Digital Commons Network^™

Inherited Local Shrinkage For Adaptive Functional Form Discovery, Jacob Colestin Schultz

Dissertations and Theses

Statistical models frequently employ nonlinear effects, interactions, and multiresolution basis expansions to represent complex relationships between predictors and responses. Determining the appropriate level of model complexity, however, remains a fundamental challenge. This dissertation introduces Inherited Local Shrinkage (ILS), a Bayesian global-local shrinkage framework for adaptive functional form discovery that enforces strong heredity among hierarchically related predictors.

ILS propagates shrinkage through directed acyclic graphs representing predictor inheritance, ensuring that increasingly complex terms are retained only when supported by simpler parent structure. The framework applies broadly to polynomial regression, interaction models, wavelets, splines, and other hierarchical basis expansions, while naturally extending to …

Invasion Dynamics, Environmental Conditions, And Community Impacts Of Yellow Sweetclover (Melilotus Officinalis) Across The Northern Great Plains, Sakshi Saraf

Dissertations and Theses

Understanding how environmental conditions and invasion dynamics shape native plant Communities is critical for conserving and managing the semi-arid grasslands of the Northern Great Plains (NGP). Invasive plant species are increasingly altering ecosystem structure and function across this region, yet knowledge gaps remain regarding the drivers of invasion, their spatiotemporal dynamics, and their associations with native plant communities. This dissertation investigates three questions: (1) what environmental conditions are associated with the distribution and abundance of the invasive legume Melilotus officinalis (yellow sweetclover; MEOF), (2) how does MEOF vary across space and time under climatic conditions, and (3) how are environmental …

Systematics And Phylogeography Of Mundochthonius Chamberlin, 1929, In The Pacific Northwest (Chelicerata, Pseudoscorpiones), Amanda Rai Montoya-Cowan

Dissertations and Theses

Understanding the processes that drive genetic divergence and species formation is central to evolutionary biology. Invertebrates with low dispersal ability, such as pseudoscorpions, are especially prone to cryptic diversification due to their occupancy of niche microhabitats and sensitivity to landscape barriers. Despite their ecological roles as predators and bioindicators, pseudoscorpions remain one of the least studied arachnid groups, with limited taxonomic resolution and few integrative studies. This research focuses on the genus Mundochthonius in the Pacific Northwest, particularly M. pacificus, a morphologically conserved species whose true diversity and distribution remain poorly understood.

Field surveys guided by a GIS-based habitat …

Urban Wildlife In Your Backyard: Community Experiences With Coyotes And Outdoor Cats, Clarissa Emma Cressotti

Dissertations and Theses

Urbanization reshapes ecological processes by fragmenting habitat and altering patterns of human-wildlife interaction, often reducing biodiversity. However, at the household scale, residential yards can either enhance or inhibit ecological connectivity - functioning as informal habitat stepping stones or barriers to wildlife. This thesis examines how residents' environmental attitudes, wildlife experiences, and socio-demographic characteristics influence yard-level behaviors and shape the presence of urban-adapted wildlife species, particularly coyotes and domestic cats, across the Portland, Oregon metropolitan region. A mixed-methods, social-ecological framework guided the analysis, integrating survey data from 244 households with wildlife detections from motion-triggered cameras (Urban Wildlife Information Network, UWIN), citizen …

Urban Beavers At The Crossroads: How Ecological Knowledge, Sociodemographic, And Spatial Context Shape Public Perception And Coexistence Preferences, Matthew Guziejka

Dissertations and Theses

Urban beavers demonstrate synurbization by adapting to urban environments, offering ecological benefits such as biodiversity enhancement and flood mitigation, while also occasionally conflicting with infrastructure. This study examines how ecological knowledge, sociodemographics, and spatial context influence public perceptions and management preferences for urban beavers in the Tualatin River watershed, Oregon.

A voluntary survey of 176 participants from peri-urban areas assessed demographic characteristics, ecological knowledge, and attitudes toward management approaches. Spatial factors, such as proximity to watercourses and green spaces, were also analyzed. Logistic regression analyses were used to explore relationships between these factors and management preferences. Political orientation was significantly …

Influence Of Inselbergs On Bat Diversity In Afrotropical Ecosystems, Amanda Lee Grunwald

Dissertations and Theses

Humans are altering biological communities on local to global scales, driving profound changes in biodiversity and ecosystem functioning. However, significant gaps and biases in biodiversity data hinder our understanding of ecosystem interactions, making it challenging to develop effective, data-driven policies to protect remaining biodiversity. Bats, the second most species-rich groups of mammals, have a global distribution, and perform a broad array of vital ecosystem functions. Their diversity peaks in the tropics, where they often constitute more than 50% of mammal species diversity. The Afrotropics host substantial bat diversity, yet have historically been perceived as having lower species richness compared to …

Integrative Approaches To Climate Resilience Planning: Application Of A Plan Evaluation Framework, Maulsri Jha

Dissertations and Theses

In the last two decades, urban governments have streamlined and prioritized the creation and implementation of climate resilience plans to cater to the communities' vulnerabilities. Existing research illustrates that there is a gap in understanding how, or if, empirical (evidence-based) data are incorporated into the design and implementation of such plans and the extent to which their inclusion impacts outcomes in terms of vulnerability reduction. There is also a gap in the systematic study of their outcomes in terms of community resilience, and whether equity and environmental justice are promoted as priorities.

The purpose of the research is to understand …

Sptiotemporal Changes In Aboveground Biomass, Canopy Cover And Livestock Movements Across Mongolia Grasslands, Abhinav Chandel

Dissertations and Theses

This study presents an integrated geospatial framework for understanding grassland productivity dynamics and livestock movement behavior across the Mongolian steppe. Mongolia’s grasslands constitute one of the world’s largest pastoral ecosystems, yet they face increasing vulnerability due to climate variability, overgrazing, and land degradation. To quantify vegetation change and grazing responses, this research combines multi-decadal remote sensing with high-frequency GPS-based livestock movement tracking. Using Landsat imagery from 1990 to 2023, Aboveground Biomass (AGB) and Canopy Cover (CC) were estimated through Random Forest regression models integrating key spectral vegetation indices (e.g., NDVI, OSAVI, CTVI, TNDVI, IPVI) and climatic predictors such as summer …

Restoring, Protecting, And Expanding Abortion Access In The United States: Seeking Consensus Through The Delphi Method, Sarah Pickering

Dissertations and Theses

Background: The Dobbs v. Jackson Women’s Health Organization Supreme Court decision exacerbated inequitable access to abortion in the US. Agreement is needed on which strategies should be prioritized to restore, protect, and expand abortion access.

Methods: We convened a multidisciplinary, geographically diverse Delphi panel of clinical, research, policy, legal, and advocacy experts to reach consensus (i.e., agreement >67%) on recommended actions. Using feedback from three rounds of surveys, and input from a select expert advisory group (N=10), we iteratively refined the statements and recommendations.

Results: The panel (N=85) developed 25 consensus statements and 32 recommendations for action by advocates, funders, …

Application Of Methods To Population-Based Surveys To Reduce Bias In Estimates Of Sars-Cov-2 Infection Burden In The Population, Saba Qasmieh

Dissertations and Theses

BACKGROUND: Population-based surveys designed to randomly sample the population can be a critical and complementary tool to traditional surveillance approaches. Probability-based surveys enable the measurement of SARS-CoV-2 testing and outcomes that avoid issues around self-selection into testing, making them an effective approach to address ascertainment bias in passive surveillance. For surveys to be a useful and reliable surveillance tool for understanding the burden and distribution of SARS-CoV-2 infection, they need to capture prevalence estimates that are both valid and reliable to be optimally informative for public health measures. The dissertation was undertaken to address three main gaps that have implications …

Tiny Drifters Amidst Global Change: Examining Environmental Drivers, Trophic Impacts, And Management Strategies Of Estuarine Plankton Communities In The Anthropocene, Taylor Nicole Dodrill

Dissertations and Theses

Plankton productivity supports estuarine food webs, and has been tied to the success of fisheries, macroinvertebrates, and cultured shellfish yields. Climate change and alterations to nutrient loads are thought to be influencing plankton assemblages, with toxin-producing harmful algal blooms (HABs) on the rise and nutritional quality of plankton declining globally. These shifts in plankton communities may contribute to low biomass yields and toxin-based closures of important fisheries. The objectives of this dissertation are to identify environmental drivers, trophic impacts, and management strategies to understand and respond to changing estuarine plankton communities. To address these objectives, I used a combination of …

A Mixed Methods Approach To Understanding The Links Between Mining, Climate Change And Selected Health Outcomes In India, Mary J. Cheruvillil

Dissertations and Theses

Despite ample evidence of the significant role that mining activities play in determining health outcomes, in India there is a dearth of comprehensive health studies that draw linkages between mining and health. The purpose of the following study is to investigate the impact of mining activities on population health in India using three different methods: ecological multivariable regression, exploratory spatial data analysis (ESDA) and content analysis of government documents using a phenomenological approach. The first aim uses the ecological multivariable regression to examine associations between mining activities and children’s malnutrition outcomes at the district level. Census data, the Demographic Health …

Drivers And Dynamics Of Phytoplankton Communities And Harmful Algal Blooms In Mountain Lakes, Lara Stephanie Jansen

Dissertations and Theses

Harmful cyanobacterial blooms (cyanoHABs) are a complex and widespread disturbance in freshwater water bodies, impacting water quality for wildlife and human populations. While cyanobacteria often bloom in warm lakes impacted by human development like agriculture, blooms are increasingly reported in cooler waters with limited development in the surrounding watershed. As much of cyanoHAB research has focused on lakes in highly developed watersheds, the understanding of factors leading to cyanobacteria dominance and blooms in the absence of major development remains limited. Mountain lakes can serve as ideal systems to study bloom-forming cyanobacteria in watersheds with minimal development. In addition, mountain lakes …

Spatial Analysis Of Burn Severity And Streamflow Response In The Western Conus, Will Brendan Long

Dissertations and Theses

Wildfire increases the magnitude of runoff in catchments, which can lead to the degradation of ecosystems, risk to infrastructure, and loss of life. The Labor Day Fires of 2020 provided an opportunity to compare multiple large and severe wildfires with the objective of determining potential changes to hydrologic processes in Oregon Cascades watersheds. Geographic information systems (GIS) were implemented to determine the total percentage burned and percentage of high burn severity class of six watersheds on the west-slope of the Oregon Cascade Range. In addition, two control watersheds were included to contrast the influence of climatic effects. Spatial arrangement of …

Efficiency In The Upper Deschutes Basin: Understanding The Hydrosocial Implications Of Irrigation Canal Piping, Rebecca Anderson

Dissertations and Theses

In response to water scarcity, irrigation efficiency projects aim to conserve water for in-stream flow and agricultural use. Piping irrigation canals is a common irrigation efficiency method which reduces the loss of incidental recharge, resulting in trade-offs within a hydrosocial system. Few studies have focused on the consequences of canal piping and none have integrated a critical analysis of the social factors involved in deciding what constitutes 'efficient' water use. This study seeks to fill this gap by combining natural and social science to give attention to the scales and perspectives involved in irrigation efficiency canal piping and the material …

"We've Created Cheap Energy Off The Backs Of Salmon": Dam Removal Politics And Alliances In The Lower Snake River Basin, Krista Harrington

Dissertations and Theses

Dams, once considered by many to be good for water development in the Western U.S., might not be a part of a climate resilient future. Dams have come under increasing scrutiny due to undesirable ecological implications. Although dam removal proposals are growingly popular in recent decades, they are controversial since they impact different stakeholders in different ways. In the Pacific Northwest, the Lower four Snake River dams have long been criticized for their negative impacts on salmon. In February 2021, US Congressman Mike Simpson (R-Idaho) proposed a comprehensive framework to deconstruct the Lower four Snake River dams as an attempt …

Factors Associated With Racial And Ethnic Disparities In Cesarean Delivery Among Women With Low-Risk Pregnancies At New York City Hospitals, 2012-2017, Ellen Brazier

Dissertations and Theses

BACKGROUND: While Cesarean delivery is a life-saving procedure when certain complications arise, it is associated with increased risks of maternal mortality and morbidity, as well as neonatal and childhood morbidities, and increased risks for women during subsequent pregnancies. Stark and persistent racial/ethnic disparities in Cesarean delivery that are not explained by clinical risks raise concerns about overuse of the procedure, as well as the contribution of potentially avoidable Cesareans to disparities in maternal mortality and morbidity. Understanding the extent to which disparities in Cesarean delivery may be attributable to differences in care during labor is critical for addressing these disparities. …

Digging For Information: Investigating The Efficacy Of Tracking And Augmenting Lacunicambarus Nebrascensis For Endangered Dragonfly Conservation, Danielle Elaine Tesar

Dissertations and Theses

Restoration and preservation of habitat for threatened and endangered species can proceed in many ways. Augmentation strategies can be used to supplement threatened and endangered populations or the species and resources on which those imperiled species depend. Comprehensive knowledge of species movement and home range is necessary to formulate effective augmentation plans. For freshwater burrowing crayfish, this type of information is generally lacking. The studies reported here were designed to acquire detailed information that is essential for augmentation of the plains devil crayfish, Lacunicambarus nebrascensis (formerly, Cambarus diogenes). Although L. nebrascensis populations are not considered threatened, this crayfish provides vital …

Poly(Β-Gal-Thr): A New Scalable Synthetic Mucin, Manuel A. Lema

Dissertations and Theses

A method for the preparation of glycosylated polypeptides via the nucleophilic ring-opening polymerization of a glycosylated N-carboxyanhydride (NCA) monomer is reported. The synthesis of 2,3,4,6-tetraacetyl-β-galactose-threonine N-carboxyanhydride (β-AcO-Gal-Thr-NCA) monomer in 5 steps with an 8 % overall yield is described, and the single-crystal X-ray structure is provided. The effect of a series of Ni⁰-based organometallic initiators, nucleophilic amine initiators, co-catalysts, and solvents on the polymerization were explored. The kinetics of the three most promising conditions were studied in greater detail. The conditions that provided the highest yield, low polydispersity (Ð), and …

Modeling Environmental Factors Related To Drought-Induced Tree Mortality Based On Lidar And Hyperspectral Imagery, Lauren Nicole Sharwood

Dissertations and Theses

Climate change is projected to bring more frequent and prolonged droughts, causing widespread forest die-off. Identifying tree mortality over large spatial extents in response to the most recent California drought will help forest managers and conservationists understand where there may be a greater likelihood of future die-offs. In order to find more at-risk areas, this study evaluated how interacting site-specific topographic, climate, substrate, and stand characteristics mediated tree mortality in the Central Sierra Nevada during the 2012-2016 drought. The author used lidar and hyperspectral imagery provided by the National Ecological Observatory Network to identify individual dead trees using the Random …

Exploring Linkages Between Landscape Patterns And Freshwater And Estuarine Bivalves In The Coast Range Of Oregon, Kaegan Michael Scully-Engelmeyer

Dissertations and Theses

Spatial configurations of landscape variables (biotic, abiotic, and socio-ecological) affect and are affected by ecological processes and species in watersheds. This dissertation explores relationships among landscape patterns, ecosystem processes and bivalve species dynamics in coastal watersheds in Oregon, USA. I approached this broad topic through two primary avenues of research: investigating cross-ecosystem threats from pesticide use in forestland management to downstream aquatic environments, and the landscape ecology of an at-risk freshwater mussel species.

Terrestrial land use activities present cross-ecosystem threats to riverine and marine species and processes. Specifically, pesticide runoff can disrupt hormonal, reproductive, and developmental processes in aquatic organisms, …

A Historical Ecology Of Aridland Springs In Desert National Wildlife Refuge, Nuwu/Nuwuvi (Southern Paiute/Chemehuevi) Ancestral Territory, Nevada, Yarrow Sarah Valentine Geggus

Dissertations and Theses

Aridland springs are among the most threatened ecosystems in the world. Vital to desert ecologies and Indigenous cultures, these complex and individualistic ecosystems have layered histories. To inform management in the changing landscape of Desert National Wildlife Refuge, a 1.6 million acre protected area in Southern Nevada, I conducted a historical ecology study of a sample of ten upland springs. Through a six-part interdisciplinary methodology including interviews, archaeological survey, botanical survey, and archival research, I summarize findings into three broad eras: the Nuwu/Nuwuvi pre-Contact Era, the Settler Era, and the U.S. Fish and Wildlife Service Era.

For millennia, Nuwu/Nuwuvi drank …

Wildfire Risk Assessment For A Municipal Watershed In Western Oregon, Usa: Methods For Projecting The Impact Of Mid-21st Century Climate Change On Wildfire Hazard, Andy Mcevoy

Dissertations and Theses

In the western United States, climate change is projected to lead to significant changes in regional wildfire regimes. Historically, forests west of the Cascade crest in Oregon and Washington, USA (westside) have been characterized by low-frequency wildfire events, but climate change projections indicate that wildfire could become a more common disturbance, altering ecological processes and impairing ecosystem services like surface water quality and quantity. Wildfire risk assessments based on simulation models have been used in high frequency fire regimes to evaluate contemporary and future risk, but present unique challenges in westside forests because characteristic low annual burn probabilities result in …

Mathematical Silences, Matthew Nathan Petersen

Dissertations and Theses

Previous studies have shown that mathematicians employ lengthy silences in their collaborations, contrary to the norms that govern every-day collaborations. Such results shows the relevance of an investigation of silence in mathematical collaboration. This dissertation builds off these results in a series of three papers. The first paper describes a methodology that can be employed in the investigation of silence in mathematical collaboration. The second paper analyses silence in the mathematical collaboration of students in junior-level introductory proof classes. It identifies two forms of mathematical activity, reading and ruminating, that students regularly engage in, and which violate the norms of …

The Role Of Strategic Governance In Reducing Infant Mortality Under Crisis Conditions, Lynn Christine Finley

Dissertations and Theses

The infant mortality rate (IMR) in some developing countries has decreased faster than the global average even though these countries lack strong economic growth, good governance, and democracy (often acknowledged precursors to improved health outcomes). What accounts for the improvement of the IMR in the absence of these traditional pathways to health gains? Some scholars suggest that the concept of "strategic governance" might help direct attention to intermediary factors that reduce neonatal deaths in countries that experience crisis conditions. The main objective of this dissertation is to investigate the set of governance practices that have reduced IMR in two such …

More Than Meets The Eye: A Taxonomic Revision Of The Nearctic Species In The Eye-Gnat Genus Amiota Loew (Diptera: Drosophilidae), Lance E. Jones

Dissertations and Theses

Thorough biotic inventories are still needed even in families as seemingly well-studied as fruit flies (Diptera: Drosophilidae). Drosophilidae have had an outsize effect on the history of biology because of their pivotal role in the study of genetics, development, and evolution. Even with more than a century of intensive study, large gaps remain in our understanding of diversity in this fly family, including well-studied areas such as North America. This thesis presents a taxonomic revision of the Nearctic species of the genus Amiota Loew. Twenty-three species are identified as being new to science for publication at a later date. This …

Burdern Of Chronic Health Conditions And Healthcare Utilization Among Mobile Populations In Sub-Saharan Africa, Elizabeth M. Ortiz

Dissertations and Theses

Background: Much of public health research in sub-Saharan Africa on mobile occupations, such as truck drivers and sex workers, has focused on HIV risk. However, evidence is emerging to suggest that the HIV epidemic among these groups is coupled with a high prevalence of chronic health conditions (CHC), specifically hypertension, diabetes, and obesity. For people living with HIV, increased risk of CHC may also be linked to HIV-related chronic inflammatory cascade. In Africa, there has been little research on CHC risk factors or patterns of healthcare utilization among mobile populations. Therefore, the objectives of this study are to examine the …

Do Saproxylic Curculionids Affect The Fitness Of Co-Occurring Cerambycids?, Sheila R. Heath

Dissertations and Theses

Saproxylic insects sometimes coexist in incredibly high numbers under bark and share common resources. Thus, interactions between species are possible and could even explain their coexistence. This study investigates evidence of negative or positive effects of curculionid beetles (Coleoptera: Curculionidae) on cerambycid beetles (Coleoptera: Cerambycidae) that coexisted in dead tree branches in Costa Rica. Co-occurrence analysis and generalized regressions were used to test associations between cerambycid and curculionid species. Three cerambycid species that each co-occurred with a curculionid species were selected to measure fitness. Fitness measures of the cerambycid were compared with abundance of the co-occurring curculionid to assess the …

Fungal Endophytes In A Seed-Free Host: New Species That Demonstrate Unique Community Dynamics, Brett Steven Younginger

Dissertations and Theses

Fungal endophytes are highly diverse, cryptic plant endosymbionts that form asymptomatic infections within host tissue. They represent a large fraction of the millions of undescribed fungal taxa on our planet with some demonstrating mutualistic benefits to their hosts including herbivore and pathogen defense and abiotic stress tolerance. Other endophytes are latent saprotrophs or pathogens, awaiting host plant senescence to begin alternative stages of their life cycles. Most, however, are likely plant commensals with no observable benefits to their hosts while under study. Yet, when considering the context-dependence that may determine plant resistance to pathogen attack, the consortium of endophytes present …

Recovery Of Zooplankton Communities To Whole-Lake Disturbance, Brian Newton Mcgann

Dissertations and Theses

Community assembly following disturbance is a key process in determining the composition and function of the future community. However, replicated studies of community assembly at whole ecosystem scales are rare. Here is described a series of whole-lake experiments in which the recovery of zooplankton communities is tracked following an ecosystem-scale disturbance. Fourteen lakes in eastern Washington were chosen: seven lakes were treated with rotenone, while the remaining seven were reference. Each lake was monitored up to six months before and one to two years after the rotenone treatments. Zooplankton tows were taken monthly, at a shallow, intermediate, and deep site …