Physical Sciences and Mathematics Commons^™

Ecological Impacts Of Stream Bank Stabilization In A Great Plains River, Christopher M. Pracheil

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

Reduced ecological complexity, decreased water quality, and accelerated stream bank erosion are common disturbances in rivers with agriculturally dominated watersheds. Massive bank failures, increased sediment loads, and decreased riverine habitat are current problems in the agriculturally dominated Cedar River of central Nebraska. In an effort to slow erosion and prevent further ecological degradation, 20 reach scale stream bank stabilization projects were installed on the Cedar River from 2001 to 2004. The objective of this study was to determine the impact of the Cedar River stream bank stabilization projects on the ecological conditions within the Cedar River. Stream bank erosion, suspended …

Shovelnose Sturgeon Age And Growth Characteristics And Fish Community Characteristics Of The Lower Platte River And Missouri River Near Nebraska, Tara L. Anderson

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

There have been documented widespread losses of freshwater biodiversity over the past several decades. Many of these losses may be due to anthropogenic causes such as habitat alterations, pollution, and overharvest. Shovelnose sturgeon may also be influenced by anthropogenic causes and have experienced declines in population abundance near Nebraska. My objectives were to first to describe the age, growth and mortality of shovelnose sturgeon found in the lower Platte River (LPR). Second, I quantitatively evaluated similarities and differences between the Missouri River (MR) and the LPR fish community composition (presence-absence of species) and structure (abundance of species). We used trammel …

Propagating And Non-Propagating Intraseasonal Oscillations In The Tropical Atmosphere: Their Vertical And Horizontal Structures And Developing Mechanisms, Zhaoning Liang

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

A fixed beamformer is proposed and designed to identify source regions of Intra-Seasonal Oscillations (ISO) in the tropical atmosphere. After tested by simulations of single and complex sources of waves, the fixed beamformer is applied to the ECMWF interpolated data grids to detect and identify source regions of the ISO in the tropical Indian and Pacific Ocean region. Results show that the fixed beamforming technique can uniquely identify the source region of the ISO, the source regions of all major ISO in the tropical Indian and western equatorial Pacific region from 1974 to 2002 have been identified.

Examinations of ISO …

Multi-Scale Perspectives On Paddlefish Populations: Implications For Species Conservation And Management, Brenda M. Pracheil

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

The Order of fishes containing paddlefish and sturgeon has been named the most endangered group of organisms on the planet by the International Union of Conservation of Nature (IUCN). Population trajectories of paddlefish, whose native range is entirely encompassed within the United States of America, are currently unknown, although the IUCN has considered them to have a high extinction risk in the wild. The declaration of the vulnerability of paddlefish to extinction, coupled with the global plight of other sturgeon species create urgency to establish population and species-level population trajectories. Moreover, this declaration creates a great need for swift management …

Scraping Behavior In Male White-Tailed Deer As A Potential Means Of Transmitting Chronic Wasting Disease, Travis C. Kinsell

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

Chronic wasting disease (CWD) has become a concern for wildlife managers and hunters across the United States. High prevalence of chronic wasting disease (CWD) in older male white-tailed deer (Odocoileus virginianus) suggests that sex-specific social behavior may contribute to the spread of the disease among males. Scraping is a marking behavior performed by male white-tailed deer during the rut in which a pawed depression and associated over-hanging branch are marked with saliva, glandular secretions, urine, and feces. We placed 71 and 35 motion-activated cameras on scrapes in DeSoto National Wildlife Refuge in western Nebraska and eastern Iowa from …

Evaluating Hydroperiod Response In The Rainwater Basin Wetlands Of South-Central Nebraska, Richard D. Wilson

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

A collection of wetlands in south-central Nebraska make up a region called the Rainwater Basin. This basin contains closed-basin wetlands formed in loess. The wetlands receive water from precipitation and irrigation runoff. Since the early 1900s, wetland area in the basin has decreased dramatically due to intensive agriculture which either altered or removed the wetlands. The Rainwater Basin wetlands provide many ecological services and thus, should be preserved, but are most noted for the resting, breeding, and feeding habitat they provide for millions of migratory birds that is not provided elsewhere in this region along the continental flyway.

Given the …

Seasonal Energy And Water Balance Of A Phragmites Australis-Dominated Wetland In The Republican River Basin (Southwestern Nebraska, Usa), Gregory J. Cutrell

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

Climate and vegetation can dramatically alter the water cycle on local to regional scales. A change in the surface energy and water balance, especially in arid regions, can have significant impacts on local water availability and, therefore, water resource management. The purpose of this study is to understand the role of climate and vegetation in the energy and water balance of a riparian wetland in the central Great Plains. The site is located near the Republican River in southwestern Nebraska, where decreases in streamflow have been observed in recent decades. In an effort to reduce consumptive use from evapotranspiration (ET), …

Chloroacetamid Spray Drift And Leaf Tatters In Hackberry, Ariana P. Miller

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

During the last decade, leaf tatters has been reported in white oak and hackberry across several Midwestern states. Herbicide spray drift studies have shown that chloroacetamides can induce leaf tatters. The objectives of this research were to: 1) identify vulnerable bud developmental stages in hackberry and 2) determine if different commercial chloroacetamides affect severity of leaf tatters. In 2008, a preliminary spray drift experiment was conducted on mature trees from a former hackberry provenance test stand. Acetochlor (Harness), S-metolachlor (Dual II Magnum), and dimethenamid (Outlook) were applied at concentrations approximating 27%, 54%, 81%, or 108% of the recommended field rate. …

Ecology, Stable Isotopes, And Management Of Grassland Songbirds At National Park Service Properties On The Great Plains, Sarah E. Rehme

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

Grassland ecosystems have been severely reduced and grassland bird populations have experienced consistent declines. National Park Service (NPS) properties on the Great Plains provide breeding habitat for grassland songbirds, though little is known about the quality of this habitat. A short-term study on songbirds at three NPS properties complemented current monitoring, providing an among park comparison addressing grassland bird productivity and fidelity relative to NPS property size. During 2008-2009, I assessed avian species richness, and estimated bird density and grassland songbird nest success. Bird species richness was greatest at small and medium sites, while number of nesting obligate species was …

The Textural Discontinuity Hypothesis And Its Relation To Nomadism, Migration, Decline, And Competition, Aaron L. Alai

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

The causes of nomadism, migration, and decline in vertebrates are debated issues in the ecological sciences. Literature suggests nomadism may arise in species that specialize in granivory, nectivory, or the utilization of rodent outbreaks. Migration is thought to arise as a result of the exploitation of certain scarce or variable food resources. Species decline is hypothesized to be the result of many different factors as well; large species, island species and specialists may be more prone to decline.

A fresh perspective regarding the causes for species nomadism, migration, and decline is being investigated utilizing the ideas within the Textural Discontinuity …

Seasonal Variation In Terrestrial Insect Subsidies To Tropical Streams And Implications For The Diet Of Rivulus Hartii, David C. Owens

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

Terrestrial invertebrates subsidize fish diets in lotic ecosystems. Seasonality strongly influences terrestrial invertebrate abundance in temperate regions and alters their delivery to streams. Seasonal changes in the tropics are characterized by distinct wet and dry periods, with marked variation in invertebrate abundance. However, little is known about how these seasonal changes affect invertebrate subsidies and their ecological consequences for tropical streams. We measured the effect of rainfall and canopy density on terrestrial invertebrate falling input, as well as seasonal variation in falling input, benthic and drifting invertebrate, and Rivulus hartii (Hart’s Rivulus) diet composition during both the wet and dry …

Influence Of Canopy Cover, Nutrients, And Season On Stoichiometric Variation Of Epilithon In Neotropical Streams., Tyler J. Kohler

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

Light and nutrient availability are strong factors determining the nutrient composition of epilithon in temperate stream ecosystems. However, little work has been performed regarding this association in tropical streams. In our study, we investigated 1) how gradients of canopy cover and nutrients and 2) wet/dry seasonality influence epilithon standing stocks and nutrient quality. We surveyed 18 stream locations within six watersheds that varied in nutrient and light conditions during both the wet and dry seasons on the island of Trinidad to test these questions. Additionally, we sampled four stream reaches bimonthly for three years, thinning the canopy of two of …

Carbon Dynamics In A Phragmites Australis Invaded Riparian Wetland, Steven Walters

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

Invasive plant species are widely recognized as a major threat to biodiversity and ecosystem stability. Wetland ecosystems tend to be much more susceptible to invasions because of their location on the landscape where water, nutrients, and the impacts of disturbances accumulate. Invasive plants have the ability to alter ecosystem processes and community/population dynamics. The ability of invasive plants to alter these processes can have profound economic consequences. In the United States, control of invasive wetland species alone costs approximately 155 million dollars annually. The state of Nebraska spends 2 million dollars annually controlling invasive plant species in the Platte River …

Connection To Nature In Park Visitors: A Look At Structured And Unstructured Recreational Activities, Chelsea D. West

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

There is evidence that park visitation is on the decline (Pergams & Zaradic, 2008) and if this is the case, and budgets decrease proportionately, there is a chance park land will be lost. Definitive explanations of the decline in park visits and time spent in nature are not available. In addition, there has been some discussion and research pertaining to the possible effects on people of not going into the natural environment and experiencing a connection with nature.

This study represents the first research known to focus on connectedness to nature and its relationship to structured and unstructured recreational activities. …

Retention, Movement, And The Biotic Response To Large Woody Debris In The Channelized Missouri River, Michael W. Archer

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

Large woody debris (LWD) is an important component of a healthy aquatic ecosystem. However, little is known about the dynamics of LWD in a large, channelized river such as the Missouri River. My objectives were to first, assess the abundance of LWD found along the channelized portion of the Missouri River. Second, I documented movement of LWD that entered the river. Lastly, using PRIMER software I analyzed what effect, if any, river segments, bend types, and LWD had on the community composition of the macroinvertebrate and fish that inhabit the river. Abundance of LWD was greater along bends that have …