Theses and Dissertations at Montana State University (MSU)
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Item A multi-scale assessment of the coupling between the nitrogen cycle and the terrestrial carbon sink under global change(Montana State University - Bozeman, College of Agriculture, 2022) Gay, Justin David; Chairperson, Graduate Committee: Jack Brookshire; This is a manuscript style paper that includes co-authored chapters.It is now unequivocal that the main driver of greenhouse gas (GHG) accumulation in Earth's atmosphere over the industrial era has been due to anthropogenic global change. Despite the recent and rapid rise in GHGs, global terrestrial ecosystems have slowed the rate of carbon dioxide accumulation in the atmosphere, and thus the rate of climate change, through the uptake and storage of carbon (C) in plant biomass and soil organic matter. However, the global cycles of C and nitrogen (N) are tightly coupled through primary production and the turnover of soil organic matter, highlighting a stoichiometric relationship that is critical to understanding the future stability and strength of the terrestrial C sink. Thus, our ability to understand the response of the terrestrial C sink to global change hinges on critical -- but often overlooked -- feedback with N cycling. In this dissertation, I examine how different aspects of global change and land management practices are impacting the terrestrial C sink by evaluating interactions with the N cycle in both managed and natural ecosystems. I use observational and experimental methods to quantitatively assess C and N dynamics at plot, landscape, and global scales. I focus this work on crop- and range-lands of the Upper Missouri River Basin in the United States, and in equatorial mountain forests across the globe to address three overarching research questions: 1. What are the controls over the soil-atmosphere gas exchange of greenhouse gases, and how do they change in response to management and vegetation cover? 2. How do changes in plant community composition influence ecosystem C and N dynamics? 3. How is global change altering the stability and rate of C and N accumulation and storage?Item Pulse crop management to enhance biological nitrogen fixation in the northern Great Plains(Montana State University - Bozeman, College of Agriculture, 2022) Baber, Kaleb Wade; Chairperson, Graduate Committee: Clain Jones; Clain Jones, Perry Miller, Sydney Atencio, Samuel Koeshall and Peggy Lamb were co-authors of the article, 'Lentil nitrogen fixation response to fertilizer and inoculant in the northern Great Plains' submitted to the journal 'Agronomy journal' which is contained within this thesis.; Clain Jones, Kevin McPhee, Perry Miller and Peggy Lamb were co-authors of the article, 'Assessment of nitrogen fixation among pea and lentil varieties in the semiarid northern Great Plains' submitted to the journal 'Agronomy journal' which is contained within this thesis.Pulse crop production has increased dramatically in Montana and the surrounding northern Great Plains over the past few decades. Through N fixation, pulse crops, including pea and lentil, can reduce N fertilizer requirements, both by replacing non N-fixing crops and positively contributing to soil N pools for subsequent crop uptake. Three studies were conducted in Montana over three years to investigate pulse crop management practices that enhance N fixation of pea and lentil. The first study investigated lentil N fixation response to fertilizers and inoculant types. Inoculant and S fertilizer each increased N fixed by lentil in 40% of site-years, but response was not well correlated with cropping history or soil sulfate-S levels. In one site-year, N fixation appeared to continue increasing at the highest tissue S concentration while seed yield plateaued below that highest level, indicating that S fertilizer could increase the soil N benefit of lentil even if a yield response is not expected. Potassium fertilizer nor inoculant type influenced N fixed. The second study assessed differences in N fixation among lentil and pea varieties. Amounts of N fixed varied in 75% and 50% of site-years for lentil and pea, respectively. Differences among varieties were sometimes large, up to 45 kg N ha-1. Two lentil varieties, CDC Richlea and Riveland, were frequently among the top N-fixers, while no pea varieties consistently fixed more N than others. Correlations between N fixed and seed yield ranged from weak to moderate, and pea more frequently had positive relationships than lentil. The third study evaluated N fixation response of two pea varieties to inoculant formulations. Inoculant formulation did not impact N fixed by either variety, and the uninoculated treatment performed as well as the inoculated treatments. This suggests producers may not need to inoculate pulse crops to achieve sufficient N fixation when effective rhizobia populations exist in their fields. These results contribute to the researchers' understanding of N fixation by pulse crops in the region. Together, these studies can help producers in the northern Great Plains better manage pea and lentil, improving both economic and environmental sustainability of the region's cropping systems.Item Understanding mechanisms of invasion and restoring lands impacted by non-native annual grasses(Montana State University - Bozeman, College of Agriculture, 2020) Majeski, Michelle Lynn; Chairperson, Graduate Committee: Jane M. Mangold; Catherine Zabinski, Lisa J. Rew and Jane Mangold were co-authors of the article, 'Ventenata dubia growth responds to field soil inocolum but not phosphorous and potassium treatments' which is contained within this thesis.; Catherine Zabinski, Lisa J. Rew and Jane Mangold were co-authors of the article, 'Ventenata dubia was associated with perennial grasses, bare ground and soil potassium concentration' which is contained within this thesis.; Stacy C. Simanonok, Zach Miller, Lisa J. Rew and Jane Mangold were co-authors of the article, 'Spring seeding provides a seasonal priority effect for Pseudoroegneria spicata in Bromus tectorum-invaded rangelands' which is contained within this thesis.European settlement and development of rangelands in the western U.S. has led to a shift in vegetation from native species to introduced species, some of which have become weedy and invasive. Effects of invasive plant species can vary but often include replacing native vegetation, altering ecosystems, affecting wildlife that relied on the native plants for food and shelter, and toxicity to livestock. Two introduced annual grasses of concern are Ventenata dubia and Bromus tectorum. These grasses are at different stages in their invasion in the western U.S. Ventenata dubia is a recent invasive species in the past ten years and B. tectorum has been dominant in the Intermountain West since the mid-1900s. Three independent studies were conducted to understand characteristics of V. dubia invasion and to test whether a seasonal priority effect could be shifted to Pseudoroegneria spicata to outcompete B. tectorum in range/pasturelands. A full-factorial design was executed in a greenhouse setting to examine if a plant-soil feedback contributes to V. dubia invasion and if V. dubia preferred specific nutrients for growth. Ventenata dubia biomass, shoot height and number of leaves and tillers (per plant) were higher when grown with field soil inoculum compared to sterilized greenhouse soil. Ventenata dubia growth varied among nutrient treatments, but trended higher with a full nutrient solution. A nested observational study was conducted to examine abiotic and biotic characteristics associated with V. dubia infestations. Ventenata dubia was positively associated with non-native perennial grasses and negatively associated with native perennial grasses, bare ground/rock and soil potassium concentration. A randomized split-plot design was performed in B. tectorum-infested range and pasturelands to test whether timing of herbicide application and seeding of P. spicata could create a seasonal priority effect for P. spicata. Bromus tectorum had lower cover and biomass (per m2) with spring herbicide application. Higher P. spicata density, cover and biomass resulted with spring seeding after B. tectorum was reduced. These studies show that established and seeded native perennial grasses can compete with nonnative, invasive annual grasses. When existing management tools (herbicide and revegetation) are applied in a different way, native perennial grasses benefit.Item Optimizing efficacy of Bromus tectorum (cheatgrass, downy brome) biological contorl in crops and rangelands(Montana State University - Bozeman, College of Agriculture, 2017) Ehlert, Krista Ann; Chairperson, Graduate Committee: Fabian D. Menalled; Jane M. Mangold (co-chair)Management of Bromus tectorum L., an annual grass invasive in western North America, has focused on single and integrated methods across crop and non-crop settings. Extensive literature does not exist on the integration of Pyrenophora semeniperda, a generalist grass pathogen for B. tectorum control, which has been used experimentally with some success to control B. tectorum. However, questions remain about (1) the risk of non-target effects on grassy species, (2) efficacy as part of an integrated management plan, and (3) efficacy under different environmental conditions and on different B. tectorum populations. I sought to answer these questions with three distinct studies. First, I assessed the risk of P. semeniperda on B. tectorum and 15 co-occurring grass species in a greenhouse setting. Pyrenophora semeniperda reduced B. tectorum density by 40% but also negatively affected density of 60% of the non-target species tested, particularly native rangeland grasses. Second, I integrated P. semeniperda as part of a two-year rangeland revegetation management plan that included an herbicide (imazapic), a fungicide seed treatment, and different perennial grass seeding rates. Application of P. semeniperda did not increase inoculum loads above ambient levels, and there was no effect of seeding rate or seed treatment on B. tectorum or seeded perennial grass density or biomass. However, B. tectorum density was reduced by 60% the first year with a single imazapic application. Lastly, I compared the effects of temperature (13°C, 17°C, 21°C, 25°C, 32°C) and B. tectorum populations (range, crop, sub-alpine) on infection and mortality rates caused by P. semeniperda using a temperature gradient table. Infection rates by P. semeniperda peaked at intermediate temperatures (17°C, 21°C, 25°C) for range and sub-alpine populations, but were generally low and not as influenced by temperature in the crop population. Overall, B. tectorum control with P. semeniperda is possible, provided (1) non-target effects are considered, especially for range species, (2) research is conducted to increase P. semeniperda inoculum loads above ambient levels and revegetation is used with other control tactics, and (3) we take into account how distinct B. tectorum populations respond to P. semeniperda.Item Sampling and modeling plant infestations : alternatives for identifying invasive plant distributions in rangeland environments(Montana State University - Bozeman, College of Agriculture, 2001) Roberts, Elizabeth AnnItem Using successional theory to guide restoration of invasive plant dominated rangeland(Montana State University - Bozeman, College of Agriculture, 2003) Anderson, Jennifer Lisa; Chairperson, Graduate Committee: Douglas J. Dollhopf.Item Effects of short duration, concentrated livestock grazing on soil density(Montana State University - Bozeman, College of Agriculture, 1989) Riggle, Lex AlanItem Characterizing rangeland using multispectral remotely sensed data and multi-scale ecological units(Montana State University - Bozeman, College of Agriculture, 2003) Maynard, Catherine Cae Lee; Chairperson, Graduate Committee: Rick Lawrence.Item Estimating range production from thickness of mollic epipedon and other soil or site characteristics(Montana State University - Bozeman, College of Agriculture, 1983) Cannon, Mary EllenItem Nonindigenous plant species distributions : modeling the role of human disturbances and predicting management responses(Montana State University - Bozeman, College of Agriculture, 2012) Bridges, Melissa Elaine; Co-chairs, Graduate Committee: Lisa J. Rew and Bruce D. Maxwell; Bruce D. Maxwell and Lisa J. Rew were co-authors of the article 'Human disturbance regimes influence the transferability of nonindigenous plant distribution models' in the journal 'Biological invasions' which is contained within this thesis.; Bruce D. Maxwell and Lisa J. Rew were co-authors of the article 'The role of current and historic land uses on the local occupancies of nonindigenous plant species' in the journal 'Landscape ecology' which is contained within this thesis.; Bruce D. Maxwell and Lisa J. Rew were co-authors of the article, 'Nonindigenous population and off target plant community responses to management along an environmental suitability gradient' in the journal 'Journal of applied ecology' which is contained within this thesis.The current paradigm of nonindigenous plant species (NIS) management assumes all NIS populations are invasive and ignores that different populations of the same species have different dynamics and respond differently to perturbations in dissimilar environments. Species distribution models (SDM) can predict spatial patterns of NIS environmental suitability and form a link between management objectives and species distributions. The objectives of this dissertation were to evaluate the utility of SDMs for NIS management. Specifically, the spatial transferability of models, the importance of land uses in explaining NIS distributions, and the relationships between management efficacy and SDM predictions were assessed. The first objective evaluated the transferability of SDMs for two NIS among neighboring regions representing a three-point gradient of human disturbance intensities. The models did not adequately transfer between the two management units representing the least and greatest intensities of human disturbances. This suggested NIS might be distributed differently in response to human disturbances. The second objective compared the relative roles of environmental, current land use, and historical land use variables on explaining occupancies for six NIS. Historical land use explained greater amounts of the variation in NIS occupancies as compared to only environmental variables or environmental plus current land use variables. Land uses currently or previously irrigated for agriculture increased predicted probabilities of occurrence for multiple NIS, including an introduced perennial forage species. The final objective assessed the applicability of SDMs to prioritize NIS populations for management treatments. Herbicide treatments were applied to populations of two NIS located along a gradient of their respective SDM predictions. The effect of herbicide treatment on NIS densities varied either positively or negatively with predicted environmental suitability depending on the specific species. Thus, NIS population responses may be predictable and treatment prioritized using SDM predictions; however, contrasting responses between the two NIS evaluated suggested management should be adapted for species and site specific conditions. This study showed that human disturbance history can affect how NIS are distributed, and, thus, SDMs should be generated from site specific data. Further, SDMs can guide managers as to which NIS populations should be prioritized for management.