Browsing by Author "James Gregory, Committee Chair"

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    Epilithic diatom assemblages in headwaters streams of North Carolina and Virginia
    (2003-07-01) Karoly, Cynthia Bell; James Gregory, Committee Chair; JoAnn Burkholder, Committee Member; James Gilliam, Committee Member
    Using data collected by the Environmental Protection Agency during synoptic sampling for the Environmental Monitoring and Assessment Program, I studied the quantitative composition of diatom communities in 112 samples distributed in first through third-order streams within the Blue Ridge, Southeastern Plain, Coastal Plain and Piedmont ecoregions of the eastern U.S. The sampling sites studied were located predominantly in North Carolina and Virginia. The main objective was to identify dominant diatom species using both species density values and importance values incorporating estimated biovolumes. A secondary goal was to determine whether distinct diatom assemblages could be defined within the set of streams studied. Six diatom assemblages were defined based upon increasing diversity, richness and evenness of species within the groups. No trends could be detected in the cluster separation associated with ecoregions, sample years, and instream habitats, and paired riffle/pool samples. Diatoms were observed in all 112 samples, and 390 diatom species were identified. Achnanthes biasolettiana was the dominant species, comprising 54% of the relative density of the total dataset and observed in 89% of all samples. Only twelve additional species equaled or exceeded 1% of the total sample relative density or importance value. Use of estimated biovolume size classes for entire diatom genera did not alter the determination of dominant species. The same species were considered dominant using either measure of dominance. Within samples, the ten most dominant species consistently contributed > 50-75% of the total relative density of the sample.
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    Surface and Substance Hydrology of a Drained Carolina Bay Prior to Restoration
    (2004-05-21) Luginbuhl, Sarah C; James Gregory, Committee Chair; Rodney Huffman, Committee Member; Michael Vepraskas, Committee Member; David Genereux, Committee Member
    Juniper Bay is a 330 ha Carolina Bay located 13 km southeast of Lumberton in Robeson County, North Carolina. Carolina Bays are elliptical depressions in the landscape primarily located in the Coastal Plain region of North and South Carolina and Georgia. They are oriented with major axes northwest to southeast and their origin is unknown. Juniper Bay was drained beginning in the 1970's for agriculture. In the year 2000 the North Carolina Department of Transportation bought the bay to restore to a wetland. North Carolina State University wrote a proposal to do research at Juniper Bay and the overall goal is to evaluate the strategy and performance of the restoration of wetland functions in Juniper Bay and to test alternative restoration methods. This research focuses on the hydrology of the bay prior to restoration. The objectives are the determination of the current ground water flow paths and the water table regime both inside and outside the bay, the identification of a strategy for hydrologic restoration, the documentation of the variability in the properties of the water table regime across Juniper Bay and the reference bays that will affect the success of the restoration, and the assessment of the usefulness of reference ecosystems for defining required hydrologic factors necessary for long-term restoration success. There are three reference Carolina Bays, located in neighboring Bladen County, North Carolina. The hydrologic properties of these bays is the hydrologic goal of Juniper Bay once restoration is complete. Twenty-nine water table monitoring wells were installed to a depth of 2.44 meters in and around Juniper Bay in early 2001, and four water table monitoring wells were installed in each of the reference bays. Seventeen piezometers equipped with pressure transducers were installed in and around Juniper Bay along two main transects, with depths ranging from 2.44 to 10.36 meters. The results from the water table wells show that 4% of Juniper Bay in 2001 and 22% in 2002 met wetland hydrology requirements, which are that the water table is within 30 cm of the soil surface continuously for 12.5% of the growing season in most years. The percentages of the reference bays that meet the wetland hydrology requirements range from 20% to 100%. Results show that ground water may be entering Juniper Bay from the northwest and southeast boundaries of the bay, which are higher in elevation, and exiting the bay through the northeast and southwest boundaries of the bay, which are lower in elevation. The ditches likely have a significant influence on the water table and the ground water, and the hydrology of the bay will likely be altered once they are plugged. The reference bays provide useful information in the determination of what conditions were probably like prior to disturbance and what the restoration effort in Juniper Bay should try to accomplish.