Graduate Degree in Natural Resource Sciences

• Thesis Defense
• 04/17/2026

Quantitative flash drought definitions have characterized rapid onset or intensification of drought conditions via precipitation, evapotranspiration, and soil moisture. However, flash drought definitions that integrate direct observations of vegetation conditions are rare. Vegetation monitoring has historically been the domain of optical remote sensing. Resulting products have long observation windows due to atmospheric interference. Microwave-based observations exhibit little atmospheric attenuation and 1–2-day return times. Vegetation optical depth (VOD) derived from X-band AMSR-E /AMSR2 or L-band SMAP observations may be able to bridge the flash drought community's vegetation observation gap, if it can be validated.

• Thesis Defense
• 04/15/2026

Banana production in Saint Lucia has historically played a critical role in supporting rural livelihoods and the national economy but has experienced significant variability and long-term decline due to both economic and environmental pressures. This study evaluates the relationship between climate variability and banana production using the Standardized Precipitation Evapotranspiration Index (SPEI) as a measure of drought conditions. Banana production data from 1971–2022 were analyzed alongside SPEI metrics derived from George F. L. Charles Airport, selected based on its proximity to primary production regions. To isolate climate effects, production data were analyzed in both raw and detrended forms, with detrending accounting for structural changes associated with trade policy shifts. Pearson correlation analyses were conducted across multiple SPEI timescales and thresholds to assess the strength of climate–production relationships. Results indicate weak correlations overall (R² ≤ 0.14), with relationships diminishing further after detrending (R² ≈ 0.02–0.03), suggesting that apparent associations in raw data are influenced by long-term trends rather than direct climate effects. Additional analysis of optimal versus extreme moisture conditions similarly revealed limited explanatory power of SPEI alone. These findings suggest that banana production in Saint Lucia is not strongly controlled by moisture variability alone, but rather influenced by a combination of factors including trade policy changes, management practices, and extreme events not captured by SPEI. This study highlights the importance of considering structural and non-climatic drivers when assessing agricultural vulnerability and demonstrates the limitations of relying solely on drought indices to explain production variability.

• Thesis Defense
• 04/15/2026

The Southwestern Contagious United States (SWCONUS), comprised of California, Arizona, Nevada, and Utah, is a vast region that tens of millions of people call home. Hosting ecosystems ranging from grasslands to temperate forests and climate zones ranging from Mitterrandian climates to arid deserts, the region is nearly unanimously prone to intense droughts and devastating wildfires. While fire weather conditions and drought are often studied separately or mentioned as background conditions for the other, there are relatively few studies that compare the typical meteorological conditions between the two. This study aims to more closely understand the meteorological relationship between drought and extreme fire weather by comparing synoptic climatologies of 200 (upper), 500 (middle), and 700 hPa (low-level) heights during droughts and extreme fire weather events in four subregions of the SWCONUS. Synoptic climatologies were generated using the K-means clustering algorithm fit on the principal components of daily averaged geopotential fields on days with drought in at least one of four subregions of the SWCONUS. Droughts and extreme fire weather conditions often share hot, dry conditions and can have temporal overlaps, driven by the same global teleconnections and synoptic-scale weather patterns. Given the expectation of some temporal overlap and the general presence of similar driving weather conditions, there was an expectation of similar-looking geopotential clusters for SWCONUS extreme fire weather and drought events. This study found that both extreme fire weather and drought events have an overwhelming majority of their variance explained by clusters with dominant ridges over or in close proximity to the areas experiencing either drought or fire events. Despite similar-looking patterns at the macro-level, the exact shape and placement of the ridges were different between drought and fire weather events, with fire weather events showing clusters with slightly more amplified patterns. Understanding the synoptic climatologies of drought and fire weather can serve as a building block for improved long-term forecasts of drought and wildfires.

• Thesis Defense
• 04/15/2026

Accurate estimation of terrestrial Gross Primary Productivity (GPP) is critical for quantifying global carbon sequestration and understanding terrestrial carbon cycle. While eddy covariance (EC) towers provide standard flux measurements to quantify the carbon dynamics, upscaling these measurements to have continuous global coverage remains challenging due to the sparse distribution of flux towers and small footprint, among other limitations. Remote sensing (RS), especially coupled with eddy covariance data, has been used to estimate GPP at global scale. Different RS productivity models have been developed such as vegetation indices or solar-induced fluorescence (SIF), light use efficiency (LUE) models, dynamic global vegetation models (DGVM), and machine learning. One of widely adopted RS productivity model is LUE framework which calculates GPP as the production of absorbed photosynthetically active radiation (APAR) and plant light use efficiency term (ε). Traditional LUE models often rely on greenness vegetation index (e.g., NDVI) as proxies for fraction of absorbed photosynthetically active radiation (fAPAR) and meteorological data to estimate ε, both of which introduce significant uncertainties in GPP estimation. This study explores the use of hyperspectral data from NASA’s latest hyperspectral mission, Plankton, Aerosol, Cloud, ocean Ecosystem (PACE), to directly parameterize the LUE model. We evaluated multiple models using NDVI and the near-infrared reflectance of vegetation (NIRv) as proxies for fAPAR, photochemical reflectance index (PRI) and chlorophyll-carotenoid index (CCI) as direct proxies for ε. Using data from 54 sites within the AmeriFlux network, we compared the LUE model predictions to both EC measured GPP and GPP from other RS-based models including NIRv and solar induced fluorescence. Our results illustrated that LUE models using PRI as proxy for ε (GPPAPAR,PRI and GPPNIRv, PRI) emerged as the best proxy for GPP. Decomposing the LUE model components revealed distinct ecosystem specific drivers for GPP intra-annual variations. fAPAR and NIRv were main drivers for productivity changes in ecosystems which undergo seasonal structural changes (e.g., croplands). In contrast, physiological proxies were the main drivers in ecosystems without sounding seasonal pattern such as in water-limited environments (e.g., savannas). This study establishes parameterization of LUE model with hyperspectral data, demonstrating how next generation hyperspectral data can improve modeling of terrestrial ecosystem productivity.

• Thesis Defense
• 04/14/2026

Collaborative learning environments provide opportunities for students to construct scientific understanding through dialogue, yet the conditions that support sustained conceptual reasoning in group settings remain incompletely understood. While prior research has identified individual discourse moves associated with productive collaboration, less is known about how these moves function together across turns and conceptual boundaries, or how individual student characteristics shape their emergence.This study explores collaborative sensemaking in an undergraduate General Biology II course through analysis of student discourse during a bryophyte life-cycle modeling activity. Using an inductive coding framework, discourse from eight focal groups was analyzed to characterize how students introduced, evaluated, and developed biological ideas. All groups demonstrated moments of sensemaking; however, sustained sensemaking occurred only when students engaged in strong peer accountability and conceptual exploration.The analysis also investigates how students’ prior knowledge and intrinsic motivation relate to their participation in sensemaking and post-assessment performance. Neither variable independently predicted participation. Instead, students with higher prior knowledge or motivation contributed productively only when group interactional norms supported accountability and conceptual deepening. Frequency of participation alone was insufficient and what mattered more was whether contributions advanced shared understanding. Post-assessment performance was higher among students in groups characterized by sustained sensemaking and group-level interaction patterns can mediate individual outcomes.

• Thesis Defense
• 04/13/2026

Freshwater mussels are one of the most imperiled groups of organisms in North America, with over two-thirds of species considered threatened, endangered, or of special concern. These long-lived bivalves are essential to stream ecosystems, acting as filter feeders that improve water quality and as indicators of aquatic health. In Nebraska and Wyoming, native mussel populations have declined sharply due to habitat modification, pollution, and reduced connectivity. Two species of particular concern are the Plain Pocketbook (Lampsilis cardium), listed as Tier I at-risk in Nebraska, and the Fatmucket (Lampsilis siliquoidea), a Tier II at-risk species. In response, state agencies and conservation groups have initiated reintroduction programs, stocking thousands of hatchery-reared mussels since 2016. This project evaluates the outcomes of those stocking efforts across 11 study sites in Nebraska and Eastern Wyoming. Using passive integrated transponder (PIT) tags and glue-dot marking, we monitor survival, growth, and potential recruitment of reintroduced mussels. Field surveys also collected habitat and water quality data, while fish assemblages were sampled to assess the availability of host species necessary for mussel reproduction. Data will be analyzed with mark-recapture models to estimate survival rates and population dynamics, and growth will be assessed by comparing and selecting three different growth models. By combining ecological monitoring with quantitative modeling, this study will provide critical insight into the success of mussel reintroduction efforts in the Nebraska and eastern Wyoming. Results will also inform management strategies for sustaining and restoring native mussel populations, with implications that extend beyond Nebraska and Wyoming to other regions facing similar conservation challenges.

• Thesis Defense
• 04/03/2026

Understanding animal dispersal at the individual and population levels are essential for uncovering life-history patterns and important areas for management and conservation. Marine fish species often face minimal geographic barriers to dispersal, but intrinsic barriers like philopatry and site fidelity can dictate gene flow. Atlantic nurse sharks (Ginglymostoma cirratum) are an International Union for Conservation of Nature (IUCN) listed ‘vulnerable’ species and present a unique opportunity to investigate patterns of population structure and connectivity in large-bodied sharks. They are benthic and display reproductive philopatry, with recent work suggesting they have the capacity for seasonal, large-scale movements. By using acoustic telemetry and genomics, we investigate patterns of dispersal in individuals and between populations of nurse sharks. We used data from 20 nurse sharks tagged with acoustic transmitters from 2015–2017 in Bimini, The Bahamas. We additionally use collected tissue samples from 95 nurse sharks throughout four islands in The Bahamas and one atoll in Brazil from 1996–2020, performing double digest restriction site-associated DNA sequencing and multiple qualitative (fixation indices, heterozygosity, pairwise differentiation) and quantitative (clustering algorithms) metrics. Acoustic telemetry revealed that some nurse sharks perform seasonal, repeated migrations of moderately far distances and across international jurisdictions, consistent with partial migration, but overwhelmingly show extreme site fidelity to Bimini. Our genomic analysis uncovered weak but significant population structure among regions, however, most of the genetic diversity occurred within samples. Nurse sharks experienced a recent expansion according to our data, leading to an excess of rare variation that could be creating the weak signatures of population differentiation and explaining the higher diversity within samples. We attribute the weak population structure to strong reproductive philopatry that is present in this species. In light of nurse sharks being wide-ranging and performing seasonal migrations, it is possible that migrants are also the reason we observe low genetic structure. The data shows that nurse sharks can be more wide-ranging than previously understood and exhibit gene flow between populations. Since gene flow is relatively maintained with weak genetic structure, current management implementation throughout The Bahamas is likely providing sufficient coverage, minimizing the need for localized strategies.

• Thesis Defense
• 12/01/2025

Per- and polyfluoroalkyl substances (PFASs) are a family of synthetic chemicals that were used to improve the quality of several commercial products by making them resistant to heat, oil, stains, and grease. By containing a fluorinated carbon tail and a hydrophilic head (-COOH, -SO3H), PFASs act as surfactants that are attracted to bubble–water interfaces. Foam fractionation is the process of facilitating PFAS–air bubble interactions for the purpose of removing contaminants from tainted water. In this paper, we report on the use of foam fractionation and electrochemical oxidation (EO) under stirred batch conditions (200 mL) to remediate PFAS-contaminated water. We used radiolabeled PFOA (perfluorooctanoic acid; 14C-PFOA) as a representative surrogate to quickly screen treatment variables of flow rate, pH, temperature, and soap mass. Using radiolabeled PFASs eliminated the possibility of cross-contamination and greatly reduced analytical costs and processing time. The results showed that foam fractionation can remove 80 to 90 percent of PFOA from water within 30 min and that 90 to 100 percent of the PFOA in the concentrated foamate can be oxidized via electrochemical oxidation (-14COOH → 14CO2). We also tested the efficacy of the combined foam fractionation–EO treatment in natural waters by spiking 14C-PFOA and a cosolvent (CTAB) into PFAS-contaminated water obtained from two field sites with divergent PFAS concentrations and differing sources of PFAS contamination (natural drainage ditch vs. WWTP). Using a larger-scale tank (3500 mL), we observed that foam fractionation was 90% effective in removing 14C-PFOA from the WWTP effluent but only 50% effective for the drainage ditch water. Regardless, EO was highly effective in oxidizing 14C-PFOA in the foamate from both sources with half-lives (T1/2) ranging from 8.7 to 15 min. While water chemistry differences between source waters may have influenced foam fractionation and require additional investigations, tank experiments provide the first proof-of-concept experiment using 14C-PFASs that foam fractionation and electrochemical oxidation can be used in tandem to treat PFAS-contaminated water.

• Dissertation Defense
• 11/24/2025

• Zoo-managed African elephant (Loxodonta africana) bull populations exhibit substantial individual- and population-level variation in reproductive success, creating challenges for genetic management and long-term population sustainability.
• This dissertation evaluates semen quality, identifies physiological, behavioral, social, and environmental determinants of semen motility, and advances ex situ conservation through the expansion of the African elephant sperm bank.
• From January 2023 and July 2025, 209 semen collections were conducted from 13 sexually mature bulls across 10 North American zoos.
• Semen samples were classified by motility: low (0–29%), moderate (30–59%), and high (60–100%).
• High motility was consistently linked to greater viability, acrosome integrity, normal morphology, and reduced agglutination, while volume and concentration were less predictive.
• Physiological factors associated with high motility included testosterone the glucose-to-insulin ratio and triglycerides; insulin showed a negative association. Management and environmental factors also influenced semen quality: high motility with female LH surges, increased exercise, forage-based enrichment, time outdoors, and higher ambient temperatures, while greater time indoors was negatively associated.
• The African elephant sperm bank was expanded to store 13,070 straws from eight bulls, including 10,125 straws from previously unrepresented individuals, enhancing genetic diversity and supporting artificial insemination.
• This work establishes the most detailed multi-institutional dataset on African elephant bull semen quality, elucidates key fertility determinants, and highlights the critical role of cryobanking in ex situ conservation.

• Dissertation Defense
• 11/11/2025

Remote sensing is a promising tool for effectively researching ring-necked pheasant (Phasianus colchicus) habitat. Satellite based landcover data, such as the National Land Cover Dataset (NLCD), are often used to monitor pheasant habitat; however, they do not provide specific habitat classifications relevant for pheasants (Chapter 1). Pheasants rely on distinct grassland characteristics across their life stages including highly structured vegetation for nesting; moderately open grassland for brood-rearing that allows chick movement; and tall, residual cover for winter survival that provides thermal protection and concealment from predators. This information is not present in common remote sensing landcover products. In this dissertation, I developed disturbance detection algorithms to improve the classification of grassland structure and address the limitations of existing landcover products. Disturbance can serve as a useful proxy for grassland structure because it alters vegetation composition and resets successional stages. Unlike structural attributes, disturbances are easier to detect with current freely available remote sensing products. In the Great Plains, prescribed fire, haying, and grazing are significant sources of disturbance, so I developed disturbance-specific detection models for Northeast Nebraska from 2020 to 2023 to produce grassland disturbance landcover layers. I derived remote sensing data from Sentinel-2 imagery and integrated them with weather variables to train Random Forest models for detecting prescribed fire (Chapter 2), haying (Chapter 3), and grazing (Chapter 4). The algorithms performed well, with only 3% error for fire detection and 10% error for haying and grazing. Unlike the NLCD, this disturbance dataset provides land managers with information to evaluate disturbance patterns and adapt practices to sustain habitat for pheasants and other grassland species.

• Thesis Defense
• 07/29/2025

Enhanced Rock Weathering (ERW) is emerging in the voluntary carbon market as a viable negative emissions technology that sequesters atmospheric CO₂ in soils as inorganic bicarbonate (HCO₃⁻). Its market appeal lies in leveraging existing agricultural infrastructure for rapid deployment and scalability. ERW can also replace agricultural liming, raising soil pH while eliminating CO₂ emissions from lime dissolution. This makes it attractive for generating verifiable carbon credits, provided the technology is rigorously validated.

Measurement, Reporting, and Verification (MRV) research focuses on ERW's impacts on soil health, crop productivity, and potential groundwater contaminants. Accurate modeling of weathering and CO₂ sequestration rates is essential; however, measurements of carbon dioxide removal (CDR) rates using alkalinity from leachate are not feasible at large scale, thus a soil mass balance cation approach may improve MRV. However, this method has mostly been tested in soil columns and not in field conditions. The proposed project addresses this by improving understanding of how ERW functions in Midwest U.S. agricultural soils at a research center in eastern Nebraska by studying a cation mass balance approach using magnesium (Mg) and nickel (Ni) as indicators of inorganic carbon sequestration.

This study tested olivine due to olivines high sequestration potential; as a soil amendment at an intermediate field scale and found that crop yield was not affected: olivine-treated plots averaged 4.18 Mg/ha, compared to 4.15 Mg/ha in control plots. Although not statistically significant (p= 0.064), olivine application increased average soil pH from 5.55 ± 0.09 to 5.83 ± 0.10 after one year. Leachate pH also rose from a control average of 6.37 ± 0.06 to 6.58 ± 0.14 with olivine. Plant uptake of chromium remained similar (olivine: 11.48 ± 1.12 ppm, control: 9.63 ± 1.66 ppm), and while nickel uptake increased (olivine: 14.87 ± 1.71 ppm, control: 8.78 ± 1.45 ppm), it remained well below phytotoxic levels.

CDR rates estimated from lysimeter leachate were 0.015 ± 0.0003 tCO₂e/ha, whereas estimates based on the soil cation mass balance method were significantly higher, at 1.11 ± 0.12 tCO₂e/ha. However, only 60% of field plots yielded plausible CDR estimates, likely due to soil heterogeneity, repeat soil sample collection, and measurement uncertainty. These results underscore a key challenge: while leachate-based estimates are likely more direct, they are logistically and economically unscalable, whereas soil-based methods are feasible but prone to background variability.

Although Electromagnetic Induction (EMI) geophysical mapping was employed to explore whether spatial variability, in the 4-ha experimental plot, in soil properties such as texture, pH, cation exchange capacity, and organic matter could explain the inconsistent CDR estimates across plots, no clear spatially mappable relationships with changes in Mg or Ni concentrations were identified. This suggests that, while these soil characteristics may influence weathering processes, EMI alone did not adequately resolve the spatial uncertainty observed in soil-based CDR estimates, underscoring the broader challenge of scaling MRV in heterogeneous field conditions.

Ultimately, this study highlights that a mass-balance soil approach alone is insufficient for robust MRV at scale. Accurate quantification of ERW-based CDR will require methods that reduce the effects of soil heterogeneity and sampling variability, such as improved soil sampling strategies, higher-resolution spatial models, and integrated measurement approaches that combine soil and leachate data to better constrain field-scale uncertainty.

• Thesis Defense
• 07/24/2025

    Quantitative reasoning (QR) is one’s ability to apply mathematics and statistics in real-life contexts and scientific problems. It is an important skill that students require to make sense of complex biological phenomena, handle large datasets in biology courses and research as well as in professional contexts. Biology educators and researchers are responding to the increasing need for QR instruction through curricular reforms and research into biology education. This qualitative study investigates how undergraduate biology instructors integrate QR in their teaching. Using pedagogical content knowledge (PCK) and a QR framework, the study explored instructors’ instructional goals, strategies, and perceived challenges and affordances in undergraduate biology instruction. The participants included 21 biology faculty across various institutions in the United States, who intentionally integrated QR in their instruction. Semi-structured interviews were used to collect data focusing on participants’ teaching goals, awareness about student understanding, and instructional practices. Findings indicated that instructors adapt their QR instruction based on course level and student preparedness. In lower-division courses, strategies emphasized building foundational skills, reducing math anxiety, and using scaffolded instruction to promote confidence. In upper-division courses, instructors expected greater math fluency but still encountered a wide range of student abilities, prompting a focus on correcting misconceptions in integrating math knowledge and fostering deeper conceptual understanding in biology. Many instructors reported that their personal and educational experiences, especially struggles with math, often shaped their inclusive and empathetic teaching practices. Additionally, instructors’ research backgrounds influenced instructional design, particularly in the use of authentic data, statistical tools, and real-world applications. Instructors’ teaching experiences led to refinement in lesson planning, pacing, and active learning strategies. Despite their efforts, instructors faced both internal and external challenges in implementing QR, including discomfort with teaching math, time limitations, student resistance, and institutional barriers. However, affordances such as departmental support, interdisciplinary collaboration, and curricular flexibility helped to overcome some of these challenges. This study highlights the complex relationships between instructors’ experiences, beliefs, and contextual factors in shaping QR instruction. This calls for professional development to build interdisciplinary competence and instructional strategies that bridge biology and mathematics to develop students’ QR skills. These findings offer valuable guidance for professional development programs that aimed at helping biology instructors incorporate quantitative reasoning into their teaching.

• Thesis Defense
• 07/10/2025

This study examines the regeneration dynamics, growth patterns, and coarse woody debris (CWD) characteristics of Vachellia xanthophloea (fever tree) in the Makuleke Contractual Park (MCP), located in the northern region of Kruger National Park, South Africa. Fever trees are pioneer species establishing in low-lying floodplain woodlands, yet many stands in the MCP exhibit signs of senescence and decline. Field data were collected from 20 1/4-acre plots within a monospecific fever tree stand in Rietbok Vlei and a mixed-species fever tree and ana tree (Faidherbia albida) stand in the western portion of the Nhlangaluwe Floodplain. Measurements included seedling abundance, root collar diameter (RCD), mature tree diameter at breast (DBH) and height, CWD accumulation and decay class, and observational damage codes. Results indicate that fever tree regeneration was more successful in the mixed-species stand, which had higher seedling abundance and significantly larger RCD values. Mature trees in this stand also exhibited greater DBH, while tree height remained comparable between stands. The monospecific stand had a greater volume and diversity of CWD, more snags, and a wider spread of decay classes, pointing to increased rates of mortality, disturbance, and even-aged senescence. These data reflect contrasting dynamics between stands and suggest that stand composition may influence fever tree population dynamics in the MCP.

• Oral Presentation
• 05/01/2025

Cooperation between individuals is a key component of understanding the behavioral ecology of animals. Cooperative foraging commonly occurs between individuals of the same species, but also occurs more rarely between individuals across species. Coyotes and American badgers sometimes work together to hunt burrowing rodents using complementary hunting skills. Badgers are excellent diggers and usually hunt belowground, whereas coyotes are opportunistic hunters that mostly hunt aboveground. The relationship was described by Indigenous people and early European settlers, but very little formal scientific research has been conducted. We investigated spatial and temporal characteristics of coyote and badger associations at five sites in South Dakota, Wyoming, Colorado, and New Mexico to better understand the costs and benefits of this unique relationship. Preliminary results indicate that coyote-badger associations are more common in the fall and early winter as compared to spring and summer, when both species are raising offspring. In terms of temporal patterns across the 24-hour daily cycle, we detected coyote and badger associations mostly during diurnal periods, whereas we did not detect them together at night. Furthermore, we detected coyotes and badgers mainly within or close to prairie dog colonies, reinforcing that this relationship is associated with predation on burrowing mammals. I will share our research about the coyote-badger relationship and their larger prairie ecosystem home through short videos, photos, and a comprehensive online Storymap about these species and the unique relationship they form with one another. Ultimately, I hope this work will provide new scientific insight and foster appreciation for grasslands, a highly endangered biome that is home to a wide variety of fascinating and valuable species.

• Thesis Defense
• 04/24/2025

Forensic entomology scientists use blow flies' developing patterns to estimate the postmortem interval (PMI), with temperature significantly increasing growth rates. However, larval aggregations produce metabolic heat, resulting in complex microclimates that may change growth timetables. This study investigates how larval density and associated temperature changes affect the development and survival of two forensically essential blowfly species, Lucilia sericata and Calliphora vicina. This study examined how larval density and associated thermal profiles affect both blowfly species' development. Larvae colonies were reared at 25°C under controlled conditions, with adults at 23.3°C on a 16:8 light cycle. Using a split-plot design, we tested four larval densities of 50, 200, 1000, and 2000 individuals at 25°C and 30°C, with temperature gradients measured via thermocouple at four mass positions three times daily. We recorded the number of pupae and measured the larvae’ weight to assess the extent of the density effect on the blowflies studied. Key findings revealed density-dependent developmental patterns, with 1000 larvae representing an optimal threshold where thermoregulatory benefits balance competition costs. Temperature gradients showed edge-to-center differentials up to 5.2°C, yet high-density masses exhibited prolonged development despite warmer microclimates due to hypoxia and waste accumulation. L. sericata demonstrated greater thermal tolerance than C. vicina, particularly at 30°C, as C. vicina showed 58% reduced emergence. Lethal temperature assays (32-49°C) revealed species-specific survival thresholds, with preconditioning enhancing heat resistance in L. sericata but not C. vomitoria. These results challenge conventional PMI models that prioritize temperature over the density effect. We demonstrated that maggot mass temperature might not be reliable, as they may overestimate developmental rate by 18-22% at densities over 1000 larvae. We recommend a bigger container for maggot mass-related studies, starting with 1000 larvae per container. The study provides a framework for density-adjusted ADD models and highlights climate change implication for blowfly communication dynamics in forensics contexts.

• Oral Presentation
• 04/22/2025

This study examines whether hyperspectral reflectance data from white-tailed deer ear tissue can reveal differences related to age and sex. The work is part of a broader investigation into novel, non-invasive tools for Chronic Wasting Disease (CWD) detection. By analyzing spectral patterns across individuals, the research explores the biological variation that may be relevant for future CWD surveillance strategies.

• Dissertation Defense
• 04/17/2025

This dissertation examines the role of public participation in strengthening drought risk management across both developed and developing country contexts. Using a mixed-methods approach, it explores how participatory practices enhance drought preparedness, response, and policy effectiveness. A case study from Nebraska, USA, highlights the benefits of stakeholder engagement in raising awareness, clarifying responsibilities, and improving water resource management. A proposed evaluation framework provides drought managers with a tool to assess participatory efforts in state drought planning. In Zambia, research reveals significant gaps in drought governance, including limited public involvement, inadequate preparedness, and weak institutional coordination. The study concludes that while participation is context-dependent, its strategic integration enhances adaptive capacity, stakeholder ownership, and policy legitimacy in drought risk management worldwide.

• Dissertation Defense
• 01/08/2025

The determination of the postmortem interval (PMI) is essential for the investigation and successful prosecution of suspected cases of homicide. While the forensic pathologist might be able to draw fairly accurate conclusions during the initial 24 – 36 hours, beyond this period, the assistance of other experts like forensic entomologists and forensic taphonomists would be required; in rare instances, forensic acarologists and palynologists might be invited. The present study was designed to observe the postmortem changes in Sus scrofa placed in cage in Nebraska, located in the American Central Great Plains. The setting is in an open grassland in late spring to early summer. The observed variables with respect to biotic and abiotic factors affecting the activities of necrophagous insects native to Nebraska, and the interplay between the environment and the carrion were studied. The result revealed delayed decomposition caused by late oviposition precipitated by low ambient temperature and rainfalls typical of the season, as well as the invasion of the carrion by Silphids and the attendant predatory action on the eggs and larvae of the necrophagous insects. These two factors are mainly responsible for the observed increase in the PMI. When the results are directly extrapolated to humans, it can be assumed that a decedent placed within the same taphonomic setting will start showing signs of skeletonization after 39 days of being deposited in the open grassland of the Central Great Plain.

• Thesis Defense
• 12/04/2024

The Photochemical Reflectance Index (PRI) provides an indicator of plant photoprotection under changing environmental conditions. PRI responds to photoprotection associated with the xanthophyll cycle and pigment pool size adjustments, and these represent distinct mechanisms regulating short- and long-term changes in photosynthesis. Consequently, PRI responses arise from a variety of factors, complicating the interpretation of the underlying photoprotective mechanisms associated with environmental change across species and functional types. This study aimed to assess the variation in photoprotective mechanisms within canopies of several deciduous and evergreen species over the 2023 growing season. We quantified species pigment responses by exposing dark-adapted leaves to high irradiance (“dark-to-light” method) while sampling reflectance to measure constitutive responses (PRI0) associated with photoprotective pigment investments and facultative responses (ΔPRI) representing the xanthophyll cycle. PRI was also measured in situ from canopies under high (“sun”) and low (“shade”) irradiance conditions to derive PRI-light responses, analogous to the dark-to-light method (PRI0 and ΔPRI). Evergreen species had lower PRI0 and ΔPRI values at mid-growing season, indicating greater constitutive investments in photoprotective pigments and less facultative xanthophyll cycle activity. In contrast, deciduous species had larger PRI0 and ΔPRI values, reflecting less constitutive investments but greater facultative xanthophyll cycle responses. Deciduous species had a larger seasonal PRI change compared to the more stable pigment responses of evergreen species. PRI in situ values were lower in high irradiance (“sun”) canopy positions than lower irradiance (“shade”) positions. Differences among functional groups were detected in low irradiance PRI in situ values, but not high irradiance PRI values. The patterns of facultative and constitutive pigment responses across seasons indicated variation in photoprotective mechanisms were distinct among deciduous and evergreen species having trade-offs in photosynthesis and photoprotection. PRI-light responses derived from canopy positions in contrasting irradiance conditions resembled differences detected among functional groups using the dark-to-light method. By separating facultative and constitutive PRI responses across conditions, species, and functional groups, these findings offer insights for understanding the diversity in photoprotection and presents a systematic sampling approach for understanding canopy PRI-light responses using proximal methods. These also provide further insight into recent PRI-light responses detected from airborne imaging spectrometry.

• Dissertation Defense
• 11/20/2024

Science and society are inseparably linked, shaping each other in ways that define our world. Recognizing the importance of teaching science for empowering students to take meaningful action toward building sustainable society, Vision III science literacy advocates bridging science education with civic and ethical responsibility, emphasizing the development of competencies that prepare citizens capable of addressing global challenges. Using controversial socio-scientific issues (SSI) as teaching context provides a valuable platform to develop such competencies, as these issues require students to analyze interdisciplinary evidence and consider the social, economic impacts of potential solutions. However, recognizing the unique perspectives individuals bring to the classroom is essential for tailoring effective instruction, particularly with controversial SSIs, as perspectives often shape learning, decision-making, and engagement. This study employed a qualitative approach to understand educators' needs for teaching complex SSIs, identifying areas for support, and exploring students' diverse perspectives on issues like climate change and equity. A constructivist grounded theory framework facilitated an in-depth exploration of these nuanced perspectives. This work highlights educators' lower confidence in teaching complex SSI and their need for targeted professional development. Also, undergraduate students’ learning of SSI concepts in a science literacy classroom context is described. An investigation was conducted of how students develop understanding of the connection between climate change and extreme flooding during an independent activity we designed to foster active learning. This instructional strategy may serve as a model for educators aiming to effectively teach controversial SSIs. Additionally, this study presents a framework illustrating individuals’ diverse approaches to equity in the context of complex, controversial SSI, encompassing perspectives from a narrow individual focus to a critical analysis of broader historical and systemic power dynamics. This framework offers educators a tool to assess students' perspective of equity, enabling the design of targeted interventions that foster deeper engagement with science issues embedded in social justice. Additionally, it may aid policymakers in understanding how individuals engage with equity dimensions in complex issues across various sectors, given its adaptable nature.

• Thesis Defense
• 07/24/2024

      Cyanobacterial Harmful Algal Blooms (CyanoHABs) detrimentally affect human, animal, and ecosystem health. Remotely sensed early warning systems for algal blooms in inland lakes could contribute to more proactive water quality monitoring and help mitigate negative impacts. Advances in freely available remote sensing imagery, with finer spatial, temporal, and spectral resolutions, present new opportunities for the development and comparative analysis of methods to detect sudden deterioration in lake water quality. In this thesis, I compared and tested for temporal and spatial early warning signals of CyanoHABs in field-based and remotely sensed datasets from 2019 to 2023 in Pawnee Lake in southeast Nebraska, U.S.A. Field data consisted of biweekly microcystin (MC) levels from the Nebraska Department of Environment and Energy’s Beach Watch Dataset and remotely sensed data consisted of two-week Normalized Difference Chlorophyll Index (NDCI) composites from the Sentinel 2B surface reflectance satellite. In Chapter 1, I tested for rising variance in biweekly MC and NDCI time series from May-September of each year at three rolling window sizes. I also computed the correlation between MC and mean lake wide NDCI and examined within year trends in each variable. Both MC and NDCI tended to increase from May-September of each year and the relationship between MC and NDCI approached statistical significance (p=0.06) but rising variance did not provide early warning of documented CyanoHAB events for either variable. In the second chapter, with a landscape ecology-based approach, I computed the number of high-NDCI patches (i.e., contiguous pixels with elevated NDCI values) within Pawnee Lake, computed the correlation between MC and the high-NDCI patch count, and tested for rising variance in high-NDCI patch count at three rolling window sizes. Although both MC and high-NDCI patch count tended to increase from May – September of each year, I found no relationship between MC and high-NDCI patch count and no evidence of early warning of documented CyanoHABs. Reasons for the lack of advanced warning could include small seasonal sample sizes and insufficient temporal resolution in both the field- and remotely sensed observations, examination of only a subset of temporal and spatial early warning indicators and limited geographic scope. This study provides a baseline for guiding future analyses with higher-resolution observations and alternative metrics and locations.

• Thesis Defense
• 06/28/2024

Understanding and conserving ecological connectivity is critical to the preservation of vulnerable landscapes. Circuit theory, in which landscapes are imagined as circuit boards with varying resistances to the flow of current, is being increasingly used to model spatially explicit connectivity of landscapes and to inform land management and conservation decision-making. Utilizing continuous, quantitative estimates of percent cover by five land cover functional groups to create a conductance surface, this study expanded upon an established application of circuit theory that used the open-source software Circuitscape to model species-agnostic, omnidirectional connectivity. This model was automated using Python to create time-series connectivity maps from which comparisons could be made across time to assess pre- and postfire land cover patterns across the landscape. By applying this methodology to a U.S. Great Plains landscape affected by a large wildfire in 2012, this study found that for most functional land cover types, spatial configurations of areas of high and low connectivity changed in response to the wildfire disturbance, but quickly returned to pre-fire conditions. Exceptions were the tree and shrub functional groups, which saw persistent patterns of decreased connectivity in areas that were burned. This approach to modeling landscape connectivity over time could further enhance circuit theory-based assessments of landscapes affected by wildfire and tools for land managers promoting functional connectivity and resiliency in those landscapes.

• Dissertation Defense
• 05/08/2024

Drought is a complex phenomenon with varying degrees of impacts and monitoring methods. No drought is alike, creating a challenge for both water managers and communities. No area is immune to a drought. Due to the cyclical nature of drought events, clear information to those impacted is necessary to reduce risk and move towards proactive responses, as opposed to reactive responses. To better provide communication and mitigation tools, Drought Early Warning Information Systems (DEWIS) have been developed in various regions and contexts. To improve early warning, an understanding of the end user’s perceptions of risk, and the applicability of data and methods is valuable. This dissertation discusses findings from three related studies exploring the use of multiple methods and streams of data for drought risk in the United States. Chapter 1 provides a brief overview and outline of this dissertation. Chapter 2 presents findings from a study looking at the perceptions and usage of the term ‘flash drought’ among water managers in the United States. Chapter 3 is focused on modelling methods of using crop insurance occurrence data as a proxy of drought impacts for specialty crops. Chapter 4 is a systematic literature review of the use of mixed methods in drought science. Chapter 5 is the final study that investigates the benefits and validation of mixed methods in understanding drought risk to dry beans in North Dakota and Minnesota. Finally, in Chapter 6, I provide a brief conclusion of the findings and areas for future research. This dissertation demonstrates the use of various data types in understanding drought risk for improving drought early warning systems.

• Thesis Defense
• 04/19/2024

Piping plovers (Charadrius melodus; hereafter plovers) and interior least terns (Sternula antillarum athalassos; hereafter terns) are two avian species that nest along the Lower Platte River system (LPRS) in Nebraska. Natural nesting habitat for both species consists of sparsely vegetated expanses of sand near water. In the LPRS, river sandbars provide natural nesting habitat for plovers and terns. Sandbar habitat has been reduced from historical availability due to anthropogenic modifications and annually variable depending on hydrological fluctuations. Plovers and terns in the LPRS also nest at off-river sites, such as sand and gravel mines and their derivatives, transition sites and lakeshore housing developments. Off-river sites provide most of nesting habitat in the LPRS when sandbar habitat is scarce and are presumed to be important for the persistence of plovers and terns in the LPRS. However, the quantity of plover and tern nesting habitat provided by off-river sites is not self-sustaining and predicted to decline due to changing sand and gravel mining industry practices. Understanding the vital rates of plovers and terns in the LPRS will inform the role that off-river sites hold in the future conservation and long-term persistence of both species. To contribute to this understanding, I assessed consequences of off-river nesting between sandbars and off-river sites and among off-river site types using a long-term monitoring database collected by the Tern and Plover Conservation Partnership from 2008-2023. I also investigated additional factors that could affect vital rates such as the timing of nest initiation and hatching, extreme temperatures, conspecific and heterospecific nesting proximity, and nest exclosure usage (plovers only). For plovers, I evaluated annual and intra-seasonal adult survival, annual hatch-year survival, pre-fledging chick survival, and pre-fledging chick growth rates at off-river sites, and nest survival at off-river sites and sandbars. For terns, I evaluated pre-fledging chick growth rates and nest survival at off-river sites and sandbars. I did not find evidence for a difference between off-river sites and sandbars in nest survival for either species or for tern chick growth. Among off-river sites, plover chick growth was greatest at housing sites and tern chick growth was greatest at mine sites. There was no evidence that hatch date affected growth of plover chicks, but later hatched tern chicks had greater growth. Nest survival for plovers did not differ among off-river sites but was greatest at housing sites for terns. For both species, nest survival increased with increasing proximity to tern nests, greater proportion of incubation days with ambient temperatures above mean high temperatures, increasing nest age, and decreasing nest initiation date. Exclosed plover nests had higher survival. There was no evidence to show a difference in survival for adult plovers with exclosed nests. Plover adult, hatch-year, and chick survival was comparable to estimates of other populations. These results demonstrate the dynamics of plovers and terns in the LPRS and the importance of off-river habitat for the persistence of plovers and terns in the LPRS. Specifically, the lack of evidence for a demographic consequence of off-river nesting to nest survival or tern chick growth suggests that off-river habitat may support plovers and terns similarly to river sandbars. Furthermore, prioritization of early season nests may be most efficient for conservation and management resources, however tern chicks may benefit from investment later in the breeding season. As nesting near terns may improve plover nest success, measures to protect terns may also benefit plovers. Additionally, continued use of nest exclosures may improve nest success for plovers with limited effects to adult survival. Continued monitoring and study of plovers and terns at off-river sites and sandbars, particularly in the face of changing climatic and industry conditions, will further support the persistence of these species in the LPRS.