Publications

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 ...	2015	25692673
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 ...	2015	25695255
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 ...	2015	25304974
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 ...	2015	25629158
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 ...	2015	25822987
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 ...	2016	26920900
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 ...	2016	27103990
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 ...	2016	27791084
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 ...	2016	26950931
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 ...	2016	27695737
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 ...	2016	27509743
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 ...	2016	27090757
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 ...	2016	26839959
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 ...	2016	26796411
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 ...	2016	26645644
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 ...	2016	27405299
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 ...	2016	27357161
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 ...	2016	27859155
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.	2016	27843723
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 ...	2016	27304373
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 ...	2017	28317278
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 ...	2017	28278617
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 ...	2017	28331590
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 ...	2017	28380537