative abundance of and composition within fungal orders differ between cheatgrass (bromus tectorum) and sagebrush (artemisia tridentata)-associated soils.nonnative bromus tectorum (cheatgrass) is decimating sagebrush steppe, one of the largest ecosystems in the western united states, and is causing regional-scale shifts in the predominant plant-fungal interactions. sagebrush, a native perennial, hosts arbuscular mycorrhizal fungi (amf), whereas cheatgrass, a winter annual, is a relatively poor host of amf. this shift is likely intertwined with decreased carbon (c)-sequestration in cheatgrass-invaded soils and alterations in overall soil fungal co ...201525822987
relative abundance of and composition within fungal orders differ between cheatgrass (bromus tectorum) and sagebrush (artemisia tridentate)-associated soils.nonnative bromus tectorum (cheatgrass) is decimating sagebrush steppe, one of the largest ecosystems in the western united states, and is causing regional-scale shifts in the predominant plant-fungal interactions. sagebrush, a native perennial, hosts arbuscular mycorrhizal fungi (amf), whereas cheatgrass, a winter annual, is a relatively poor host of amf. this shift is likely intertwined with decreased carbon (c)-sequestration in cheatgrass-invaded soils and alterations in overall soil fungal co ...201525629158
the invasive annual cheatgrass increases nitrogen availability in 24-year-old replicated field plots.previous studies comparing invaded and non-invaded sites suggest that cheatgrass (bromus tectorum l.) causes soil n cycling to increase. unfortunately, these correlative studies fail to distinguish whether cheatgrass caused the differences in n cycling, or if cheatgrass simply invaded sites where n availability was greater. we measured soil c and n concentrations and net and gross n-cycling rates on 24-year-old replicated field plots in a sagebrush-steppe ecosystem that had been plowed, fumigate ...201525304974
vegetation response to western juniper slash treatments.the expansion of piñon-juniper woodlands the past 100 years in the western united states has resulted in large scale efforts to kill trees and recover sagebrush steppe rangelands. it is important to evaluate vegetation recovery following woodland control to develop best management practices. in this study, we compared two fuel reduction treatments and a cut-and-leave (cut) treatment used to control western juniper (juniperus occidentalis spp. occidentalis hook.) of the northwestern united states ...201323811771
nitrogen limitation, 15n tracer retention, and growth response in intact and bromus tectorum-invaded artemisia tridentata ssp. wyomingensis communities.annual grass invasion into shrub-dominated ecosystems is associated with changes in nutrient cycling that may alter nitrogen (n) limitation and retention. carbon (c) applications that reduce plant-available n have been suggested to give native perennial vegetation a competitive advantage over exotic annual grasses, but plant community and n retention responses to c addition remain poorly understood in these ecosystems. the main objectives of this study were to (1) evaluate the degree of n limita ...201323001622
trajectories of change in sagebrush steppe vegetation communities in relation to multiple wildfires.repeated perturbations, both biotic and abiotic, can lead to fundamental changes in the nature of ecosystems, including changes in state. sagebrush steppe communities provide important habitat for wildlife and grazing for livestock. fire is an integral part of these systems, but there is concern that increased ignition frequencies and invasive species are fundamentally altering them. despite these issues, the majority of studies of fire effects in systems dominated by artemisia tridentata wyomin ...201222908714
arbuscular mycorrhizal fungal community differs between a coexisting native shrub and introduced annual grass.arbuscular mycorrhizal fungi (amf) have been implicated in non-native plant invasion success and persistence. however, few studies have identified the amf species associating directly with plant invaders, or how these associations differ from those of native plant species. identifying changes to the amf community due to plant invasion could yield key plant-amf interactions necessary for the restoration of native plant communities. this research compared amf associating with coexisting bromus tec ...201322864708
facilitation and interference of seedling establishment by a native legume before and after wildfire.in semi-arid ecosystems, heterogeneous resources can lead to variable seedling recruitment. existing vegetation can influence seedling establishment by modifying the resource and physical environment. we asked how a native legume, lupinus argenteus, modifies microenvironments in unburned and burned sagebrush steppe, and if l. argenteus presence facilitates seedling establishment of native species and the non-native annual grass, bromus tectorum. field treatments examined mechanisms by which l. a ...201221833643
positive effects of native shrubs on bromus tectorum demography.there is increasing recognition that overall interactions among plant species are often the net result of both positive and negative effects. however, the positive influence of other plants has rarely been examined using detailed demographic methods, which are useful for partitioning net effects at the population level into positive and/or negative effects on individual vital rates. this study examines the influence of microhabitats created by the native shrubs artemisia tridentata and purshia t ...201020380204
investing in rangeland restoration in the arid west, usa: countering the effects of an invasive weed on the long-term fire cycle.in large areas of the arid western united states, much of which are federally managed, fire frequencies and associated management costs are escalating as flammable, invasive cheatgrass (bromus tectorum) increases its stronghold. cheatgrass invasion and the subsequent increase in fire frequency result in the loss of native vegetation, less predictable forage availability for livestock and wildlife, and increased costs and risk associated with firefighting. revegetation following fire on land that ...200919781845
interaction of historical and nonhistorical disturbances maintains native plant communities.historical disturbance regimes are often considered a critical element in maintaining native plant communities. however, the response of plant communities to disturbance may be fundamentally altered as a consequence of invasive plants, climate change, or prior disturbances. the appropriateness of historical disturbance patterns under modern conditions and the interactions among disturbances are issues that ecologists must address to protect and restore native plant communities. we evaluated the ...200919769101
post-fire seeding on wyoming big sagebrush ecological sites: regression analyses of seeded nonnative and native species densities.since the mid-1980s, sagebrush rangelands in the great basin of the united states have experienced more frequent and larger wildfires. these fires affect livestock forage, the sagebrush/grasses/forbs mosaic that is important for many wildlife species (e.g., the greater sage grouse (centrocercus urophasianus)), post-fire flammability and fire frequency. when a sagebrush, especially a wyoming big sagebrush (artemisia tridentata ssp. wyomingensis (beetle & a. young)), dominated area largely devoid ...200918790557
the adaptive value of remnant native plants in invaded communities: an example from the great basin.changes in the species composition of biotic communities may alter patterns of natural selection occurring within them. native perennial grass species in the intermountain west are experiencing a shift in the composition of interspecific competitors from primarily perennial species to an exotic, annual grass. thus traits that confer an advantage to perennial grasses in the presence of novel annual competitors may evolve in invaded communities. here i show that such traits are apparent in populat ...200818686583
net carbon exchange and evapotranspiration in postfire and intact sagebrush communities in the great basin.invasion of non-native annuals across the intermountain west is causing a widespread transition from perennial sagebrush communities to fire-prone annual herbaceous communities and grasslands. to determine how this invasion affects ecosystem function, carbon and water fluxes were quantified in three, paired sagebrush and adjacent postfire communities in the northern great basin using a 1-m3 gas exchange chamber. most of the plant cover in the postfire communities was invasive species including b ...200616151860
microbial dynamics and carbon and nitrogen cycling following re-wetting of soils beneath two semi-arid plant species.sporadic summer rainfall in semi-arid ecosystems can provide enough soil moisture to drastically increase co(2) efflux and rates of soil n cycling. the magnitudes of c and n pulses are highly variable, however, and the factors regulating these pulses are poorly understood. we examined changes in soil respiration, bacterial, fungal and microfaunal populations, and gross rates of n mineralization, nitrification, and nh(4) (+) and no(3) (-) immobilization during the 10 days following wetting of dry ...200515490245
impact of early root competition on fitness components of four semiarid species.plant demographic and root exclusion approaches were used to examine the influence of roots of adult artemisia tridentata, agropyron desertorum, and agropyron spicatum individuals on seedling survival of four c3 semiarid species, three perennials, ar. tridentata, ag. desertorum, ag. spicatum, and an annual, bromus tectorum. furthermore, height of ar. tridentata seedlings and seed production of b. tectorum were assessed. the probability of a seedling being alive significantly depended on the seed ...199028312551
edaphic limitations to growth and photosynthesis in sierran and great basin vegetation.soils derived from hydrothermally altered andesite support unique communities of sierran conifers (pinus ponderosa laws. and p. jeffreyi grev. and balf.) amongst sagebrush (artemisia tridentata nutt.) vegetation in the western great basin. plants grown in soil derived from hydrothermally altered bedrock had lower growth rates, total biomass, and net photosynthetic rates than plants grown in soil derived from unaltered andesite of the same formation. total dry mass was 10 to 28% lower for conifer ...198928312357
native seed preferences of shrub-steppe rodents, birds and ants: the relationships of seed attributes and seed use.this study established the preferences of shrubsteppe granivores among seeds of 6 common sagebrushsteppe plants and related the preferences observed to physical and nutritional attributes of the seeds. seeds of big sagebrush (artemisia tridentata), cheatgrass (bromus tectorum), indian ricegrass (oryzopsis hymenoides), western wheatgrass (pascopyrum smithii), bitterbrush (purshia tridentata) and green needlegrass (stipa viridula) were placed in groups of petri dishes designed such that seed remov ...198628311774
effect of sagebrush distillate on the germination of cheatgrass seed. bnwl-714. 19685306302
allergen of the month--downy chess. 201222840262
when perception reflects reality: non-native grass invasion alters small mammal risk landscapes and survival.modification of habitat structure due to invasive plants can alter the risk landscape for wildlife by, for example, changing the quality or availability of refuge habitat. whether perceived risk corresponds with actual fitness outcomes, however, remains an important open question. we simultaneously measured how habitat changes due to a common invasive grass (cheatgrass, bromus tectorum) affected the perceived risk, habitat selection, and apparent survival of a small mammal, enabling us to assess ...201728331590
species' traits help predict small mammal responses to habitat homogenization by an invasive grass.invasive plants can negatively affect native species, however, the strength, direction, and shape of responses may vary depending on the type of habitat alteration and the natural history of native species. to prioritize conservation of vulnerable species, it is therefore critical to effectively predict species' responses to invasive plants, which may be facilitated by a framework based on species' traits. we studied the population and community responses of small mammals and changes in habitat ...201728317278
phytotoxic activity against bromus tectorum for secondary metabolites of a seed-pathogenic fusarium strain belonging to the f. tricinctum species complex.the winter annual grass bromus tectorum (cheatgrass) has become highly invasive in semiarid ecosystems of western north america. in these areas, a natural phenomenon, complete cheatgrass stand failure ('die-off'), is apparently caused by a complex interaction among soilborne fungal pathogens. several fusarium strains belonging to the fusarium tricinctum species complex were isolated from these soils and found to be pathogenic on b. tectorum seeds. one of these strains was produced in cheatgrass ...201728278617
biotic resistance and disturbance: rodent consumers regulate post-fire plant invasions and increase plant community diversity.biotic resistance and disturbance are fundamental processes influencing plant invasion outcomes; however, the role of consumers in regulating the establishment and spread of plant invaders and how disturbance modifies biotic resistance by consumers is unclear. we document that fire in combination with experimental exclusion of rodent consumers shifted a native desert shrubland to a low-diversity, invasive annual grassland dominated by bromus tectorum (cheatgrass). in contrast, burned plots with ...201627859155
development of single-nucleotide polymorphism markers for bromus tectorum (poaceae) from a partially sequenced transcriptome.bromus tectorum (poaceae) is an annual grass species that is invasive in many areas of the world but most especially in the u.s. intermountain west. single-nucleotide polymorphism (snp) markers were developed for use in investigating the geospatial and ecological diversity of b. tectorum in the intermountain west to better understand the mechanisms behind its successful invasion.201627843723
soil aggregate dynamics and plant community response after biosolids application in a semiarid grassland.biosolids may improve the ecological function of degraded semiarid grasslands, but an understanding of the plant community is essential. an experiment was established in 2001 to determine the effects of a single surface application of biosolids on soil aggregate stability and the composition of the plant community in a semiarid grassland in british columbia, canada. four treatments were evaluated: (i) surface biosolids application at 20 (bio-20) and (ii) 60 mg ha (bio-60), (iii) mineral fertiliz ...201627695737
cascading effects of fire retardant on plant-microbe interactions, community composition, and invasion.climate change, historical fire suppression, and a rise in human movements in urban-forest boundaries have resulted in an increased use of long-term fire retardant (ltfr). while ltfr is an effective fire-fighting tool, it contains high concentrations of nitrogen and phosphorus, and little is known about how this nutrient pulse affects terrestrial ecosystems. we used field surveys and greenhouse experiments to quantify effects of ltfr on plant productivity, community composition, and plant intera ...201627509743
imposing antecedent global change conditions rapidly alters plant community composition in a mixed-grass prairie.global change drivers are altering climatic and edaphic conditions of ecosystems across the globe, and we expect novel plant communities to become more common as a result. in the colorado front range, compositional changes have occurred in the mixed-grass prairie plant community in conjunction with shifts in winter precipitation and atmospheric nitrogen (n) deposition. to test whether these environmental changes have been responsible for the observed plant community change, we conducted an in si ...201627405299
selective foraging by pogonomyrmex salinus (hymenoptera: formicidae) in semiarid grassland: implications for a rare plant.selective foraging by granivores can have important consequences for the structure and composition of plant communities, and potentially severe consequences for rare plant species. to understand how granivore foraging behavior affects common and rare plant species, diet selection should be viewed relative to the availability of alternative seed options, and with consideration of the individual attributes of those seeds (e.g., morphology, nutrient content). we examined the foraging decisions of o ...201627357161
polycyclic aromatic hydrocarbons in biomass-burning emissions and their contribution to light absorption and aerosol toxicity.in recent years, brown carbon (brc) has been shown to be an important contributor to light absorption by biomass-burning atmospheric aerosols in the blue and near-ultraviolet (uv) part of the solar spectrum. emission factors and optical properties of 113 polycyclic aromatic hydrocarbons (pahs) were determined for combustion of five globally important fuels: alaskan, siberian, and florida swamp peat, cheatgrass (bromus tectorum), and ponderosa pine (pinus ponderosa) needles. the emission factors ...201627304373
cheatgrass is favored by warming but not co2 enrichment in a semi-arid grassland.elevated co2 and warming may alter terrestrial ecosystems by promoting invasive plants with strong community and ecosystem impacts. invasive plant responses to elevated co2 and warming are difficult to predict, however, because of the many mechanisms involved, including modification of phenology, physiology, and cycling of nitrogen and water. understanding the relative and interactive importance of these processes requires multifactor experiments under realistic field conditions. here, we test h ...201627090757
revisiting the life cycle of dung fungi, including sordaria fimicola.dung fungi, such as sordaria fimicola, generally reproduce sexually with ascospores discharged from mammalian dung after passage through herbivores. their life cycle is thought to be obligate to dung, and thus their ascospores in quaternary sediments have been interpreted as evidence of past mammalian herbivore activity. reports of dung fungi as endophytes would seem to challenge the view that they are obligate to dung. however, endophyte status is controversial because surface-sterilization pro ...201626839959
the invasive annual cheatgrass releases more nitrogen than crested wheatgrass through root exudation and senescence.plant-soil feedbacks are an important aspect of invasive species success. one type of feedback is alteration of soil nutrient cycling. cheatgrass invasion in the western usa is associated with increases in plant-available nitrogen (n), but the mechanism for this has not been elucidated. we labeled cheatgrass and crested wheatgrass, a common perennial grass in western rangelands, with (15)n-urea to determine if differences in root exudates and turnover could be a mechanism for increases in soil n ...201626796411
postdispersal infection and disease development of pyrenophora semeniperda in bromus tectorum seeds.the ascomycete fungus, pyrenophora semeniperda, attacks a broad range of cool-season grasses. while leaf and predispersal infection of seeds (i.e., florets containing caryopses) have been previously characterized, little is known about the pathogenesis of mature seeds following dispersal. in this study, we examined infection and disease development of p. semeniperda on dormant seeds of bromus tectorum. inoculated seeds were hydrated at 20°c for up to 28 days. disease development was characterize ...201626645644
constraints on coastal dune invasion for a notorious plant invader.although most biological invasions are not successful, relatively few studies have examined otherwise notorious invaders in systems where they are not highly problematic. the annual grass bromus tectorum is a dominant invader in western north america, but is usually confined to human-dominated and disturbed systems (e.g. roadsides and parking lots) in the east where it remains virtually unstudied. this study aims to address fundamental ecological questions regarding b. tectorum in a cape cod dun ...201526558705
diel patterns of colaspis brunnea and colaspis crinicornis (coleoptera: chrysomelidae) in southeastern nebraska.a field study was conducted to increase our understanding of diel activity patterns of colaspis brunnea (f.) and colaspis crinicornis schaeffer (coleoptera: chrysomelidae) in key crop habitats. within 24-h periods, c. brunnea was sampled in clover fields (primarily red clover, trifolium pretense (l.), with some sweet clover, melilotus officinalis (l.) pallas, and downy brome, bromus tectorum (l.)) and soybean, glycine max (l.) merrill, fields, using a sweep-net, while whole-plant-count sampling ...201526314034
increased primary production from an exotic invader does not subsidize native rodents.invasive plants have tremendous potential to enrich native food webs by subsidizing net primary productivity. here, we explored how a potential food subsidy, seeds produced by the aggressive invader cheatgrass (bromus tectorum), is utilized by an important guild of native consumers--granivorous small mammals--in the great basin desert, usa. in a series of field experiments we examined 1) how cheatgrass invasion affects the density and biomass of seed rain at the ecosystem-level; 2) how seed reso ...201526244345
hydrothermal time models for conidial germination and mycelial growth of the seed pathogen pyrenophora semeniperda.population-based threshold models using hydrothermal time (htt) have been widely used to model seed germination. we used htt to model conidial germination and mycelial growth for the seed pathogen pyrenophora semeniperda in a novel approach to understanding its interactions with host seeds. germination time courses and mycelial growth rates for p.semeniperda were measured on pda amended to achieve a series of five water potentials (ca. 0 to -6 mpa) at six constant temperatures (5-30 °c). conidia ...201526228560
effects of precipitation change and neighboring plants on population dynamics of bromus tectorum.shifting precipitation patterns resulting from global climate change will influence the success of invasive plant species. in the front range of colorado, bromus tectorum (cheatgrass) and other non-native winter annuals have invaded grassland communities and are becoming more abundant. as the global climate warms, more precipitation may fall as rain rather than snow in winter, and an increase in winter rain could benefit early-growing winter annuals, such as b. tectorum, to the detriment of nati ...201526227366
consequences of seed origin and biological invasion for early establishment in restoration of a north american grass species.local, wild-collected seeds of native plants are recommended for use in ecological restoration to maintain patterns of adaptive variation. however, some environments are so drastically altered by exotic, invasive weeds that original environmental conditions may no longer exist. under these circumstances, cultivated varieties selected for improved germination and vigor may have a competitive advantage at highly disturbed sites. this study investigated differences in early establishment and seedli ...201525741702
using high-resolution future climate scenarios to forecast bromus tectorum invasion in rocky mountain national park.national parks are hallmarks of ecosystem preservation in the united states. the introduction of alien invasive plant species threatens protection of these areas. bromus tectorum l. (commonly called downy brome or cheatgrass), which is found in rocky mountain national park (hereafter, the park), colorado, usa, has been implicated in early spring competition with native grasses, decreased soil nitrogen, altered nutrient and hydrologic regimes, and increased fire intensity. we estimated the potent ...201525695255
interacting agricultural pests and their effect on crop yield: application of a bayesian decision theory approach to the joint management of bromus tectorum and cephus cinctus.worldwide, the landscape homogeneity of extensive monocultures that characterizes conventional agriculture has resulted in the development of specialized and interacting multitrophic pest complexes. while integrated pest management emphasizes the need to consider the ecological context where multiple species coexist, management recommendations are often based on single-species tactics. this approach may not provide satisfactory solutions when confronted with the complex interactions occurring be ...201525692673
suppression of annual bromus tectorum by perennial agropyron cristatum: roles of soil nitrogen availability and biological soil space.worldwide, exotic invasive grasses have caused numerous ecosystem perturbations. rangelands of the western usa have experienced increases in the size and frequency of wildfires largely due to invasion by the annual grass bromus tectorum. rehabilitation of invaded rangelands is difficult; but long-term success is predicated on establishing healthy and dense perennial grass communities, which suppress b. tectorum. this paper reports on two experiments to increase our understanding of soil factors ...201525603967
differing effects of biosolids on native plants in grasslands of southern british columbia.the objective of this study was to determine if application of biosolids is beneficial for restoring semiarid grasslands. the effects of a one-time surface application of biosolids at a rate of 20 mg ha on individual plant species and plant community composition were examined at three degraded semiarid grassland sites located in the southern interior of british columbia, canada. biosolids application did not result in desirable changes in plant species composition at the two drier sites (with an ...201425603253
plastic responses of native plant root systems to the presence of an invasive annual grass.201525587150
altered snowfall and soil disturbance influence the early life stage transitions and recruitment of a native and invasive grass in a cold desert.climate change effects on plants are expected to be primarily mediated through early life stage transitions. snowfall variability, in particular, may have profound impacts on seedling recruitment, structuring plant populations and communities, especially in mid-latitude systems. these water-limited and frequently invaded environments experience tremendous variation in snowfall, and species in these systems must contend with harsh winter conditions and frequent disturbance. in this study, we exam ...201525539620
identification of the infection route of a fusarium seed pathogen into nondormant bromus tectorum seeds.the genus fusarium has a wide host range and causes many different forms of plant disease. these include seed rot and seedling blight diseases of cultivated plants. the diseases caused by fusarium on wild plants are less well-known. in this study, we examined disease development caused by fusarium sp. n on nondormant seeds of the important rangeland weed bromus tectorum as part of broader studies of the phenomenon of stand failure or "die-off" in this annual grass. we previously isolated an unde ...201425389704
native and exotic plant cover vary inversely along a climate gradient 11 years following stand-replacing wildfire in a dry coniferous forest, oregon, usa.community re-assembly following future disturbances will often occur under warmer and more moisture-limited conditions than when current communities assembled. because the establishment stage is regularly the most sensitive to climate and competition, the trajectory of recovery from disturbance in a changing environment is uncertain, but has important consequences for future ecosystem functioning. to better understand how ongoing warming and rising moisture limitation may affect recovery, we stu ...201525345790
negative effects of an exotic grass invasion on small-mammal communities.exotic invasive species can directly and indirectly influence natural ecological communities. cheatgrass (bromus tectorum) is non-native to the western united states and has invaded large areas of the great basin. changes to the structure and composition of plant communities invaded by cheatgrass likely have effects at higher trophic levels. as a keystone guild in north american deserts, granivorous small mammals drive and maintain plant diversity. our objective was to assess potential effects o ...201425269073
pyrenophoric acids b and c, two new phytotoxic sesquiterpenoids produced by pyrenophora semeniperda.two new phytotoxic sesquiterpenoid acids, named pyrenophoric acids b and c, were isolated together with the related pyrenophoric and abscisic acids from solid bromus tectorum (cheatgrass) seed culture of the seed pathogen pyrenophora semeniperda. this fungus has been proposed as a mycoherbicide for biocontrol of cheatgrass (bromus tectorum), a eurasian annual grass that has become invasive in rangelands and is also a serious agricultural weed in the western u.s. pyrenophoric acids b and c were c ...201425264583
granivory of invasive, naturalized, and native plants in communities differentially susceptible to invasion.seed predation is an important biotic filter that can influence abundance and spatial distributions of native species through differential effects on recruitment. this filter may also influence the relative abundance of nonnative plants within habitats and the communities' susceptibility to invasion via differences in granivore identity, abundance, and food preference. we evaluated the effect of postdispersal seed predators on the establishment of invasive, naturalized, and native species within ...201425163110
pyrenophoric acid, a phytotoxic sesquiterpenoid penta-2,4-dienoic acid produced by a potential mycoherbicide, pyrenophora semeniperda.a new phytotoxic sesquiterpenoid penta-2,4-dienoic acid, named pyrenophoric acid, was isolated from solid wheat seed culture of pyrenophora semeniperda, a fungal pathogen proposed as a mycoherbicide for biocontrol of cheatgrass (bromus tectorum) and other annual bromes. these bromes are serious weeds in winter cereals and also on temperate semiarid rangelands. pyrenophoric acid was characterized as (2z,4e)-5-[(7s,9s,10r,12r)-3,4-dihydroxy-2,2,6-trimethylcyclohexyl)]-3-methylpenta-2,4-dienoic aci ...201424641210
despite spillover, a shared pathogen promotes native plant persistence in a cheatgrass-invaded grassland.how pathogen spillover influences host community diversity and composition is poorly understood. spillover occurs when transmission from a reservoir host species drives infection in another host species. in cheatgrass-invaded grasslands in the western united states, a fungal seed pathogen, black fingers of death (pyrenophora semeniperda), spills over from exotic cheatgrass (bromus tectorum) to native perennial bunchgrasses such as squirreltail (elymus elymoides). previous theoretical work based ...201324597221
de novo genome assembly of the fungal plant pathogen pyrenophora semeniperda.pyrenophora semeniperda (anamorph drechslera campulata) is a necrotrophic fungal seed pathogen that has a wide host range within the poaceae. one of its hosts is cheatgrass (bromus tectorum), a species exotic to the united states that has invaded natural ecosystems of the intermountain west. as a natural pathogen of cheatgrass, p. semeniperda has potential as a biocontrol agent due to its effectiveness at killing seeds within the seed bank; however, few genetic resources exist for the fungus. he ...201424475219
indirect effects of an invasive annual grass on seed fates of two native perennial grass species.invasive plants exhibit both direct and indirect negative effects on recruitment of natives following invasion. we examined indirect effects of the invader bromus tectorum (cheatgrass) on seed fates of two native grass species, elymus elymoides and pseudoroegneria spicata, by removing b. tectorum and by adding inoculum of the shared seed pathogen pyrenophora semeniperda in factorial experiments at xeric and mesic field sites. we also included a supplemental watering treatment to increase emergen ...201424399482
eco-evolutionary responses of bromus tectorum to climate change: implications for biological invasions.how plant populations, communities, and ecosystems respond to climate change is a critical focus in ecology today. the responses of introduced species may be especially rapid. current models that incorporate temperature and precipitation suggest that future bromus tectorum invasion risk is low for the colorado plateau. with a field warming experiment at two sites in southeastern utah, we tested this prediction over 4 years, measuring b. tectorum phenology, biomass, and reproduction. in a complim ...201323762522
consequences of pathogen spillover for cheatgrass-invaded grasslands: coexistence, competitive exclusion, or priority effects.with the rise in species invasions and emerging infectious diseases, pathogen spillover from abundant reservoir hosts to their competitors is increasingly common. although the potential for pathogen spillover is widespread, its consequences for host community composition remain poorly understood. to address this gap, i examine the consequences of fungal seed pathogen spillover from an exotic annual grass (cheatgrass) to a native perennial bunchgrass in the intermountain west, united states, usin ...201323669537
the ghost of outcrossing past in downy brome, an inbreeding annual grass.we investigated the frequency of outcrossing in downy brome (bromus tectorum l.), a cleistogamous weedy annual grass, in both common garden and wild populations, using microsatellite and single nucleotide polymorphic (snp) markers. in the common garden study, 25 lines with strongly contrasting genotypes were planted in close proximity. we fingerprinted 10 seed progeny from 8 individuals of each line and detected 15 first-generation heterozygotes for a t-value (corrected for cryptic crosses) of 0 ...201323564960
severe plant invasions can increase mycorrhizal fungal abundance and diversity.invasions by non-native plants can alter ecosystem functions and reduce native plant diversity, but relatively little is known about their effect on belowground microbial communities. we show that invasions by knapweed (centaurea stoebe) and leafy spurge (euphorbia esula, hereafter spurge)--but not cheatgrass (bromus tectorum)--support a higher abundance and diversity of symbiotic arbuscular mycorrhizal fungi (amf) than multi-species native plant communities. the higher amf richness associated w ...201323486251
temperature and functional traits influence differences in nitrogen uptake capacity between native and invasive grasses.performance differences between native and exotic invasive plants are often considered static, but invasive grasses may achieve growth advantages in western north america shrublands and steppe under only optimal growing conditions. we examine differences in n uptake and several morphological variables that influence uptake at temperatures between 5 and 25 °c. we contrast two native perennial grasses in western north america: elymus elymoides and pseudoroegneria spicata; two invasive annual grass ...201322744743
population genetic analysis of bromus tectorum (poaceae) indicates recent range expansion may be facilitated by specialist genotypes.the mechanisms for range expansion in invasive species depend on how genetic variation is structured in the introduced range. this study examined neutral genetic variation in the invasive annual grass bromus tectorum in the intermountain western united states. patterns of microsatellite (ssr) genotype distribution in this highly inbreeding species were used to make inferences about the roles of adaptively significant genetic variation, broadly adapted generalist genotypes, and facultative outcro ...201222358042
a novel plant-fungal mutualism associated with fire.bromus tectorum, or cheatgrass, is native to eurasia and widely invasive in western north america. by late spring, this annual plant has dispersed its seed and died; its aboveground biomass then becomes fine fuel that burns as frequently as once every 3-5 y in its invaded range. cheatgrass has proven to be better adapted to fire there than many competing plants, but the contribution of its fungal symbionts to this adaptation had not previously been studied. in sampling cheatgrass endophytes, man ...201222208608
invasive competitor and native seed predators contribute to rarity of the narrow endemic astragalus sinuatus piper.the conservation of rare plant species hinges on our ability to identify the underlying mechanisms that limit rare plant populations. theory on rarity suggests that both predispersal seed predation and competition can be important mechanisms influencing abundance and/or distribution of rare plant populations. yet few studies have tested these interactions, and those that have evaluated each mechanism independently. astragalus sinuatus piper (whited's milkvetch) is a narrow endemic plant species ...201122073639
ecotoxicological study of arsenic and lead contaminated soils in former orchards at the hanford site, usa.the purpose of this study was to assess ecotoxicity of former orchard soils contaminated with lead arsenate pesticides at the hanford site in washington state (usa). surface soil, plant, and invertebrate samples were collected from 11 sites in former orchard areas. mean (standard deviation [sd]) for as and pb in soil were 39.5 (40.6) and 208 (142) mg/kg dry wt, respectively (n = 11). these concentrations exceeded hanford background levels but were similar to orchard soils elsewhere. in our study ...201421922631
allometry of root branching and its relationship to root morphological and functional traits in three range grasses.the study of proportional relationships between size, shape, and function of part of or the whole organism is traditionally known as allometry. examination of correlative changes in the size of interbranch distances (ibds) at different root orders may help to identify root branching rules. root morphological and functional characteristics in three range grasses {bluebunch wheatgrass [pseudoroegneria spicata (pursh) löve], crested wheatgrass [agropyron desertorum (fisch. ex link) schult.×a. crist ...201121868398
competitive seedlings and inherited traits: a test of rapid evolution of elymus multisetus (big squirreltail) in response to cheatgrass invasion.widespread invasion by bromus tectorum (cheatgrass) in the intermountain west has drastically altered native plant communities. we investigated whether elymus multisetus (big squirreltail) is evolving in response to invasion and what traits contribute to increased performance. seedlings from invaded areas exhibited significantly greater tolerance to b. tectorum competition and a greater ability to suppress b. tectorum biomass than seedlings from adjacent uninvaded areas. to identify potentially ...201125567997
population genetic structure of the seed pathogen pyrenophora semeniperda on bromus tectorum in western north america.we examined genetic variation in the ascomycete pathogen pyrenophora semeniperda cultured from seeds of the invasive grass bromus tectorum in the intermountain west of north america. we sequenced the internal transcribed spacer (its) region of the nuclear ribosomal rna genome in 417 monoconidial cultures collected from 20 sites in washington, idaho, utah and colorado, usa. its sequence diversity was surprisingly high; 12 unique haplotypes were identified, averaging 1.3% pairwise sequence diverge ...201120943557
effects of climate and snow depth on bromus tectorum population dynamics at high elevation.invasive plants are thought to be especially capable of range shifts or expansion in response to climate change due to high dispersal and colonization abilities. although highly invasive throughout the intermountain west, the presence and impact of the grass bromus tectorum has been limited at higher elevations in the eastern sierra nevada, potentially due to extreme wintertime conditions. however, climate models project an upward elevational shift of climate regimes in the sierra nevada that co ...201020740291
winter annual cover crop has only minor effects on major corn arthropod pests.we studied the effects of downy brome, bromus tectorum l., winter cover crop on several corn, zea mays l., pests in the summer crop after the cover crop. an experiment was conducted that consisted of two trials with two levels of irrigation, two levels of weed control, and two levels of downy brome. corn was grown three consecutive years after the downy brome grown during the winter. banks grass mites, oligonychus pratensis (banks), twospotted spider mites, tetranychus urticae koch, and predator ...201020429447
the quick and the deadly: growth vs virulence in a seed bank pathogen.*we studied the relationship between virulence (ability to kill nondormant bromus tectorum seeds) and mycelial growth index in the necrotrophic seed pathogen pyrenophora semeniperda. seed pathosystems involving necrotrophs differ from those commonly treated in traditional evolution-of-virulence models in that host death increases pathogen fitness by preventing germination, thereby increasing available resources. because fast-germinating, nondormant b. tectorum seeds commonly escape mortality, we ...201020406404
remote sensing-based time-series analysis of cheatgrass (bromus tectorum l.) phenology.the western united states is under invasion from cheatgrass (bromus tectorum l.), an annual grass that alters the pattern of phenology in the ecosystems it infests. this study was conducted to investigate methods for monitoring this invasion. as a result of its annual phenology, cheatgrass is not only an extremely competitive invader, it is also detectible from time series of remotely sensed data. using the moderate resolution imaging spectro-radiometer (modis) normalized difference vegetation i ...201020400591
variability in c(3)-plant cell-wall biosynthesis in a high-co(2) atmosphere by solid-state nmr spectroscopy.we have used a frequency-selective rotational-echo double-resonance (redor) solid-state nmr experiment to measure the concentrations of glycine-glycine pairs in proteins (and protein precursors) of intact leaves of plants exposed to both high- and low-co(2) atomospheres. the results are interpreted in terms of differences in cell-wall biosynthesis between plant species. we illustrate this variability by comparing the assimilation of label in cheatgrass and soybean leaves labeled using (15)n-fert ...201020394366
genetic variation and local adaptation at a cheatgrass (bromus tectorum) invasion edge in western nevada.cheatgrass (bromus tectorum) is an invasive weed in western north america found primarily growing at elevations less than 2200 m. we asked whether cheatgrass is capable of becoming adapted to a marginal habitat, by investigating a population at a high elevation invasion edge. we used a combination of methods, including reciprocal field transplants, controlled environment studies and molecular analysis. high levels of ssr gene diversity (0.50 vs. 0.43) and comparable variation in phenotypic trait ...200919769691
responses of wild plant species to polycyclic aromatic hydrocarbons in soil.responses of plants to polycyclic aromatic hydrocarbons (pahs) contamination were determined with fifty-five korean wild plants. responsiveness of species was evaluated based on germination and shoot weight and shoot length of plants grown in soil spiked with four pahs (pyrene, fluorene, phenanthrene and fluoranthene). seeds of test plants were germinated with mixtures of pahs of 0, 10, 30, 100, 300 mg kg(-1) spiked in soil. seed germination of test plants changed when subjected to pahs. as comp ...200919724837
herbicidal activity of glucosinolate degradation products in fermented meadowfoam ( limnanthes alba ) seed meal.meadowfoam ( limnanthes alba ) is an oilseed crop grown in western oregon. after extraction of the oil from the seeds, the remaining seed meal contains 2-4% of the glucosinolate glucolimnanthin. this study investigated the effect of fermentation of seed meal on its chemical composition and the effect of the altered composition on downy brome ( bromus tectorum ) coleoptile emergence. incubation of enzyme-inactive seed meal with enzyme-active seeds (1% by weight) resulted in complete degradation o ...200919170637
bromus tectorum (poaceae) in midcontinental united states: population genetic analysis of an ongoing invasion.biological invasions can be substantially influenced by the genetic sampling associated with a species' introduction. as a result, we assessed the genetic and evolutionary consequences of the entry and spread of the invasive grass bromus tectorum (cheatgrass) across the united states midcontinent through an analysis of 54 populations, using enzyme electrophoresis. on average, these populations display 1.04 alleles per locus (a), 4.1% percent polymorphic loci per population (%p) and an expected m ...200821628165
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