Ecological problems of the southeastern United States coastal plain

Abstract

Geographically the southeastern United States coastal plain may arbitrarily be delimited by southern Virginia and the Mississippi River. In width it varies from 115 miles on the Virginia-North Carolina line to nearly 600 miles in the Mississippi basin. It involves the southern part of the geographers' (17a) Embayed Section of the plain, extending to Cape Lookout; the Sea Island Section, extending to the Florida (peninsula) Section; and the East Gulf Section extending to the bottom land of the Mississippi, which is separated into an Alluvial Plain Section. Physiographically it may be divided into sea terraces of which the following six are commonly recognized, beginning at the piedmont border: the LaFayette, Coharie, Sunderland, Wicomico, Chowan (Talbot) and Pamlico. These terraces record the Pleistocene changes of sea level believed to have been due to volume changes in polar ice masses associated with glacial and interglacial periods. The upper coastal plain may, however, be largely fluvial in origin rather than marine (18). The older or upper three terraces have been eroded into an uneven topography with enough relief to drain the uplands, while the lower three are largely in a flat condition of low relief with emphasis on lack of drainage. Variation in rate of water movement of the earlier ocean and sounds has resulted in local variation in sand textures, a basic factor of the utmost importance in later determination of upland vegetation. Climatically the area is characterized by a uniformity unusual for a region extending nearly 900 miles in a north and south direction. Most of the coastal plain has mean annual temperatures between 60? and 70? F. Only the lower half of Florida goes above this. Other significant temperature data (37a) follow: The average normal daily temperatures for the coldest 14 days of the year range from 400 southward to 60?. The absolute minimal temperatures range from slightly below 0? F. southward to 14? F. in middle Florida. The number of days of the average frostless season ranges from 220 southward to 320 in middle Florida. The