Physical Sciences and Mathematics Commons^™

Interactions Of Zooplankton And Phytoplankton With Cyanobacteria, Rebecca Alexander

School of Natural Resources: Dissertations, Theses, and Student Research

Cyanobacteria are a major concern in Nebraska reservoirs and are capable of producing toxins that can cause skin irritations and gastrointestinal problems, as well as affect the nervous system. It is important to determine the mechanisms that can cause cyanobacteria blooms due to the effect they can have on human health. The interaction of zooplankton and other phytoplankton groups with cyanobacteria is important because there is a biological component in surface waters that should be taken into consideration along with the physical and chemical parameters that have been noted to promote cyanobacteria. For example, zooplankton have the ability to alter …

Interactions Of Zoo Plankton And Phytoplankton With Cyanobacteria, Rebecca J. Alexander

School of Natural Resources: Dissertations, Theses, and Student Research

Cyanobacteria are a major concern in Nebraska reservoirs and are capable of producing toxins that can cause skin irritations and gastrointestinal problems, as well as affect the nervous system. It is important to determine the mechanisms that can cause cyanobacteria blooms due to the effect they can have on human health. The interaction of zooplankton and other phytoplankton groups with cyanobacteria is important because there is a biological component in surface waters that should be taken into consideration along with the physical and chemical parameters that have been noted to promote cyanobacteria. For example, zooplankton have the ability to alter …

Impacts Of Climate Change On The Surface Water Balance Of The Central United States, 1984-2007, Bo Dong

School of Natural Resources: Dissertations, Theses, and Student Research

The climate system and the hydrologic cycle are strongly connected with each other. Understanding the interactions between these two systems is important, since variations in climate can trigger extensive changes in the hydrologic cycle, with significant impacts on agriculture, ecosystems, and society. Observations over the central U.S. in recent decades show numerous changes in climatic variables. This includes decreases in cloud cover and wind speed, increases in air temperature, and seasonal shifts in precipitation rate and rain/snow fraction. To assess the impacts of these variations in climate on the regional water cycle, a terrestrial ecosystem/land surface hydrologic model (Agro-IBIS) is …

Role Of The Leguminous Shrub Amorpha Canescens (Leadplant) In The Nebraska Sandhills Grasslands: Water Relations And Patterns Of Water Uptake, Adam Yarina

School of Natural Resources: Dissertations, Theses, and Student Research

This study investigated the ecophysiological role of Amorpha canescens, a leguminous shrub native to the Nebraska Sandhills. Although A. canescens is an important ecological player in the Sandhills, its impacts on the surrounding plant community are poorly understood. To remedy this, two sites were selected for study at the Gudmundsen Sandhills Laboratory near Whitman, Nebraska – one with A. canescens (G-L) and one without A. canescens (G-NL). Both sites contained five representative herbaceous species: two C₃ grasses (Hesperostipa comata and Koeleria macrantha), two C₄ grasses (Andropogon hallii and Calamovilfa longifolia), and one forb …

Interactions Among Evaporation, Ice Cover, And Water Temperature On Lake Superior: Decadal, Interannual, And Seasonal Variability, Katherine Van Cleave

School of Natural Resources: Dissertations, Theses, and Student Research

Lake Superior, the largest freshwater lake in the world by surface area, has enormous impacts on the regional weather and climate. The lake also comprises over half of the total water volume in the Great Lakes system and is an important resource for commercial shipping, water supplies, hydropower, recreation, and aquatic ecosystems. Water temperature and evaporation on Lake Superior have been found to be increasing in recent decades, while ice cover has been decreasing at a very rapid pace. A careful analysis of the long-term trends, however, shows that these changes have not been linear through time. Rather, a step-change …

River Otter (Lontra Canadensis) Home Range, Habitat Use, Overnight Movement, And Survival In The Platte River Of Nebraska, Samuel P. Wilson

School of Natural Resources: Dissertations, Theses, and Student Research

River otters (Lontra canadensis) are native to Nebraska but were extirpated by the early 1900s. The Nebraska Game and Parks Commission (NGPC) reintroduced river otters during 1986­–1991 to restore the species in the state but little is known regarding the habitat needs and status of this high profile threatened species. To provide information for management I conducted research to determine home range, habitat use, overnight movement distance, and annual survival of river otters in the central Platte River of Nebraska.

I trapped, implanted telemetry transmitters, and tracked 18 river otters during 2006–2009. I obtained 996 locations and constructed …

Channel Catfish Population Dynamics, Abundance Estimates, And Short-Term Trends In The Platte River, Nebraska, Aaron J. Blank

School of Natural Resources: Dissertations, Theses, and Student Research

Fishing for channel catfish (Ictalurus punctatus) is popular in Nebraska and channel catfish are the most sought after fish species in the Platte River. Anglers on the Platte River are also harvest oriented. Little is known about the effects anglers have on channel catfish population dynamics in the lower Platte River. The goal of this study was to determine if there were effects of angling on channel catfish at two high use fishing areas in the lower Platte River. My first objective was to evaluate differences in relative abundance, size structure, condition, age structure, growth, and mortality between …

Modeling Field-Scale Vulnerability To Pesticide Runoff, Atefeh Hosseini

School of Natural Resources: Dissertations, Theses, and Student Research

Identifying areas vulnerable to off-site agrichemical movement and surface and ground water contamination through conventional data collection is labor-intensive, costly and time-consuming. To promote efficient pesticide use and protect water resources, a process-based index model was previously developed to estimate landscape vulnerability to pesticide runoff and leaching at a watershed or regional scale using Soil Survey Geographic (SSURGO) data. Because mitigation of contamination requires implementation of best management practices, the model was adapted to the field scale. The field-scale model was developed based on a Digital Elevation Model (DEM) with 5 ´ 5 m resolution for a research site in …

A Climatological Analysis Of The Warm-Season Wind Regimes Of The Beaufort/Chukchi Seas Coasts, William J. Baule

School of Natural Resources: Dissertations, Theses, and Student Research

Climate records for wind speed, wind direction, and temperature are analyzed for the period from 1979-2009 for the Beaufort/Chukchi Seas region of the Arctic. Wind records have historically been subject to far fewer analyses than other meteorological variables, such as temperature or precipitation. This is particularly true for data sparse regions. Data were collected for a large area in the Beaufort/Chukchi Seas region, which includes portions of Russia, the United States, and Canada. Data from 250 stations were collected from a variety of networks throughout the region and uniformly quality controlled. Eight long-term stations were identified for data completeness and …

Agricultural Landuse Change Impacts On Bioenergy Production, Avifauna, And Water Use In Nebraska's Rainwater Basin, Daniel R. Uden

School of Natural Resources: Dissertations, Theses, and Student Research

Agriculture is an economically important form of landuse in the North American Great Plains. Since 19^th Century European settlement, conversion of grasslands to rowcrops has increased food and bioenergy production, but has decreased wildlife habitat. Future agricultural landuse changes may be driven by alternative energy demands and regional climatic changes. Landuse change and its drivers could affect bioenergy production, wildlife populations and natural resources, and considering the potential impacts of impending changes in advance could assist with preparations for an uncertain future.

This study addressed how the conversion of marginally productive agricultural lands in the Rainwater Basin region of …

Characterization Of The Stream-Aquifer Hydrologic Connection In The Elkhorn River Basin, Zhaowei Wang

School of Natural Resources: Dissertations, Theses, and Student Research

In this study, the hydrologic relationship between the Elkhorn River and the surrounding aquifer at eight study sites were studied. The calculated hydraulic gradient showed that the adjacent aquifer recharges the Elkhorn River all year. Reversed gradient was only found at Atkinson site during pumping seasons from 2008 to 2010. Geoprobe log data and in-situ permeameter test data were combined to calculate the equivalent hydraulic conductivity (K) and unit-length streambed conductance (C) at eight sites, where the greatest values were found at Neligh and the lowest values found at Hadar. Accordingly, the result of cross correlation analysis on the lag …

The Impact Of Place Attachment On Land Succession Of Nebraska Agriculturists, Shari Kunert

School of Natural Resources: Dissertations, Theses, and Student Research

Many Nebraska agriculturists rely on small family farms for their livelihood. The farm is their source of income and may be an important inheritance for their family when they retire or die. Land succession planning is a process to allow landowners to pass farmland on to the next generation without incurring a potentially debilitating tax liability for the heirs. The purpose of this study is to determine the influence of place attachment on land succession planning of Nebraska agriculturists. This comparative research, mixed methods in nature, involves Nebraska agriculturists who have a land succession plan and Nebraska agriculturists who do …

Chlorophyll-Based Approach For Remote Estimation Of Crop Gross Primary Production: From In Situ Measurements To Satellite Imagery, Yi Peng

School of Natural Resources: Dissertations, Theses, and Student Research

The synoptic and accurate quantification of crop gross primary production (GPP) is essential for studying carbon budgets in croplands and monitoring crop status. The objective of this dissertation is to develop a quantitative technique to estimate crop GPP using remotely sensed data collected from close range to satellite altitudes. In this study, a model based on a recently developed paradigm, which relates crop GPP to a product of total crop chlorophyll content and incident radiation affecting vegetation photosynthesis, was justified for the remote estimation of GPP in crops. The model was tested with ground-observed incoming photosynthetically active radiation (PAR_{in …}

Near Infrared-Red Models For The Remote Estimation Of Chlorophyll-Α Concentration In Optically Complex Turbid Productive Waters: From In Situ Measurements To Aerial Imagery, Daniela Gurlin

School of Natural Resources: Dissertations, Theses, and Student Research

Today the water quality of many inland and coastal waters is compromised by cultural eutrophication in consequence of increased human agricultural and industrial activities and remote sensing is widely applied to monitor the trophic state of these waters. This study explores near infrared-red models for the remote estimation of chlorophyll-a concentration in turbid productive waters and compares several near infrared-red models developed within the last 35 years.

Three of these near infrared-red models were calibrated for a dataset with chlorophyll-a concentrations from 2.3 to 81.2 mg m^-3 and validated for independent and statistically significantly different datasets with …

An Evaluation Of Stocking And Habitat Influences On Channel Catfish In Lentic Ecosystems Of The Great Plains, Lindsey K. Chizinski

School of Natural Resources: Dissertations, Theses, and Student Research

Channel catfish Ictalurus punctatus is an important sport fish, particularly in the Great Plains. In Nebraska, a majority of anglers target channel catfish, and fishing activities are a vital part of the state’s economy. Lentic water bodies provide the primary fishing opportunity for catfish anglers in Nebraska. Despite the popularity and economic importance of channel catfish, little is known of its population dynamics or habitat requirements, and existing studies often profile river populations. Current standards for sampling channel catfish in lentic systems often yield inadequate catch to assess populations. The objective of this study was to utilize a recently developed …

Understanding Of The Hydrologic Connections Between Wide-Channel And Adjacent Aquifers Using Numerical And Field Techniques, Cheng Cheng

School of Natural Resources: Dissertations, Theses, and Student Research

Streambed sedimentary structure plays a vital role in controlling the interactions between surface water and groundwater. In the study, three rivers -the Big Blue River, the Little Blue River, and the lower reach of the Platte River in Nebraska were chosen to characterize the shallow streambed for the two types of rivers (braided and meandering rivers) and investigated the variations of the streambed electrical and hydraulic conductivities with depth. In-situ and laboratory permeameter tests were conducted to determine streambed hydraulic conductivity up to 20 m below the channel surface in the three rivers. Additionally, the electrical conductivity logs were obtained …

Predictors Of Insect Diversity And Abundance In A Fragmented Tallgrass Prairie Ecosystem, Kody M. Unstad

School of Natural Resources: Dissertations, Theses, and Student Research

Despite providing many services, the tallgrass prairie and its ecological community is one of the most endangered ecosystems in North America. Remaining habitat exists as remnants in a highly-fragmented landscape. To make informed conservation decisions we need to better understand the effects of this fragmentation. Using the ecologically important insect groups, ants and ground beetles, this study provides baseline data on the biological diversity of southeast Nebraska prairies and investigates what management, landscape, and habitat characteristics affect them. Pitfall trap sampling was conducted in 23 tallgrass remnants scattered throughout the Southeast Prairies Biologically Unique Landscape in 2010 and 2011. Multi-model …

Groundwater Pollution Risk Assessment Under Scenarios Of Climate And Land Use Change In The Northern Great Plains, Ruopu Li

School of Natural Resources: Dissertations, Theses, and Student Research

Modeling groundwater vulnerability to pollution is critical for implementing programs to protect groundwater quality. Traditionally, groundwater vulnerability was modeled based on current hydrogeology and land use conditions. However, groundwater vulnerability is strongly dependent on factors such as depth-to-water, recharge and land use conditions that may change in response to future changes in climate and/or socio-economic conditions. For example, global warming may lead to northward shifts in cropping patterns and changes in crop mixes (and use of farm chemicals). Meanwhile, growing demands for biofuels are resulting in expanding corn acreage, and may lead to pressures to remove land from the Conservation …