Landscape properties of pocosins and associated wetlands

Abstract

Most pocosins occur on broad, relatively flat interfluves or near estuaries where rising sea level affects their hydrology. Traditionally accepted ecological functions are low when compared on a unit area basis with other wetland types. An understanding of the interaction of pocosins with the atmosphere is fundamental to revealing mechanisms for their formation and their importance in landscape-level biogeochemical processes such as producing and consuming greenhouse gases and receiving and processing acid deposition. At least four interactions between pocosins and estuaries are important at landscape scales: (1) maintaining landscape elevation in the context of rising sea level, (2) representing a platform upon which landward migrating brackish marshes can develop, (3) exporting high concentrations of organic carbon, and (4) influencing the quality of habitat in primary nursery areas for fish and shellfish. Since pocosins have lower rates of cycling for most elements, greater surface area of pocosin is required to provide the same function and life support as floodplain wetlands. Major habitat attributes are (1) the large contiguous blocks of land that they occupy in contrast to the narrow, linear configurations of riverine forests and (2) their location at the uppermost reaches of wetland continua. Because of these attributes, individual impacts to small areas are relatively inconsequential until their cumulative effects begin to encroach upon the landscape-level processes and functions that they display. Fragmentation by drainage ditches and roads and interspersion of agriculture and silviculture expose the organic soils to peat fires and biological oxidation. The historically slow rate of organic matter accretion is reversed to a more rapid process of degradation. Accelerated oxidation and subsidence create a net efflux of carbon to the atmosphere in contrast to the net influx that has been occurring for millennia.