Graduate Student Defense Presentations

• 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.

• Dissertation Defense
• 07/17/2025

The Pallid Sturgeon (Scaphirhynchus albus), a long-lived, benthic fish that has inhabited the Mississippi–Missouri River system for over 70 million years, plays a vital ecological role. However, extensive habitat degradation and limited natural recruitment have pushed the species to the brink of extinction, prompting large-scale conservation efforts centered on hatchery propagation. Despite these interventions, hatchery-reared Pallid Sturgeon often exhibits reduced post-release survival and frequent disease outbreaks, raising concerns about their long-term viability. These issues have drawn attention to gut microbiome as a key factor in host health, disease resistance, and environmental adaptability.

Using 16S rRNA gene sequencing, I found that hatchery-reared sturgeon harbored substantially lower microbial diversity (147 ASVs across 44 fecal samples) compared to wild counterparts (369 ASVs from 20 individuals), alongside marked shifts in taxonomic structure. Seasonal patterns also emerged as significant drivers of microbial composition, indicating that timing of stocking could be optimized to favor beneficial microbial colonization.

I conducted a six-month probiotic intervention in hatchery fish to address microbiome restoration. Probiotic exposure promoted the enrichment of beneficial taxa such as Cetobacterium, Clostridiaceae, Peptostreptococcaceae, and Lachnospiraceae, which are linked to nutrient metabolism, mucosal integrity, and pathogen resistance. Probiotic-treated fish also demonstrated improved thermal tolerance. A pilot study on Flathead Catfish revealed that microbial shifts could begin within just 30 days of captivity, even in the absence of major changes in diversity or abundance.

Altogether, these findings emphasize the ecological importance of the gut microbiome and support the integration of microbial strategies-such as seasonally informed stocking and probiotic supplementation into conservation aquaculture. Incorporating microbiome science offers a novel and effective tool for improving the health and adaptability of endangered fish in recovery programs.

• 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.

• Dissertation Defense
• 06/27/2025

Biofuel and bioenergy systems are critical components of most proposed climate stabilization strategies aimed at reducing greenhouse gas (GHG) emissions and limiting global warming. In the United States, corn (Zea mays) is the dominant feedstock for bioenergy production. However, the reliance on large-scale monoculture agriculture has contributed to the degradation of natural resources and the disruption of key ecological processes. One of the most severe consequences of agricultural expansion for bioenergy is the widespread loss of native grassland habitats, a largely unprotected ecosystem, across the Great Plains. This habitat loss has been a major factor in the decline of many grassland bird species, more than any other avian group. To meet renewable fuel targets while also addressing biodiversity loss, particularly among declining grassland bird populations, alternative bioenergy crops must be considered. Switchgrass (Panicum virgatum), a native C4 perennial grass, has emerged as a promising candidate. It offers the dual benefit of producing substantial biomass for bioenergy while supporting biodiversity and enhancing ecological function. Understanding how the integration of bioenergy-dedicated grasslands into agricultural landscapes affects grassland bird communities is essential for informed land management decisions. This study aimed to assess how low-diversity perennial grasslands, similar to grasslands suitable for bioenergy production, influence focal grassland bird species across multiple spatial scales. We employed both innovative technologies, including autonomous acoustic monitoring, and conventional methods such as point count surveys, to gain comprehensive insights into avian responses to bioenergy-driven land-use changes. Along with ecological research, we also employed qualitative interviews with landowners in the region to explore Nebraska landowners' perspectives on land use in the Great Plains. The results of this study enabled a direct comparison of the effects of perennial grassland and cropland habitats on avian populations at multiple scales as well as informed recommendations for the successful integration of switchgrass fields into agricultural landscapes.

• Dissertation Defense
• 06/13/2025

Long ago, in a time forgotten, a wet climate threw the dunes of the Nebraska Sandhills out of balance. Grasslands proliferated, stabilizing dune complexes as upwelling groundwater birthed a horde of shallow lakes. In a land where temperatures can exceed 100 degrees Fahrenheit and plummet well-below freezing, change is afoot. The cold is returning, and in the frozen wastes of the Nebraska Sandhills, ice is amassing across lakes. Yet, summer grassland wildfires abound; initiating novel environmental circumstances for Sandhills lakes. At the center of these events lies climate change, a disturbance as harsh and unyielding as the windswept and sun-bleached Sandhills. Sweeping from a harsh land of cold to a summertime of scorching heat, A Study of Ice and Fire tells a tale of nitrogen, phosphorous and algae, who come together in the unrelenting maelstrom of biogeochemical cycles and environmental change. Here, groundwater inputs and evaporation form complex and nutrient-rich brines; lake color reveals cryptic ecological dynamics; seasonal and interannual variability carries limnologists off into madness; algal biomass proliferates; lake ice cover waxes and wanes in accordance with atmospheric temperatures; dissolved oxygen is consumed entirely under ice cover, ferrying fish beyond the Wall; wildfire ash blunts the advance of light into aquatic environments; and nitrogen-limited lakes remain unspoiled by the hot tongue of fire. Amid sinking watercraft and labyrinths of undocumented R code, treacherous lab and field work, cruel budget cuts and victorious grant applications, high-stakes committee meetings and conspiratorial coffee breaks, allies and crafty PhD advisors, the story of the Sandhills lakes unfolds, as an intrepid limnologists endeavors to survive that deadliest of conflicts: graduate school.

• 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
• 04/28/2025

Spatial ecology and predator-prey interactions are central to ecology and conservation. We used GPS telemetry data to evaluate mountain lion ( Puma con color) home range size, predator-prey interactions, and resource selection in California’s San Francisco North Bay, USA. In Chapter 1, we evaluated home range size, prey composition, and black-tailed deer ( Odocoileus hemionus columbianus ) kill rates across an urban-rural gradient to investigate how human disturbance influences these aspects of mountain lion ecology. We found sex-specific differences in home range size as both males and females increased their home range size at low to moderate levels of development but at higher levels, female home ranges stabilized while male home ranges decreased, possibly due to constrained movement. Feeding time, prey composition, and deer kill rates did not vary relative to human infrastructure or natural landscape features relevant to predation (e.g., cover, productivity). However, the rate at which mountain lions killed deer in the North Bay was generally comparable to estimates reported in both natural and disturbed systems. In Chapter 2, we investigated scale-dependent strategies by mountain lions relative to their primary limiting factors along a gradient of human disturbance. Mountain lions appear to adopt flexible, scale-dependent strategies in human- dominated landscapes, allowing them to select home ranges in more developed and natural portions of the urban-wildland interface. Our results also highlight that ecological theories conceptualized in relatively undisturbed landscapes do not necessarily predict large carnivore behavior in landscapes heavily modified by humans. In Chapter 3, we evaluated resource selection by mountain lions at locations where they consumed black-tailed deer. Mountain lions selected vegetative cover more strongly than productivity, suggesting they prioritize structural habitat features that promote successfully killing prey, rather than productive areas that maximize encounters with prey. However, selection of productivity increased as a function of cover, indicating that mountain lions exhibited the strongest selection of areas with vegetative features in which prey were likely both abundant and vulnerable. Collectively, our results offer valuable insight into predator-prey interactions in human-dominated landscapes, a key knowledge gap in ecology and conservation, by quantifying these interactions, evaluating multi-scale responses to prey availability and human disturbance, and identifying features that mountain lions selected and avoided when feeding on their primary prey, black-tailed deer.

• 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
• 04/21/2025

Urban forests are valued as green infrastructure for the variety of benefits they provide across ecological, social, public health, and economic domains. To understand the distribution of trees, maps are required. Many methods of mapping tree cover use expensive and data-intensive datasets such as hyperspectral and LiDAR imagery, making these methods inaccessible to municipal forest managers. Variations in the modelling approaches of existing, freely available methods are not addressed in sufficient enough detail to understand the trade-offs implicit in these variations. Further, characteristics of urban tree canopy mapping (high spatial resolution imagery, heterogeneous urban environments, the importance of the tree class) make it unclear to what extent results derived from other contexts apply. This dissertation addresses uncertainties related to feature selection methods, spatial variability of accuracy assessments, trade-offs involved in the use of different training sampling schemes and sample sizes, sources of classification error, and error in the reference map. Further, this dissertation proposes an optical method for change detection in urban tree canopy maps and compares estimates of tree cover derived from simple image differencing, a correspondence change detection method, and change detection performed with a reference method that incorporates LiDAR data. Random forest-based feature importance was found to be a more effective feature selection method than Kruskal-Wallis test of independence and correlation-based feature selection. The accuracy assessment varies spatially due to low inter-class variability, which can be characterized by unsupervised clustering. Sampling schemes should be determined considering the relative cost of error. Simple random sampling minimized commission error, stratified even sampling minimized omission error, and disproportionate stratified random sampling balanced commission and omission errors. Stratified even sampling was able to produce accurate maps with fewer samples. Maps produced with optical methods had overall agreement between 84.0-87.4% with optical + LiDAR maps when reference errors were corrected. Simple image differencing produced similar estimates of stable tree cover and tree canopy gain, but not tree canopy loss. The correspondence method visually improved parallax-induced errors and yielded high user’s accuracy for the stable tree class at the cost of greater omission error.

• 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.

• Thesis Defense
• 04/16/2025

Silver Carp Hypophthalmichthys molitrix and Bighead Carp H. nobilis (collectively bigheaded carp) have invaded tributaries to the Missouri River and Platte River in Nebraska, USA. Information pertaining to efficient sampling protocols for assessing bigheaded carp populations as well as benefiting removal efforts is needed. Herding is a method used to increase the capture efficiency and detection probability of adult bigheaded carp by simultaneously using active and passive sampling gears. During June-July 2023, four herding techniques were assessed regarding their ability to elicit directional movement past an enclosure gate. The combination of sound and electrofishing resulted in the highest mean number of bigheaded carp successfully herded, followed by electrofishing, sound, boat and motor only, and the control. Mean depth was shown to influence herding effectiveness and exhibited a positive relationship. During the summer of 2024, boat electrofishing and herding with gill nets were conducted on three tributaries of the Missouri River and one tributary of the Platte River and compared based on capture efficiency and cost-effectiveness. A total of 6,205 bigheaded carp were collected, with herding resulting in the capture of 2.8 times more bigheaded carp than electrofishing. Herding (437.3 fish/hr) had a higher mean catch-per-unit-effort (CPUE) than electrofishing (155.0 fish/hr) when accounting for gear effort (i.e., run time). However, electrofishing (39.0 fish/person-hr) had a greater CPUE than herding (20.1 fish/person-hr) with the inclusion of overall effort (i.e., labor hours and crew size). In achieving an equivalent weekly catch, electrofishing was more cost effective than herding. The results of this study will provide managers, researchers, and stakeholders knowledge regarding efficient and cost-effective sampling strategies for invasive bigheaded carp that enable assessments of presence and population status as well as provide control options for population reduction and potential removal.

• 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.

• Dissertation Defense
• 01/06/2025

Walleye Sander vitreus and Sauger Sander canadensis are both socioeconomically important sportfish species in Lewis and Clark Lake, an interjurisdictionally-managed mainstem Missouri River reservoir fishery. Since 2011, adult catch per unit effort (CPUE) of both Walleye and Sauger has remained at approximately 50% of pre-2011 levels. A presumed reason for the suppressed CPUE of adult Walleye and Sauger is substantial entrainment of larval and adult fish resulting from the reservoir’s high turnover rate (7.2 d). Acoustic telemetry was used to quantify adult movement and entrainment and ichthyoplankton trawls were used to assess larval entrainment. Relative importance of factors driving larval entrainment through Gavins Point Dam (GPD), abundance of age-0 fish in the reservoir, and adult movement patterns were assessed using an information theoretic approach. The models with the most support for explaining variation in larval entrainment were week of year and air temperature for Fort Randall Dam (FRD) and water temperature, day of year, and cumulative days of sustained high discharge for GPD. Age-0 Walleye abundance was most supported by mean outflow through GPD, mean annual precipitation, and delta April gage height. Age-0 Sauger abundance was most supported by adult conspecific abundance, April heating degree days, and annual precipitation. Mean weekly adult Walleye movement was most supported by reservoir elevation, season, and mean weekly air temperature. Mean weekly adult Sauger movement was most supported by discharge through FRD and season. We observed that annual larval entrainment (both total including all species and Walleye and Sauger entrainment) through GPD is greater than larval entrainment through FRD during 2021-2024. Further, entrainment and exploitation are considerable sources of loss for adult Walleye and Sauger. Our findings suggest flow is a driving factor affecting abundances of larval Walleye and Sauger and flow is affecting abundances and movement patterns of adult Walleye and Sauger in the reservoir.      

• 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.

• Thesis Defense
• 12/03/2024

American bison (Bison bison) are a keystone species that impact grassland productivity, plant diversity, and landscape heterogeneity. We used GPS telemetry and a replicate herbivore grazing experiment on Vermejo Park Ranch in northeastern New Mexico to advance understanding of bison spatial ecology and grazing dynamics. First, we evaluated the potentially disparate influences of forage productivity and site fidelity on the size and selection of home ranges of bison. Home range size was strongly negatively influenced by forage productivity. However, home range selection was influenced more strongly by site fidelity than spatial variation in forage, as bison selected home ranges with lower forage productivity relative to what was available across Vermejo. Second, we investigated whether collective grazing by bison in lower elevations modified plant growth to produce high-quality forage that released them from the need to migrate to higher elevations. Although forage productivity and graminoid quality were greater in higher elevations, bison in lower elevations maintained a diet of similar quality to bison translocated to higher elevations. Vegetation responded to ungulate grazing (mainly bison and elk) with equal or enhanced productivity in both years of our study, indicating that grazing levels likely improved (rather than degraded) ecosystem productivity. Third, we evaluated movement-based resource selection by bison during migratory-like travel. During these long-distance movements (mean = 19.0 km, range = 11.0 – 23.3 km), bison alternated between stationary, meandering, and directed movement states. Bison selected higher forage productivity in stationary and meandering states, whereas they avoided higher elevations and steeper slopes during directed movement. These results suggest an expanded perspective of stopover ecology that includes short-term shifts between directed travel and periods of foraging and rest whereby animals can alternatively prioritize optimal foraging and efficient travel during migration. Our work advances understanding of energetic tradeoffs between site fidelity and migration, the influence of grazing by large ungulates on ecosystem productivity, and behavioral strategies used by animals to fuel migration.

• Thesis Defense
• 11/22/2024

Consideration of spatial patterns and processes is fundamental to developing research studies, implementing management actions, and planning restoration efforts. The Red River of the North basin spans a broad geographic area, where jurisdictional oversight is divided among several entities (Manitoba, CAN; North Dakota, USA; Minnesota, USA; South Dakota, USA), creating a mosaic of regulatory and functional process zones. In this disjointed landscape, understanding the spatial ecology of freshwater fish is essential to address diverse life history requirements and the movement constraints imposed by anthropogenic structures. Long-term acoustic telemetry revealed that large bodied ichthyofauna employ a diverse range of movement strategies throughout the basin. Lake Whitefish showed the highest likelihood of migratory behavior, averaging the longest linear distance between migratory ranges (196.5 km, SD = 23.9), and a strong fidelity to spawning and overwinter locations. Lake Sturgeon, Bigmouth Buffalo, Freshwater Drum, and Walleye displayed the capacity to make annual displacements exceeding 350 km. Lake Sturgeon were the most rigid in their annual movement strategy, forming distinct groups with consistent movement patterns. Bigmouth Buffalo crossed over anthropogenic structures and across the international border more frequently than all species. Burbot and Channel Catfish movements were more restricted, typically remaining in the region in which they were tagged. Examination of demographic rates of Freshwater Drum found no differences in mortality, growth coefficient, or asymptotic length among sampling reaches in the United States, potentially owing to this species’ capacity for broad-scale movement. Our growth estimates (K, Brody growth coefficient) align with studies conducted as far south as Alabama, while mortality rates (4–10%) and longevity (up to 62 years) reflect established latitudinal trends. Recruitment variability (recruitment variability index = 0.53) was associated with thermal and hydrologic factors, including a positive relationship with growing season degree days and negative associations with cold-season discharge and rise rate. These insights into both movement and population dynamics provide further understanding of species ecology, which can be used to improve management practices and direct future conservation actions.    

• Thesis Defense
• 11/21/2024

Pallid Sturgeon (Scaphirhynchus albus) are centenarian, potamodromous, rheophiles that historically occupied the Missouri River and Mississippi River basins. Listed on the U.S. Endangered Species Act in 1990, population declines are attributed to habitat fragmentation and degradation, as well as overharvest, and hybridization. A knowledge gap exists regarding the extent to which tributaries facilitate key life stages for Pallid Sturgeon. This study evaluated the capacity of acoustic telemetry to monitor the movements of Pallid Sturgeon in a shallow, braided tributary to the Missouri River. The specific objectives were to (1) evaluate the environmental variables influencing the performance of acoustic telemetry, and to (2) quantify movement, residency, and seasonal space use of adult and sub-adult Pallid Sturgeon in the lower Platte River, Nebraska. Rigorous range testing protocols were employed, revealing relatively low detection ranges (<200 m) compared to other rivers throughout the region. Long-term reference tags revealed high variability in detection range, influenced primarily by line-of-sight, discharge, and water depth. Viewshed analyses were also employed to quantify detection range and may be a cost-effective alternative to formal range testing in systems where line-of-sight limits detection. A total of 80 Pallid Sturgeon were detected through active and passive telemetry, including sub-adults, reproductive adults, and non-reproductive adults. Space use models were created for 72 adults and 6 sub-adults. Pallid Sturgeon movements predominantly occurred at night, with a higher degree of residency in the Platte River compared to the Missouri River. Further, adult Pallid Sturgeon exhibited greater space use areas compared to subadults. Distinct migration strategies were documented, including one-step and two-step migrations, with overwintering occurring throughout the lower Platte River basin. Results confirmed that, despite low performance of acoustic telemetry in shallow, sand-braided rivers, species-specific designs can yield valuable movement information. The study emphasized that the lower Platte River basin provides important resources for the survival and persistence of multiple life-stages of Pallid Sturgeon.

• 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
• 11/18/2024

Fish species' occurrence is influenced by environmental conditions across multiple spatial and temporal scales. Alteration to stream systems has the potential to affect occurrence patterns of fish species. Stream systems of the North America Great Plains face threats originating from climate change and anthropogenic activities resulting in negative implications for many fish species. The Sandhills Ecoregion, Nebraska is considered one of the largest intact grasslands in North America, and thus may experience fewer threats than surrounding areas. Stream systems of the Sandhills Ecoregion are home to 12 fish species of greatest conservation need (SGCN). Little context exists regarding the environmental associations of fish SGCN and, to our knowledge, no studies have focused evaluations on how fish assemblages have changed through time in the Sandhills Ecoregion. Therefore, this study sought to 1) identify the multiscale environmental associations of fish SGCN inhabiting Sandhills Ecoregion streams using occupancy models and 2) assess how fish assemblages have changed since statewide sampling in 1939-1941 using retrospective analyses. We sampled 95 sites for fish assemblages and environmental data throughout the Niobrara River and Elkhorn River drainages of the Sandhills Ecoregion. We also built a database of historical fish occurrence since 1939 for the Niobrara River and Elkhorn River drainages of the Sandhills Ecoregion. Occupancy models constructed using contemporary survey data highlighted that fish SGCN occurrence is low. We also identified that fish SGCN occurrence is mediated by hierarchical multiscale environmental factors. Common variables included in top-ranked models were depth-to-groundwater, index of watershed integrity, stream slope, and proportion of predators. We also identified that assemblages of the Sandhills Ecoregion have exhibited shifts in the relative frequencies of some fish species, but have experienced limited shifts in relative frequencies at the functional trait level. Results from this study provide managers with a rigorous baseline of fish species occurrence in the Sandhills Ecoregion from which to compare to future assessments and may be useful when determining conservation actions.

• Dissertation Defense
• 08/01/2024

Addressing groundwater depletion problems in heterogeneous aquifer systems is a challenge. The heterogeneous Ogallala Aquifer, a critical source of groundwater in the central United States, has undergone decades of decline in water levels due to pumping. This project aims to build a robust groundwater model to evaluate optimal scenarios for sustainable use of the groundwater resource within a section of the Ogallala aquifer located in the Middle Republican Natural Resources District (MRNRD). This study follows a comprehensive approach involving parameterization, construction, and optimization. The model is parametrized using hydraulic conductivity and recharge values obtained from a random forest-based machine learning model and deep neural network regressor-based model. The predicted hydraulic conductivity efficiently identifies heterogeneous layers and enhances the performance of the groundwater model. Similarly, the predicted recharge parameter identifies spatial variation and finds a diverse range of recharge values. Both parameters are incorporated into a Modflow-NWT-based groundwater model. Calibration uses Parameter ESTimation (PEST) algorithm within GMS 10.3.5 software targeting recharge, hydraulic conductivity, evapotranspiration, and riverbed conductance. Scenario analysis using the calibrated model demonstrates the sensitivity of groundwater level and stream flow to changes in pumping and recharge rates. The model is optimized using Genetic algorithms (GAs) and sensitivity analysis. The findings of the optimized aquifer system recommended a balanced approach of increasing recharge rates by 5.8% and decreasing pumping by 5.5 %. This recommendation is consistent with previous studies that emphasized the importance of enhancing recharge and reducing groundwater withdrawal. Using Genetic algorithms for optimization underscores the potential of advanced techniques in achieving balanced and sustainable groundwater management strategies. We recommend that future works focus on refining these models and exploring additional scenarios to ensure long-term groundwater sustainability in the study area.

• Dissertation Defense
• 07/26/2024

Mountain lions (Puma concolor) have been studied extensively throughout their wide geographic distribution in the Western Hemisphere, but most research has been conducted at relatively small spatial scales. We used GPS telemetry data contributed by researchers in 16 study areas throughout California to advance understanding of mountain lion spatial ecology. First, we investigated multi-scale resource selection of mountain lions relative to spatially varying risk of intentional human-caused mortality associated with livestock depredation management. We show that individuals that proactively avoided mortality risk when selecting home ranges were able to relax their avoidance of risk when making resource selection decisions within their home ranges. Our analysis also demonstrates that functional responses in resource selection provide a quantitative link between coarse and fine-scale resource selection decisions made by individual animals. Second, we evaluated movement-based resource selection of subadult mountain lions during dispersal, which is the primary mechanism that maintains gene flow between populations. Our results support the hypothesis that anthropogenic landscape features act as barriers to movement that limit demographic and genetic connectivity between populations, elucidating behavioral mechanisms underlying the observed genetic structure between California mountain lion populations. However, our results also suggest that preservation of even relatively small patches of natural habitat and implementing road-crossing infrastructure should enhance connectivity. Third, we investigated intrinsic, ecological, and anthropogenic factors influencing home range size of mountain lions along a statewide gradient of landscape productivity and human disturbance. Our results indicate that home range size is influenced by the abundance and distribution of prey in relatively undisturbed landscapes, whereas anthropogenic features create fragmentation and barrier effects that influence home range size in developed regions. Our work advances understanding of responses of mountain lions to mortality risk from the leading mortality cause in California, behavioral mechanisms of reduced connectivity between populations, and the influence of natural and anthropogenic factors on space use. Management and conservation informed by empirical research will contribute to promoting long-term viability of mountain lions in southern California and along the central coast, which face challenges similar to those of large carnivores around the globe associated with human-wildlife conflict, habitat loss, and fragmentation.

• Thesis Defense
• 07/26/2024

Invasive Carp species: Silver Carp Hypopthalmicthys molitrix, Bighead Carp Hypopthalmicthys nobilis, Grass Carp Ctenopharyngodon idella, and Black Carp Mylopharyngodon piceus have both potential and realized abilities to negatively impact native species. Specifically, Bighead Carp and Silver Carp as filter-feeders have been theorized to be detrimental not only to adult filter-feeding species, but to many fish which rely on plankton and algae in their early-life stages. The impact of Invasive Carp on the overall fish community remains underexplored. The fish communities below Gavins Point Dam (Invasive Carp present) and Fort Randall Dam (Invasive Carp absent) afford the opportunity to directly compare recent sampling with historic sampling done in these same reaches. This study set out to determine if there is a difference between the contemporary Gavins Point Dam and Fort Randall Dam fish communities, and whether that difference is attributed to Invasive Carp presence. Differences in the fish communities below Gavins Point Dam and Fort Randall Dam could not be directly tied to Invasive Carp presence, but decreased condition of Bigmouth Buffalo Ictiobus cyprinellus in the presence of Invasive Carp indicates that Silver Carp and Bighead Carp may be negatively impacting native species. This study also found no evidence of young-of-year and few age-1 Invasive Carp in the tailrace of Gavins Point Dam. This may allow a unique opportunity to implement barriers to Invasive Carp immigration to the tailrace, thereby decreasing their presence at the furthest upriver point of their invasion.

• 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
• 07/23/2024

As species respond to changing climate, distributions and abundances may shift and alter species interactions. Hybridization, a relatively widespread phenomenon becoming more common with climate change, can have detrimental effects on population growth rates and genetic integrity. Beneficial effects due to the introduction of advantageous alleles and increased genetic diversity may result from hybridization as well. Species may also accrue fitness costs associated with changing climates if mismatches occur between environmental variables and phenotypes. The gray-headed chickadee, Poecile cinctus lathami, is an extremely rare songbird that has experienced marked declines in recent decades within its restricted distribution in Alaska and northwestern Canada. The widespread boreal chickadee, Poecile hudsonicus, has conversely become more locally abundant. We investigated two hypotheses of mechanisms – hybridization and environmental change – that may have contributed to the apparent rapid decline of the gray-headed chickadee and influx of boreal chickadee using mitochondrial and reduced representation nuclear DNA sequence data. We analyze historical specimens of both species and contemporary boreal chickadees to investigate the occurrence of hybridization and trends of abundance and interspecific gene flow. We also test for gene-environment associations using historical, present, and future climate data sets to explore the trajectory of boreal chickadee adaptation to their local environment. We detect evidence of hybrids backcrossing to boreal chickadee populations prior to recent declines, and signatures of later-generation hybrids among both historical and contemporary boreal chickadees. We find that boreal chickadee genetic isolation-by-environment exceeds isolation-by-distance. Further, we identify temperature and precipitation bioclimatic variables which have strong associations with allelic composition, and predict areas with the highest risk of environmental-genetic mismatch due to climate change. This study identifies hybridization as playing a role in gray-headed chickadee declines despite the inability to sample any individuals today, and provides evidence that environment-genetic mismatches may occur for boreal chickadees as a result of climate change across areas of sympatry and allopatry.

• Thesis Defense
• 07/17/2024

The Nebraska Sandhills are home to Nebraska’s top agriculture industry, beef cattle production, and various wildlife and plant species. The overlap of agriculture and natural resources in this area makes it challenging to maintain a profitable agriculture operation while minimizing negative impacts on the area’s natural resources. However, with the development of precision livestock management technology, new conservation methods are becoming accessible to ranchers that can aid in optimizing rangeland profitability and habitat conservation. Our study occurred during the 2023 summer grazing season at the University of Nebraska Lincoln’s Gudmundsen Sandhills Research Laboratory. Two research studies were conducted to explore the effects of virtual fencing on beef cattle stress and examine how the Sandhills topography may influence wildlife species richness and abundance. Livestock producers who consider adopting new precision management technology, such as virtual fencing, hold animal welfare as a top priority. The first study examines how virtual fencing influences heart rate (HR) changes in cattle fitted with virtual fencing collars. The results indicated that cattle did not experience any significant increases in HR due to audio or shock cues, and the virtual fence did not appear to cause acute stress on the cattle. The second study aimed to identify critical wildlife habitats in rangeland landscapes and the factors that influence wildlife habitat selection. We explicitly focused on three main topographical areas spread throughout the ranch: dry valleys, dune tops, and wetlands/sub-irrigated meadows. The results showed no significant difference in species richness. However, there was a significant difference in overall species abundance amongst the three topographic areas, with abundance being greater in the sub-irrigated meadows. By integrating precision technology into livestock management and conservation practices, ranchers can create a sustainable and prosperous future for their livestock and the local ecosystem for future generations.

• Thesis Defense
• 07/15/2024

The grasslands of the Northern Great Plains are social-ecological systems that have undergone many changes since the start of European settlement. The sacred social-ecological relationships Indigenous people nurtured with the land were harmed as colonialism displaced and persecuted their communities, which degraded social-ecological resilience and shifted grasslands to a new state. The cultural and natural burning that evolved with migratory grazers on grasslands was also disrupted through sedentary agriculture, Western land tenure, fire suppression, and Indigenous exclusion. These changes further harmed social-ecological resilience in grasslands and exposed them to woody encroachment, invasive species, and increasing wildfires. For those reasons, my graduate research focused on assessing, restoring, and centering evolutionary and Indigenous social-ecological relationships for advancing social-ecological resilience in the Northern Great Plains grasslands. Since the mid-20th century, there has been an increase in Western studies focused on improving the social-ecological resilience of grasslands by restoring social-ecological relationships. Patch-burn grazing is being employed to mimic the ancestral coupling of fire and grazing that shaped grasslands, but additional information is still needed to understand how to best apply it. I performed a study in the Sandhills of Nebraska to assess the potential of Patch-burn grazing for restoring grassland social-ecological relationships and resilience by comparing it to that of Rotational grazing. Through vegetation and bird surveys, my research examined the impacts of these practices on vegetation structure, biodiversity, and heterogeneity and bird diversity and functional groups. The results indicate that each treatment contributes to grassland resilience in different manners. Patch-burn grazing caused higher forb and vegetation diversity, which should support more niches and ecological functions. While standing biomass did not vary by treatment, Rotational grazing had higher vegetation, indicating its potential for production, and the practice had more plot-level heterogeneity while both treatments contributed to patch-level variability, which has potential for supporting biodiversity, wildfire mitigation, and resilience. Rotational grazing also increased invertivore birds and burning increased ground nesters while grazing reduced omnivore birds and grassland obligate birds that are two functional groups of concern for grassland resilience. Grazing and burning also decreased functional diversity while natural heterogeneity supported it. The overall impacts of Patch-burn grazing indicate that it caused similar production levels as Rotational grazing while supporting heterogeneity and more diversity. Because both practices contributed to grassland resilience but with differing impacts, the decision to use one or the other is dependent on management goals and priorities. Furthermore, while Indigenous social-ecological relationships shaped the social-ecological resilience of grasslands and are also essential for restoring them, there has been a historical lack of Western research focused on understanding and supporting Indigenous priorities and resilience. I collaborated with Indigenous leaders to assess and center social-ecological relationships, resilience, and priorities of Indigenous people in Eastern Nebraska. Guided by Indigenous and Western sciences, I conducted semi-structured interviews with Indigenous leaders to center their social-ecological relationships and identify the changes that could support and restore the social-ecological resilience of their communities. Responses indicated that it is important to challenge ongoing settler colonialism that continues to harm Indigenous people and grasslands through oppression, pollution, and exploitation. Participants prioritize improving social-ecological resilience for all people by restoring their ancestral relationships with their communities, cultures, and grasslands. Overall, this interdisciplinary study has potential to inform efforts to advance resilience in grasslands in the Northern Great Plains. It highlights the complex impacts of grassland management practices on biodiversity and heterogeneity while showing the potential of Patch-burn grazing for maintaining production and advancing resilience. The study also centers how the leadership of Indigenous people is important for improving grassland social-ecological resilience as their cultures hold ancestral knowledge for restoring evolutionary social-ecological relationships and supporting equitable decision-making that benefits all communities in the Northern Great Plains.

• Thesis Defense
• 07/01/2024

Under the changing climate, the frequency of compound disaster events has increased. Specifically, the alternation between droughts and floods has become predominant globally. At least 11% of global droughts have been followed by at least one flood event. Drought-Flood Abrupt Alternation (DFAA) is a compound disaster event that refers to the abrupt shift of extreme drought events to extreme floods resulting in exacerbated impacts on already vulnerable communities and hindering their coping abilities. This study aimed to analyze drought-flood abrupt alternation events and their impacts in Kenya. The first chapter aimed to understand historical drought events in the Greater Horn of Africa and their impacts, while drawing comparisons with the recent 2020-2022 drought period, referred to as the ‘triple dip La Niña’. Datasets used in this study include the Climate Hazards Group InfraRed Precipitation with Station (CHIRPS), Normalized Difference Vegetation Index, soil moisture, and crop yield data to conduct spatial-temporal analyses of drought conditions and their impacts. The second chapter aimed to analyze the abrupt shift between drought and floods in Kenya. The Long Cycle Drought-Flood Abrupt Alternation Index (LDFAI) was used to analyze DFAA events from 1982 to 2024. In addition, DFAA events were integrated with impact and crop yield data. The results indicated a decrease in the intensity but increased frequency of drought events, resulting in increased drought impacts compared to historical high-magnitude drought events. The study also identifies two types of abrupt shift events: Drought to Droughts (DTD) and Drought to Floods (DTF). DTF events have been predominant in the last century where since 2012 there have been nine DTF events resulting to reduced crop yields. The insight from this study aims to advance understanding of climate change dynamics and offer valuable guidance in updating existing disaster early warning information to mitigate the adverse impacts of climate disasters. 

• 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.

• Dissertation Defense
• 05/07/2024

Drought is a common natural disaster with complex characteristics and broad-reaching impacts. It has cost over 356 billion dollars in losses since 1980 in the US. However, while over a hundred drought indicators have been developed in recent decades, multi-dimensional drought impacts, such as those on socioeconomic sectors, are still understudied, particularly through quantitative approaches. This dissertation explores complex drought impacts using artificial intelligence (AI) across three research projects. The first study utilizes deep learning and natural language processing to predict drought impacts from diverse text sources like social media and news, outperforming the conventional method. It highlights the varied effects of drought over time and space, using California and Nebraska as case studies for integrating innovative data sources into drought assessments. The second study develops an explainable machine learning pipeline to investigate how different drought indicators relate to diverse drought impacts, illustrated through a California wildfire case study and comparisons of the relationships for multifaceted drought impacts in the selected states. The outcomes indicate the complexity and spatiotemporal heterogeneity of the relationships between drought indicators and multi-dimensional impacts. The third study dives into a specific category of drought impacts. It examines the relationship between extreme drought events and social unrest in India, using causal machine learning to quantitatively investigate the causal effect of drought on the increasing frequency of human protests. The outcomes show promising potential to develop further studies using causal machine learning by revealing the statistically significant average causal effect of drought on social unrest. Overall, the dissertation underscores the importance of applying advanced AI techniques in understanding and addressing the broad and complex drought impacts on both the natural environment and socioeconomic sectors for better climate adaptation and water resource management under the threats from climate change.

• 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.

• Thesis Defense
• 04/17/2024

Quaternary glacial aquifers are important water sources for irrigation in many agricultural regions, including eastern Nebraska, USA. Quaternary glacial aquifers are heterogeneous and comprise sediment assemblages with a wide range of hydraulic properties. Effective management and sustainable utilization of these heterogeneous glacial aquifers necessitate the development of realistic groundwater-flow models and characterization of aquifer geometry. However, hydrofacies probabilities predicted using multiple-point statistics (MPS) and machine learning (ML) techniques are rarely used for parameterizing groundwater models and identifying management zones. This study used MPS to simulate 100 three-dimensional conditional aquifer heterogeneity realizations by combining soft data, a cognitive training image, and hard data. The most probable hydrofacies model (sand and clay probability) was then calculated at a node spacing of 200×200×3 m and validated using groundwater-level hydrographs. The resulting hydrofacies probability grids revealed variations in aquifer geometry, locally disconnected aquifer systems, recharge pathways, and hydrologic barriers. A new workflow was established using the three-dimensional hydrofacies probability generated by MPS and hydrologic data to define high-resolution groundwater management zones and enhance strategies. Subsequently, ML techniques such as Random Forest, Gradient Boosting Classifier, Extreme Gradient Boosting, Multilayer Perceptron, and Stacking Classifier were used to model three-dimensional probabilistic distributions of hydrofacies at a grid size of 200 m x 200 m x 3 m. The models were compared in terms of their capability to identify thin, permeable hydrofacies, lateral continuity, and vertical contrast between hydrofacies units. ML predicted thin, permeable, and laterally continuous hydrofacies better compared to hydrofacies predicted by MPS. Multilayer Perceptron and Stacking Classifier models show sharper vertical contrasts between fine and coarse hydrofacies compared to MPS and other ML models. Finally, three groundwater models were constructed using MODFLOW 6 with unstructured grids. The first model was parameterized using hydraulic conductivity derived from pumping and geological data, while the second and third models were parameterized using hydraulic conductivity estimated from MPS and stacking machine learning hydrofacies models, respectively. K-means clustering was used to translate the predicted hydrofacies probability into hydraulic conductivity values. While the entire water budgets of all models show minimal variation, zonal water budget analyses reveal significant differences in storage change, stream-groundwater interactions, and total inflow and outflow. This study effectively demonstrates the influence of three-dimensional aquifer heterogeneity modeling approaches on the outcomes of groundwater models. Such insights can prove invaluable for groundwater managers and policymakers in assessing the implications of groundwater model parameterizations on local groundwater management.

• Thesis Defense
• 04/16/2024

Silver Carp Hypophthalmichthys molitrix and Bighead Carp H. nobilis (collectively bigheaded carp) have invaded tributaries to the Missouri River and Platte River in Nebraska, USA. Information pertaining to efficient sampling protocols for assessing bigheaded carp populations as well as benefiting removal efforts is needed. Herding is a method used to increase the capture efficiency and detection probability of adult bigheaded carp by simultaneously using active and passive sampling gears. During June-July 2023, four herding techniques were assessed regarding their ability to elicit directional movement past an enclosure gate. The combination of sound and electrofishing resulted in the highest mean number of bigheaded carp successfully herded, followed by electrofishing, sound, boat and motor only, and the control. Mean depth was shown to influence herding effectiveness and exhibited a positive relationship. During the summer of 2024, boat electrofishing and herding with gill nets were conducted on three tributaries of the Missouri River and one tributary of the Platte River and compared based on capture efficiency and cost-effectiveness. A total of 6,205 bigheaded carp were collected, with herding resulting in the capture of 2.8 times more bigheaded carp than electrofishing. Herding (437.3 fish/hr) had a higher mean catch-per-unit-effort (CPUE) than electrofishing (155.0 fish/hr) when accounting for gear effort (i.e., run time). However, electrofishing (39.0 fish/person-hr) had a greater CPUE than herding (20.1 fish/person-hr) with the inclusion of overall effort (i.e., labor hours and crew size). In achieving an equivalent weekly catch, electrofishing was more cost effective than herding. The results of this study will provide managers, researchers, and stakeholders knowledge regarding efficient and cost-effective sampling strategies for invasive bigheaded carp that enable assessments of presence and population status as well as provide control options for population reduction and potential removal.

• Thesis Defense
• 04/16/2024

Antibiotics are a vital component of medicine, especially when treating humans and animals, however, their use can have negative consequences. Pharmaceuticals, including antibiotics, may be introduced into streams through wastewater discharge, leaching, and runoff in rural and urban settings. Even though discharging wastewater is a widespread practice, the occurrence of antibiotics in the environment may lead to changes in ecosystem processes and can influence the prevalence of antibiotic resistance. This research was established to evaluate the occurrence and type of antibiotics present in streams and determine whether urban wastewater, row cropping and manure application, or animal feeding operations are the main contributors. Three streams near Scottsbluff, Nebraska were chosen to sample based on the information gathered from other researchers and the known agricultural and urban influences. A confined animal feeding operation (CAFO) was one possible source of antibiotic presence in streams. The stream where the local wastewater treatment plant (WWTP) discharges was also chosen to study and a stream that has agricultural fields along it that may have row cropping, manure application, or livestock present throughout the year. Polar organic chemistry integrative samplers (POCIS) that allow measurement of very low concentrations of antibiotics in surface water, were placed into the streams and left for around a month to determine differences between sites influenced by wastewater, surface runoff, or seepage. Results show distinct differences in antibiotic levels between the agriculturally influenced streams and discharge from the WWTP, however, several types of antibiotics present are the same. In this review, the significance of antibiotics and water quality will be discussed, along with the fieldwork techniques, sample preparation, analysis, and conclusions. This research is important as it can lead to further exploration and understanding of the ecological impacts, antibiotic resistance, and other influences antibiotics may have when introduced to the environment.

• Thesis Defense
• 04/10/2024

Precisely measuring soil water content (SWC) is crucial for effective water resource management. This study utilizes the Cosmic Ray Neutron Sensor (CRNS) as a novel technique for area-averaged SWC measurements at an intermediate scale. However, accurate SWC measurements from CRNS require consideration of all hydrogen sources, including time-variable ones like plant biomass and plant water. Near Mead, Nebraska, three field sites (CSP1, CSP2, and CSP3) growing a maize-soybean rotation have been monitored for 5 (CSP1 and CSP2) and 13 years (CSP3). Data collection includes biomass water equivalent (BWE) biweekly with destructive sampling, epithermal neutron counts, atmospheric meteorological variables, and point-scale SWC from a sparse Time Domain Reflectometry (TDR) network (4 locations and five depths). In 2023, dense gravimetric SWC surveys were collected eight times in fields CSP1 and CSP2 and nine times in CSP3 over the growing season (April to October). The N0 parameter, presented in Desilets et al. (2010) as the transformation function between epithermal neutron counts and SWC, exhibits a strong linear relationship with BWE, suggesting a straightforward vegetation correction factor may be suitable (fb). Results from both the 2023 gravimetric surveys and long-term TDR data indicate a neutron count rate reduction of about 1% (0.6% minimum and 1.7% maximum) for every 1 kg/m2 (or mm of water) increase in BWE for all three sites and two crop types. This reduction factor aligns well with existing shorter-term row-crop studies but nearly doubles the value previously reported for forests. The higher count rate detector model #CRS-2000/B model at CSP1 and CSP2 significantly reduced the uncertainty in the BWE-N0 results (r2 of 0.8 vs. 0.3) compared to the #CRS-1000/B model at CSP3. This research strongly supports the idea that an fb correction should be applied for cropland sites. It is also possible the same fb correction can be applied to forest sites, but a long-term study is still needed to validate both the linear function and magnitude of the coefficient. This long-term study contributes valuable insights into the vegetation correction factor for CRNS, helping resolve a long-standing issue within the CRNS community.

• Thesis Defense
• 12/05/2023

Long-term and excessive fertilizer application has continuously increased nitrate in the vadose zone-groundwater integrated system. Nitrate, a highly miscible and mobile inorganic nitrogen species, leaches through the vadose zone to groundwater, posing human health implications when continuously consumed. Our study aims to evaluate the redox-based transformation of inorganic nitrogen species in a vadose zone under a row-cropped, sprinkler-irrigated field in central Nebraska. Undisturbed sections of deep vadose zone cores were packed in the columns representing the entire vadose zone, and a groundwater table was simulated. The biweekly collected porewater and sediment representative samples were analyzed for nitrate-N and ammonia-N transformations. We found that the average ammonia-N concentrations under rainfed were significantly higher than in sprinkler-irrigated system and pre-experimental soil (p.value <0.05). Pre-experimental soil nitrate concentrations were significantly higher than rainfed and sprinkler - irrigated systems (p.value < 0.05). In biweekly extracted porewater, simulation beneath the sprinkler-irrigation has significantly higher NO3-N levels in the root zone than the rainfed system porewater (p.value < 0.05). Still, no significant difference was observed at the capillary fringe. On the other hand, porewater NH4-N concentrations in the rainfed root zone were significantly higher than in the sprinkler-irrigated root zone, with comparable concentrations in the capillary fringe. Interestingly, in sprinkler-irrigated, the groundwater-irrigated system had higher NH4-N levels than the rainfed system, whereas the NO3-N concentrations were comparable in both irrigation systems. Our study suggests that differences in water volume input can impact nitrate transformation in the vadose zone.

• Thesis Defense
• 11/30/2023

A Collaborative Adaptive Management (CAM) Project was started at the University of Nebraska in 2020 to address some of key uncertainties related to the management of grasslands in the Nebraska Sandhills through stakeholder driven experiments and the adaptive management cycle. Patch-burn grazing was selected by CAM as a management tool to generate heterogeneity across the landscape and promote biodiversity while balancing economic and ecological trade-offs. The patch-burn grazing system was implemented with controlled burns in May of 2022 and March of 2023. The goal of the research present here is to understand how the use of patch-burn grazing impacts several ecological aspects of the Nebraska Sandhills. Specifically, this study asks three things 1) does patch-durn grazing negatively impact soil conditions by increasing soil erosion and depleting the thin topsoil of nutrients in burned areas, 2) is patch-burn grazing able to significantly change vegetation structure and promote vegetation heterogeneity, and 3) how does patch-burn grazing affect avian communities, abundance, and species diversity in the Sandhills? Comparison of soil conditions between burned and unburned was made using the change of soil height at installed erosion pins and a series of soil nutrient panels samples taken in the months following the fire. Vegetation structural metrics and function group covers were measured throughout each field in the study. A nonmetric multidimensional scaling (NMDS) ordinal analysis supported by a pairwise comparison using permutational multivariate analysis of variance (PERMNOVA) was used to examine the difference in vegetation structure between each of the fields in this study. Bird point counts were performed in each field throughout the two years of this study. This data was used to calculate and compare species diversity, community, and the abundance of a few select species. NMDS and PERMNOVA were used to explore the difference between fields in the composition of the avian communities, while N-mixture models were used to estimate abundance. This study provides an understanding of how patch-burn grazing, an under-utilized tool in the Nebraska Sandhills, can be used to support a more heterogeneous and resilient grassland.

• Thesis Defense
• 11/29/2023

The Nebraska Water Quality Index, under development by the Nebraska Department of Environment and Energy, summarizes in a single value eight environmental parameters that have been regularly monitored in Nebraska for nearly 20 years. The water quality parameters used in the Nebraska Water Quality Index have been shown in previous studies to be critical to bacterial growth. As such, this index has the potential to correlate with the microbial community in freshwater systems. Here, I relate the Nebraska Water Quality Index to lotic microbiome composition and structure using 16S rRNA gene amplicon sequence data collected from the North Platte River Basin, Nebraska. Gini-Simpson alpha diversity was significantly negatively correlated with Nebraska Water Quality Index ratings, as were the relative abundances of several bacterial orders: Absconditabacteriales, Burkholderiales, Campylobacterales,Oscillospirales, Rhizobiales, and Vicinamibacteria Subgroup 17. Nebraska Water Quality Index ratings were positively correlated with Flavobacteriales and Saccharimonadales. Analysis of environmental parameters suggested that total nitrogen played a substantial role in shaping the microbial community and water quality. The Nebraska Water Quality Index is a convenient method of summarizing the physiochemical parameters of a stream environment to monitor spatiotemporal trends in water quality and gauge the success of ecosystem restoration efforts. Analysis of the aquatic microbial community in conjunction with the Nebraska Water Quality Index may help identify the cause of water quality problems. For instance, Oscillospirales is associated with fresh cattle manure. The presence of Oscillospirales in areas of low Nebraska Water Quality Index Ratings could help users identify sources of cattle manure pollution

• Dissertation Defense
• 11/28/2023

Skillful, timely, and reliable seasonal forecasts are crucial in mitigating the adverse impacts of climate-induced risks in Ethiopia and the rest of Greater Horn of Africa region. However, access to skillful and usable forecasts is currently challenging. This study evaluated the skill of raw and bias-corrected deterministic and probabilistic summer (JJA) rainfall forecasts from the Climate Forecast System Version 2 (CFSv2) for Ethiopia, spanning lead times from 0.5 to 4.5 months. The investigation also considered the influence of increased ensemble size on forecast skill by comparing performance of CFSv2 with the North American Multi-Model Ensembles (NMME). The findings indicated that CFSv2 exhibited limited skill for operational use in seasonal rainfall forecasting over Ethiopia. In contrast, NMME displayed promise, suggesting that with some value addition efforts such as bias correction, statistical downscaling, and identification of smaller subset of best performing models, could position it as a valuable component in Ethiopia's seasonal climate forecast services.

Despite their potential usefulness, coarse resolution global models like CFSv2 fail to meet users' need for forecasts at local to regional scales. To address this limitation, the Weather Research and Forecasting model (WRF) was explored for its potential to enhance CFSv2 forecasts through downscaling. A sensitivity study using WRF identified optimal parameterization schemes, utilizing Climate Forecast System Reanalysis (CFSR) for initial and boundary conditions. Subsequently, the WRF model, configured with the identified optimum model configuration, was employed to downscale operational CFSv2 summer season rainfall forecasts. Despite downscaling a small subset of ensemble members, the WRF model demonstrated value in refining raw CFSv2 forecasts. However, additional research is essential to further fine-tune WRF configurations, potentially minimizing biases and enhancing forecast skill.

The findings of this study are expected to contribute towards improving access to skillful and usable seasonal predictions that could help decision-makers in mitigating adverse impacts of climate induced risks.

• Thesis Defense
• 11/21/2023

Pastoralism has long supported livelihoods and provided essential ecosystem services in landscapes of East Africa. Vegetation productivity is central to the functioning of pastoral systems but may be affected by changes in climate and land use. Vegetation monitoring is important for understanding the effects of global change in pastoral lands; however, it can be time and resource intensive. Remote sensing provides opportunities for efficient multi-scale monitoring of vegetation and climatic drivers. In this thesis, I explore the utility of satellite and UAV remote sensing for monitoring vegetation and precipitation trends and relationships in the East of Lake Turkana Region of northern Kenya. In Chapter 1, I examine regional greenness and precipitation time series at monthly, seasonal, and annual temporal resolutions, as well as relationships between greenness and precipitation from 2000 to 2022. I found evidence of long-term precipitation–greenness coupling at monthly and annual temporal resolutions. There were no trends in monthly or annual regional precipitation, while NDVI significantly increased at monthly temporal resolution but did not exhibit a significant trend at annual temporal resolution. Traditional pastoral practices, such as use of livestock corrals (bomas), also influence local vegetation composition and abundance. In chapter two, I use satellite and unmanned aerial vehicle (UAV) remote sensing data to monitor greenness in and around abandoned boma settlements at seasonal and annual temporal resolutions. Results showed that mean NDVI from UAV and Sentinel-2 data varied based on seasons (dry or wet) and from boma to boma. NDVI significantly differed between bomas and non-boma sites and there was significant positive correlation between NDVI and precipitation across all bomas, with an optimum temporal lag response of one month. Collectively, my results add to the body of literature demonstrating the utility of satellite and UAV-based remote sensing data for monitoring vegetation in pastoral systems.

• Thesis Defense
• 11/20/2023

Climate change together with the increase in demands for food, feed, fuel, and fiber are becoming a threat to sustainability and resilience of agriculture and pasture lands. Bromus inermis (smooth bromegrass) dominates pastures for cattle grazing in Eastern Nebraska, US, where it is planted in monocultures, and is considered high quality forage because of its palatability and high nutritional value, especially under intensive management practices. Sustainable management of these pastures is key to long-term resilience. This study aims to assess the performance of smooth bromegrass pastures to the combined effects of long-term management practices (since 2005) of fertilization with Supplemental Dry Distiller Grain Soluble (DDGS, Fertilizer-SF), mineral (Fertilizer-HF), or control (no fertilizer-CG), under both rotational grazing and no grazing treatments or true control (no-grazing and no-fertilizer). Soil characteristics, plant morphology (biomass, leaf area index, and specific leaf area), forage quality (acid detergent fiber, neutral detergent fiber, and crude protein), plant physiology (chlorophyll content and fluorescence), and vegetation optical properties (multispectral leaf reflectance) were measured throughout the growing season in 2022. Results showed that 2022 experienced drought with precipitation being (42 %) lower than the long-term average for the site. Pasture productivity was affected by fertilization treatments, grazing and water availability. We did not observe differences between fertilization treatments (SF and HF), where both treatments showed similar morphological and physiological trends throughout the season and differed significantly from control. These results are consistent with previous work, supporting the use of DDGS as an alternative to mineral fertilizer, thus reducing nitrate leaching and runoff from the system. Rotational grazing resulted in lower biomass and leaf area index (LAI) compared to ungrazed pastures, and higher crude protein. Several Indices (Normalized Difference Vegetation Index-NDVI, Chlorophyll Index red edge-CIre, and Vogelmann Red Edge Index-VRE) were tested as a non-invasive approach for vegetation assessment. The three vegetation indices showed significant relationship with ground measurements, demonstrating the feasibility of proximal sensing to measure different biophysical traits under different management practices and environments. HF and to a lesser extent SF resulted in improved growth conditions early in the season relative to controls, which provided a slight advantage to these treatments in a drought year over non-fertilized treatments, under both grazed and ungrazed conditions. Results from this study build on previous research on the site, and serve in the development of sustainable climate smart and adaptive management practices and contribute to land management policy planning.

• Thesis Defense
• 11/20/2023

Woody plant encroachment (WPE) is a social-ecological problem that will challenge conservation professionals and landowners to adapt their management strategies. Adaptation research has often focused on organizational characteristics such as structure and resources in lieu of individual perceptions of adaptive capacity. This research sought to understand conservation professionals’ attitudes about adaptation to vegetation transitions and if the perception of WPE and its associated risks were predictive of these attitudes. In addition, a mixed methods case study was conducted in a ranching community organization in the Loess Canyons region of Nebraska. This study illustrates the motivations and norms that have been important for the success of this community-based organization. The strong collaborative culture of this group is also described as it relates to these motivations and norms.

• Thesis Defense
• 11/17/2023

The presence and spread of invasive species have changed the way humans interact with their environment. Invasive bigheaded carp are well established throughout the Missouri River system below Gavin’s Point Dam. Nebraska and South Dakota co-manage a popular recreation paddlefish fishery, operating a snagging season (October) and an archery season (June). Satisfaction of recreational paddlefish fishers depends on many factors that may be influenced by the presence of invasive species. We used comment cards (1997-2021), mail surveys (2022), and onsite surveys (2022 and 2023) to assess the influences of bigheaded carp on paddlefish fishers’ satisfactions. Based on a content analysis of comment cards and importance grid analyses of mail and onsite surveys, we determined that bigheaded carp were not influencing paddlefish fishers’ satisfactions. Factors identified as influencing paddlefish fishers’ satisfactions were related to the catch of paddlefish. Contrary to our expectations, we documented no influence (positive or negative) of invasive species on satisfactions of recreational paddlefish fishers. Further work with other invasive species and other recreational users is needed to determine whether our findings are more broadly applicable.

• Thesis Defense
• 11/15/2023

Northern Pearl Dace Margariscus nachtriebi are a small-bodied glacial-relict fish species of greatest conservation need (SGCN) found throughout Canada and the northern U.S.A. Their distribution within the Nebraska Sandhills Ecoregion is isolated from the northern core distribution of the species following the last glaciation period approximately 18,000 years ago. Headwater streams within the Nebraska Sandhills Ecoregion are predominately groundwater fed and provide the cool water temperatures needed to support Northern Pearl Dace and other glacial-relict SGCN. Headwater streams within the Nebraska Sandhills Ecoregion have been geomorphically altered through anthropogenic processes such as channelization whereby habitat homogenization has occurred. Evidence of stream habitat changes stemming from channelization directly influencing fish population demographic parameters is limited. Capture-mark-recapture studies used to estimate population demographic parameters may provide insight into the linkages between stream habitat alteration and influences on demographic parameters of fishes. However, limited methods exist to individually mark small-bodied fish <100mm that do not alter behavior or reduce survival of marked individuals. Here, we investigated 1) small-bodied fish survival and tag retention using p-Chip microtransponder tags, and 2) annual survival of Northern Pearl Dace in channelized stream sites within the Nebraska Sandhills Ecoregion. We found tag retention of p-Chip microtransponder tags was high in small-bodied fish and did not affect fish survival. Northern Pearl Dace annual survival significantly differed between channelized stream sites and non-channelized stream sites. These results highlighted the utility of p-Chip microtransponder tags as effective marks for use in small-bodied fish where individual identification is needed. Further, these results indicate channelization may reduce Northern Pearl Dace survival when assuming complete site fidelity. As such, extensive channelization practices within the Nebraska Sandhills Ecoregion may ultimately influence distribution patterns of Northern Pearl Dace populations. Management efforts to increase Northern Pearl Dace populations may benefit from mitigation of channelized streams. Further research assessing spatiotemporal responses of Northern Pearl Dace to channel restoration practices may further refine specific habitat manipulation techniques and spatial distribution of habitat patches needed within watersheds.

• Thesis Defense
• 11/15/2023

Recreational fishing is one of the world's most popular pastimes, wherein participation is associated with sociodemographic factors. Even so, fishing license sales are declining in the USA in conjunction with a reduction in rural populations as people move to urban areas. Thus, urban areas are constantly growing in population size, population diversity, and geographic size suggesting a need to understand fishing participation in these growing areas. Natural resource managers often use participation to understand recreationists, yet avidity could provide a new way to understand recreationists. The goal of our study is to understand what sociodemographic factors influence the fishing avidity of urban anglers and what relationships exist between fishing avidity and other recreational-activity avidities of anglers who reside in urban environments. Specifically, we asked: 1) do Esri Demographics’ urbanization groups better predict fishing avidity of anglers within an urban setting than sociodemographic factors typically gathered in surveys, and 2) what relationships (positive and negative) exist among avidities of recreational activities for fishing-license holders within an urban environment? We created generalized linear models and used an information theoretic approach to evaluate influences of sociodemographic factors on fishing avidity, and we used Principal Component Analysis to evaluate relationships among avidities of recreational activities. We sent the 2020 Omaha Recreation Survey to a random subset population of 2019 fishing-license holders that resided within the four urbanization groups of Omaha, Nebraska, as designated by Esri Demographics. We determined that Esri Demographics’ urbanization groups did not predict fishing avidity better than a priori models of common sociodemographic factors. We report a weighted average model of sociodemographic factors (i.e., employment, sex, household size, household gross income, education, R3 retained, R3 reactivated, day license holder, multi-year license holder, additional fishing members in the household, and age) to predict fishing avidity for individuals residing in urban environments. No recreational-activity avidity has a strong negative relationship with fishing avidity. Recreational fishing avidity has strong positive relationships with avidities of ice fishing, hunting, and golf. Our study provides new understanding of how urban anglers recreate in urban environments throughout the USA, which could aid management agencies with development of avidity thresholds to categorize anglers, explore opportunities for co-development of recreational activities for anglers, and identify targets of fishing effort.

• Thesis Defense
• 11/13/2023

Multiscale environmental processes determine in-stream habitat conditions which drive species distributions. Habitat constitutes the physical template upon which ecological processes occur and species conduct life stage activities. Habitat heterogeneity promotes biodiversity of aquatic systems. Stream classification informs freshwater conservation by providing a useful framework to account for habitat heterogeneity, often based on landscape regions of similar environmental processes. A greater understanding of landscape-based classification frameworks as means to classify stream systems may improve understanding of drivers of biodiversity. Using Nebraska as a case study, on a statewide scale, objectives were 1) to characterize habitat availability for several at-risk fish species, and 2) to assess the categorization of stream habitat heterogeneity within multiple classification systems. Species distribution models provide a tool to characterize spatial habitat patterns and quantify species-habitat relations. Species distribution models were constructed from environmental data and historical presence data for 3 at-risk cyprinid species including Flathead Chub, Plains Minnow, and Northern Redbelly Dace. Our results support current knowledge of impactful habitat features based on species traits and environmental processes shaping site-scale habitat conditions. For all 3 species, hydrological factors such as flow velocity and discharge were among the most influential habitat conditions of examined variables. Further, variables representing stream size and position in the drainage network consistently carried high influence. We used site-level stream data collected by the Nebraska Department of Environment and Energy (NDEE) from 1995-2021 to assess stream habitat heterogeneity among Biologically Unique Landscapes (BUL) at a statewide spatial scale. Multivariate cluster analysis and statistical similarity tests were used to determine if aquatic habitat within the BULs is unique and by which features they vary. No significant differences were found between aquatic environmental conditions within and outside BULs. Evidence for unique aquatic habitat conditions among BULs was limited, shown in minimal pairwise differences among BULs in statistical similarity tests. Furthermore, the classificatory power of the BULs underperformed all other classifiers and, as such, BULs may not improve statewide stream classification.

• Dissertation Defense
• 11/06/2023

Grasslands are an important natural resource in Nebraska providing critical ecosystem services, for example, supporting the local cattle\beef production by forage production. To achieve the goal of developing adaptive grazing management strategies and operating adaptive grazing systems in Nebraska, it is necessary to understand the forage production patterns and dynamics. This presentation describes trends in forage production, responses of forage production to weather factors and management, and effects of forage condition on cattle grazing, through monitoring and assessing forage production on grazed grasslands in Nebraska. Quadrat-sampling data, drone-based remotely sensed data, and cattle GPS collar data are used in studies of this dissertation. Results of this dissertation are informative for shaping adaptive grazing management strategies in Nebraska, which provides knowledge and improves our understanding of forage production patterns in grazed grasslands in the face of climate change, various grassland management practices and grazing activities.

• Thesis Defense
• 10/30/2023

Eutrophic conditions often become prevalent in urban and stormwater retention ponds following years of external nutrient loads. In 2020, a novel biological and chemical treatment was initiated to remove accumulated nutrients from an urban retention pond (Densmore Pond, Lincoln, NE) that had severe algae and weed growth. Our approach included installing two 37 m2 (6.1 m x 6.1 m) floating treatment wetlands (FTWs) and two airlift pumps that contained slow-release lanthanum composites. The floating treatment wetlands promoted microbial denitrification and plant uptake of nitrogen and phosphorus, while the airlift pumps slowly released lanthanum to the water column over the growing season to reduce soluble reactive phosphorus. Four seasons of field sampling (2020-2023) showed median NO3-N concentrations were reduced from 23 µg L-1 in 2020 to 1.3 µg L-1 in 2023, while PO4-P decreased from 42 µg L-1 to 19 µg L-1. The reduction in N and P from the water column coincided with less algae, weeds, and pond muck (sediment), and greater dissolved oxygen concentrations and water clarity. To quantify the sustainability of this bio-chemical approach, this study focused on measuring nitrate removal rates from the FTWs. By enclosing quarter sections of the field-scale FTWs (3.05 x 3.05 m) inside vinyl pool liners in the pond, nitrate removal rates were measured by spiking nitrate into the enclosed root zone and then measuring nitrate loss under aerated and unaerated conditions. Results showed that NO3-N removal rates were roughly three-fold greater under unaerated (1485 mg NO3-N/d) versus aerated conditions (515 mg NO3-N/d). Extrapolating these removal rates to mass (kg) of nitrate-N removed, we estimate the two the full-sized FTWs installed in the Densmore Pond could remove between 0.64 to 1.82 kg of NO3-N over a growing season (May-September, 153 d), with removal mass dependent on dissolved oxygen concentrations beneath the FTWs. Complementary laboratory mesocosm experiments using similar treatments to field experiments will also be presented.

• Thesis Defense
• 08/07/2023

Agriculture intensification has increased during the past 50+ years resulting in simplified cropping systems (e.g., monocultures of high-yielding crops such as corn and soybeans). Additionally, agricultural intensification has led to the removal of non-crop habitat to maximize field size for production. Concomitantly, agricultural intensification coupled with increased chemical and mechanical inputs has led to adverse environmental impacts on soils, water, and biodiversity. To address these issues, new precision agriculture technologies and conservation planning frameworks have been developed with the goal of optimizing agricultural production systems while reducing negative environmental impacts soils, water, and biodiversity. Despite these opportunities to optimize agricultural production and environmental sustainability, farmers still face many constraints and limitations when choosing to adopt these precision technologies.

To identify the factors that facilitate or constrain farmers and farmland owners’ willingness to participate in targeted conservation delivery (via precis ion agriculture), we surveyed 7,503 individuals across Nebraska. These individuals were selected based on two criteria: 1) they were farmers and/or farmland owners who own or work land in Nebraska; and 2) were over the age of 19. We received 1,040 completed surveys (response rate = 13.9%). Our preliminary results indicate that upfront costs, upkeep costs of equipment, and the right to repair were the most common constraints identified by farmers and farmland owners’ willingness to adopt targeted conservation approaches using new precision agriculture technologies. We also found that inheritance and being a renter had a significant impact on their perceived limitations. Finally, we examined how farmers and farmland owners preferred to receive information about conservation programs across Nebraska. Survey participants preferred receiving information from: 1) farm equipment manufacturers; 2) farm-oriented news networks; and 3) farm service agencies. Non-government organizations (e.g., Pheasants Forever), university extension, Nebraska Natural Resources Districts, and the USDA-Natural Resource Conservation Service were preferred more by applicants who had applied for conservation program compared to those who had never applied for a conservation program. We also examined the perceived sufficiency of the expert advice the respondents received when applying to a conservation program. The study found that the more agencies or organizations the producer worked with, the more likely they were to find the information they received sufficient. Knowledge gained from this study will also help conservation agencies/organizations improve their outreach and engagement methods with Nebraskan farmers and farmland owners with the goal of optimizing agricultural production and environmental sustainability for future generations.

Lay Abstract Version

To improve both environmental conditions and farmer profitability, we delved into the challenges faced by Nebraskan farmers and landowners when adopting new farming technologies. We looked at data from a 2022 survey with 7,503 participants which included farmers and landowners from across the state of Nebraska. Our goal was to uncover why some adopt new precision agricultural and conservation technologies while others don't. Precision agriculture is the use of technology to improve farmland conditions. For example, using a yield monitor to monitor how many crops grow in each area. Precision conservation is similar, however it focuses on improving environmental conditions on the farm, like soil erosion. In addition, our research was designed to help agencies better share information about precision farming and conservation in a way that benefits the people of Nebraska. Our findings highlighted that finances were the main reason many people were hesitant to adopt precision farming tools. Factors like renting land or being a first-generation farmer also affected which factors influence these decisions. People also preferred getting information about precision farming technologies from friends, family, and fellow farmers, rather than government agencies. Interestingly, those who did favor information from non-governmental agencies were more likely to apply for conservation programs. This shows the importance of government agencies working together with non-government organizations and private companies to promote precision farming technologies and practices. Furthermore, our research showed that farmers and landowners were more satisfied with expert advice when they worked with more agencies and companies. As such, we should encourage cooperation between various agencies and organizations. Cooperation is key to fostering positive attitudes toward the adoption of precision agricultural and conservation technologies and practices in Nebraska.

• Dissertation Defense
• 07/17/2023

Earthquakes and tsunamis are natural hazards that cause considerable loss of life, destruction of property and infrastructure, and economic damage. A key challenge for organizations that manage hazard preparedness and response is mobilizing earthquake preparedness among individuals and families, particularly in areas of significant earthquake and tsunami risk. This dissertation provides an examination of individual earthquake and tsunami preparedness from both a global and regional perspective. It comprises two publications that explore various aspects of disaster preparedness.

The first chapter presents a systemic literature review of 49 articles published between 2010-2020, identifying the prominent social-cognitive and demographic dimensions that promote or inhibit individual earthquake preparedness actions. The review highlighted critical motivating factors for individuals to take preparedness actions, including the significance of social connections, networks, and interactions; self-efficacy; personal responsibility and preparedness knowledge; and moderate worry or concern. Measures promoting self-efficacy, psychological skills, and social interaction show promise as effective strategies for enhancing individual earthquake preparedness and fostering community resilience.

The second chapter employs a grounded theory approach to develop a model that explains the process of building tsunami and earthquake preparedness among individuals residing in coastal communities of Oregon. While the motivations and obstacles reported by the study participants align with previous research, the findings highlight that the development of preparedness occurs incrementally, with individuals cycling between motivations and barriers as they undertake preparedness actions. The resultant theoretical model demonstrates the crucial role of social connections at every stage of the process. Several outcomes emerged from the model, including a culture of preparedness integrated into daily life, a state of readiness, and confidence in surviving earthquakes and tsunamis.

The objective of this dissertation is to contribute to the broader understanding of the interconnected factors involved in establishing preparedness and identify specific areas that warrant attention in future preparedness campaigns with similar dual earthquake and tsunami hazards.

• Thesis Defense
• 07/17/2023

Algal growth has been shown to influence carbon breakdown rates in aquatic ecosystems; however, the magnitude and direction of these effects differ based on ecosystem context. To explore algal priming effects on decomposition in anthropogenically-impacted ecosystems, I conducted light manipulation experiments in three streams, each surrounded by different land uses (urban, row crop, and CAFO) across Nebraska. I measured leaf breakdown rates, metabolic activity, fungal and algal biomass, and leaf percent carbon (C) and phosphorus (P) to assess the effect of light differences. Experimental streams were impacted by sedimentation and turbidity over the course of the leaf incubation. Still, I observed significantly higher algal biomass as chlorophyll a in light treatments at two of my three streams. I observed negative relationships between algal biomass and fungal biomass as ergosterol at all my sites but contrasting relationships between algal biomass and respiration rates at my two agricultural sites. Additionally, breakdown rates were not significantly different by light treatment at any of my row crop sites, but they were higher at two of my last three collection dates at the CAFO site. Overall, leaf C:P declined over the course of the experiment. These results support prior studies that light levels can alter breakdown rates of allochthonous material in streams. They shed light on the influence that changing light levels can exert over carbon processing in streams.

• Thesis Defense
• 07/13/2023

Nebraska’s pronghorn population has been stable over the last decade, yet their presence on the landscape remains a contentious subject amongst private landowners. Conversion of grassland for agriculture and increased anthropogenic activity has drastically altered pronghorn behavior throughout their current range, however basic ecology, and resource use by pronghorn in Nebraska remains poorly understood. Establishing baseline population metrics and seasonal patterns of resource use for this population at the eastern periphery of the species range is critical to guide management actions. We deployed GPS collars on 110 adult pronghorn to quantify survival, mortality risk, and seasonal resource selection in western Nebraska. We used Kaplan-Meier and Cox Proportional Hazards modeling approaches to calculate adult survival and mortality risk. We found that annual survival was 0.65, survival significantly decreased in autumn, and mortality risk was 2.36 times higher for males than females. To investigate seasonal resource selection, we used a Step Selection Function approach, which uses conditional logistic regression to compare predictor variables at used and available locations. Seasons were delineated as winter (1 Dec-28 Feb), spring (1 Mar-31 May), summer (1 Jun-31 Aug), and autumn (1 Sept-30 Nov). Used locations showed no movement across Interstate 80 and habitat composition differed on either side so we evaluated resource selection separately between the herds north and south of the interstate. Our models included 2-way interactions with sex to determine if sexual segregation plays a role in selection. We evaluated selection of grassland/herbaceous landcover, agricultural land, human development, distance to water, and distance to roads. Pronghorn selected cropland and avoided human development regardless of herd, sex, or season. Use of agricultural areas was disproportionate to its availability on the landscape. Selection or avoidance of roads and water varied across herd, sex, and season. This work begins the complex task of understanding pronghorn ecology in an agricultural system. Our research aims to provide valuable insight into the factors influencing population dynamics so that biologists can implement effective strategies to manage pronghorn populations in western Nebraska.

• Dissertation Defense
• 07/13/2023

Interconnected wildlife health and behavior play vital roles in population dynamics, ecosystem functions, biodiversity, and wildlife conservation. Research and public interest in zoonotic pathogen transmission -- transmission from animals to humans -- has increased with the COVID-19 pandemic and ongoing concern about zoonotic spillover from wildlife to people. Diverse zoonotic pathogens have been linked to wildlife reservoirs, highlighting the importance of understanding human-wildlife interfaces and interactions. However, humans and domestic animals impact the health and conservation of threatened and endangered species, including primates. Both primate and human behavior can influence the risk of pathogen transmission at the primate-human interface. While zoonotic pathogen sharing is of concern, less research has focused on pathogen transmission among wildlife and integrating social behavior into wildlife health research.

To better understand the links between primate social behavior and pathogen transmission, we used long-term ecological transect data from the Udzungwa Ecological Monitoring Centre and a cross-sectional survey of pathogen shedding in overlapping primate populations living in forests of varying protections status and human disturbance in the Udzungwa mountains of Tanzania. Our research quantifies inter-specific associations among free-ranging primates in two forest blocks of the Udzungwa Mountains to investigate the relationship between forest protection status and inter-specific associations. Using bias-reduced logistic regression and social network analysis, we found significant and varied trends in inter-specific associations in well and less protected forests among primate species. We then examined the relationship between habitat primate inter-specific associations in the well-protected Mwanihana forest. Using mixed model logistic regression and a co-occurrence checkerboard score, we found that habitat and species were significant predictors of inter-specific associations. We found strong inter-specific associations between Udzungwa red colobus (Piliocolobus gordonorum) and Peter’s Angola colobus (Colobus angolensis palliatus) across habitats. To investigate connections between primate social interactions and health, we assessed the relationship between viral shedding and interspecific interactions observed in the field. While the relationship was not significant, the majority of animals with viral shedding detected were sampled at sites with inter-specific associations. These results highlight the need for integrated wildlife behavior and health research to understand connections between primate social interactions and pathogen transmission.

• Dissertation Defense
• 06/08/2023

Research, management, and modeling for water quality and resources, ecological processes, agricultural and urban planning, wildlife habitat, and much more depend on accurate water level and discharge measurement. Greater and more complex water resource needs for parties with competing interests demand more detailed models and effective science communication than are possible with the traditional scalar measurements. The scientific community recognizes the need for new methods that provide context for manual and programmatic extraction of a broader range information to make measurements and predictions, drive insights and facilitate communication between stakeholders and the public. Methods have been developed to accurately measure water level in ground-based imagery, but it is critical to improve those methods and create standardized tools, workflows, and software for use by the scientific community, academia, and industry. The purpose of this research was to find ways to develop and analyze tools and methods to measure and/or predict water level and streamflow in images with less artificial conditioning of the water scene than was previously possible. Three research studies were identified to accomplish this: 1) A site study to determine whether it is possible to predict water level and streamflow accurately to fill data gaps in United States Geological Survey historical data from a time-series of images with no artificial calibration or waterline target in the scene, 2) creation of a free, open-source software suitable for use by hydrologists and ecologiststo measure water level in images with a pixel to world coordinate calibration and waterline search target installed in a stream or river, and 3) creation of a new calibration target that improved the bow-tie calibration target and measurement surface used in #2 by allowing for calibration in every image and that occluded less of the scene allowing for improved contextual analysis.

• Thesis Defense
• 05/17/2023

The Nebraska Sandhills are currently undergoing a state shift to a redcedar dominated woodland due to anthropologic planting of eastern redcedar (Juniperus virginiana) and woody encroachment from the periphery of the Sandhills. To better understand this novel ecosystem and how bats are utilizing it we collected data at Barta Brothers Ranch with acoustic sensor grids consisting of 24 100m spaced acoustic sensors placed adjacent to planted windbreaks. Supplemental data from the Nebraska North American Bat Monitoring Program was used for data analysis at larger spatial scales. We used Spearman ranked correlation and kriging interpolation maps to see how bats used windbreaks during nightly activity. Eptesicus fuscus, Lasiurus borealis, and Nycticeius humeralis showed close usage pattern to the windbreaks while Lasiurus cinereus and Lasionycteris noctivagans showed usage patterns outside of our sensing area, while still showing a correlation to trees at a larger scale. We used multi model inferencing and model averaging to find the best model to explain bat species richness and call count. We found that distance to trees, with a preference to deciduous, and time through the summer to be the best predictors of bat species richness and call count. We used linear regressions of first instance calls in our grids to determine if bats are using windbreaks to roost or travel from their roost to feeding grounds. All species combined, Eptesicus fuscus and Lasionycteris noctivagans showed higher numbers of first instances closer to the windbreak, this shows that bats, in general, are using windbreaks for roosting or for roads from roost to their feeding grounds. Lasiurus cinereus reported a flat regression line, hinting that this species may travel across open grassland from roost to feeding grounds. Bat presence and use of trees in the Sandhills creates a dilemma of battling ecosystem services when there is management incentive to control the spread of woody plants for grassland diversity and forage quality and quantity.

• Oral Presentation
• 04/26/2023

Greenways are nature’s infrastructure– offering transportation of plants, animals and insects, as well as places of study, survival and solace for people. The Salt Valley Greenways weave through and around the city of Lincoln, connecting the natural and rural world into the bustle of urban life. This storytelling project explores the diversity of resources that greenspaces provide and reveals those through conversation with scientists, artists, and folks who call Lincoln home.

• Dissertation Defense
• 04/25/2023

Focus on global climate change can overlook the nuances of local weather and climate impacts. This study describes tools and methods for creating and observing weather and climatic conditions on a temporal and geographic scale that represents the environment of Nebraska. Recognition of the limited resources available for continuous application of new data and gathering of observations provides a guide for a “best practice” scientific, yet economic, model for maintaining an observational network and deriving value-added products.

Utilizing Federally maintained datasets of geographically relevant cooperative observations as a backdrop, the locally implemented and maintained weather observation network, the Nebraska Mesonet, is assessed against the official national climate records. Strategies for increasing the relevance and reliability of the Nebraska Mesonet observed parameters that show inconsistencies are discussed. Quality control techniques are tested and evaluated to provide confidence in the recorded observations, with recommendations made to mitigate and limit errant data from entering an official Nebraska Mesonet record.

• Dissertation Defense
• 04/23/2023

Rwanda has made remarkable progress on many sustainable development goals (SDGs), including reducing infant, child, and maternal mortality. However, the prevalence of child stunting has remained high, impacting 33% of children under the age of five in 2020. Stunting is a complex global health challenge that can be associated with diverse individual, family, and community factors as well as environmental risk factors such as water quality. Limited clean drinking water in dry seasons and reliance on surface water sources shared with livestock and wildlife can expose people to chemical and biological contaminants. Cohabitation of people and livestock in rural areas increases the risk of zoonotic pathogen sharing and human illness. Pathogen exposure and resulting diarrheal diseases are also linked to child stunting.

To examine the relationships among stunting, water quality, and zoonotic pathogen sharing, we used primary data collected in Karongi district in western Rwanda, an area with high stunting prevalence, as well as secondary national survey data. We linked data from the 2019-2020 Rwanda Demographic and Health Survey (DHS) with national water quality testing data. We used generalized linear regression to identify demographic, socio-economic, livestock ownership, and water quality factors associated with stunting. Child factors (birth order, age, gender) and household factors (wealth status, mother’s education, rural or urban location, number of children in the household) were associated with increased stunting. Water quality (pH) was also marginally associated with stunting.

In our Karongi district field study, we paired household surveys with biological sample collection from children, livestock, and drinking water in upstream and downstream communities in the Musogoro River watershed. Water samples from surface water, public taps, and household drinking water storage containers were tested for basic physical water quality parameters, bacterial contamination (total coliform bacteria and E. coli), and potential hazardous elements (As, Cd, Cr, Cu, Fe, Pb, Mn) with public health importance. We cultured and isolated potentially zoonotic pathogens (Campylobacter, E. coli, and Salmonella) from child stool samples, livestock fecal samples, and drinking water. Surface water sources and household drinking water containers had high levels of biological (total coliform/E. coli) and chemical contaminants (iron and manganese). The prevalence of Campylobacter was high (>60%) across child, livestock, and water samples in upstream and downstream communities. High levels of E. coli were also detected across samples (>40%), with significantly higher prevalence in upstream children and livestock. Salmonella was less commonly detected, but the prevalence was significantly higher in upstream livestock. Whole genome sequencing analyses of cultured pathogens are planned to define population structures and assess pathogen sharing at the child-livestock-water interface. Our results highlight the need for further research to assess environmental factors associated with child stunting and to facilitate development of more holistic household- and watershed-based intervention strategies to improve human, animal, and ecosystem health outcomes.

• Thesis Defense
• 04/19/2023

Rangelands are important ecologically, economically, historically, and socially. Rangelands are also threatened by regime shifts (state transitions) like woody encroachment, desertification, and exotic annual grass invasion. Management of rangelands to prevent, contain, and reverse regime shifts relies on rangeland monitoring. Innovations in rangeland monitoring—such as the generation of new landcover datasets with field data, remote sensing, and geospatial cloud computing—allow for earlier detection (screening) of regime shifts in support of proactive rangeland management. In this thesis, I screened Nebraska landscapes for woody encroachment, desertification, and exotic annual grass invasion, according to three characteristics of regime shift signals: presence, persistence, and non-stationarity. In addition to informing management, results can help advance approaches to regime shift screening in rangelands.

• Thesis Defense
• 04/18/2023

Drought is characterized by periods of below average precipitation. There are five major types of drought recognized in the literature: meteorological, hydrological, agricultural, socioeconomic, and ecological. A relatively new concept in the drought literature is “snow drought.” A key part of the definition of drought is that it is not always accompanied by extreme heat. This means drought can occur even in cold climates, cold seasons, and higher latitudes and altitudes, like Alaska. Drought is a natural part of climate variability, but Alaska’s climate is changing faster than any other state in the United States. Alaska is no stranger to dry periods; prolonged dry periods have occurred in the 1950’s, 1970’s, 1990’s, and most recently from 2016-2019. However, the frequency, duration, and intensity of drought is changing due to global climate change. There have been many impacts to Alaska hydrology, forestry, and agriculture due to drought, so the purpose of this study is to enhance the understanding of drought in Alaska by identifying and using regionally appropriate climate information to create a comprehensive picture of drought in Alaska while capturing its unique characteristics. The principal components analysis (PCA) approach was used to integrate 17 individual drought indicators and indices to identify their relative contribution on a climate division basis. Those results were then used to create a composite drought index (CDI) for the state of Alaska for the period 2003-2021. Results showed that the CDI was able to capture drought events in Alaska, a first step towards improving operational drought monitoring in the state.

• Thesis Defense
• 04/12/2023

Environmental leaders are tasked with finding innovative solutions to dynamic and ever-changing environmental challenges. Leaders must possess the ability to gain and use new knowledge and experiences that motivate resolving gaps in one’s knowledge (i.e., curiosity) to find forward thinking solutions. Curiosity is an integral part of human existence but may be experienced in various ways. Studies have shown men and women may possess different leadership styles, but the influence of curiosity on leadership between genders has not been as readily explored. Women have shown unique characteristics for successful leadership in many contexts but are often underrepresented in natural resource management. Characteristics of curiosity and those of women leaders are similar to qualities in transformational leadership who are successful environmental stewards. This explanatory mixed methods study investigated the role of curiosity in transformational leadership and seeks to understand the influence of curiosity and leadership in women environmental leaders.

We assessed gender, trait curiosity, and transformational leadership scores of participants in the year-long Nebraska Water Leaders Academy. Regression analysis found that curiosity was a strong predictor of transformational leadership while gender was not, from both the participant and rater’s perspectives. Thematic analysis of interviews with women environmental leaders produced seven themes that inform the essence of how curiosity and transformational leadership influence the women’s experiences. Participants expressed constant awareness of stereotypical gender roles and how this played into power imbalances that both limited and supported elements of their curiosity and leadership. Their people-oriented curiosity supported communication, relationship building, and perspective gaining which were strengths of women leaders.

• Thesis Defense
• 04/07/2023

Landscape composition and anthropogenic pressure can shape the transmission of pathogens between hosts in shared or adjacent habitats. Human-driven environmental changes such as urbanization can increase contact between people and animals, increasing the risk for pathogens to be transmitted at the human-domestic animal-wildlife interface. Toxoplasma gondii, a globally distributed zoonotic parasite shed by domestic and wild felids, can accumulate in terrestrial and aquatic environments leading to exposure in diverse hosts. As T. gondii can be spread through food webs (consumption of infected animal hosts) as well as by ingesting oocysts in contaminated soil, plants, and water, changes in landscape composition and configuration can impact exposure by changing contact among hosts or the potential for contacting oocysts in the environment. Although most animals and people infected with T. gondii experience mild or no clinical signs, the severity of the infection is highly dependent upon the immune system of the hosts and the strains of T. gondii involved. We used logistic regression to assess the association between landscape characteristics and T. gondii exposure as well as T. gondii genetic diversity in bobcats, coyotes, foxes and feral domestic cats from coastal California. We analyzed anthropogenic (human population density and global human footprint), demographic (sex and age), landscape composition (urbanized, agricultural, and less developed areas), and landscape configuration (diversity and evenness indices) factors as potential predictors. We found that landscape heterogeneity was positively associated with T. gondii exposure in feral cats. Animal age was consistently a strong predictor for exposure in all wild and domestic species. We also found associations between human population density and occurrence of novel atypical strains of T. gondii in wild host species. Results from this study provide insight into the ecology of T. gondii transmission among sympatric hosts in heterogeneous landscapes and highlight the need for further research to identify areas where new strains of T. gondii may emerge.

• Thesis Defense
• 11/22/2022

Native species of the Missouri River drainage inhabiting benthic habitats dominate state and federal lists of species at risk. Sicklefin Chub Macrhybopsis meeki and Sturgeon Chub Macrhybopsis gelida are two native Missouri River benthic minnows that are currently under review for federal listing due to extensive population declines and local extirpations within their native range. Substantial alterations to the Missouri River in South Dakota threaten Macrhybopsis spp. and other benthic fishes; however, large, less impacted tributaries in the state may act as refugia for native species. The extent of Sicklefin Chub and Sturgeon Chub populations is largely unknown in the state and recent assessments documenting Missouri River benthic fish assemblages are lacking. Our objectives were to: 1) update the status, evaluate distributional patterns, and characterize habitat use of Sicklefin Chub and Sturgeon Chub, and 2) describe, assess, and compare patterns of benthic fish assemblage structure in the Missouri River and its major tributaries in South Dakota. Sturgeon Chub were captured in the Cheyenne, White, and Little White rivers, but were absent from the Little Missouri and Grand Rivers. Relative abundances of both age-0 and age-1+ Sturgeon Chub were highest in the White River. Distributions of Sturgeon Chubs were limited to lower areas of all rivers where stream width, turbidity, discharge, and observed habitat complexity were greatest and abundances of Flathead Chub Platygobio gracilis and Hybognathus spp. (Plains Minnow H. placitus and Western Silvery Minnow H. argyritis) were high. Sturgeon Chub primarily used main or secondary flowing channels and were predominantly found in or near the thalweg. Velocity, depth, and percent gravel predicted Sturgeon Chub presence on smaller scales. Primarily native fish assemblages were observed in all rivers. Total species richness was lowest in the White River, where extreme environmental conditions likely limit species diversity and nonnative species establishment. Longitudinal patterns of assemblage structure were observed in the White, Cheyenne, and Little White rivers due to natural and anthropogenic changes in habitat conditions. Species additions occurred as rivers gradually increased in size and habitat complexity, but species were replaced in response to abrupt habitat changes, such as those made by impoundments. High abundances of native, benthic fishes in Missouri River tributaries of South Dakota that are experiencing overall population declines highlights the importance of large, relatively unaltered tributaries to the conservation of freshwater biodiversity in North America.

• Dissertation Defense
• 11/21/2022

Woody plant encroachment is a global threat to the persistence of grassland biomes and the ecosystem services they support. Effective conservation in the face of biome-scale threats will require new and adaptive approaches that go beyond the disciplinary traditions of natural resource management. The focus of this dissertation is co-production of science for the conservation of grasslands threatened by woody plant encroachment. Each chapter reflects an actionable research question, co-developed between scientists and managers to better understand, and manage the underlying risks of woody encroachment. Overall, findings provide a better understanding of where grasslands are vulnerable to encroachment, key drivers of grassland vulnerability, the risk of woody encroachment to ecosystem services, and how management can reduce grassland risk to encroachment.

• Thesis Defense
• 11/21/2022

The North Platte River (NPR) Valley of western Nebraska is a semi-arid watershed with row crop production, livestock production, and urban land use activity and has a population of diverse stakeholders. These land use activities contribute to the enrichment of surface waters, such as streams, which can affect human and ecosystem health, as well as economic development and recreational activities. The project objectives are to: (1) quantify the movement of dissolved inorganic nutrients from the land within the NPR Valley to the NPR via tributaries and canals, (2) identify spatiotemporal variability of nutrient limitation of periphyton growth within the NPR, and (3) explore the factors that are associated with the adoption of a web-based water quality monitoring tool. To address the first two objectives, I collected water samples and discharge measurements from canals, tributaries (streams leading back into the NPR), and the NPR from the Wyoming–Nebraska border every three weeks from June–September 2021; and I performed repeated nutrient limitation bioassays every three weeks at nine sites. I found that land use within the NPR Valley contributes to nutrient enrichment of the NPR and the subsequent export of nutrients downstream. Based on the lack of response of periphyton to the nutrient bioassays, it is likely that the nutrients coming from the watershed meet periphyton growth demands, except during the end of the growing season when some nutrient limitation of growth was detected. To meet the third objective, I created a survey tool to understand how attitudes, norms, and beliefs affect the use of a web-based water quality monitoring tool. Performance expectancy was the only significant predictor of behavioral intention for water users to use a web-based water quality monitoring tool. From a management perspective, these studies emphasize the need for better management of nutrient exports from the NPR Valley, but the incorporation of functional goals into the deployment of potential water quality tools to ensure high behavioral intention to use the tool.

• Dissertation Defense
• 11/18/2022

Ecological restoration is a critical tool in countering biodiversity collapse and can create desired positive feedbacks, i.e., native plant restoration that attracts native fauna and supports ecological function. Habitat management is critical to this process, as accelerating global change makes restored and unrestored habitat health increasingly uncertain. Because western ecological restoration is fairly new and developed alongside or after other ecology subdisciplines, there are knowledge gaps in our ability to restore at scales that can counter global degradation. Knowledge gaps include how to 1) maintain restorations over time amidst changing climate, 2) increase restoration success by partitioning controllable vs. uncontrollable factors, and 3) close the theory-application loop by using theory to predict natural systems, and natural systems to inform theory. This dissertation uses experimental and non-experimental data to investigate how factors within and outside manager control structure grassland plant communities across southern Nebraska. In a new 3-year experiment I tested the impact of seed mix (mid- and high-diversity) and haying on flowering phenology in old hay meadow restoration. Haying significantly increased flower abundance regardless of seed mix, but extra work may be needed to ensure critical spring blossoms are predominantly native, pollinator-preferred species. The non-experimental data from collaborators encompassed 19 years of sampling and 42 grassland sites (including 23 never-plowed remnants). Using those data, I explored interdecadal plant diversity in restorations, partitioned the effects of soils and management on restorations and remnants, and partitioned variance of major functional groups over five years. Plant diversity in restorations accumulated and persisted over 19 years. Soils and management impact remnant and restoration community composition, and soils also impact plant diversity. Variation within plant communities is largely stable over time, with site differences contributing most of the variance but not differing between remnants and restorations. Overall, grasslands act similarly over time regardless of restoration/remnant status and high spatial variability, and species-targeted, intensive sampling may be required to detect critical sources of variation within non-experimental plant communities.

• Thesis Defense
• 11/16/2022

Nebraska’s agricultural landscapes are rapidly changing, affecting natural resources and their successful management. I utilized two surveys and scenario planning to investigate (Chapters 1: statewide survey, 2: local survey, and 3: scenario-planning workshop) attitudes and perceptions of natural resource management and cross-boundary collaboration. My first objective focuses on what prevents Nebraskans from addressing natural resources challenges looking at demographics amongst generations and the type of area they live in (rural vs urban). The second objective focused on whether landowners engaged with their community in managing natural resources. The third objective developed alternative future scenarios for the Denton Hills landscape, and preferred alternative futures. I found that demographics matter, and that older generations are more likely to engage in community natural resource management. I found that landowners with larger acreages to manage are more likely to view collaboration positively. Scenario planning revealed how local landowners in the Denton Hills view the identity of the Denton Hills, and identified both desired and undesired future alternatives for the landscape. Generally, I found that natural resource challenges are recognized by the public and that people are willing to work in cooperative groups to address the challenges. Understanding perceptions of management, factors affecting those perceptions, collaborative management and a shared future vision will enhance resource management.

• Thesis Defense
• 11/15/2022

Soil color is easily measured in the field and holds potential to be used as an indirect measurement of soil organic carbon (SOC). Such a method would be a powerful tool, building on decades of Munsell soil color data recorded in soil surveys. The main limitation to this approach is knowledge about the specific color-SOC relationship in a region, which often vary in relation to parent material, soil texture, climate, and land use. A secondary limitation is the subjective nature of the Munsell color data. The objectives of this study are: 1) to develop and evaluate the accuracy of pedotransfer function (PTFs) for the prediction of SOC based on soil color and texture in the state of Nebraska and 2) to evaluate digital based color measurements methods as field predictors of soil organic carbon (SOC) in Nebraska. To address the first objective, data were obtained from National Soil Information System (NASIS) database, including all pedons sampled across 13 Major Land Resources Areas (MLRAs). The dataset was comprised of 1576 soil pedon description and included samples of varied soil textures, Munsell color, and SOC. The second objective was addressed using digital color measurements of 50 soil samples from Kellogg Soil Survey Laboratory archive. Methods used for digital color measurement included a portable color sensor (PCS) and smartphone camera (SPC). Regressions of moist Munsell value versus SOC using the NASIS data had R² values ranging from 0.23 to 0.69 for individual MLRAs. In contrast regression developed using the PCS for three selected MLRAs had R² values ranging from 0.49 to 0.81. Various PTFs based on the NASIS data resulted in RMSE of prediction ranging from 0.795 to 2.1. Digital color measurements using SPCs were found to be of low accuracy and were weakly related to SOC. The results indicate the potential of using soil color as a predictor for SOC, especially when PCS are used to measure soil color.

• Dissertation Defense
• 11/14/2022

Monitoring crop water stress is critical for developing strategies for improving crop productivity and mitigating water stress damage. The common approaches to monitoring crop water stress include field crop measurement (e.g., leaf water potential and relative water content), climate observation (e.g., soil moisture and precipitation), and remote sensing data (e.g., vegetation indices). Equivalent Water Thickness (EWT), defined as the ratio of water mass to leaf (leaf EWT) or ground area (canopy EWT), has been used as a direct field measurement of the vegetation water status indicator and has shown to be measurable by remote sensing data. Therefore, there is increasing interest in using EWT in important economic crops (e.g., corn and soybean) for water stress detection. However, the utilities of crop EWT and water stress detection lack the physical foundation on three domains: responsive characteristics to environmental changes and plant physiological processes, limitations of corn leaf EWT remote sensing estimation at multiple spatial scales, and variations of the standardized anomalies in different drought conditions and the associations between standardized anomalies of crop leaf EWT and vegetation indices. Therefore, the overreaching goal of this dissertation was to identify the potential role of canopy EWT in agriculture water management. Therefore, we conducted a long-term study of leaf and canopy EWT in the experimental sites near Mead, Nebraska. In this dissertation, we established the following research objectives: examine the relationships between canopy EWT with latent heat flux (LE), soil water content (SWC), vapor pressure deficiency (VPD), and leaf EWT with their associated leaf area index (LAI), gross primary productivity(GPP), and LE (Chapter II), identify the heterogeneity of corn leaf EWT vertical distribution and the accuracy of remote sensing estimations in field scales (Chapter III), and investigate the correspondences between canopy EWT standardized anomalies with other drought indicators and the associations between vegetation indices and leaf EWT standardized anomalies(Chapter IV). This dissertation provided new physical foundations in the EWT of corn and soybean and insight into crop water stress detection with remote sensing data.

• Thesis Defense
• 09/02/2022

Great Plains landscapes are undergoing changes at multiple spatial and temporal scales due to processes ranging from woody encroachment to demographic change. These changes may fundamentally alter the agroecosystems of the Great Plains such that the provisioning of ecosystem services such as biodiversity and livestock production is affected. Improving our understanding of the effects of landscape change and how humans perceive and respond to these changes is important for facilitating research and management that enhances the resilience of these agroecosystems. In order to examine landscape change in the Great Plains and the roles of scale and human response to change, I first applied discontinuity theory and graph theory to evaluate the functional connectivity of the Central Platte River Valley (CPRV) for mammal species interacting with the landscape at multiple scales. I found that the CPRV was highly connected for mammal species at larger scales and less connected for those at smaller scales. I also found limited overlap in the patches of habitat most important for connectivity for mammals interacting with the landscape at smaller and larger scales. These results suggest that a multiscale approach to management in the CPRV will be most beneficial in supporting diverse species communities. Second, I interviewed ranchers in the Great Plains states of Nebraska and Colorado in order to examine their perceptions of landscape change and potential coping strategies. The ranchers interviewed identified numerous changes affecting Great Plains landscapes, and they generally expressed a willingness to learn and adopt new practices, including in response to landscape change. These results indicate a need and opportunity for research and management partnerships between governmental and nonprofit entities and the ranching community in order to develop coping strategies. Cumulatively, by examining landscape change and the role of scale and human response to change, we gain insight into potential approaches to research and management in changing Great Plains agroecosystems, which is valuable in maintaining the resilience of these systems.

• Thesis Defense
• 08/12/2022

Across the country, Indigenous Peoples have developed and implemented adaptation plans to improve their resilience to climate and weather disturbances. An essential component of these plans is to use environmental information effectively. Institutions like universities and governmental agencies usually provide this environmental information. However, many studies have shown that much of this information is not usable for its intended users. Additionally, there has been little research into the issues that can affect Indigenous Peoples’ usage of environmental information in the U.S. Therefore, this case study aimed to assist the Santee Sioux Nations’ Office of Environmental Protection (OEP) capacity in using environmental information by investigating how to improve it. Moreover, the study also explored how others can improve their collaborative practices with the OEP since the environmental information’s usability depends not only on its quality but also on the relationships that establish its accessibility, validity, and ultimately, its usability.

Through a rigorous ethical process with employees from the OEP, a case study was developed that consisted of a focus group, document analysis, and observations. The results reveal that, unlike previous research on usable science that focuses on technical issues, the main obstacles to usability result from present-day structural issues that connect to past U.S. actions. A similarity with the previous research is that the relationship between the information producers and users is a critical factor in this study for increasing the usability of environmental information.

• Thesis Defense
• 07/22/2022

Northern bobwhites (Colinus virginianus) have experienced range wide population declines and are listed as a Tier 2 species of conservation concern in Colorado. Recent harvest data from northeastern Colorado suggests fewer bobwhites and managers aim to identify the vital rates and habitat features by which population growth rate may be limited to guide management actions. Although many studies have suggested that bobwhite populations are most sensitive to changes in reproductive factors, recent work suggests that some populations can be sensitive to adult non-breeding season survival. Additionally, northeastern Colorado has habitat and weather dynamics unique to the northern periphery of the northern bobwhite range. We monitored bobwhites in northeastern Colorado for the 2019-2020 and 2020-2021 non-breeding seasons to estimate non-breeding season survival and habitat selection. This included constructing known-fate survival models for each study season to determine any variation in survival between the winter stages of early-winter, mid-winter, and late-winter, as well as sex, age class, and mass at the time of capture. The highest performing model for each season estimated weekly survival that varied between the winter stages. We also monitored bobwhite habitat selection by performing weekly covey habitat surveys. Predictor variables include vegetation cover percentages, micro-climate variables, vegetative structure variables, and species richness estimates at used and random sites. We then used step-wise backward selection modeling to determine if any variables were being selected disproportionate to their availability. Our final habitat selection model included visual obstruction, percent bare ground and percent litter cover. The coefficients for relative probability of use were positive for each variable in the model. Our research aims to provide demographic and habitat selection data to managers to assist them in management action decision making.

• Thesis Defense
• 07/21/2022

Woody species encroachment is occurring within the sandhills region in Nebraska, primarily driven by Juniperus virginiana and Pinus ponderosa, altering ecosystems and the services they provide. Effective, low cost, and cross-scale monitoring of woody species growth and performance is necessary for integrated grassland and forest management in the face of climate variability and change, and anthropogenic management. In this study, we sought to establish a relationship between remote sensing-derived vegetation indices (VIs) and dendrochronological (raw and standardized tree ring width) measurements to assess the performance of encroaching woody J. virginiana and P. ponderosa located within the Nebraska National Forest in the sandhills. We hypothesized that environmental stresses that impact foliage growth and photosynthetic capacity also impact annual tree ring growth of woody species, including invasive J. virginiana and P. ponderosa, which can be detected using remote sensing techniques, and that abiotic stresses that affect tree performance would be decoupled from that of native grasslands due to differences in physiology, response to stress, and rooting depth. We evaluated relationships between the abiotic environment (precipitation, temperature, PDSI, and soil water content 0 – 3 m depth), tree ring growth, and VIs. Our results indicated that precipitation, temperature, and PDSI were significant (p < 0.05) predictors of J. virginiana and P. ponderosa growth based on dendrochronological and VI measurements (1984 – 2013), while soil water content from 40 – 300 cm was a significant predictor of J. virginiana performance (2005 – 2013). Out of six tested VIs, four (NDVI, GCI, GRVI, and LSWI) were significant predictors of tree ring growth for both species. R2 values between grassland VIs and growing season climate were greater than those of J. virginiana or P. ponderosa, while grassland performance was decoupled from soil water content. We determined via Least Absolute Shrinkage and Selection Operator (LASSO) regressions that previous year climate was an important determinant of current year growth of both tree species but did not affect current year grassland performance. This study provides evidence for the efficacy of VIs in monitoring interannual variations in the growth of woody species, while determining abiotic factors significantly impacting the growth of grasslands, J. virginiana, and P. ponderosa in the sandhills region.

• Dissertation Defense
• 07/21/2022

Global climate change (GCC) presents a spectrum of unprecedented global issues. Increased em-phasis is being placed on empowering citizens through outreach and education in response to the urgency of the phenomenon. It is imperative to cultivate 'climate literacy,' particularly in stu-dents, to sufficiently prepare the next generation of scientists, policymakers, industry leaders, and other citizens. Opportunities for teaching and learning about Earth's climate system and GCC are decentralized across topics and grades, and Earth science is increasingly de-emphasized in the K-12 curriculum (Banilower et al., 2018). Furthermore, teachers feel under prepared in their science content knowledge for teaching about GCC, describe instruction in this area as a low priority, and report limited resources to support teaching and learning about GCC. This presentation will present findings from three related manuscripts, each investigating secondary science teachers' enactment of a curricular intervention using a cloud-based global climate model within different contexts and across time, building toward a greater understanding of teaching and learning about Earth's climate.

• Dissertation Defense
• 07/05/2022

Current Use Pesticides (CUPs), which are important for continued productivity within the agricultural industry, exhibit a growing influence on water resources and aquatic ecosystems. Worldwide, over 411,000 kilograms of pesticides (e.g., herbicides, insecticides, and fungicides) are applied annually, leading to chronic pollution in streams and rivers. While substantial work has been completed on the occurrence and distribution of neonicotinoid in both surface and groundwater environmental, little is known on the degradation and transformation of neonicotinoids in natural river environments. Therefore, the overarching goal of this study was to quantify the potential role of two rivers on the photochemical transformation of neonicotinoids and potential fate and transport mechanisms of these insecticides and their degradants in aquatic environments. To evaluate this, we established the following objectives: review the current knowledge of neonicotinoids insecticides in aquatic environments (Chapter 1), evaluate the impact of neonicotinoids fate and transport in watersheds with varying land uses (Chapter 2), and evaluate specific photochemical transformation rates, mechanisms, and byproduct formations of two neonicotinoids (imidacloprid and thiamethoxam) in river water with varying dissolved organic matter (Chapter 3). Findings from this study provide an improved understanding of pesticide and their degradants fate and transport mechanisms in river environments.

• Thesis Defense
• 06/30/2022

The Delphi Method is used throughout a wide range of scientific disciplines for collecting copious amounts of qualitative data about topics of interest. However, the structure and process can be vague and variable. Within 81 peer-reviewed scientific journals, we identified 115 publications addressing the use of the Delphi Method in the fields of natural resources, fisheries, wildlife, and conservation. Our research showed that the Delphi method can successfully provide insight into a wide range of natural resources topics when reported and explained in the methodological structure. Specifically, this project used the example of the adoption of precision agriculture for conservation purposes, to display the Delphi methods abilities to address prominent questions and provide feedback that will help guide researchers to the best next steps in research and management decisions. Our research meets the demonstration of a complex issue by the need for strategic development of agricultural lands to ensure we can feed a growing world, while simultaneously reducing impacts on our natural resources such as water pollution from runoff, soil degradation, and habitat fragmentation.

To address these growing concerns, researchers are looking for ways to optimize both agricultural production and natural resource conservation. Therefore, precision conservation was developed to ensure sustainable ecosystems for future generations. Precision conservation leverages various precision agricultural tools like yield monitor data, and Geographic Information Systems (GIS). to identify areas in fields that can be diversified to optimize financial return on investment while benefiting conservation. The role conservation specialists play and their influence on the implementation and adoption of emerging precision agricultural practices remains in question. To ensure conservation specialists can clearly articulate how precision conservation can help agricultural producers feed a growing world, while simultaneously reducing impacts on our natural resources, we convened a panel of 20 conservation specialists to examine the current diverse perspectives on the progression and integration of precision agriculture in conservation management prescriptions. We used the E-Delphi method to gather data through a series of three surveys to test the hypothesis that the use of precision agriculture is becoming increasingly prevalent in the field of conservation. Our results support the hypotheses, suggesting that conservation specialists are, in fact, using precision agriculture practices in their conservation positions, but with noticeable variance in the confinements of which practices were utilized. Furthermore, the results highlight the need to provide a united message when delivering precision agriculture across varying agency and organizational platforms

• Dissertation Defense
• 06/16/2022

Wetland is one of the most important natural resources which provide human society lots of ecosystem services. Human actions and disturbances have caused critical wetland degradation and losses on earth. The main impact factors, including pollution, biological resources use, natural system modification, agriculture, and aquaculture, are significant reasons for wetland degradation. This study focuses on the wetland conservation efforts in Nebraska. In general, this study assesses the wetland conservation in Nebraska from three aspects: 1) How wetland conservation was integrated into Nebraska’s local planning system; 2) What’s the contemporary status of public-owned saline wetlands in Nebraska; 3) What’s the inundation condition of private-owned conservation easements. The first aspect uses a planning evaluation approach to analyze the most current local comprehensive plans. Findings suggest that local governments need more direct and proactive inputs to improve wetland conservation. The second and third aspects adopt machine learning and Google Earth Engine to classify the Sentinel-2 imageries for Nebraska's public and private-owned wetlands. Different machine learning models are applied and compared in the study process. This study shows the possibility of an observation approach for long-term continuous monitoring of Nebraska’s eastern saline wetlands and conservation easements lands efficiently and cost-effectively. The research findings also provide solid scientific evidence for conservation decision-making in these saline wetland areas.

• Thesis Defense
• 04/27/2022

Outdoor play is an important aspect of young children’s health social-cognitive development. However, play in natural environments is declining due to urbanization and various safety concerns. Many urban preschools have outdoor play spaces that lack natural elements that stimulate children’s autonomy, creativity, and imaginative play. Furthermore, parents who find outdoor environments intimidating and fraught with danger limit young children’s outdoor experiences that inhibit their motor fitness, socialization with peers, and ecological awareness. Two qualitative case studies examined preschool children’s outdoor play. Study one focused on preschool children’s loose parts play in urban settings while study two examined parent’s attitudes towards outdoor play with young children. Key findings included that children engaged in dramatic play more with natural loose parts than manufactured loose parts. And playgrounds with age/developmentally appropriate equipment, barriers/fences, and open/centralized play spaces with clear views would make parents more comfortable in providing outdoor play.

• Dissertation Defense
• 04/21/2022

Artificial Intelligence (AI) in computer vision is revolutionizing the geoscience and remote sensing domains. Convolutional neural network (CNN), as a typical Automated machine learning (AutoML), automatically represents image contexts (spatial-spectral correlation) from remote sensing imagery into spatially and spectrally relevant knowledge. The end-to-end design relieves researchers from tedious feature engineering and local tuning work. Considering the vital role of long-term frequent land cover monitoring in assessing the local ecosystem health cost-effective adaptations of AutoML, such as CNN, in local cases are vital to support in-time conservation and proactive ecological management. This study aims to explore the adaptation of these cutting-edge AutoML techniques in wetland monitoring and delineation, which can improve traditional wetland mapping pipelines by facilitating cost savings. Three publicly managed playa wetlands in the Rainwater Basin, Nebraska, USA, were selected as the study areas. By implementing AutoML techniques, I want to address three critical aspects in wetland ecosystem monitoring: 1) automatic waterfowl censusing using thermal sensors, 2) automatic wetland inundation delineation during the spring season using multi-spectral sensors, 3) and automatic aquatic vegetation segmentation under dynamic environments (during the fall season) using optical sensors. The remote sensing data in this study mainly relies on high spatial resolution UAV imagery. Different levels of computer vision techniques, including image processing, machine learning, and deep learning approaches, were developed and tested. The results indicate that CNN with proper designs and configurations can facilitate significant cost-savings on wetland mapping.

• Thesis Defense
• 04/19/2022

As changes in climate, land-use, and vegetation alter the landscape of the Great Plains, new threats to public health are emerging. Incidences of tick-borne disease contraction in Nebraska have increased nearly 250% over the past two decades – newly established species like Ixodes scapularis may introduce challenges for health practitioners, including more cases of Lyme disease. Strategies for tick-borne disease prevention must incorporate effective health messaging. Audience segmentation may be a useful technique to provide health communication, as it allows for targeted messaging that speaks to specific attitudes and beliefs of a given population. One tool for usefully segmenting populations is the Risk Perception Attitude Framework (RPAF) – this groups individuals into four categories based on their perceived risk towards a threat and their efficacy in protecting themselves from the threat. We applied the RPAF to a sample of hunters in Nebraska to assess differences in level of intention to perform preventative behaviors between the four RPAF groups. Our Analysis of Variance (ANOVA) model found significantly higher behavior intent among individuals in the RPAF group with highest perceived risk and self-efficacy, backing up previous RPAF literature. This information can be used to identify clusters of individuals with similar beliefs towards tick-borne disease and provide more effective health messaging about this threat.

• Thesis Defense
• 04/14/2022

The degree to which sustainability is taught is often varied and inconsistent across colleges, departments, and higher education institutions. However, educating students and future generations regarding the different pillars of sustainability, including economic, social, and environmental topics, is increasing in importance and urgency.

A mixed methods case study utilizing surveys and interviews investigates why instructors incorporate sustainability, what impacts course incorporation of sustainability, and barriers that instructors face.

The study found that instructors’ beliefs regarding the importance of sustainability transfers to the level of incorporation in their curriculum. Topics of sustainability incorporated are determined by instructors’ industry and college versus instructors' specific beliefs. Instructors are more intrinsically versus extrinsically motivated to teach the topic and face a variety of external barriers, such as lack of resources, time, and opportunities. By investigating instructors’ beliefs regarding sustainability from multiple fields, this research fills a void in the published literature and provides general recommendations for how to support faculty and university change.

• Thesis Defense
• 04/13/2022

Marginal cropland is cropland that is suboptimal due to historically low and variable productivity and limiting biophysical characteristics. To support future agricultural management and policy decisions in Nebraska, it is important to understand where cropland is marginal for its two most economically important crops: corn (Zea mays) and soybean (Glycine max). A multi-criteria evaluation model was conducted using Google Earth Engine to identify and classify marginal cropland in Nebraska. Eight criteria, including crop yield, slope, climate and soils criteria, were individually thresholded then aggregated to create crop-specific marginal classifications. A new method for classifying long-term crop rotations was devised to examine differences in marginality classification between rotation classes. The results show statewide spatial trends in, as well as the net positive benefits of crop rotation on, marginality classification. The identification of marginal land will also provide evidence to facilitate discussion on biofuels production using perennial biomass crops, targeted land for conservation practices and solar energy capture, both of which have potential to be integrated into current cropping systems. Future work will involve connecting the results of this study with researchers and outreach professionals to aid in ensuring the long-term viability of agriculture in Nebraska.

• Thesis Defense
• 04/08/2022

To keep up with the global food demand, modern agriculture seeks to optimize production on current agricultural land. One method of optimization is through precision management, where field zones are managed according to variation in soil properties. For instance, activities such as irrigation, fertilization, and seeding can be guided by soil maps of available water capacity, organic matter content, and bulk density. The conventional method for obtaining soil maps is extensive soil sampling, which involves significant time and labor costs. On-the-go geophysical sensors can potentially obtain soil maps that are still accurate enough for precision management but less costly. Physical properties of the earth, such as the electrical conductivity and naturally emitted radiation of the top meter of the ground, can be correlated with various soil properties. Geophysical sensors can provide information about the variability of the soil between soil sample locations and reduce the number of soil samples needed. However, across different field conditions, the geophysical data tends to have varying correlations with the actual soil properties.

A study was conducted in three agricultural fields in North Dakota to better understand geophysical sensors’ performances in soil mapping. Electrical conductivity data from an electromagnetic-induction sensor, radioelement concentrations from a gamma-ray sensor, and neutron intensities from a cosmic-ray neutron sensor were used to build simple linear models that predict soil properties across each field. At each of the sites, different soil properties such as bulk density, texture, or available water content were predicted with satisfactory accuracy. The study shows that using just a few soil samples alongside geophysical data is a feasible method for creating soil maps for precision management. While electromagnetic induction and gamma-ray surveys are currently commercially available to producers, future work must be done to establish which sensors are best for each setting and the method’s economic value.

• Thesis Defense
• 04/05/2022

The United States is approaching a critical juncture regarding aging dam infrastructure. Recently, a common path forward has been to decommission and remove dams, returning rivers to a free-flowing state.

The primary focus of most literature on ecological restoration, especially dam removal, has been the ecological impact of the restoration. Attention from practitioners and researchers is shifting toward the importance of participation and the social dimensions of ecological restoration. The social situation surrounding a dam removal can lead to expedited success, delayed progress, or an abandoned removal effort. This study seeks to connect selected social dimensions of dam removal with the broader literature of ecological restoration by exploring the question, “how are social dimensions of ecological restoration expressed within public participation in a dam removal process?”

A qualitative research design using a directed content analysis was used to study selected social dimensions of dam removal contained in public comment letters sent to the federal agency in charge of removing two dams on the Elwha River of Washington. A codebook was developed to explore the social dimensions of restoration attitude, environmental attitude, place attachment, connectedness to nature, sense of community, and economics.

The findings of this study revealed those with positive restoration attitude more frequently referenced the social dimensions of environmental attitude, place attachment, connectedness to nature, and sense of community. While participants with negative restoration attitude centered more of their testimonies around the economic situation surrounding dam removals. Additionally, participants with a positive restoration attitude framed their comments and references to other social dimensions around the potential ecological, economic, and social gains following dam removal, while participants with a negative restoration attitude framed their comments around the possible ecological, economic, and social losses that would ensue following dam removal.

Findings from this study emphasize the importance of public participation in the dam removal process as well as the continued exploration of the social dimensions of dam removal. As this river restoration method becomes more commonplace, environmental managers will need to be able to effectively engage with the public and understand not only the ecological dimensions, but also the social dimensions of dam removal.

• Dissertation Defense
• 04/05/2022

The world’s population is growing and an increasing populace requires more resources. These requirements place increasing pressure on the environment and the soil. Soils serve many important functions throughout the world. These functions range from offering a media for food production, providing a sink for organic carbon, nutrient cycling, and improving water quality. It is important to focus on the human impact on soils and their change over time.

For my research I examined how soils across Nebraska have changed over a time period of roughly 65 years. I sampled and analyzed 39 pedonsfrom four Major Land Resource Areas (MLRAs) across the state of Nebraska. These sites were selected because they each represent a distinctive combination of climate, geology, and land use within Nebraska. At the time of original sampling (1951-1961), nearly all the sites were under row-crop production. I created a correlation for estimating soil organic carbon for four MLRAs using loss-on-ignition organic matter values. Next, I examined how the soils in MLRAs 67 and 71 have changed over 65 years of continued irrigation and agricultural production. Lastly, I assessed how the soils MLRAs 102 and 106have changed after 65 years of non-irrigated agricultural production.

• Thesis Defense
• 03/29/2022

Land use land cover change, including irrigation, impacts weather and climate. In this thesis a precipitation event that occurred during the Great Plains Irrigation Experiment (GRAINEX) is investigated. The event was observed on the morning of 23 July 2018. Six model-based experiments were conducted which involved increase or decrease of soil moisture by 5% and up to 15% over the irrigated croplands. These changes were approximation of soil moisture content in response to different levels of irrigation applications. An additional experiment, where irrigated land use was changed to grassland, was conducted to capture pre-irrigation land use and its impacts. It was found that regardless of level of irrigation, average precipitation decreased. However, precipitation decrease was greater under drier conditions. In addition, as observed, the model did not produce precipitation over non-irrigated land use. When grassland replaced the irrigated agriculture, increases in precipitation was reported. With increased irrigation, latent heat flux increased compared to control simulation and decreased when irrigation decreased. On the other hand, sensible heat flux was decreased compared to control when irrigation increased. The planetary boundary layer over irrigated land use was shallower than over non-irrigated land use while over grassland it was higher than irrigated but lower than non-irrigated land use. The changes in precipitation, the surface energy balance, and the planetary boundary layer served as a reminder of irrigation’s complex effects on the atmosphere. Additional analysis of the other precipitation events during GRAINEX would be helpful to better understand the effects of irrigation.

• Dissertation Defense
• 03/28/2022

Natural resource professionals, political leaders, and environmental organizations recognize the need for more informed and educated stakeholders to tackle today’s complex natural resource challenges. This dissertation investigates the nature of stakeholder engagement and its influence on natural resource management. The purpose of this study is to: 1) examine the attitudes that influence agricultural producers’ involvement in stakeholder engagement and community capacity building, 2) determine if boundary spanning skills can be developed through a professional development program, and 3) investigate the role of boundary spanners within a stakeholder-directed engagement process. Data was collected from interviews of Nebraska agricultural producers and natural resource professionals with experience in stakeholder engagement and from a survey of Nebraska Water Leaders Academy participants and their raters.

The first study explores the factors that enable or constrain agricultural producers’ engagement and community capacity building in Nebraska. A survey of agricultural producers was conducted identifying several barriers to producer participation. The findings also included enabling factors which may act as an incentive for more engagement by producers. The second study develops and evaluates an evidence-based boundary spanner development program for natural resource professionals. Nebraska Water Leaders Academy participants were asked to take part in a boundary spanner workshop as part of the year-long Academy and surveyed to assess their boundary spanning skills. The third study investigates boundary spanning skills evident among participants in an eighteen-month stakeholder engagement process in Nebraska. Twenty-five participant interviews were conducted covering a range of issues to determine if individuals participating in the stakeholder-directed engagement process exhibited boundary spanning skills and if so, how these skills were applied in practice.

These three research projects identify strategies that can lead to more effective and sustainable stakeholder engagement processes and highlight the challenges inherent in bringing a diverse group of individuals together to solve complex natural resource concerns.

• Dissertation Defense
• 01/14/2022

IMPACTS OF ANTHROPOGENIC PRESSURES ON OCELOTS (LEOPARDUS PARDALIS) IN THE MAYABIOSPHERE RESERVE IN GUATEMALA By Gabriela Palomo-Munoz Advisor:Andrew J Tyre and co-advisor Jeffrey Thompson January 14th 2022 9:00 CST via Zoom. Request link via DM or gabriela.palomo@huskers.unl.edu Abstract Ocelots are a Neotropical mesocarnivore distributed from the South of Texas to northern Argentina.Despite being one of the most studied mesocarnivores, there is still need to understand the effects of human activities on their populations.The Maya Biosphere Reserve (MBR) in Guatemala is a human impacted landscape that ranges from highly protected areas, sustainable forest concessions, to areas with human activities (e.g., cattle ranching,agriculture,urbanization).The MBR provides a study area in which we can investigate the anthropogenic effects on ocelots' demography and behavior. We estimated the effects of human activities on ocelot's density and space use.We also quantified the effects of forest integrity on jaguars, pumas.gray foxes, and ocelots space use, co-occurrence, and spatio-temporal patterns. Despite ocelots' tolerance to human activities, their populations heavily rely on permeable matrices surrounded by protected areas. Our results contribute to our understanding on ocelot ecology in modified landscapes.

• Thesis Defense
• 11/30/2021

In Nebraska and other regions of the Great Plains, the conifer Juniperus virginiana (J. virginiana, eastern redcedar) is converting grasslands to dense woodlands. This is driven by the interacting drivers of fire suppression, altered grazing regimes, climate change and other anthropogenic factors, impacting the provisioning of ecosystem services. This vegetation regime shift modifies water resource regulation and biogeochemical cycles leading to altered edaphic properties including soil microbial community composition. To restore these grasslands and control J. virginiana spread, prescribed extreme burns are implemented as a management tool through local prescribed burn associations. We hypothesized that the alternative stable state shift to dense J. virginiana woodlands leads to a corresponding stable state shift below-ground that persists post-extreme burn and may facilitate J. virginiana re-establishment. To address this hypothesis, paired grasslands and J. virginiana woodlands in the Loess Canyons of Central Nebraska were subjected to one prescribed extreme burn between 2005 and 2019 to provide a natural burn chronosequence. We quantified J. virginiana re-establishment, soil chemistry, soil microbial biomass and microbial community composition in these paired sites across the chronosequence. Our results partially supported our hypothesis where differences in edaphic variables between J. virginiana sites and grassland sites observed post-burn were largely temporary; however, differences in soil magnesium and microbial community composition were more persistent (> 14 years post-burn). Soil magnesium values were significantly higher in the J. virginiana sites both pre-burn and post-burn across the 14 year chronosequence. Microbial communities were also distinct between J. virginiana and grassland sites pre-burn and across the burn chronosequence. Rapid recovery and/or persistence of specific edaphic factors and soil microbial communities in J. virginiana woodlands post-burn may facilitate early J. virginiana re-establishment. Management at intervals less than 14 years is needed to prevent long term changes to soil function that may facilitate J. virginiana re-establishment.

• Thesis Defense
• 11/29/2021

Nitrogen (N) fertilizer is an essential nutrient for agricultural production worldwide, especially in Nebraska where corn requires a large amount. Historical N fertilizer input and poor environmental management practices resulted in unintended consequences in the ecosystem and environment. Lack of spatially complete N fertilizer application time series data in the US, in particular, the state of Nebraska makes N fertilizer quantification in the vadose zone challenging. The state of Nebraska needs spatial time series fertilizer maps to better address its N fertilizer input and potential nitrate-N (NO3--N) migration and storage in the vadose zone (VZ). This thesis assesses 50 years of Nebraska's spatial N fertilizer inputs on cropland, cropping patterns, timings of application, and soil type impact to NO3--N leaching and compares it with the estimated VZ NO3--N mass stored in the Bazile area and the Lower Platte South Natural Resources Districts (LPSNRD).

• Thesis Defense
• 11/22/2021

Per- and polyfluoroalkyl substances (PFAS) are a recalcitrant suite of chemicals that are environmentally persistent and have been detected worldwide in numerous human and environmental matrices. Human exposure to PFAS has been associated with a myriad of human health impacts due to their carcinogenic nature. A better understanding of various transportation routes that instigate human and environmental exposure in the Midwest will assist communities in making management decisions regarding PFAS usage and treatment. However, current PFAS research is limited due to existing analytical constraints and limitations. This thesis focuses on assessing current extraction methodologies for PFAS for four environmental matrices (POCIS, non-potable water, solids, plant tissue) and a study looking at the transportation of PFAS within a wastewater treatment plant, adjacent surface waters, and agricultural ecosystem land applied with municipal biosolids for a better assessment of PFAS within the Midwest.

• Dissertation Defense
• 11/03/2021

Groundwater is an essential resource throughout Nebraska. Land use and climate change can impact groundwater quality and quantity, both of which are necessary for sustaining agriculture, industry, and human consumption. A better understanding of various factors that influence groundwater movement and contamination will assist water managers in making management decisions. However, since groundwater is not as easily visualized as surface water, it can be difficult and costly to create a complete picture of the subsurface environment and different factors impacting groundwater quality and quantity. This dissertation focuses on groundwater seasonality (when groundwater infiltrates below the root zone), a novel remote sensing approach for assessing groundwater quality, and a case study looking at groundwater recharge and nitrate movement around a groundwater mound and how these different methods can come together to form a more cohesive understanding of the subsurface to assist groundwater managers in decision making.

• Dissertation Defense
• 07/29/2021

Monitoring vegetation dynamics in an efficient and non-invasive way has become increasingly more important for assessing and modeling their responses to the environment and mitigating for climate change. Vegetation optical properties can be used to derive vegetation indices (VIs) which can be used as proxy measures for plants’ biophysical traits. The goal of this dissertation is to use proximal and remote sensing techniques to identify scalable indices and indicators that can be used efficiently to assess vegetation health and performance. The dissertation consists of four studies, each of which tackles different ecological questions utilizing proximal and/or remote sensing methods.

Results from this study are important for the ability to monitor vegetation shifts across multiple scales, important for predicting directional changes of these ecosystems in the face of anthropogenic management and climate change, and the development of effective mitigation plans.

• Thesis Defense
• 07/19/2021

The idea of "working landscapes" has received considerable notoriety as a tool to better engage with private landowners for the purposes of conservation. These frameworks often rely on top-down approaches that do not account for the socioeconomic conditions of rural areas nor elicit feedback about program design or implementation from its participants. Through a discrete choice analysis, we asked ranchers across Nebraska's remaining grassland ecoregions to assess a series of program offerings that would compensate participants for an array of conservation and environmental objectives. Using an ecosystem services framework, adapted to Nebraska’s statewide wildlife management plan (Nebraska Natural Legacy Project), we explore what attributes of "conservation ranching" are most preferable and why such an approach is necessary for both public and private interests.

• Thesis Defense
• 07/19/2021

Haemosporidian parasites are a significant source of morbidity and mortality for birds. However, factors influencing haemosporidian transmission, especially transmission between species, are poorly understood. To gain insight into these influences, we compared prevalence and diversity of haemosporidian blood parasite infections among avian species in a behaviorally and ecologically diverse host assemblage. We studied whether interspecific associations could explain community-wide trends in infection by pairing molecular diagnostics with direct observations of species interactions. Haemosporidian prevalence in the community was low (8.6%), but varied substantially with host phylogeny. Most (94.8% of all infections) infections were identified as Haemoproteus spp. Few Plasmodium spp. infections were detected, and no Leucocytozoon spp. infections were found. We found no evidence for an effect of interspecific sociality on Haemoproteus infections, but we did find evidence for an effect of intraspecific sociality. Individuals of species that had smaller average conspecific group sizes were more likely to be infected than those of species with larger groups. We also found that species with relatively long lifespans had higher prevalences than species with shorter lifespans. No other individual- or species-level traits were associated with Haemoproteus infection. We identified 7 Haemoproteus mitochondrial cytochrome b lineages, which clustered at the host family level. Two Plasmodium lineages were also identified, each of which was previously detected in different host species in the region. The apparent host-family specificity of the parasite lineages may partly explain the lack of effect of interspecific sociality on Haemoproteus infection probability, and implies the presence of barriers to transmission that are associated with host phylogeny.

• Thesis Defense
• 07/16/2021

Efforts to improve water quality in eutrophic ponds often involve implementing changes to watershed management practices to reduce external nutrient loads. While this is required for long-term recovery and prevention, eutrophic conditions are often sustained by the recycling of internal nutrients already present within the water body. In particular, internal phosphorus loads have been shown to delay lake recovery for decades. Thus, in-situ pond management techniques are needed that not only reduce external nutrient loading over the long-term but also mitigate the effects of internal nutrients already present. Our objective was to demonstrate a biological and chemical approach to remove and sequester nutrients present or entering a eutrophic pond. We designed a novel biological and chemical management technique by constructing a 37 m2 (6.1 m x 6.1 m) floating treatment wetland (FTW) coupled with a slow-release lanthanum composite inserted inside an airlift pump. The FTW promoted microbial denitrification and plant uptake of N and P, while the airlift pump slowly delivered lanthanum to the water column over the season to adsorb and precipitate soluble reactive phosphorus (SRP). The design was tested at the microcosm and field scales, where N and P removal was significant (α=0.05) at the microcosm scale and validated at the field scale. The proposed treatment provides a unique and effective technology to address internal phosphorus loads and minimize the effects of nutrient runoff entering urban retention ponds.

• Thesis Defense
• 07/14/2021

Over the past few decades, there has been a resurgence in the popularity of foraging for wild products and foods. Despite the cultural importance and ubiquity of foraging, there have been relatively few scientific investigations of social factors influencing foraging behavior, landscape preferences, and the types of materials foraged in the United States. As such, there is a fundamental need to better understand more about those who participate and their foraging behaviors. Two surveys were conducted to gather information on foragers’ motivations and characteristics and to contextualize foraging within the larger recreation landscape. The first survey used snowball sampling to reach foragers throughout the United States and collected information on motivations, types of land foraged, and the type of taxa foraged. Results indicated that respondents were motivated to relax and escape, to feel self-empowered and know about food sourcing, and for the social benefits of participation. We grouped respondents into four clusters based on motivations: 1) self-empowered foragers, 2) multimotivation foragers, 3) casual foragers, and 4) social foragers. While there were differences in in the reasons why individuals forage, there was little difference among the socio-demographic variables as well as where and what they forage.

A second survey was used to estimate the recreational demand among 16 recreational activities among the general population of Nebraska. The results indicated that approximately 13% of the Nebraska population engaged in at least one day of foraging. While activities such as recreational sports, spectator sports, culture and arts were more preferred than foraging, other outdoor activities such as hunting & shooting sports, fishing, and wildlife viewing were less preferred than foraging. Older Nebraskans gained more utility from foraging than their younger counterparts, but there was little difference in utility gained among other sociodemographic factors. Further, there was indication that foraging by Nebraskans was already at satiation, whereas other activities like the arts and culture were still not at satiation. By understanding the behaviors and motivations of foragers and how foraging fits into the recreation landscape, we gained further insight into the importance of foraging and the behaviors of those participating, which has important implications in the formulation of appropriate policies and management of recreational opportunities.

• Thesis Defense
• 07/12/2021

Wetlands contribute important ecosystem services such as water filtration and storage, wildlife habitat, and carbon sequestration. The objective of this study was to compare both the morphology and the carbon and nitrogen stocks between the upland, basin edge, and basin floor in playa wetlands of eastern Nebraska. This work was conducted in three playa wetlands in the Todd Valley. Morphological descriptions were evaluated to two meters’ depth using cores collected along three transects from the upland to the playa floor in three playas, carbon and nitrogen stocks were evaluated in two of those playas. Results show evidence of erosion, deposition, and both leaching and accumulation of clay in all three playas, and presence of calcium carbonate in one playa. In one playa, both carbon and nitrogen stocks were lower at the basin edge compared to the surrounding uplands and in the other, there was no significant difference in carbon and nitrogen stocks between the upland, basin edge, and playa floor. Morphological features of the soils show colluvium deposition and clay accumulation in two basins and calcium carbonate accumulation in one basin. Profile distributions of carbon suggest that the limited carbon storage in these playa wetlands is, at least in part, due to leaching losses of dissolved organic carbon. The playas of eastern Nebraska show evidence of colluvium deposition caused by human-accelerated erosion and, compared to other depressional wetlands in the region, a limited capacity to accumulate organic matter and store carbon.

• Thesis Defense
• 06/28/2021

One Health, or the holistic approach of viewing human, animal and ecosystem health as interconnected, can play an important role in developing solutions to address diverse health challenges. For young people to grasp contemporary societal and planetary challenges, this understanding is critical. Using data collected through a classroom activity and an iterative coding approach, I analyzed art and written elements developed by primary school students in a biodiverse, rural region of Tanzania to explore their understanding of links among the health of people, animals, and local environments. The students perceived human health in an expansive way, tying it to the health of domestic animals and wildlife, water sources, forests, and ecosystems. They drew varied connections, identifying both direct and indirect impacts on their own health, as well as the broader health of their communities. The students made connections at microscopic and landscape levels, including issues of polluted water and disease and impacts of forests on rainfall and drought. Learning how students understand these connections can aid the efforts of teachers and environmental and health educators in the region, as well as inform curriculum development for students in Tanzania, East Africa, and beyond.

• Dissertation Defense
• 06/22/2021

High interannual variability of forage production in semi-arid grasslands leads to uncertainty when livestock producers make decisions. To inform proactive drought decision making at the ranch level, I developed a largescale model that estimates the amount of annual forage production using environmental and weather variables and the remote sensing-based Normalized Difference Vegetation Index as a proxy for grassland productivity. This model can be used with up-to-date spring climate data and summer climate scenarios (e.g., warm and dry, cool and wet) to create a range of possible end-of-season forage scenarios in a specific year. When provided on an operational basis, these scenarios can serve as a decision support tool for livestock producers, rangeland managers, and other decision makers.

• Dissertation Defense
• 04/13/2021

Through a mixed methods approach, my work explored students’ decision-making practices as they worked through a structured decision-making tool to reason about socioscientific issues (e.g., how do we manage water?). The resulting tools can help researchers explore how students:

• Provide reasoning using interdisciplinary evidence
• Engage with tradeoffs in their decision-making process