Theses and Dissertations at Montana State University (MSU)
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Item Comparing juvenile physiology and morphology of two high-elevation pines, Pinus albicaulis and Pinus balfouriana(Montana State University - Bozeman, College of Letters & Science, 2023) Sparks, Katherine Elizabeth; Chairperson, Graduate Committee: Danielle UlrichWhitebark pine (Pinus albicaulis, PIAL) and foxtail pine (P. balfouriana, PIBA) are slow-growing, high-elevation, five needled ("high five") white pines and are foundation and keystone species in alpine and subalpine environments, providing essential resources and habitat for many species including the Clark's nutcracker and grizzly bears. In recent years, PIAL has experienced significant decline due to an amalgamation of climate change, white pine blister rust, and mountain pine beetle. As a result, PIAL is listed as endangered under the Canadian Species at Risk Act and threatened under the United States Endangered Species Act. Conversely, PIBA has experienced minimal decline. PIBA also exists in two disjunct populations, one in southern California (PIBAS) and one in northern California (PIBA N), resulting in the species being split into two sub-species (P. balfouriana subsp. austrina and balfouriana). Our study compared the physiology and morphology of the two species (PIAL and PIBA) and the two foxtail populations (PIBA N and PIBAS) to better understand how they interact with and respond to abiotic and biotic stressors in their high-elevation environments. We grew four-year-old PIAL and PIBA juveniles in a common greenhouse environment. In total, we measured 159 traits describing their morphology, biomass, stomata, xylem, budburst phenology, physiology, whole plant Volatile Organic Compounds (wpVOCs), phloem volatile resin (PVR) compounds, and Non-Structural Carbohydrates (NSCs). We found that PIAL and PIBA displayed different suites of traits that enable them to persist in their high elevation habitats, characterized by similar abiotic stressors (cold temperatures, high winds, summer drought) and biotic stressors (white pine blister rust, bark beetle). The two foxtail populations were similar for most traits except for wpVOC concentration and composition where PIBAS had significantly higher wpVOC concentration than PIBA N. For most traits, PIAL was most similar to PIBA N and differed the most with PIBAS while PIBA N was the intermediate being more similar to both groups, especially in wpVOC composition and concentration.Item Investigating the ability of arbuscular mycorrhizal fungi to mitigate the negative effects of warming and drought on native perennial forbs(Montana State University - Bozeman, College of Letters & Science, 2022) Eggers, Jessica Avery; Chairperson, Graduate Committee: Laura Burkle; This is a manuscript style paper that includes co-authored chapters.The ability of arbuscular mycorrhizal fungi (AMF) to mitigate the negative effects of warming and drought on plant hosts is known for crop species but is poorly understood for native, perennial forbs. Examining the indirect influence of AMF on forbs' responses to these stressors will provide a more complete understanding of how native forbs will be affected by climate change. In an experimental greenhouse study, we inoculated two native forb species (Achillea millefolium and Linum lewisii) with three separate AMF species (Rhizophagus clarus, Claroideoglomus etunicatum, and Gigaspora rosea), then exposed plants, including an uninoculated control treatment, to varying degrees of drought and heat stress in a factorial design. We tested the effects of warming or drought treatments on plants' physical, floral, phenological, and physiological traits, including biomass, height, floral abundance, flower size, first date of flowering, floral scent, and photosynthetic performance. For both forbs, AMF ameliorated the negative effects of drought and warming on plant survival and vegetative growth, but the magnitude of effect was specific to the forb species, climate treatment, and AMF inoculant. AMF also produced changes in forb phenology, floral scent (volatile organic compounds), and flowering success and duration, which have broad implications for plant-pollinator interactions and the links between belowground and aboveground symbioses. Together, these results indicate that AMF can assist native forbs in surviving, growing, and reproducing in a warmer and drier climate.Item Physiological traits and stress tolerances of three high-elevation pine species(Montana State University - Bozeman, College of Letters & Science, 2023) Wasteneys, Chloe Elizabeth; Chairperson, Graduate Committee: Danielle UlrichThe increasing frequency and intensity of drought and heat events are increasing forest mortality rates worldwide. To improve restoration and management effort effectiveness for at- risk tree species and to accurately predict how these species will respond to future climates, the physiological mechanisms of seedling establishment and survival need to be fully understood. Using a greenhouse common garden approach, we compared the physiological traits and stress tolerances of three high-elevation five-needle pine species, Pinus albicaulis (PIAL), P. flexilis (PIFL), and P. longaeva (PILO). We measured a suite of physiological response curves to determine photosynthetic capacity, high-light tolerance, drought tolerance, and heat tolerance traits. We compared these traits among the three species (Q1), among three different ages of PIAL seedlings (2-, 3-, and 5-years-old; Q2), and among seven families of 2-year-old PIAL originating from different locations (Q3). Among species (Q1), only one heat tolerance trait (Tcrit, the temperature at which minimal fluorescence begins to increase) significantly differed and increased from PILO to PIFL to PIAL, suggesting that PIAL had greater heat tolerance than PIFL and PILO. Among PIAL ages (Q2), two drought tolerance traits, saturated water content (SWC) and leaf mass per area (LMA), and two heat tolerance traits, Tcrit and T50_EL (temperature that results in a 50% increase in electrolyte leakage), significantly differed among ages. SWC decreased, LMA and Tcrit increased, and T50_EL partially increased with increasing age, suggesting that older PIAL seedlings may be more drought and heat tolerant than younger PIAL seedlings. Among PIAL families (Q3), no traits significantly differed. However, we observed four significant correlations between our measured traits and growing season mean temperature and vapor pressure deficit of the seven PIAL families. Families from relatively cooler, wetter locations tended to have greater high-light tolerance and greater heat tolerance (based on T50_EL) while families from relatively warmer, drier locations tended to have greater heat tolerances (based on Tcrit and T50 measured with chlorophyll fluorescence). Together, these findings improve our understanding of physiological mechanisms underlying seedling establishment and our ability to predict how these species may be affected by future climates.Item Evaluating the effects of climate change and pathogens on pollinator health using plant functional traits and longitudinal monitoring(Montana State University - Bozeman, College of Letters & Science, 2017) Glenny, William Robb; Chairperson, Graduate Committee: Laura Burkle; Michelle Flenniken (co-chair)Pollinators are essential for the maintenance of biodiversity, ecosystem function, and economic productivity. In particular, bee pollinators are required for plant reproduction and pollination of agricultural crops. However, land use change, climate change, pathogens, pesticide exposure, among other factors likely act alone and in combination to negatively impact bee pollinators and the services they provide. Further resolution of the effects of these stressors, both individually and combined, on bee pollinators is important to understand the global decline of pollinator health. Abiotic conditions associated with climate change may alter plant traits important for pollinator attraction leading to in shifts in plant-pollinator communities. Floral visual and chemical traits were measured in four species of forbs subjected to elevated or ambient concentrations of carbon dioxide, and decreased or normal water availability in a fully factorial crossed design. Treated plants were observed for pollinator visitation rates and community composition to better understand the mechanisms by which climate change can influence pollinator attraction. Results indicate that changes in both visual and chemical cues of plants will alter plant-pollinator interactions. Furthermore, plant functional trait responses to climate change increase competition for pollinators in forbs with overlapping flower types, while facilitating pollinator visitation to forbs with dissimilar flower types. Pathogens contribute to annual honey bee colony losses and the declining populations of some wild bee species. Bee pathogens, including viruses, fungi, microparasites and ectoparasites, can vary across geographic location and season. To examine the impact of pathogens on honey bee colony health, using colony size as a proxy for health, we longitudinally monitored pathogen prevalence and abundance of pathogens in honey bee colonies involved in California almond pollination. Individual honey bee associated pathogens varied throughout the one year monitoring period, but Deformed wing virus in parallel with increasing levels of Varroa destructor mite infestation predominated shifts in honey bee pathogen profiles by the end of the sampling period. Our results indicate that bee populations experience multiple concurrent threats operating at multiple scales to affect pollinator health. Continued investigation into factors affecting pollinator health both independently and in concert are needed to develop strategies mitigating declines in pollination services.Item Some effects of ACTH, STH, noradrenaline and thyroid hormone on young rats starved at two different temperatures(Montana State University - Bozeman, College of Agriculture, 1969) Bradshaw, Blaine StuartItem The effects of supplemental feeding on stress hormone concentrations in elk(Montana State University - Bozeman, College of Letters & Science, 2009) Patrek, Victoria Elizabeth; Chairperson, Graduate Committee: Scott Creel; Paul Cross (co-chair)On twenty-two feedgrounds in western Wyoming, elk (Cervus elaphus) are provided with supplemental feed throughout the winter. Brucellosis seroprevalence of feedground elk is 26% whereas other elk in the Greater Yellowstone Ecosystem have historically had a brucellosis seroprevalence of 2-3%. The aggregation of elk during peak transmission allows brucellosis to persist in the feedground populations. In addition to creating the opportunity for disease transmission, the aggregation of elk on feedgrounds may have detrimental physiological effects. Studies have shown that chronically high stress hormone concentrations can suppress the immune system and lead to increased disease susceptibility. Potential stressors on the feedgrounds include high densities, large group sizes and aggressive social interactions. In this study I investigated how factors associated with supplemental feeding affect stress hormone levels, as indexed by fecal glucocorticoid levels, in elk on feedgrounds and elk on native winter range. I also worked with managers to experimentally alter the feeding distribution on the feedgrounds to examine how feeding density affects stress hormone levels and aggression rates. Results show that elk on feedgrounds have stress hormone levels 31% higher than elk on native winter range (Welch's t₂₇.₂₃=2.39, p=0.024). Experimental reduction of feed density did not have an effect on stress hormone level or aggression rates. But note the relationship between fGCs and local densities here. Although the feeding treatments did appear to reduce local feeding densities,s this effect was not significant and was small relative to the large differences in density among sites. Regardless as to the cause of the high stress hormone levels seen in supplementally fed elk, the feedgrounds are creating an epidemiological setting for disease transmission and a physiological state that may increase susceptibility to disease. The impact of these stress hormone concentrations on disease susceptibility remains unknown, but may be an important driver of disease dynamics in these elk populations.