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Full-Text Articles in Life Sciences
Descriptions, Ecological Associations And Predictive Species Distribution Models Of New Species Of Psilochalcis Kieffer (Hymenoptera; Chalcididae) Occurring In Utah's Eastern Great Basin, Mark J. Petersen
Theses and Dissertations
The genus Psilochalcis, of the Family Chalcididae, was originally described in 1905 by Kieffer. Mainly considered an Old-World taxon, the first North American Psilochalcis were not identified until 1981 by Grissell and Schauff. Little is known about the species distributions, biologies and ecological relationships of these parasitic wasps. This dissertation describes research conducted in central Utah setting arrays of Malaise traps in 4 different habitat types common to the Great Basin at three separate locations. A result of this sampling revealed a high abundance of multiple species of Psilochalcis wasps, particularly from one location and two habitat types. Chapter 1 …
Improving Perennial Bunchgrass Seeding Success In Annual Grass Invaded Areas Using Pre-Emergent Herbicide And Furrowing Techniques, Spencer Chad Camp
Improving Perennial Bunchgrass Seeding Success In Annual Grass Invaded Areas Using Pre-Emergent Herbicide And Furrowing Techniques, Spencer Chad Camp
Theses and Dissertations
Exotic annual weeds have transformed western North America, particularly in sagebrush-steppe systems. Restoration of these invaded sites has been met with low levels of success. Pre-emergent herbicide provides a means to control annual weeds, but typically, this treatment does not allow for the concurrent seeding of desired species. Seeding within a deep, U-shaped furrow following herbicide application may be a method to reduce pre-emergent herbicide effects by transferring the herbicide away from the seed at the time of planting. We tested this potential planting technique by spraying plots with or without the pre-emergent herbicide imazapic, and planting bunchgrass seeds either …
Using Herbicide And Planting Techniques To Restore A Native Bunchgrass To Cheatgrass Invaded Systems, Tyson Jeffrey Terry
Using Herbicide And Planting Techniques To Restore A Native Bunchgrass To Cheatgrass Invaded Systems, Tyson Jeffrey Terry
Theses and Dissertations
This thesis explores potential seeding techiniques to limit harmful effects of preemergent herbicide on a seeded species while simultaneously reducing abudance of annual invasive grasses. The first chapter examines the use of activated carbon seed coatings and furrows to limit herbicide effect on seeds of a perrenial bunchgrass. We found that both carbon coatings and furrows mitigated some of the herbicide effects, but that only when the two techniques were combined did we observe unaffected seedling emergence, plant density, and aboveground growth. Therefore, we suggest to management that use of carbon coatings and furrows after herbicide application can likely be …
Of Fire, Mammals, And Rain: Mechanisms Of Plant Invasions, Tara Boyce Bishop
Of Fire, Mammals, And Rain: Mechanisms Of Plant Invasions, Tara Boyce Bishop
Theses and Dissertations
Biological invasions are driving environmental state changes on a global scale. Exotic plant species must be successful at passing several abiotic and biotic filters to establish and disrupt the native plant community assembly. Understanding where exotic plants are on a regional scale and being able to characterize how exotic plants are generally interacting with their environment is crucial information for exotic species management (chapter 1). In the western United States human-related activities are augmenting the spread of exotic plant species by increasing the ignitions of wildfire. Wildfire can lead to nutrient pulses through the removal of intact native communities and …
Evaluating Fungal Pathogen Inoculum Loads In Field Seed Banks, Taryn Lori Williamson
Evaluating Fungal Pathogen Inoculum Loads In Field Seed Banks, Taryn Lori Williamson
Theses and Dissertations
Quantification of soilborne pathogen inoculum loads is important in both agricultural and wildland settings. Quantitative Polymerase Chain Reaction (qPCR) methods using SYBR Green chemistry have been shown to be useful for quantifying fungal inoculum loads in environmental samples. The purpose of this study was to develop a method to quantify fungal pathogen inoculum loads in soil seed banks using a qPCR method with SYBR Green chemistry. The invasive annual grass Bromus tectorum was chosen for this seed bank study. There were three objectives: 1) to design target-specific primers for three fungal pathogens known to be important in Bromus tectorum seed …
The Responses Of Ants And Other Invertebrates To Fire And Rodent Activity In North American Deserts, Joshua David Day
The Responses Of Ants And Other Invertebrates To Fire And Rodent Activity In North American Deserts, Joshua David Day
Theses and Dissertations
Human activities are increasing the size, frequency and severity of disturbance across earth’s ecosystems including deserts. Exotic annual grasses have altered fire regimes by increasing the size, frequency, and severity of fires in these systems. Invertebrates make up a large proportion of ecosystem diversity, provide a wide range of ecosystem functions, and are good indicators of ecosystem function and resilience. Ants are particularly good indicators of ecosystem stability. The ability of rodents to modify plant community structure post-fire, could result in rodent communities having important indirect effects on invertebrate communities. In chapter 1 we report changes in ant forager abundance …
Cheatgrass Die-Off Phenomena: What Are The Short And Long Term Recovery Factors Of Bromus Tectorum Stand Failure?, Joshua Alan Nicholson
Cheatgrass Die-Off Phenomena: What Are The Short And Long Term Recovery Factors Of Bromus Tectorum Stand Failure?, Joshua Alan Nicholson
Theses and Dissertations
Observations of Bromus tectorum L. (cheatgrass or downy brome) monocultures have shown that populations are susceptible to stand die-off or replacement failures. Die-offs, where the seed bank from the previous year fails to emerge, occurs in cheatgrass stands and it is unclear the trigger or cause. The fungus Fusarium has been identified in plant and seed samples from die-offs and may drive die-off activity through pathogenicity. Die-off recovery may take several years but cheatgrass populations eventually reestablish. The purpose of our study was to determine whether Fusarium is a potential player in a die-off, and understand how die-offs recover after …
Identification Of The Infection Route Of A Fusarium Seed Pathogen Into Non-Dormant Bromus Tectorum Seeds, Janalynn Franke
Identification Of The Infection Route Of A Fusarium Seed Pathogen Into Non-Dormant Bromus Tectorum Seeds, Janalynn Franke
Theses and Dissertations
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 Fusarium-caused diseases of wild plants are less well-known. In this study we examined Fusarium sp. n-caused disease development on non-dormant 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 undescribed species in the Fusarium tricinctum species complex from die-off soils and showed that it is pathogenic on seeds. It can cause high …
Wet-Thermal Time And Plant Available Water In The Seedbeds And Root Zones Across The Sagebrush Steppe Ecosystem Of The Great Basin, Nathan Lyle Cline
Wet-Thermal Time And Plant Available Water In The Seedbeds And Root Zones Across The Sagebrush Steppe Ecosystem Of The Great Basin, Nathan Lyle Cline
Theses and Dissertations
Following wildfires, plant materials are direct-seeded to limit erosion and annual weed invasion. Seedlings often fail to establish because selected plant materials are not always well adapted to local soil moisture and temperature conditions. In an effort to help improve plant materials selection and to evaluate sites potential revegetation, we have worked toward developing methodology to predict germination and root growth based on site specific soil moisture and temperature conditions. First, we characterized the seedbed environment of 24 sagebrush (Artemisia spp.) steppe sites throughout the Intermountain West to determine the wet-thermal time of five temperature ranges relevant to germination …
Population Genetic Structure Of Bromus Tectorum In The American Desert Southwest, Desiree Rochelle Eldon
Population Genetic Structure Of Bromus Tectorum In The American Desert Southwest, Desiree Rochelle Eldon
Theses and Dissertations
Following its introduction to North America in the late nineteenth century, Bromus tectorum L., an inbreeding invasive winter annual grass, has become dominant on millions of hectares of sagebrush steppe habitat throughout Intermountain Western North America. It appears that within the last 30-40 years, B. tectorum has expanded its range southward into the Mojave Desert and also into more climatically extreme salt desert environments. Previous research using microsatellite markers and experimental studies has suggested that lineages found in desert habitats are genetically distinct from those found in the sagebrush-steppe habitat and possess suites of traits that pre-adapt them to these …
Cultural Thinning Of Native Sagebrush Stands To Increase Seed Yields, Kurt David Elder
Cultural Thinning Of Native Sagebrush Stands To Increase Seed Yields, Kurt David Elder
Theses and Dissertations
Wyoming big sagebrush (Artemisia tridentata Nutt.) is an important native shrub in the Great Basin because of its wide distribution where it dominates over 60 million ha and provides essential habitat and forage for many varied species. The hand collection of sagebrush seed often results in seed scarcity and the available seed quantities are at times inadequate to revegetate large areas that have been disturbed, resulting in a demand for sagebrush seed. Study locations were selected near Scipio and Sahara sand dunes of Utah, and treatments were 1-) control, no treatment applied area left undisturbed 2-) general chemical strip …
Plant Establishment And Soil Microenvironments In Utah Juniper Masticated Woodlands, Kert R. Young
Plant Establishment And Soil Microenvironments In Utah Juniper Masticated Woodlands, Kert R. Young
Theses and Dissertations
Juniper (Juniperus spp.) encroachment into sagebrush (Artemisia spp.) and bunchgrass communities has reduced understory plant cover and allowed juniper trees to dominate millions of hectares of semiarid rangelands. Trees are mechanically masticated or shredded to decrease wildfire potential and increase desirable understory plant cover. When trees are masticated after a major increase in tree population density and associated decrease in perennial understory cover, there is a risk that invasive annual grasses will dominate because they are highly responsive to the increased resource availability that commonly follows removal of the main resource user. To determine if tree mastication increases …
Usage And Development Of Molecular Markers For Investigation Of The Population And Ecological Genetics Of Bromus Tectorum L., Keith R. Merrill
Usage And Development Of Molecular Markers For Investigation Of The Population And Ecological Genetics Of Bromus Tectorum L., Keith R. Merrill
Theses and Dissertations
This thesis includes two studies: The first examined patterns of neutral genetic diversity within Bromus tectorum L. across the IMW region, and uses patterns of microsatellite (SSR) genotype distribution to make inferences about the respective roles of adaptively significant genetic variation, adaptive phenotypic plasticity, and facultative outcrossing in the ongoing invasion and recent range expansion of B. tectorum. It has been previously demonstrated that, due to extremely low outcrossing rates, it is possible to characterize individual genotypes of this species using four SSR loci. We sampled 20 individuals from each of 96 B. tectorum populations (classified by region and …
The Grass Seed Pathogen Pyrenophora Semeniperda As A Biocontrol Agent For Annual Brome Grasses, Thomas E. Stewart
The Grass Seed Pathogen Pyrenophora Semeniperda As A Biocontrol Agent For Annual Brome Grasses, Thomas E. Stewart
Theses and Dissertations
Bromus tectorum and other annual brome grasses have invaded many ecosystems of the western United States, and because of an annual-grass influenced alteration of the natural fire cycle on arid western range lands near monocultures are created and conditions in which the native vegetation cannot compete are established. Each year thousands of hectares become near monocultures of annual brome grasses. Pyrenophora semeniperda, a generalist seed pathogen of annual grasses, shows major potential as a possible mycoherbicide that could help in reducing the monocultures created by annual grasses. The purpose of this research was to identify the requirements for isolating …
Genetic Variation In Ustilago Bullata: Molecular Genetic Markers And Virulence On Bromus Tectorum Host Lines, Mikel Stevens, Daniel J. Fairbanks, Susan E. Meyer, David L. Nelson, Suzette Clement, Jennifer Waters
Genetic Variation In Ustilago Bullata: Molecular Genetic Markers And Virulence On Bromus Tectorum Host Lines, Mikel Stevens, Daniel J. Fairbanks, Susan E. Meyer, David L. Nelson, Suzette Clement, Jennifer Waters
Faculty Publications
The pathogen Ustilago bullata often causes epidemic levels of head smut disease in Intermountain populations of the inbreeding annual grass Bromus tectorum. We examined patterns of genetic variation for virulence and for amplified fragment length polymorphism (AFLP) markers in four U. bullata populations on B. tectorum in northern Utah and southern Nevada. Patterns of disease incidence generally supported a genefor-gene model for virulence and resistance in this pathosystem. Most host lines were susceptible to most or all paired isolates included in cross-inoculation tests, but we found evidence for the existence of four avirulence genes. Host lines with alleles conferring resistance …