Theses and Dissertations at Montana State University (MSU)
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Item 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.Item Soil legacy effects alter plant volatile emissions in response to diversified cropping systems(Montana State University - Bozeman, College of Agriculture, 2020) Malone, Shealyn Chelsea; Chairperson, Graduate Committee: David K. Weaver and Amy Trowbridge (co-chair); David K. Weaver, Fabian Menalled, Tim Seipel, Justin B. Runyon, Lila Hamburg, Megan L. Hofland and Amy M. Trowbridge were co-authors of the article, 'Cropping systems alter crop volatile cues important for insect pests through soil legacy effects' which is contained within this thesis.; David K. Weaver, Tim F. Seipel, Fabian D. Menalled, Megan L. Hofland, Justin B. Runyon and Amy M. Trowbridge were co-authors of the article, 'Soil microbes alter herbivore-induced volatile emissions in response to cereal cropping systems' submitted to the journal 'Plant and soil' which is contained within this thesis.Soil microbes can influence the emissions of plant volatile organic compounds (VOCs) that serve as host-location cues for insects and their natural enemies. The influence of the soil microbial community on the plasticity of plant VOC synthesis and emissions is particularly important in agricultural settings where crop rotations and management practices cause significant shifts in the soil microbiome. Studies have shown agricultural soils to influence plant-insect interactions through changes in foliar chemistry, but their potential to alter VOC emissions is unknown. To determine the effect of diversified agricultural practices on crop VOC emissions through microbe-mediated soil legacy effects, I measured VOCs from wheat (Triticum aestivum L.) in a series of field and greenhouse experiments. In Chapter II, I determined the effect of the soil microbiome on VOCs in the greenhouse by first measuring VOCs from wheat plants grown in sterilized soil or soil with added inoculum from an agricultural field. Next, to determine the effect of diversified agricultural practices on VOC phenotypes, I measured VOCs from wheat plants in the field in rotation with either fallow or a mixture of cover crops that was terminated by grazing cows. Finally, in Chapter III, I explored the interactive effect of herbivory and the soil microbiome on VOC emissions in a full factorial experiment in which wheat grown in soil inoculum from wheat-fallow or wheat-cover crop rotation that was subjected to larval feeding by the wheat stem sawfly (WSS; Cephus cinctus Norton), a major pest of wheat. Across all studies I found that soils associated with a higher microbial diversity--cover crop soils and inoculated soils--tended to emit more total VOCs and blends that would likely increase pest resistance to the WSS through 1) shifts in key bioactive compounds and 2) enhanced herbivore-induced VOC emissions. Results also suggest that soil microbes may be more likely to alter plant VOCs when plants experience abiotic or biotic stressors. Together, these results suggest that agricultural practices may indirectly influence plant resistance through microbe-altered VOCs, and these effects are more likely to occur when plants experience additional stressors, such as herbivory or drought.Item Remote sensing for wetland restoration analysis: Napa-Sonoma Marsh as case study(Montana State University - Bozeman, College of Agriculture, 2019) Bryne, Charles; Chairperson, Graduate Committee: Scott PowellHuman-caused ecosystem change and habitat loss is a major worldwide concern. Wetland loss has been remarkable worldwide and in the US. In the San Francisco Bay system, the largest estuary on the eastern rim of the Pacific Ocean and a biodiversity hotspot, more than 90 percent of the wetlands have been lost to urban development, salt production and agriculture, a loss that primarily occurred in the century following 1850. Restoration is our primary mechanism for confronting this challenge. While wetland restoration design has advanced dramatically since the early designs of the 1980s, restoration analysis and evaluation remain challenges that until now have wholly or primarily required on-site sampling. This is a major challenge for larger restoration projects, such as the Napa- Sonoma Salt Marsh restoration in California. Previous studies have indicated that the Normalized Difference Vegetation Index (NDVI) has been used in some restoration analyses with apparent success, but data is limited. To better understand its potential, this study examines issues in restoration analysis in the context of wetland restorations. By comparing pre- and post-restoration remote sensing data, I found that two sites in the Napa-Sonoma Marsh restoration demonstrated mixed NDVI results and that changes depended on subarea and whether median or maximum NDVI was analyzed. The mixed results are explained by several factors: the inherent limitations of NDVI; the large restoration size; the fact that wetlands, less vegetated, present special challenges for analysis; and the fact that it is early in the post-restoration period. The case study supports the use of remote sensing and GIS for restoration analysis and evaluation, but also emphasizes their current limitations. Many of these limitations, which hinge on the complexity of the potential data involved, are likely to be addressed in the next generation as the relevant technology continues to develop.Item Long-term and over winter phytoplankton community dynamics in Lake Bonney, Antarctica(Montana State University - Bozeman, College of Agriculture, 2017) Patriarche, Jeffrey Dennis; Chairperson, Graduate Committee: John C. PriscuLake Bonney is a hypersaline permanently ice-covered lake in the Taylor Valley, Antarctica that hosts simplified microbial food-webs. Studied since the 1960s, there are many aspects which are poorly understood. Logistical constraints have prevented sampling during the austral winter, a 4-month period of 24-hour darkness. Our knowledge of how the resident photosynthetic microorganisms respond during this period is limited. With inputs from ephemeral glacial-melt streams the lake level (stage) of Bonney has risen more than 3 m since 2004. With no outflow streams, the only known water loss is via ablation of the permanent ice-cover. A study of the spatial and temporal changes in the phytoplankton community structure during this period of rapid lake level rise is lacking. During the summers (November-January) from 2004-05 to 2014-15 an in situ submersible spectrofluorometer was deployed in Lake Bonney to quantify the chlorophyll-a concentrations (microgram L -1) of four functional groups of microalgae (green algae, brown/mixed algae, cryptophytes, cyanobacteria) using known excitation/emission spectra. During the 2013-14 field season this same instrument was mounted on autonomous cable-crawling profilers deployed in both east and west lobes of Lake Bonney, obtaining the first ever daily profiles of chlorophyll-a concentration at an annual scale. Following a summer of rapid lake level rise (2010-11), an increasing trend in depth integrated chlorophyll-a concentration was observed in Lake Bonney. During the same period, the nutrient poor surface water has become increasingly dominated by green algae. Dramatic shifts were also observed in the phytoplankton communities during the polar night. The highest concentrations of mean chlorophyll-a were measured during the 24-hour darkness. Algal spectral groups containing species capable of a mixotrophic metabolism (brown/mixed and cryptophytes) increased in concentration and relative abundance when photosynthetically active radiation was unavailable. This work provides valuable contributions to our knowledge of long-term and year-round phytoplankton community dynamics in Lake Bonney, and improves our understanding of the metabolic strategies employed by organisms in this high latitude permanently ice-covered lake.Item Patch dynamics in grazed arid ecosystems(Montana State University - Bozeman, College of Agriculture, 2014) Bao, Sarina; Chairperson, Graduate Committee: Lisa J. RewSpatially heterogeneous, or patchy, vegetation patterns are widely distributed in arid and semiarid ecosystems and their water-redistributing role is of great ecological interests. Studies have shown effects of rain and wind, vegetation interactions, and disturbances on patch pattern formation and dynamics. In the absence of a synthesis, I have undertaken a review to systematically understand effects of these interacting factors in patch pattern formation and dynamics for two types of spotted and banded patterns. These two patterns are widely distributed and have distinctive, yet complementary features that encompass most of the patch pattern characteristics. I found that: 1) wind is as important as rain in patch pattern formation; 2) shrubs have a facilitation effect on the surrounding vegetation via several mechanisms, and 3) grazing disturbances that include foraging, excretion, and trampling have different effects on vegetation dynamics depending on the patch type and amount of annual precipitation (e.g. wet or dry years).Item Iron nutrition of plants and interactions with vascular wilt disease and light(Montana State University - Bozeman, College of Agriculture, 1989) Macur, Richard EugeneThe relationship between iron nutritional status and Verticillium Wilt disease in tomato possessing single gene resistance to Race 1 of Verticillium dahliae was investigated using hydroponic culture media. Iron limiting conditions increased the sensitivity of resistant tomatoes to the pathogen as expressed by wilting and chlorosis. Distance of fungal vascular invasion was approximately the same in both iron replete and iron limited treatments. Comparison of near-isolines revealed that the magnitude of disease expressed in Fe deficient Pixie II (resistant) was considerably less than that expressed by the susceptible Pixie variety. Infection of tomato did not enhance iron stress severity as quantified by root peroxidase activity and chlorophyll content of young leaves. The release of iron from horse spleen ferritin through photochemical reduction of Fe(III) to Fe(II) was studied in vitro. Spectrophotometric measurement of the Fe(ferrozine)3^2+ complex (specific for Fe(II)) was used to quantify rates of Fe mobilization: Cool white fluorescent plus incandescent light effectively promoted the rate of Fe release. Compounds known to be present in plants may provide further regulation of photorelease. Reductive removal from ferritin was inhibited by phosphate, and hydroxide, whereas citrate, oxalate, tartrate, and caffeate enhanced the release. Of the organic acids studied, caffeate was the only compound which induced detectable Fe release in the absence of irradiation. Rate constants ranged from 2.7 x 10^-3 sec^-1 (pH = 4.6) to 2.1 x 10^-3 sec^-1 (pH = 7.1) at 26.5°C. Synthesis of the photosynthetic apparatus is dependent on both light and iron. Thus, the findings provide one possible mechanism coupling chloroplast iron demand with iron release from ferritin. Treatments known to alter either phenolic metabolism or overall enzyme activity were utilized to examine the Fe reductive mechanisms involved in iron stress response at the roots. Although specific compounds caused elevation of internal o-dihydroxyphenol content, the overall root reduction capacity of Fe stressed plants was significantly suppressed. However, plant roots retained significant capacity to reduce Fe after tissues were subjected to severe protein denaturizing treatments. Thus, indications for both secreted reductant and enzymatic reduction mechanisms were observed.Item Band applications of elemental sulfur inoculated with Thiobacillus thioparus to enhance nutrient availability(Montana State University - Bozeman, College of Agriculture, 1987) DeLuca, Thomas HenryItem Spatial and temporal variations of phytoplankton populations in Lake Bonney, Antarctica(Montana State University - Bozeman, College of Agriculture, 2003) Tursich, Nicole LeaItem Establishment of native and invasive species along a riparian resource gradient(Montana State University - Bozeman, College of Agriculture, 2000) LeCain, Ronald RoyItem The influence of calcium carbonate on the availability and plant uptake of potassium in Montana soils(Montana State University - Bozeman, College of Agriculture, 1991) Moore, Thomas Glen
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