Theses and Dissertations at Montana State University (MSU)

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Using remote sensing indices to analyze the influence of bare ground in dust source areas to total dust-on-snow load in the san juan mountains, colorado
(Montana State University, 2021) Bilbrey, Christopher Edward; Chairperson, Graduate Committee: Scott Powell
The movement of dust across the western United States (US) has increased exponentially over the last 20 to 30 years driving a positive feedback regime altering the timing and magnitude of snowmelt. Dust radiative forcing of snowmelt can potentially exceed present day and likely future greenhouse gas forcing by two orders of magnitude. The semiarid landscape of the Colorado Plateau is one of the largest sources of dust in the western US. MODIS satellite imagery has been used to identify frequent, large-scale dust plumes that originate in the dust source area of northeastern Arizona, US and deposit that dust in the San Juan Mountains, Colorado. My study attempted to distinguish a "tele-link" between vegetation vigor in the dust source area and end of season total dust load in the San Juan Mountains from October 1 to June 30 for the years 2016 to 2021. The Normalized Difference Vegetation Index (NDVI) is a principal index tool used in multitemporal vegetation monitoring, and is commonly used as a direct indicator of vegetation health and growth. NDVI allows us to delineate the distribution of vegetation and bare soil based on the characteristic reflectance patterns of green vegetation. My study compared monthly NDVI mean values acquired by MODIS and Sentinel-2 to evaluate each satellites efficacy at modeling vegetation cover. Results suggest the association between vegetation vigor, bare soil, and total dust load is more complex and a number of factors could influence the inter-annual variability of dust-deposition. Statistical analysis employing ANOVA and multiple means comparison effectively identified pairwise groups who's monthly NDVI mean values were significantly different from others and 95% confidence intervals of the true expected difference, but failed to distinguish a "tele-link" between change in vegetation vigor and end of season total dust load. Finer-spatial resolution imagery captured more local variability in change in vegetation vigor over time and expanded the significant NDVI sampling window from 30 to 60 days. Projected climate change will likely increase aridity in the southwestern US, reduce the amount of vegetation cover, increase the amount of bare soil and enhance dust emission throughout the years.
Improving restoration of breeding sites to increase recruitment of anaxyrus boreas in western montana
(Montana State University, 2021) Johns, Nathanael David; Chairperson, Graduate Committee: Scott Powell
The Montana native western toads (Anaxyrus boreas) have, like most amphibians, been declining in recent years. Although it is endangered and at high risk of extirpation in many states, there are still several healthy breeding populations in Montana. Montana can increase recruitment of this increasingly rare anuran species through habitat restoration. However, using habitat restoration to addressing the decline of this species is not well researched. Here, I evaluate potential restoration methods that could increase recruitment. I provide an overview of the habitat requirements and preferences of A. boreas as well as effective restoration methods for this and other anuran species. To increase recruitment, restoration efforts should include construction of permanent ponds with low turbidity and extensive shallows that gradually increase to a maximum depth of 40 cm. Trees should be removed along the pond perimeter if they shade the water. Active management measures such as sediment removal in ponds, strict regulation of livestock grazing, periodically prescribed burns, and removal of invasive species such as the American bullfrog (Lithobates catesbeianus) should also be implemented. Farther from the breeding site, native deciduous shrubs should be planted, if they are not otherwise present. For existing breeding sites, the area within a 3-km radius should be protected from development and clearcuts. Introduction of beaver (Castor canadensis) to their historical range will also have a significant beneficial impact on the restoration of A. boreas. The locations of these efforts should also be carefully chosen to take into account the continuing effects of climate change. Taking these actions now, based on the data that are available, will help increase recruitment and improve the chances of this species recovering.
'Hypertemporal' remote sensing of plant function: a comparison of phenocam and geostationary operational environmental satellite NDVI data products
(Montana State University - Bozeman, College of Agriculture, 2019) Douglas, James Thomas; Chairperson, Graduate Committee: Paul C. Stoy
Ongoing climate warming is changing the seasonality of plant canopy function, but common approaches to explore these changes via polar-orbiting satellites often miss rapid canopy transitions due to infrequent observations. I explored the ability of satellites designed for studying weather systems, namely The Geostationary Operational Environmental Satellite (GOES), to track plant canopy status on time scales of minutes. With new capabilities to remotely sense in the infrared, the GOES weather satellites now have the capability to detect photosynthetic activity. Satellite observations of the normalized difference vegetation index (NDVI) are compared against near-surface phenological camera ("PhenoCam") observations from the National Ecological Observation Network (NEON, Inc.) at six sites every 15 minutes for one week in April 2019. Diurnal trends across both observation platforms showed the expected diurnal parabolic structure in NDVI with critical differences in NDVI magnitude between PhenoCams and GOES observations. One tailed T-test results show that there is variability between methods when measuring NDVI, with P-values less than 0.05 in all cases. This was anticipated due to correction factors needed for PhenoCam NDVI observations. However, additional variability can be attributed to other areas such as cloud cover, plant type, and heterogeneity. My proof-of-concept study demonstrates that raw NDVI data from both methods are often comparable, which lends credit to the notion that NDVI can be accurately observed from space at high (up to five minute) temporal resolution. With current research underway on the topics of atmospheric corrections and further surface validation, GOES has the potential to observe land surface attributes at up to 5-minute intervals across entire hemispheres for identifying phenology, disturbance and other vegetation dynamics in real time. With two hypertemporal methods at different spatial scales recently introduced, the research is primed to move towards a real time understanding of plant canopy function across the United States.
Evaluating growth-defense trade-offs in ponderosa pine (Pinus ponderosa) in response to stimulated bark beetle attack
(Montana State University - Bozeman, College of Agriculture, 2019) Hull-Jones, Jessica Wrae; Chairperson, Graduate Committee: Amy Trowbridge
The mountain pine beetle (MPB; Dentroctonus ponderosae, Hopkins, Coleoptera: Curculionidae: Scolytinae) and its associated blue stain fungi are considered to be among the greatest natural threat to conifer ecosystems worldwide. In response to a rapidly changing climate, namely more frequent and hotter droughts, bark beetles benefit through a combination of higher reproductive capacity and greater availability of weakened and stressed host trees. Conifers have potent constitutive and induced chemical defenses to resist the bark beetle-fungi complex, but investment in these carbon-based defenses may be constrained by trade-offs associated with a tree's inherent growth rate. Although there are trade-offs that exist among all processes, it is unclear whether those particular growth-defense trade-offs are measurable and can be compared between individuals within various populations. Here we assess the concentration and composition of constitutive and induced terpene chemical defenses as a function of intraspecific variation in growth rates (slow-versus fast-growing mature ponderosa pines). We examine these relationships in the context of classical plant defense theories as well as the current state of the field. By determining the variation in chemical responses to stimulated bark beetle attack we can further our understanding of potential resistance trade-offs that might exist in stands that are being selectively bred for fast growth.
A critical assessment of technologies for the study of organic matter in glaciers and ice sheets
(Montana State University - Bozeman, College of Agriculture, 2019) Willis, Madelyne Claire; Chairperson, Graduate Committee: Christine Foreman
Polar and temperate glaciers harbor active microbial communities and a substantial storage of organic carbon. These frozen ecosystems are especially sensitive to the effects of climate change and are expected to release roughly 15 teragrams of carbon by 2050. This creates a sense of urgency for further experimentation to increase our understanding of glacier ecosystem function and the impact glacier habitats have on local and global biogeochemical cycles. Due to the complex nature of organic matter, there is no single method which is suitable for every study. Technological advancements have improved methods for determining the quantity and quality of organic matter and emerging new technologies are providing faster and less-costly ways to overcome the challenges of working in these harsh environments. Consequently, a synthesis of peer-reviewed literature was conducted to summarize the current state of microbial ecology of glaciers and ice sheets, and to explore the techniques and new tools which are being developed to aid in the study of these rapidly disappearing ecosystems. The culmination of this work is an introduction and guide for analysts interested in examining the source, transformation history, and fate of organic matter in glacial systems. It was found that there is not one single technique superior to another, rather the appropriate technique is dependent on the questions being addressed and the resources available.
Multi-scale assessment of semi-arid vegetation communities: climate, disturbance, and environment as spatiotemporal drivers of phenology and composition
(Montana State University - Bozeman, College of Agriculture, 2021) Wood, David Jonathan Adrian; Chairperson, Graduate Committee: Scott Powell and Paul C. Stoy (co-chair); This is a manuscript style paper that includes co-authored chapters.
Ecosystems processes and functions include hierarchical and complex drivers. Assessing drivers of variation at multiple scales therefore helps predict biotic responses and improves our overall understanding of ecosystems. For example, the seasonal cycle and duration of events, phenology, represents a foundational process sensitive to changes in climate, and has cascading impacts across the ecosystem. The long-term record and expansion of remote sensing techniques provides an opportunity to both assess phenological changes through time at broad spatial extents while also assessing variability at finer spatial scales. At regional extents, satellite-based measurement can provide key insights into community level shifts, while finer scaled techniques such as unpiloted aerial vehicles (UAVs), spectral sensors, and automated digital cameras (phenocams) can investigate pattern differences at centimeter scales (i.e., plant and functional groups). I analyzed the year to year and spatial variability of phenology and composition of rangeland systems over multiple spatial scales to explore interrelated aspects of ecosystem functions. I used the AVHRR satellite record of phenology to examine spatial and temporal variability in phenological drivers and to identify key drivers and differences between the phenology of communities, including the role of ecological memory, the legacy impact of prior climate over months to years. In addition, by employing UAVs, spectral sensors, and phenocams I investigated the pattern and influence of heterogeneity on the phenology of grasses and shrubs. Finally, I investigated the interaction of multiple disturbances on the relative proportions of vegetation functional groups within a community. Key findings include productivity tradeoffs, where higher annual temperature increased peak but decreased growing season long productivity; climate conditions from the prior season and up to four prior years influenced date and productivity phenological measures; near earth sensors can characterize phenological variation at the microsite level; and there is an interactive effect of fire and development disturbance on non-native annual grass expansion. The vegetation of U.S. rangelands is projected to have consequential impacts from climate change, especially summer drying, and these impacts can be better quantified by including antecedent conditions and incorporating microsite differences into predictive models.
Response of soil bacterial communities to cropping systems, temporal changes, and environmental conditions in the northern Great Plains
(Montana State University - Bozeman, College of Agriculture, 2021) Ouverson, Laura Tindall; Chairperson, Graduate Committee: Fabian D. Menalled
Soil bacterial communities are essential components of the soil ecosystem that support crop production. However, agriculture in semiarid drylands and their associated soil bacterial communities face increasingly warmer and drier conditions due to climate change. Two complementary studies were conducted to assess the response of soil bacterial communities to cropping systems, temporal changes, and soil temperature and moisture conditions in semiarid, dryland agricultural systems of the Northern Great Plains. The first study focused on soil bacterial community response to crop phase in contrasting cropping systems (chemical inputs and no-till, USDA-certified organic tilled, and USDA-certified organic sheep grazed) over a growing season. Organic grazed management supported more diverse bacterial communities than chemical no-till, though diversity in all systems decreased over the growing season. Organic grazed bacterial communities were distinct from those in the organic tilled and chemical no-till systems. An interaction between cropping system and crop phase affected community dissimilarity, indicating that overarching management systems and environmental conditions are influential on soil bacterial communities. The second study evaluated soil bacterial communities in a winter wheat - cover crop or fallow rotation. Observations were conducted in the summer fallow and two cover crop mixtures differing by species composition and phenologies, terminated by three different methods (chemical, grazing, or haying), and subjected to either induced warmer/drier or ambient soil conditions. Only the presence and composition of cover crops affected bacterial community dissimilarity, where mid-season soil bacterial communities were distinct from early season and fallow communities. Bacterial communities responded to an interaction between the presence and composition of cover crops and environmental conditions, but not termination. No treatment effects were observed in bacterial communities in 2019, which could be attributed to above average rainfall. The results of these studies suggest cover crop mixtures including species tolerant to warmer and drier conditions can foster diverse soil bacterial communities compared to fallow soils. Overall, these studies contribute to a better understanding of how soil bacterial communities respond to soil health building practices in the Northern Great Plains. Cropping systems can foster unique soil bacterial communities, but these effects may be moderated by environmental and temporal conditions.
Investigating the impacts of agricultural land use change on regional climate processes in the northern North American Great Plains
(Montana State University - Bozeman, College of Agriculture, 2021) Bromley, Gabriel Trees; Chairperson, Graduate Committee: Paul C. Stoy; Jack Brookshire (co-chair); Tobias Gerken, Andreas F. Prein and Paul C. Stoy were co-authors of the article, 'Recent trends in the near-surface climatology of the northern North American Great Plains' in the journal 'Journal of climate' which is contained within this dissertation.; Andreas F. Prein, Shannon Albeke and Paul C. Stoy were co-authors of the article, 'Simulating the impacts of agricultural land use change on the climate of the northern North American Great Plains: validating a convection-permitting climate model' submitted to the journal 'Climate dynamics' which is contained within this dissertation.; Andreas F. Prein, Shannon Albeke and Paul C. Stoy were co-authors of the article, 'The decline in summer fallow in the northern plains cooled near-surface climate but had minimal impacts on precipitation' submitted to the journal ' ' which is contained within this dissertation.; Andreas Prein and Paul C. Stoy were co-authors of the article, 'Recent enhancement of thermodynamic environments in the northern North American Great Plains' submitted to the journal 'Geophysical research letters' which is contained within this dissertation.
The northern North American Great Plains (NNAGP) is the area defined by the Upper Missouri River Basin and the Canadian Prairies. It is a semi-arid region categorized by large stretches of grassland, pasture, and crops. During the last century and extending to the present day, a standard agricultural practice was to utilize a wheat-summer fallow rotation schedule, where the fields were left unplatted and an herbicide was often applied to keep weeds at bay. Concerns over soil health and profitability have led to the systematic decline of summer fallow, and nearly 116,000 km 2 that used to be fallow during the summer in the 1970s are now planted. An observational analysis discovered that from 1970-2015, during the early warm season, the NNAGP have cooled at -0.18 °C decade -1, nearly the same magnitude as the annual global warming rate. The near-surface atmosphere also moistened, evidenced by a decreasing vapor pressure deficit (VPD) trend, and monthly mean precipitation increased in excess of 8 mm per decade. Monthly mean convective available potential energy (CAPE) increased by 80% at Glasgow, MT and by 35% at Bismarck, ND based on atmospheric sounding observations. To test whether a reduction in summer fallow is responsible for these observed changes, a set of convection-permitting model experiments were performed over the NNAGP. Two sets (4 total) of three-year simulations were driven by ERA5 data with the vegetative fraction adjusted using satellite estimated fallow amounts for 2011 and 1984. The control simulations were extensively validated against an ensemble of observations with large temperature biases in Winter by ~ -3 °C and Summer by ~3°C. The areas where fallow area declined from 1984-2011 were cooler by about 1.5 °C and had a lower VPD by 0.15 kPa compared to where it did not. CAPE increased where fallow declined from 1984-2011 but so did convective inhibition (CIN). These findings insinuate that the observed change to monthly mean precipitation cannot be explained by summer fallow reduction alone. Trends in observed low level moisture transport show that the Great Plains Low Level Jet has been intensifying, bringing increased moisture to the NNAGP and partially responsible for the precipitation increase.
Pest management challenges and climate change in water limited winter wheat agroecosystems in southwestern Montana
(Montana State University - Bozeman, College of Agriculture, 2020) Nixon, Madison Grace; Chairperson, Graduate Committee: Fabian D. Menalled
Dryland winter wheat production is influenced by many environmental factors including climate, disease, and resource availability. In Montana, Bromus tectorum (cheatgrass) and Fusarium pseudograminearum (a fungus causing root crown rot) are major winter wheat pests; reducing yield and grain quality. However, little is known how climate change and resource availability impact winter wheat, B. tectorum, and F. pseudograminearum individually as well as their multi-trophic interactions. Thus, this research aimed to 1) Determine the susceptibility of B. tectorum to F. pseudograminearum and assess how CO 2 and nitrogen impact their growth, and 2) Evaluate how elevated temperature, reduced precipitation, and plant competition impact winter wheat and B. tectorum growth and reproduction. Utilizing growth chambers, high and low nitrogen treatments, fungal inoculated and uninoculated treatments, and ambient and elevated CO 2 treatments, Bromus tectorum was found to be a host of F. pseudograminearum, and the fungus significantly reduced root, shoot and total biomass, as well as primary physiological processes of B. tectorum. Fusarium pseudograminearum infection was not impacted by nitrogen or CO 2 level. Low nitrogen increased emergence and root production early on, while high nitrogen increased shoot production at later growth stages. Low nitrogen also improved stomatal conductance and transpiration rate. High CO 2 increased B. tectorum root, shoot, and biomass production, as well as intercellular CO 2. An interaction between ambient CO 2 and low nitrogen resulted in the greatest shoot relative growth rate between the first and second harvest. Field tests, using three climate treatments (ambient, increased temperature, reduced precipitation with increased temperature) and three plant competition levels (monoculture winter wheat, monoculture B. tectorum, and biculture of the two), found that for both winter wheat and B. tectorum monocultures, ambient and warmer climates produced similar yields and biomass, respectively, whereas the drier with warmer treatment reduced these factors. Additionally, B. tectorum presence increased winter wheat grain protein. A quadratic interaction model of winter wheat yield as a function of B. tectorum biomass by climate treatment suggests that at low to moderate B. tectorum biomass levels, winter wheat yield was negatively impacted by the warmer and drier treatment, whereas ambient and warmer treatment results were similar.
An experimental approach to understanding how Bromus tectorum will respond to global climate change in the sagebrush-steppe
(Montana State University - Bozeman, College of Agriculture, 2016) Larson, Christian Douglas; Chairperson, Graduate Committee: Lisa J. Rew
Global climate change, including elevated atmospheric CO 2 concentrations, increases in global surface temperatures, and changes in resource availability, has significant consequences for global plant communities, one of which is the expansion of invasive species. The invasive grass species Bromus tectorum dominates areas of the North American sagebrush-steppe. In these areas, B. tectorum responds positively to elevated nutrients after fire and a positive feedback with fire has been initiated. Bromus tectorum dominance and its positive response to fire are limited by cold and moist climates. Global climate change is predicted to expand the climate suitability for B. tectorum dominance, as well as that of its response to fire. Using a field study and controlled setting experiments, I investigated this prediction. In a cold and moist southwestern Montana sagebrush-steppe, my field experiment assessed the response of B. tectorum and the native plant community to increased growing season temperatures, decreased growing season precipitation, and a prescribed burn. We found that both B. tectorum and a dominant native perennial grass, Pseudoroegneria spicata, responded negatively to experimental warming, and warming and drying. Bromus tectorum's response to fire was limited to an increase in individual fecundity across the climate scenarios and compensatory growth in warm and dry conditions. In controlled settings, using differing densities of B. tectorum and P. spicata, I performed replacement series experiments that altered temperature, water availability, nutrient availability, and, secondly, atmospheric CO 2 concentration and water availability. Bromus tectorum competitiveness was enhanced by warmer and drier conditions and elevated nutrient availability. When grown in monoculture, both species responded positively to elevated CO 2. When grown in competition, elevated CO 2 increased P. spicata's already significant suppressive effect on B. tectorum. This effect was magnified when soil moisture was limited. Due to B. tectorum's significant negative response to the field climate treatments, its limited response to fire, and the significant suppressive effect of the native grasses in both experiments, especially in elevated CO 2, I conclude that similar future climate scenarios will not promote the expansion of B. tectorum dominance and its positive response to fire within the cold and moist northern region of the sagebrush-steppe.

Theses and Dissertations at Montana State University (MSU)

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