Holocene environmental history of panthertown valley in the blue ridge mountains of North Carolina.

摘要

Panthertown is a high-elevation valley in the Nantahala National Forest, and is one of few sites in western North Carolina with natural wetlands. Radiocarbon dating of multiple cores at a Panthertown valley wetland shows continuous deposition through the Holocene. This is one of the oldest continuous records in the Southern Appalachians; as such, this wetland is uniquely suited to provide information on vegetation dynamics and climatic regimes of the Holocene in the region. Using standard palynological techniques, pollen was extracted from sediment core samples and identified to genus or family at 400x; the resulting pollen percentages were used to describe the environmental history of Panthertown valley. Presence of Alnus, Salix, Asteraceae, and ferns throughout indicate a consistent open, moist wetland site. The early to mid-Holocene (~8,700-7,000 yr BP) forest appears to have been dominated by Castanea and Quercus, with minor contributions by Betula, Carya, Acer, and Pinus. The mid-Holocene (~7,000-3,500 yr BP) is characterized by decreases in Castanea and Pinus, with increases in Quercus and Poaceae, and, to a lesser extent, ferns, Asteraceae, and Betula; these increases coincide with increases in a13C and organic C/N at the site. Increased a13C values are likely the result of contribution of organic matter derived from C4 plants to the sediment pool. Greater variability in C/N values during that period indicate increased fluctuations in deposition of terrestrial organic matter. The late Holocene (~3,500 yr BP -present) assemblage shows a more diverse forest, with significant contributions from Castanea, Quercus, Betula, Pinus, and Tsuga. Taken together, these data support the idea of a warm, possibly dry, mid-Holocene "Hypsithermal" (~6,500-3,500 yr BP), and indicate the presence of temperate deciduous forests dominated by oak in the Blue Ridge Mountains from the early Holocene to the present.