Physical Sciences and Mathematics Commons^™

Assessing The Drivers Of Legacy Phosphorus Loading And Distribution In Shallow Eutrophic Lake Sediments And The Impacts Of Intervention, Ashton P. Kirol

Graduate College Dissertations and Theses

The eutrophication of freshwater lakes from excessive nutrient runoff leads to decreased water quality and worsening cyanobacteria blooms. Water quality improvements in shallow eutrophic lakes can be delayed by decades due to the seasonal recycling of legacy phosphorus (P) enriched lake sediments, even when external nutrient loads are addressed. It is critical to understand the drivers of internal P loading to suppress this source of P through intervention to meet water quality goals. This study contrasts two shallow eutrophic systems, Lake Carmi and Missisquoi Bay in Lake Champlain, impacted by legacy P loading driven by the occurrence of low dissolved …

Anaerobic Soil Disinfestation And Vermicompost To Manage Rhizoctonia Solani In Organic Lettuce, Anna Rissland Brown

Graduate College Dissertations and Theses

Rhizoctonia solani Kühn is an aggressive saprophytic soilborne fungal plant pathogen that is distributed globally and infects many crops including Solanaceae, Fabaceae, and Asteraceae. The lack of effective organic methods to control R. solani and the resulting yield losses contribute to the economic insecurity of farms and farmers. The overall aim of this study was to compare two organic certifiable approaches to manage bottom rot caused by R. solani (subspecies AG1-IB) in field-grown organic lettuce: anaerobic soil infestation (ASD) and thermophilic compost cured by vermicompost (vermicompost). A commercially available biocontrol product and an untreated control were used as references.

Two …

Relationships Between Deformation, Magmatism, And Sedimentary Geology Along The Mongol-Okhotsk Suture Zone: Ulz Gol Region, Mongolia, Jarret William Pidgeon

Graduate College Dissertations and Theses

The Mongol-Okhotsk Suture Zone (MOSZ) is a continental-scale structure that signifies the closure of a Paleozoic ocean basin. Though suturing of the Siberian Craton and southern Mongolian terranes is thought to have occurred in the Mesozoic Era, the exact timing and mechanisms remain debated. This prolonged period of orogenic activity is believed to be responsible for forming much of the Central Asian Orogenic Belt (CAOB) that encompasses essentially all of Mongolia, part of China, Siberia, and Kazakhstan. Also permeated throughout the CAOB are intra-continental, post-suturing structures. In the Late Jurassic–Early Cretaceous, a significant, crustal-scale extensional episode affected central and eastern …

In-Situ Weathering Of Calcium Bearing Minerals In Forested Ecosystems, Victoria Treto

Graduate College Dissertations and Theses

Timber harvests in the northeastern United States are integral to its economy but shifts in land management, biotic stresses, and nutrient limitations are diminishing forest productivity levels. The effects of harvesting severity and repeated harvests result in net losses of base cation nutrients which decreases woody biomass, potentially as much as 20%. Calcium (Ca) serves to regulate critical processes linked to tree growth and ecosystem health, but it is the quickest depleting base cation from northeastern forest soils. As a result, the quantification of nutrient-bearing minerals in forest soils is fundamental in predicting long-term sustainability of wood production. Further, the …

Examining The Relationship Between The Ereendavaa Metamorphic Core Complex And Duch Gol Basin In Northeast Mongolia In The Context Of The Mongol-Okhotsk Suture, Gavin Pirrie

Graduate College Dissertations and Theses

The Mongol-Okhotsk suture is integral in understanding the closure of the Mongol-Okhotsk Ocean, an ocean basin that once separated the Siberian craton from terranes of the Central Asian Orogenic Belt in southern Mongolia. However, the timing of closure and exact location of the suture are poorly known. This study examines two areas in northeastern Mongolia adjacent to the suture, the Ereendavaa Metamorphic Core Complex (EMCC) and the Duch Gol Basin, to aid in this understanding. The EMCC is an Early Cretaceous metamorphic core complex with an associated top-to-the-NW extensional detachment fault. Two sets of mineral lineations have previously been documented …

Drivers And Controls On Soil Carbon Storage In Temperate Forest Soils, Adam Noel

Graduate College Dissertations and Theses

Elevated atmospheric CO2 levels pose a threat the global climate stability but large amounts of carbon can be held within soils worldwide. Forests function to capture carbon and eventually, through litter inputs and decomposition, add this carbon to soil systems. This process is driven by climate, landscape conditions, forest and soil characteristics, that have complex interactions with one another across spatial scales. In this dissertation, I examine drivers of carbon contributions to the mineral soil, via litter decomposition and forest floor carbon pools, and how these contributions vary with forest composition and soil conditions. First, using data from a 10-year …

Phosphorus Dynamics In Restored Riparian Wetlands On Former Agricultural Land In Vermont, Adrian Robert Hendrick Wiegman

Graduate College Dissertations and Theses

Wetland restoration has numerous potential ecological and societal benefits, one of which is the retention of phosphorus (P) and consequent protection of downstream water bodies from eutrophication. Past studies focused on influents to and effluents from a variety of wetland types have documented net P retention. However, some wetland systems are less effective at P capture and wetland P retention capacity can change over time. Certain wetland types - especially riparian wetlands restored on former agricultural land - remain understudied. In Vermont, most of the over 4000 potential wetland restoration sites in the Lake Champlain Basin are located on current …

Characterizing Phosphorus Transport To Agricultural Tile Drains In Vermont, Ryan Andrew Ruggiero

Graduate College Dissertations and Theses

Dairy agroecosystems use subsurface or tile drainage to improve trafficability and crop yield. One of the main concerns of tile drainage is that it acts as a major source of non-point phosphorus (P) pollution because of preferential flow pathways (PFP). PFP are large conduits in the soil that allow rapid movement of water. This reduces contact time infiltrate has with deeper soil horizons, which are not saturated with P and that could act as a sink for this nutrient. Also, PFP are responsible for channeling manure applied at the surface to tile drains. The rate of tile drain installation is …

Assessing Assumptions And Applying Cosmogenic Nuclide Methods To Earth Surface Processes, Christopher T. Halsted

Graduate College Dissertations and Theses

Terrestrial in situ cosmogenic radionuclides are powerful tools for quantifying rates and durations of Earth surface processes. Among the many applications of cosmogenic radionuclides are quantification of basin-scale erosion rates, burial durations of paleosols and terrace sediments, and unraveling of glacial chronologies. In this dissertation I use large data sets to investigate methodological assumptions critical for using cosmogenic radionuclides to interpret Earth surface processes, and I apply this isotope system to reconstruct the deglacial history of the Laurentide Ice Sheet in the northeastern United States.

I use new and previously-published measurements of in situ 26Al and 10Be concentrations, over 300 …

Ghgs From Bmps: Examining The Factors That Mediate Soilborne Greenhouse Gas Emissions From Agricultural Best Management Practices, Sarah Brickman

Graduate College Dissertations and Theses

Agricultural best management practices (BMPs) promote soil health and achieve multiple positive environmental outcomes. However, practices that are intended to solve one environmental challenge may have unintended climate impacts, therefore presenting a potential tradeoff. For example, manure injection is a BMP that can reduce runoff and nitrogen loss as ammonia gas (NH3) but can increase N2O and CO2 emissions compared to manure broadcast application. This thesis explores how CO2 and N2O emissions from manure injection compare to other soil fertility practices as well as the conditions that may enhance or reduce these greenhouse gas (GHG) fluxes. First, during a two-year …

Soil Invertebrates In Agriculture: Assessing Ecosystem Services, Biodiversity Impacts, And Farmer Perceptions, Eva Kinnebrew

Graduate College Dissertations and Theses

Harmonizing biological diversity and crop production is a major goal towards building more sustainable food systems. Soil invertebrates are diverse and abundant organisms in agriculture, but relatively little is known about their benefits or how agricultural management impacts them. In this dissertation, I dig into the complex interactions between agricultural land use and soil invertebrate biodiversity to better inform farmer decision-making. I find that soil invertebrate communities have major potential contributions to agroecosystems (Chapter 2) and are shaped heavily by agricultural land use (Chapters 3, 4), but remain too uncertain to contribute to farmers’ management choices (Chapter 5). First, I …

Elements Of Biocontrol Strategies For Pheretimoid Earthworms, Maryam Nouri-Aiin

Graduate College Dissertations and Theses

Jumping worms (Megascolecidae) in the pheretimoid complex, have raisedconsiderable environmental concerns with conservationists, ecologists, policy makers, and the public. Their impacts on North American forests and high density is distinct from earthworms in other families. Most of the infested forests are near horticultural settings. Practicable options to manage their dispersal into forests do not exist. This dissertation examines the potential of an entomopathogenic fungus to control them in horticulture. It also investigates major barriers to managing their spread and studying their ecology including species identification, phenology, and genetic diversity. First, to discover the best time to apply biocontrol agents, I …

Disentangling The Separate And Intersecting Pathways Of Carbon And Nitrogen Response To Overlapping Drivers, Manya Ruckhaus

Graduate College Dissertations and Theses

Anthropogenic activities have drastically altered atmospheric composition — leading to unprecedented disturbances that might push ecosystems across thresholds where important ecosystem services, such as clean water and healthy soils are at risk. Such disturbances include increased heavy precipitation, rain on snow events, and longer-term shifts in rain composition and precipitation amount. Catchment response to such perturbations is widely variable, indicating that specific catchment characteristics may govern the resistance and resilience of the system. Forested catchments in the northeastern, U.S. have reported increasing dissolved organic carbon (DOC) concentrations in streams, and links to shifts in drivers—such as precipitation chemistry, season, and …

Trace Metal Contamination In Urban Soils: A Field To Laboratory Methodological Framework For Characterization And Education, Sandra Leighanne Walser

Graduate College Dissertations and Theses

Urban soils around the world have been found to possess elevated concentrations of toxic trace metals such as As, Cd, Cu, Pb, Mn, Hg, Zn known to pose human health risks. Tightening environmental legislation and further elucidation of the detrimental health impacts from trace metals has necessitated more efficient means of contamination assessment, as well as greater public awareness. Within this thesis, I sought to develop an array of tools to holistically approach the socially relevant environmental challenges derived from heavy metal soil contamination. These tools consist in providing means to simplify Pb, Zn and Cu analysis in-situ, develop strategies …

Assessing The Impact Of Changes In Acid Deposition On Dissolved Organic Carbon Mobilization From Two Forested Headwater Catchments: A Combined Lab And Field Study, Caitlin Bristol

Graduate College Dissertations and Theses

Over the past few decades, dissolved organic carbon (DOC) concentrations in headwater streams in the northern hemisphere changed. Because these changes in DOC coincided with decreased acid deposition, a potential link was proposed early on. More recent research indicated that catchment attributes, especially soil characteristics and the presence of Ca-bearing minerals, play an important role in modulating DOC release from watersheds, but further research is necessary.

To investigate the role of catchment characteristics on DOC dynamics, I use several watersheds in the Northeastern United States with similar attributes and well-constrained differences. Sleepers River Research Watershed (SRRW) has naturally occurring Calcium …

Distinguishing Different Styles Of Transpressional Deformation At An Obliquely Convergent Plate Margin, Fiordland, New Zealand, Emily Sarah Lincoln

Graduate College Dissertations and Theses

Fiordland, New Zealand provides one of the best-known and deepest (to 65 km) exposures of an Early Cretaceous magmatic arc root known to geologists. These exposures allow for us to study tectonic deformational processes at varying crustal depths, including the role of pre-existing structures on later reactivation. The well-preserved Grebe shear zone (GSZ) marks the boundary between major basement terranes in southern Fiordland and has undergone multiple episodes of deformation during the Cretaceous and Cenozoic time periods. The primary focus of this study is to recognize and characterize the differing phases of deformation that occurred along this shear zone. To …

Organic Amendments Alter Soil Hydrology And Belowground Microbiome Of Tomato (Solanum Lycopersicum), Taylor Readyhough

Graduate College Dissertations and Theses

Manure-derived organic amendments are a cost-effective tool that provide many potential benefits to plant and soil health. For example, amendment applications may increase soil fertility, improve soil structure, stimulate microbial activity, and suppress plant pathogens. Yet, responses to these applications may have unintended consequences. Inherent variability in the physical, chemical, and biological characteristics of these materials can result in inconsistent outcomes observed after their application. These differences are manifested in plant growth, soil physiochemical properties, and soil microbial community composition. Popular manure-derived organic amendments include dairy manure compost and poultry manure pellets. Dairy manure is an abundant resource on many …

Phosphorus And Nitrogen Losses In Runoff From Fields With And Without Tile Drainage, Leanna Thalmann

Graduate College Dissertations and Theses

Nutrient losses in surface and subsurface drainage from crop fields have important water quality implications. The deterioration of water quality in segments of Lake Champlain has led to efforts to reduce phosphorus (P) and nitrogen (N) export from agricultural fields. This thesis presents data from two years of edge-of-field monitoring in two adjacent corn (Zea mays L.) silage fields in Keeseville, New York. One field has only surface drainage improvements with monitoring equipment, and the other has both surface and subsurface drainage modifications and monitoring equipment. The study took place from October 2018 to September 2020 and quantified flow and …

Cluster Analysis Of Time Series Data With Application To Hydrological Events And Serious Illness Conversations, Ali Javed

Graduate College Dissertations and Theses

Cluster analysis explores the underlying structure of data and organizes it into groups (i.e., clusters) such that observations within the same group are more similar than those in different groups. Quantifying the ``similarity'' between observations, choosing the optimal number of clusters, and interpreting the results all require careful consideration of the research question at hand, the model parameters, the amount of data and their attributes. In this dissertation, the first manuscript explores the impact of design choices and the variability in clustering performance on different datasets. This is demonstrated through a benchmark study consisting of 128 datasets from the University …

Geomechanical, Geochemical, And Hydrological Aspects Of Co2 Injection Into Saline Reservoirs, Maziar Foroutan

Graduate College Dissertations and Theses

Carbon dioxide Capturing, and Sequestration (CCS) is a promising technique that helps mitigate the amount of CO2 emitted into the atmosphere. CCS process mainly involves capturing CO2 at the industrial plant, followed by transportation and injection into a suitable geological storage, under supercritical conditions. Saline aquifers are among the best geological storage candidates due to their availability, high storage capacity and injectivity. Despite the CCUS technology promise, several public safety concerns remain to be address, including but not limited to reservoir/wellbore stability and integrity, CO2 leakage, ground deformation (uplift) and induced seismicity.

The injected supercritical CO2 is trapped through different …

Enhancing Ecosystem Services And Climate Resilience In Agriculture: A Transdisciplinary Approach, Alissa White

Graduate College Dissertations and Theses

A complex of social, economic and environmental factors influences agricultural management in the northeastern US. Farmers often balance goals of farm viability, environmental stewardship, and resilience to climate change, while also under public pressure to enhance the provisioning of ecosystem services from their landscapes. Changes in farm management have been identified as cost-effective ways to address both local water quality issues, and global anthropogenic influences on greenhouse gas concentrations. Individual decision-making on the part of farmers that determines the fate of ecosystem service provisioning from agroecosystems, placing increasing importance on understanding how policy, outreach and research can support farmers’ capacity …

Characterizing Mass Loss In Central Cuba Using Long-Term Sediment Generation Rates And Rock Dissolution Rates, Mae Kate Campbell

Graduate College Dissertations and Theses

Knowledge of denudation rates over geologic timescales provides important insight into the processes that govern soil formation, the regulation of Earth’s climate, and the evolution of landscapes. Accurately establishing long-term denudation rates is also key to understanding how human actions have altered the rates and patterns of erosion over time. While cosmogenic nuclides are often used to measure long-term denudation rates at the basin scale, these rates can be unrepresentative of total landscape denudation in areas where significant mass loss occurs through rock dissolution. In tropical landscapes, mass loss by solution often represents a significant portion of total landscape mass …

Guide To Urban Gardening In Winooski Valley, Vermont, Grace Claire O'Neil

Graduate College Dissertations and Theses

Urban gardens have become a growing interest in the Burlington, Vermont area. As interest grows, soil management, amendment, and health are integral to garden productivity. A baseline of soil health for the Burlington Area Community Gardens was created. Explored hypotheses include how nutrient concentrations changed over time (2011 to 2018) in till and no-till scenarios.

Ten sites in the Winooski Valley area were soil sampled in the Fall of 2018, along with eight sites in the Chittenden County vicinity in the Spring of 2019 for comparison. Using the Modified Morgan’s Universal Extraction Solution, soil nutrients such as phosphorus (P), potassium …

The Architecture Of A Lower-Crustal Shear Zone And Evidence For Along-Strike Variations In Strain Localization And Partitioning, Fiordland, New Zealand, Peter Carl Lindquist

Graduate College Dissertations and Theses

Rocks exposed in Fiordland, New Zealand provide a record of magmatic and tectonic processes that were active in the middle to lower crust of a magmatic arc during the Early Cretaceous. The George Sound shear zone (GSSZ) is one expression of those processes, and is a steep, lower-crustal shear zone that accommodated oblique sinistral motion within the continental margin of Gondwana. I have compiled structural and petrologic observations from five field areas that span the 50 km length of the exposed GSSZ. Directional and orientation statistics allow me to compare the orientation of fabrics at each field area to characterize …

Evidence For Polyphase Deformation In The Shear Zones Bounding The Chester And Athens Domes, Southeastern Vermont, From 40ar/39ar Geochronology, Kristin Schnalzer

Graduate College Dissertations and Theses

The Chester and Athens Domes are a composite mantled gneiss dome in southeast Vermont. While debate persists regarding the mechanisms of dome formation, most workers consider the domes to have formed during the Acadian Orogeny. This study integrates the results of 40Ar/39Ar step-heating of single mineral grains, or small multigrain aliquots, with data from microstructural analyses from samples collected in multiple transects across the dome-bounding shear zone(s) in order to understand the relationship between metamorphism and deformation. Results from the sheared units along the north and south transects are presented from west to east. In the north, hornblende from the …

Assessing The Biogeochemical Drivers Of Dissolved Organic Carbon (Doc) In Forested Headwater Catchments: A Multi-Scaled Approach, Thomas Adler

Graduate College Dissertations and Theses

Variability in export of dissolved organic carbon (DOC) from forested headwater catchments has been attributed to an array of hydrologic, biotic and geochemical drivers. In the Northeast United States specifically, one of the most commonly cited drivers is recovery from acid rain. A major challenge in understanding DOC dynamics has been relating long-term regional trends and patterns to catchment-scale processes and we address this challenge by integrating data driven and experimental methods to analyze trends and processes across spatial scales. On the regional scale, we quantify long-term trends of stream DOC concentrations in USGS headwater catchments with flow adjusted Seasonal …

The Environmental Microbiome In A Changing World: Microbial Processes And Biogeochemistry, Stephanie Juice

Graduate College Dissertations and Theses

Climate change can alter ecosystem processes and organismal phenology through both long-term, gradual changes and alteration of disturbance regimes. Because microbes mediate decomposition, and therefore the initial stages of nutrient cycling, soil biogeochemical responses to climate change will be driven by microbial responses to changes in temperature, precipitation, and pulsed climatic events. Improving projections of soil ecological and biogeochemical responses to climate change effects therefore requires greater knowledge of microbial contributions to decomposition. This dissertation examines soil microbial and biogeochemical responses to the long-term and punctuated effects of climate change, as well as improvement to decomposition models following addition of …

Seasonal Water Column Dynamics Exert Strong Control On The Chemical Partitioning Of Benthic Phosphorus Pools Of Shallow Eutrophic Freshwater Systems, Meagan Leduc

Graduate College Dissertations and Theses

In shallow lake systems, phosphorus (P) availability to cyanobacteria populations is often controlled by the release (internal loading) or sequestration of sediment P. This study provides novel insight into the feedbacks between the water column and benthic P pools across multiple time scales and explain how these dynamics influence chemical partitioning of P in lake sediment. Phosphorus partitioning in seasonal sediment core time series collected from a shallow eutrophic bay of Lake Champlain were quantified with SEDEX and enzyme hydrolysis selective extraction schemes. Time series extraction data were interpreted with concurrent water column physical and biogeochemical monitoring data to examine …

Multiscale Expression Of Apatite Dissolution, Adele Conde

Graduate College Dissertations and Theses

The weathering of apatite is the foundation of the phosphorus cycle and essential to life, yet little is known about the nanoscale mechanisms driving apatite weathering. Deciphering nanoscale dissolution in apatite is a significant step to understand phosphate weathering behavior, that was key to the development of life. Determining what controls apatite weathering can impact many areas of environmental and medical mineralogy such as dentistry, contaminant scavenging, geochronology, and paleoenvironment studies. The aim of this study was to characterize apatite dissolution across scales with an emphasis on the nanoscale mechanisms. Recent research on the weathering of silicate minerals at the …

Phosphorus Mobility And Speciation Under Dynamic Redox Conditions In Shallow Eutrophic Freshwater Systems, Austin Wilkes

Graduate College Dissertations and Theses

Internal loading of phosphorus (P) from lake sediments can delay the recovery of lakes from eutrophication for years to decades following decreases in external nutrient inputs. While internal P loading is a pervasive problem in freshwater systems, molecular speciation of P in benthic sediments of these systems remains poorly characterized. As different P species will exhibit different responses to changing sediment-water interface (SWI) geochemistry, quantifying P speciation in sediments is a critical step in understanding P dynamics in sediment-water systems. Here, various synchrotron-based techniques were employed to directly probe the bonding environments of P and iron (Fe) in natural and …