• 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.

• 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
• 07/26/2024

E000

• 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
• 07/23/2024

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
• 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
• 11/21/2023

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
• 11/15/2023

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
• 11/13/2023

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.

• 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.

• 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.

• 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.

• 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
• 04/07/2023

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.

• 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
• 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

• 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.

• 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.