Rapid Genesis of Redoximorphic Features, Soil Structure, and Carbon-Rich Horizons.

Constructed wetlands are often characterized with lower organic carbon, higher density, compacted structure, and fewer active redoximorphic features than nearby wetlands.  The length of time required to alter post-construction wetland soil properties is understudied. Therefore, a set of constructed wetlands in Eastern Virginia were described and properties measured post-construction, three years later, and 11 years later to determine the minimum time needed for property alteration. The wetlands ranged from sandy dredged material to loamy topsoil to clayey subsoil left exposed at an excavated site. Organic matter or was applied at different rates and tree seedlings planted. Preliminary data show that both the matrix color became more gray and redoximorphic features developed near the surface of the sandy wetland, and organic matter was completely decomposed. In the loamy wetland, redoximorphic concentrations and a depleted matrix have developed near the surface. In the clayey wetland, a surface horizon has developed. Relict redox concentrations have decreased. Added organic matter decomposed and enriched the surface horizons, accelerated the formation of improved soil structure in the upper subsoil of the loamy and clayey wetland soils, and increased the reduction of Iron. Organic carbon capture may be detectible after 11 years due to vegetation inputs and decreased decomposition. The changes in soil properties and vegetation after 11 years are evident and indicate increased wetland functionality.