Soil Carbon Storage in Barrier Island Landscapes As a Function of Topography and Landform.

Barrier islands of the Mid-Atlantic coast are estimated to be between 5000 and 7000 years in age, but many of the surfaces and landforms on the islands are far younger, on the order of tens to hundreds of years.  Initial soil development in these weathering resistant parent materials is often limited to the formation of O and A horizons as organic matter accumulates.  Barrier island landscapes provide a unique opportunity to study these early soil formation processes.  Depth to water table and duration of saturation controls plant growth, development of anaerobic or reducing conditions in the soil, and decomposition and accumulation of organic matter.  High infiltration rates, high hydraulic conductivities, and low water holding capacities result in water tables that are fairly level despite greater variation in topography.  Topographic position becomes an analog to the depth of the water table and drainage.  The objective of this study is to assess the magnitude of soil organic carbon stocks in barrier island landscapes as a function of topography and landform.  Ten topographic transects were identified in a range of landforms at Assateague Island National Seashore, located along the Mid-Atlantic coast of Maryland.  Soil carbon stocks were assessed to a depth of 1 m at three positions (ranging from poorly or very poorly drained to excessively or well drained).  Water table levels and reducing conditions were monitored along transects to determine the role of saturation and reduction in the accumulation of soil organic carbon.  Organic carbon stocks and the formation of O and A horizons were compared across topographic positions (drainage classes) and landforms.  The magnitude of organic carbon stocks and the potential for carbon sequestration in barrier island soils will be assessed relative to other soils and wetland environments.