Paleoecosystematics of the Dismal Swamp, Virginia-North Carolina / by Brenda Joyce Smith.
| Author/creator | Smith, Brenda J., 1953- author. |
| Other author | Otte, Lee J., degree supervisor. |
| Other author | East Carolina University. Department of Biology. |
| Format | Theses and dissertations |
| Production | 1985. |
| Description | 85 leaves 27 unnumbered leaves of plates : illustrations, maps ; 28 cm |
| Supplemental Content | Access via ScholarShip |
| Subjects |
| Summary | Peat deposits of the Virginia portion of the Dismal Swamp were mapped and 13 cores were analyzed for plant macrofossils and sediments. Plant macrofossils from the peat deposit indicate a successional pattern of two extensive, stable wetland ecosystems separated by a relatively short transitional period. The earliest stages of wetland development in the Dismal Swamp occurred eight to ten thousand years before present. A relatively deep, ponded environment, probably created by a blocked drainage system, supported a highly productive marsh dominated by sedges (Cyperaceae) and deep-water aquatics. The presence of floating-leaved, submergent and emergent marsh vegetation suggests that a mosaic of deeper open water and shallower water environments was present. Following an initial deposition of fluvial clays, mineral sediment influx into the marsh decreased markedly as the vegetation became dense enough to trap incoming sediments and as the source area for sediments became inundated with peat. Dissolved nutrients present in runoff from surrounding uplands were the primary nutrient source for the marsh, since the vegetation root mat was quickly out of reach of the underlying mineral sediments in the permanently saturated peat-forming environment. This freshwater, highly productive marsh ecosystem remained stable, with an to 3,500 years before present. Once peat accumulation exceeded the upper water level of the blocked drainages, the marsh would have been an unsuitable environment for the accumulation of organic material. Decomposition of peats, now exposed above the water level, concentrated the more resistant organic sediments and released abundant humic compounds into the water. Under these conditions of a lower local water table and an exposed peat surface, the marsh would have provided an environment conducive to fire and to the establishment of acidophilous terrestrial vegetation. Chamaecyparis thyoides, which was present over the peaty sands and peats of adjacent interfluves, invaded the exposed marsh peat deposits. C. thyoides needs open areas , with high organic and water saturated soils, such as those of the marsh to become established and to thrive. The high lignin and cellulose content of C. thyoides leaf litter, in addition to the existing acidic edaphic conditions associated with decomposition of the surface peats, probably contributed to renewed organic accumulation. The enormous water-retaining capacity of this organic material would have contributed to the build up of peat beyond the upper levels of the blocked drainages and to its spread across the interfluves. As the C. thyoides forests matured to a closed canopy stage, ground cover probably became sparse, with little vegetation for trapping any influxing mineral material. A corresponding increase in terrigenous sediments is present in the upper horizons of forest peats. Allochthanous dissolved materials were probably the primary source of nutrients for the forest, as they were for the marsh. The acidic, brown water Chamaecyparis thyoides -dominated forest ecosystem was present from approximately 3,500 to 200 years before present. Extensive logging and drainage efforts began in the Dismal Swamp about 200 years ago. C. thyoides seedlings were unable to survive beneath the dense tangles of slash left at the timbering sites and, as a result, very little C. thyoides forest remains in the Dismal Swamp. With continued logging, and the addition of over 190 km of ditches, edaphic conditions in the swamp became more suitable for mesic species such as Acer rubrum and Liriodendron tulipifera. A. rubrum is now the most common canopy species in the Dismal Swamp. |
| General note | "Presented to the faculty of the Department of Biology ... in partial fulfillment of the requirements for the degree Master of Science in Biology." |
| General note | Advisor: Lee J. Otte |
| Dissertation note | M.S. East Carolina University 1985 |
| Bibliography note | Includes bibliographical references (leaves 82-85). |
| Genre/form | dissertations. |
| Genre/form | Academic theses. |
| Genre/form | Academic theses. |
| Genre/form | Thèses et écrits académiques. |
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