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'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.
Factors influecing the abundance of microorganisms in icy environments
(Montana State University - Bozeman, College of Agriculture, 2016) Santibanez-Avila, Pamela Alejandra; Chairperson, Graduate Committee: John C. Priscu; Joseph R. McConnell and John C. Priscu were co-authors of the article, 'A flow cytometric method to measure prokaryotic records in ice cores: an example from the Wais Divide drilling site' submitted to the journal 'Journal of glaciology: instruments and methods' which is contained within this dissertation.; Mark Greenwood, Joseph R. McConnell and John C. Priscu were co-authors of the article, 'Prokaryotic concentration changes between the last glacial maximum and the early Holocene from the Wais Divide ice core' submitted to the journal 'Quaternary science reviews' which is contained within this dissertation.; Alexander B. Michaud, Trista J. Vick-Majors, Juliana D'Andrilli, Amy Chiuchiolo and John Priscu were co-authors of the article, 'Bacterial response to progressive freezing in perennially and seasonally ice-covered lakes' submitted to the journal 'Journal of geophysical research (JGR) biogeosciences' which is contained within this dissertation.
Microbial life can easily live without us; we, however, cannot survive without the global catalysis and environmental transformations it provides' (Falkowski et al., 2008). Despite of the key role of microbes on Earth, microbial community characteristics are not explicitly part of climate models because our understanding of their responses to long-term environmental and climatic processes is limited. In this study, I developed a Flow Cytometric protocol to access a long-term record of non-photosynthetic prokaryotic cell concentration archived in the West Antarctic Ice-Sheet (WAIS; chapter 2). The WD ice core was retrieved between 2009 and 2011 to a depth of 3,405 m, extending back to 68,000 before 1950. Once a 17,400 year-record of prokaryotic cell concentration was acquired, I investigated its temporal variability and patterns, determined the potential sources of prokaryotic cells between the Last Glacial Maximum and the early Holocene, and assessed the environmental factors that might have the largest influence on the prokaryotic response (chapter 3). The observed patterns in the prokaryotic record are linked to large-scale controls of the Southern Ocean and West Antarctica Ice-Sheet. The main research findings presented here about the first prokaryotic record are: (i) airborne prokaryotic cell concentration does respond to long-term climatic and environmental processes, (ii) the processes of deglaciation, sea level rise and sea-ice fluctuation were key; the abundance of prokaryotic cells covariate with ssNa and black carbon, and (iii) the prokaryotic cell record variate on millennial time scale with cycles of 1,490-years. In addition, I studied 'congelation ice' (i.e., ice forms as liquid water freezes) from ice-covered lakes to understand prokaryotic cell segregation between liquid and solid phases during the physical freezing process. Five mesocosm experiments were designed to understand prokaryotic responses to the progressive freezing in concert with field observations from ice-covered lakes from Barrow, Alaska. As a result of this last study (chapter 4), I concluded that prokaryotic cells are preferentially incorporated in the ice with segregation coefficients (K eff) between 0.8 - 4.4, which are higher than for major ions. Prokaryotic cells avoid rejection more effectively from the ice matrix.
Resilience of Montana's agroecosystems to economic and climatic change
(Montana State University - Bozeman, College of Agriculture, 2015) Lawrence, Patrick Glenn; Chairperson, Graduate Committee: Bruce D. Maxwell; Bruce D. Maxwell and Lisa J. Rew were co-authors of the article, 'A probabilistic bayesian framework for progressively updating site-specific recommendations' in the journal 'Precision agriculture' which is contained within this thesis.; Bruce D. Maxwell, Lisa J. Rew, Anton Bekkerman, Clain Jones and Perry Miller were co-authors of the article, 'Managing uncertainty in semiarid dryland agriculture: a data-driven approach to optimize inputs and crop rotations based on farmer risk preferences' submitted to the journal 'Agricultural systems' which is contained within this thesis.; Bruce D. Maxwell, Lisa J. Rew, Colter Ellis and Anton Bekkerman were co-authors of the article, 'Vulnerability of dryland agricultural regimes to economic and climatic change' submitted to the journal 'Climatic change' which is contained within this thesis.
Semiarid dryland agricultural systems in the western United States are faced with a highly uncertain production environment that complicates decision-making and makes static agronomic prescriptions unreliable for maintaining sustainability. The primary sources of uncertainty for farmers are weather, fluctuations in prices, and site-specific environmental and ecological variability, some of which may be amplified by climate change. To effectively respond to the risks posed by these uncertainties requires knowledge of the vulnerability of these agricultural systems. The aim of this dissertation was to meet this need for Montana by analyzing the economic resilience of the state dryland agricultural systems at site-specific and county-wide scales. To begin, a framework was created to integrate weather, prices, nitrogen inputs, and spatial soil variability within a statistical model for site-specific crop responses and net returns. Simulations suggest that six crop years of simulated data collection and parameter tuning were required to derive an accurate model, suggesting that an extended period of observation and targeted nitrogen rate experimentation was required to optimize spatial fertilizer management. The framework was subsequently applied to a spatiotemporal precision agricultural dataset from a farm near Great Falls, MT, and was modified to account for several crop rotations and different farmer risk preferences. Regardless of farmers' level of risk aversion, winter wheat-pea rotations resulted in higher value (utility) for the farmer than winter wheat-fallow and continuous winter wheat rotations. For most levels of risk adversity, it was also optimal to apply no nitrogen fertilizer. Net returns at the field site were always threatened by drought. Subsequently, a qualitative analysis of farmer adaptability in Montana based on survey and interview data determined that farmers had few options for responding to drought but were more adaptable to high input prices. On-farm experimentation and crop rotations could greatly increase adaptability in the future. Finally, simulations of alternative price, precipitation, and crop rotation scenarios were completed. The most resilient agricultural systems were located in northeastern Montana where pulses have been more widely adopted; systems in north-central Montana were less resilient. State-wide, over 50% of dryland farmers may not be resilient to future economic or climatic variability.

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