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Bottles, Butterflies, And Biomass: Recycled Glass Sand, Microbial Additions, And Herbivory Effects On Milkweed Growth, Kealey Skinner

Honors Theses

Plant-soil-microbe interactions are integral components of ecological networks and drive ecosystem function from the bottom-up. Whereas herbivores regulate ecosystem function from the top-down, having opposing and potentially complementary effects on ecosystem function. My thesis sought to understand how below-ground microbial communities contribute to herbivore preference and plant biomass across varied soil substrates. My thesis asked: how do substrate and soil microbial communities influence herbivore preference and plant biomass accumulation on swamp milkweed (Asclepias incarnata)? To address this question, seedlings of A. incarnata were sown in 2.5 cm wide × 10 cm deep pots filled with either natural beach sand or …

Distribution Mapping And Modeling Of The Invasive Japanese Knotweed, Jossalyn Rogalski

Masters Theses

This thesis investigates the distribution of invasive Japanese knotweed across Michigan. This plant poses significant challenges to land management due to its rapid growth, environmental impacts, and difficulty of removal once established. Using geographic information systems (GIS), remotely sensed data, and secondary environmental datasets, this research maps current infestations and analyzes key factors influencing the species’ growth and dispersal, such as soil composition, hydrology, land use, and a range of environmental variables, including climatic (annual mean temperature, temperature seasonality, annual precipitation, precipitation seasonality), elevation, vegetation and hydrological indices (NDVI, EVI, NDWI), percent tree cover, and distance to roads. Spatial analysis …

Evaluating The Impact Of Intercropping Vegetables And Cut Flowers On Yield And Conservation Biological Control, Alliance Igiraneza

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Specialty crops such as vegetables are some of the most susceptible to yield losses and increased management difficulty over time due to pests. One of the potential solutions to this problem, which aims at ensuring the sustainability of the sector, is using conservation biological control practices such as intercropping to increase diversity, while maintaining the economic feasibility and profitability of the system. This study was conducted to evaluate the impact of this management practice using Bell pepper (Capsicum annuum var. King Arthur) as the main crop, intercropped with flowers including zinnia (Zinnia elegans var. Benary’s Giant), sunflower ( …

Herbivory Of Phragmites Australis Along A Salinity Gradient In Connecticut Wetlands, Sydney H. Kolz

Honors Scholar Theses

Invasive Phragmites australis (common reed) is widely distributed in New England wetlands, where it often outcompetes native plants and decreases biodiversity throughout the food web. Controlling its invasion is a priority, especially in salt marsh habitat, but current management techniques are inefficient. Leveraging natural processes may improve control strategies, but in order to do so, we must first better understand how abiotic and biotic stressors interact and affect Phragmites. This study focuses on herbivory and salinity, two factors limiting Phragmites’ fitness. I measured soil salinity and quantified the damage of three herbivore guilds (i.e. gall-formers and stem-borers, leaf-chewers, and …

Investigating The Taxonomic Uncertainties Of Potentilla Rupincola, Natalie Elizabeth Hieber

Master's Theses

Landscape stewardship is an integral role for land managers that becomes more important when rare or endangered species occur within managed areas. Conservation across the landscape is a primary concern for land managers, but resources allocated for conservation can be limited due to many competing goals. Taxonomic uncertainty surrounding rare and endangered taxa, particularly plant taxa, that have historically been classified solely using morphological features further complicates conservation planning. One such taxon is Potentilla rupincola, a rare plant endemic to the eastern Rocky Mountains in Colorado. For over a century, botanists have debated whether P. rupincola is a distinct species …

Sorghum Grain Secondary Metabolites And Underlying Genetics To Reduce Foodborne Pathogens In Poultry, Maria A. Conti

All Dissertations

The rise in antibiotic-resistant pathogens poses a threat to the poultry industry's ability to maintain animal health, prompting growing interest in alternatives to synthetic antibiotics. The use of non-tannin sorghum [Sorghum bicolor (L.) Moench] in poultry rations offers a valuable alternative, as this cereal grain has a high bioactive profile that can provide health benefits, including antimicrobial (AM) activity. The scope of this study was to examine the AM potential of non-tannin sorghum grain against Clostridium perfringens, a major foodborne pathogen that negatively impacts poultry health and production. To that end, the inhibitory effects of a non-tannin sorghum …

Dendroclimatic Response Of The Wet Miombo Woodland Species: A Case Study Of Mufulira District, Copperbelt Province, Zambia, Collins Chibuye Malubeni

All-Inclusive List of Electronic Theses and Dissertations

Zambia is a tropical, landlocked country that lies in the South-Central part of Africa. The climate in Zambia includes distinct dry and rainy seasons, mainly influenced by the north-south movement of the Intertropical Convergence Zone (ITCZ), which shifts seasonally. This research is focused on understanding the relationship between tree growth and climate using dendrochronology. Forty-nine tropical species, including Julbernardia paniculata, Brachystegia longifolia, and Pericopsis angolensis, were analysed for dendroclimatic potential, and 70% showed clear ring formation, indicating that trees in this locality produce distinct annual ring boundaries. For the single species chronology, thirteen cores from eight trees that were initially …

Evaluating Fungal Endophytes Inoculation As A Mechanism For Salt Tolerance In Juncus Roemarianus, Rani Badve

Honors Theses

Salinity stress is increasing in coastal and estuarine ecosystems due to increasing temperatures and the reduction of freshwater inputs via precipitation pattern changes. Elevated salinity can negatively affect plant survival, threatening the stability of coastal wetlands and the ecosystem services they provide. Juncus roemerianus is a common and dominant marsh plant in the Northern Gulf Coast that lives in varying salinities. Growing evidence suggests that root-associated fungal endophytes may contribute to enhanced stress tolerance; however, the response of fungal communities to salinity remains poorly understood.

This study evaluated how salinity influences the abundance and diversity of culturable root-associated fungal communities …

Discerning Patterns Of Floral Sugar-Feeding: Dynamics Of The Mosquito Culex Antillummagnorum In Puerto Rico, Ella J. Branham

Master's Theses

Mosquitoes rely on sugar feeding for survival, primarily from flowering plants, yet mosquito–plant interactions remain understudied. I examined plant-feeding associations of the mosquito Culex antillummagnorum in the Luquillo Experimental Forest of Puerto Rico, which may clarify patterns of habitat use, disease dynamics, and broader species interactions. First, plant DNA was extracted from field-collected Cx. antillummagnorum to identify potential nectar sources. DNA barcoding produced positive matches to the flowering plant genera Billia, Aesculus, Cladium, Fimbristylis, Xyris, Cakile, and Habenaria. Habenaria was the most compelling result because it belongs to the same subtribe of orchids …

Leveraging Historic Collections: Investigating Morphometric Differentiation In Members Of The Arisaema Triphyllum (L.) Schott (Araceae) Species Complex, Morgan Bradley Russell

Graduate Theses and Dissertations

The Jack-in-the-pulpit (Arisaema triphyllum (L.) Schott) is an herbaceous perennial herb of North America, and its taxonomic history is full of confusion and rank shifts. Now split into six species, the A. triphyllum species complex consists of morphologically similar taxa that have differing ploidy levels. In Chapter I, I compiled a detailed introduction and history for these taxa, focusing on their taxonomic complexity and morphological ambiguity in herbarium specimens and immature plants. I also presented their ploidy distinctions and how the implications of polyploidy may hold answers to parsing them apart, especially in dried herbarium specimens where defining characteristics are …

Preliminary Vascular Plant Checklist Of The City Of Chattanooga, Matthew J. Scott

Honors Theses

The City of Chattanooga, Tennessee was designated as a National Park City in April 2025 by the National Park City Foundation. Yet, there has not been a comprehensive vascular flora compiled for the city, though there have been extensive collections and observations made of the plant biodiversity in the area from the late 1800s onward. The goal of this project was to examine both the existing herbarium collections and public observation records from iNaturalist to compile a preliminary vascular plant checklist for Chattanooga, and to include conservation and ecological data for the species currently documented to provide a holistic review …

Cis-Variant Gene-Expression Association Analysis: A Targeted Approach To Identify Functional Cis-Regulatory Variation, Sofiya Arora

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Phenotypic diversity in plants is largely driven by changes in gene function arising from mutations in both the coding and regulatory regions. Regulatory variation is particularly pervasive because it can fine-tune gene expression without disrupting protein function and is therefore less likely to be strongly selected against in natural populations. As a result, it has played a central role in evolution and domestication. In our previous genome-wide eQTL mapping study in maize, nearly two-thirds of the expressed genes were found to harbor detectable cis-expression quantitative trait loci (cis-eQTLs) with strong local effects on gene expression. Though these cis-variants are widespread, …

Quantitative Genetics, Genomics, And Phenomics In Maize And Sorghum, Nikee Shrestha

Complex Biosystems Program: Dissertations and Student Research

Generating the best crop varieties and hybrids requires identifying genes associated with the phenotype of interest and screening thousands of varieties across multiple locations. Quantitative genetics, along with comparative genomics, phenomics, and machine learning approaches, can help us identify target genes associated with the phenotype of interest to develop the right genotypes. Satellite platforms offer logistical and technical advantages in scalability and accessibility and could facilitate plot-level predictions, especially with steadily improving spatial resolution, thereby empowering the large-scale screening of thousands of genotypes across diverse locations. In the first chapter, I evaluated over 20,000 plot-level images of over 80 hybrid …

Forest Overstory Mortality & Recruitment Patterns Eight Years Following Wildfire In The Southern Appalachians, Ruth Cumberland

All Theses

In this study, we investigated patterns of forest overstory mortality and recruitment eight years after wildfire in a large wildfire site the Southern Appalachians, a topic that has not been thoroughly investigated to date. With evidence that pre-fire drought promotes post-fire mortality through impaired physiological function and increased fuel consumption, unknown patterns following wildfire are important to study under shifting climate and land-use conditions. In Chapter 1, three areas of interest were investigated: (a) functional group mortality response to wildfire effects, (b) temporal differences in early (1-3 years) and late (5-8 years) periods of delayed forest overstory mortality patterns following …

Assessment Of Super Absorbent Polymer In Soybean Cultivation Under Variable Irrigation Conditions In Nebraska, Ankit Chandra, Abia Katimbo, Ronaldo Marchezan, Martha Nabaggala

Department of Agricultural and Biological Systems Engineering: Presentations and White Papers

Water limitation is a primary constraint to soybean productivity in both irrigated and rainfed systems. Soil-applied superabsorbent polymers (SAPs) have been proposed as a strategy to buffer crops against episodic drought stress; however, their physiological and agronomic performance under varying irrigation regimes remains insufficiently quantified. Here, we evaluate three biodegradable polymer formulations: broader granules (BB), original granules (OG), and powder (PWR) applied at low (17.7 lb/ac) and high (120 lb/ac) rates under full (100% ET), reduced (50% ET), and no irrigation conditions in western Nebraska. Polymer application had negligible effects under full irrigation, with yields comparable to untreated controls. Under …

Degradation And Metabolic Analysis Of Synthesized Quorum-Sensing Signals By The Model Eukaryote Chlamydomonas Reinhardtii, Adam Josef Bach

Theses and Dissertations

Bacterial organisms can “talk” with one another on a colony-wide scale using a communication system known as quorum-sensing (QS) via chemical signals. These signals are produced at a basal rate throughout the life of the bacteria and are classified as autoinducers, which diffuse across the cell membrane. Once the critical concentration is reached, they begin to diffuse back into the cell and initiate a phenotypic change. As these signals exist outside the membrane of their producer, they are also accessible to other organisms. It has already been noted that some plant species uptake these compounds through their roots and break …

Diffuse Radiation Controls On Southern Pine Forest Ecosystem Functioning, Jeremy Forsythe

All Dissertations

Diffuse solar radiation, sunlight scattered by atmospheric aerosols and/or clouds, enhances plant photosynthesis through the diffuse fertilization effect (DFE), increasing ecosystem gross primary productivity (GPP) per unit of incoming radiation. Despite this known effect, pine forests of the southeastern United States remain comparatively understudied in the diffuse light literature. This is a critical knowledge gap, as the southeastern United States sequesters more carbon than any other region of the conterminous country (approximately 176 ± 26 Tg C yr⁻¹, or roughly 56% of national forest net carbon exchange), and the region experiences some of the highest biogenic aerosol loads in North …

Evaluation Of The Weed Control Efficacy And Potential Economic Returns Of An Autonomous Weeder In Vegetable Production Systems, Claire Plassmeyer

Graduate Theses and Dissertations

Vegetable production requires intensive weed management. Conventional producers rely on herbicide applications to manage weeds effectively at low costs; however, growers are under pressure to minimize chemical use due to environmental concerns and increased incidences of herbicide resistance. Non-conventional systems, including organic and sustainably focused small-scale production, rely primarily on cultural practices and physical weed control methods, which are labor-intensive and costly due to limited labor availability and rising wages. These concerns have prompted the development of autonomous weeding devices, such as unmanned ground vehicles (UGVs) equipped with navigation sensors and implements to provide repeated, high-precision weed control. Compact devices …

Effects Of Applying Humic Acid In-Furrow At Potato Planting, Jonathan Tyler Price

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Many products are marketed towards potato farmers that purport to have a positive return on investment for yield and quality. Humic acids, which are comprised of long chained, organic molecules that can be naturally or industrially made, are currently being marketed in this way. The use of these materials is reported to improve nutrient uptake, increase soil health, encourage vigorous growth, and most importantly, increase yields.  From 2023-2025, the in-furrow application of humic acid containing commercial products was evaluated in Pennsylvania on the cultivars ‘Lehigh’ and ‘Waneta’. Black Label Zn, Duo Maxx, Fertiactyl RhiZn, Humi-flex FA, Hydra-Hume, and Monty's Liquid …

Passive Microwave Remote Sensing Of Flash Drought Impacts On Vegetation, Quinton R. Deppert

School of Natural Resources: Dissertations, Theses, and Student Research

In 2002, Dr. Mark Svoboda characterized a new form of drought known as flash drought. Flash drought was defined as a rapid decline in vegetation health caused by severe heat and drought. In recent years, attempts to quantify the impacts of flash drought via precipitation, soil moisture, evapotranspiration, and temperature indicators have proliferated. What has rarely been quantified is what the rapid decline in vegetation health amid flash drought looks like through remote sensing. This is because vegetation health indices like the Normalized Difference Vegetation Index (NDVI) are derived from the visible and infrared regions of the electromagnetic spectrum and …

Cannabis: A Model Plant To Study Light-Mediated Reproductive Development, Madigan J.H. Eckels

All Graduate Theses and Dissertations, Fall 2023 to Present

Cannabis (Cannabis sativa) is a plant of increasing importance for research, medical, recreational, industrial, and agricultural purposes, but a strict legal landscape means that it was chronically understudied. Now that research institutions can utilize this plant for study, we require updated terminology to describe various cannabis flowering types that occur under ideal and non-ideal growing conditions. We introduce new flowering terminology and describe them in text and with photographs.

Plants use light as a resource to power photosynthesis, and a greater total sum of photons generally increases yield. In controlled environment agriculture where growers utilize light fixtures instead …

Dried Water Treatment Residuals Might Be An Option To Reduce Soluble Reactive Phosphorus Release From Soils, Katie B. Mckay

Biological and Agricultural Engineering Undergraduate Honors Theses

Nonpoint source pollution from agricultural landscapes contributes to freshwater eutrophication, with legacy phosphorus (P) in soils potentially driving soluble reactive phosphorus (SRP) losses to surface waters. The objectives of this study were to evaluate SRP adsorption by dried water treatment residuals (WTRs) produced by Beaver Water District, quantify reductions in soil SRP release across increasing WTR application rates, and compare dried WTR performance to prior WTR studies.

Dried WTRs (~98% solids) were assessed using batch sorption experiments and soil core incubations. Phosphorus sorption was measured by mixing WTRs with CaCl₂ solutions containing increasing SRP concentrations and fitting results to …

Arkansas Soybean Research Studies 2024, Jeremy Ross

Arkansas Agricultural Experiment Station Research Series

The 2024 Arkansas Soybean Research Studies includes research reports on topics pertaining to soybean across several disciplines from breeding to post-harvest processing. Research reports contained in this publication may represent preliminary or only data from a single year or limited results; therefore, these results should not be used as a basis for long-term recommendations. Several research reports in this publication will appear in other University of Arkansas Division of Agriculture’s Arkansas Agricultural Experiment Station publications. This duplication is the result of the overlap in research coverage between disciplines and our effort to inform Arkansas soybean producers of the research being …

Sequential Products Of Anaerobic Denitrification In Calcareous And Noncalcareous Soils By Use Of The Gas Chromatograph, Grant S. Cooper

All Graduate Theses and Dissertations, Fall 2023 to Present

The sequential products of anaerobic denitrification were determined on seven Western soils (four alkaline, two acid, and one neutral) by soil and gas analysis. The soils with 1% alfalfa and added KNO3 were incubated at moistures slightly greater than field capacity and with an atmosphere of He. The soils and gases were periodically analyzed and balance sheets prepared. The sequence of NO3-->NO2-->N2O-->N2 operated in all soils. The rates of nitrogen interchanges and maximal amounts of nitrate, N2O2 and N2 were determined. From this data it was postulated that the rate-limiting process for denitrification in acid soils is …

Evaluation Of Fertilizer Recommendation And Soil Amendment Impacts On Crop Production In The Intermountain West, Megan Baker

All Graduate Theses and Dissertations, Fall 2023 to Present

Fertilizers improve crop yield and quality by supplying crops with essential nutrients, but can also be a significant input cost. Determining what nutrients and rates to apply for optimal crop growth can be difficult, leading many growers to use external sources for these decisions. Land-grant universities are a common source for fertilizer recommendations, but often based on decades-old research and should be evaluated periodically to verify effectiveness and calibrated to current soil analysis methods. Current Utah State University (USU) guidelines for sulfur (S) and zinc (Zn) were tested across Utah in on-farm trials in 2021-2025. Zinc applications of 5 or …

Forage Responses To Biological Inoculant And Seed Rates In The Intermountain West, Roy Reid

All Graduate Theses and Dissertations, Fall 2023 to Present

Improving the efficiency of fertilizer and seed use is increasingly important for forage producers in the Intermountain West, where alfalfa and silage corn form the foundation of dairy and livestock feed. This thesis evaluates two strategies designed to boost crop productivity: microbial fertilizer coatings and variable-rate seeding.

The first study examined whether Powercoat®, a fertilizer-applied microbial inoculant, could enhance yield, forage quality, or soil phosphorus availability in alfalfa grown on four commercial fields in northern Utah. Across all locations, fertilizer increased yield at only two sites, and Powercoat did not provide additional improvements in yield, forage quality, or soil nutrient …

Alfalfa Yield, Quality, And Nutrient Use Response To Pivot Sprinkler Technology, Deficit Irrigation, And Genetics, Dakota Boren

All Graduate Theses and Dissertations, Fall 2023 to Present

In water limited environments, alfalfa is often criticized for its high water use, prompting implementation of new irrigation technologies, deficit irrigation, and adapted crop genetics. Cumulative potential benefits from combining, or stacking, these water-optimizing practices have not been identified. The objective of this on-farm research study was to determine how irrigation technologies, deficit irrigation, genetics, and combinations of these practices impact alfalfa yield and forage quality. Trials were conducted at three sites in Utah from 2020 to 2022 on young alfalfa stands (establishment and first one to three production years). Treatments included five irrigation technologies, four irrigation rates, and two …

Discovering The Genetics Underlying Speciation Traits In Heuchera (Coral Bells), Tajinder Singh

Honors Theses

Hybridization is a key evolutionary mechanism for generating biological diversity, ultimately shaping diversification and adaptation of plant lineages in natural and agroecosystems.  Our understanding of the frequency, distribution, and significance of hybridization is rapidly increasing, but the external driving forces that dictate why certain species hybridize, and others do not remain obscure. The physical traits that shape gene flow and trait sharing among species are likely to be among the key factors that directly control hybridization. Gene flow in most plants is mediated by pollinating insects and thus by pollination syndromes, which are suites of floral traits that have evolved …

The Effect Of Liquid Foliar Fertilizer And Pruning Combinations On The Growth Of Productive Phase Arabica Coffee Plants (Coffea Arabica L.), Syifa Djuita Putri, Alvito Krishna Balapradhana, Mira Ariyanti, Intan Ratna Dewi Anjarsari, Yudithia Maxiselly

Jurnal Kultivasi

In recent years, productivity decline in arabica coffee has become a real issue in Indonesia. This decay has been brought about by various external and internal factors that are beyond human control. Various factors, including suboptimal cultivation practices, take part in this process. The objective of the present study was to evaluate the effect of pruning combined with foliar fertilizer application (coconut water and sugarcane molasses) and 6-benzylaminopurine (BAP) on the vegetative growth of arabica coffee plants during the production phase. The research was conducted at Ciparanje Experimental Field, Universitas Padjadjaran, using a randomized complete block design with seven treatments …

Morphology And Bioactive Compounds Of Gurmar (Gymnema Sylvestre) With Potential As Antidiabetics, Neny Novita Yuliany, Abdillah Maulana Farhan, Putry Lazimatu Ziyaroh, Edia Fitri Dwinianti, Husnatun Nihayah, Mukhamad Su'udi

Jurnal Kultivasi

The medicinal plant Gymnema sylvestre is widely known for its ability to lower blood sugar levels. This study reviewed the physical characteristics and bioactive compounds of G. sylvestre sourced from different regions, emphasizing its potential as an antidiabetic agent. Morphological analysis includes leaf structure, trichome presence, and other anatomical features, which can influence the plant's chemical profile. Phytochemical analysis, performed using techniques like GC-MS, identifies key bioactive compounds such as saponins, flavonoids, and gymnemic acids, which contribute to its hypoglycemic effect. The findings indicate that regional variations can affect the concentration and presence of these compounds, suggesting that environmental factors …