Effects of amendments and microtopography on created tidal freshwater wetland soil morphology and carbon.

Created wetlands used to mitigate impacts to natural wetlands often have lower organic matter, less microtopography, fewer hydric soil field indicators (HSFIs), and higher bulk density (BD) than natural wetlands. Organic matter amendments may improve soil properties soon after wetland construction, but long-term effects are seldom studied. This study investigated changes with time in soil properties of a sandy freshwater tidal created wetland in the Coastal Plain of Virginia. During construction in 2003/2004, five compost and topsoil treatments were applied, along with pit–mound microtopography. Soil descriptions were made in 2005, 2007, and 2015; samples were taken in 2006 and 2015. Four years after wetland construction, 69% of sandy plots met one or more HSFIs (S5, S6), and 62% of loamy plots met an HSFI (F3). Plots with loamy topsoil additions exhibited greater horizon and structure development, HSFI stability, greater soil mass C (0–30 cm), and higher soil C accumulation. Average soil C accumulation to 30 cm was 2.86 Mg ha−1 yr−1 in topsoil plots. With time, soils became darker (lower value, chroma) and higher in A horizon total C, and grayer (lower chroma) in C horizons, regardless of treatment. In 2015, microtopographic pits had lower color value (2.4), chroma (1.9), BD (0.87 g cm−3), and higher total C (2.39%) than mounds. We recommend adding pit and mound microtopography to created wetlands for increasing diversity of habitat. Further study is needed to see if topsoil and compost amendments improve long-term plant community development in sandy created wetlands and in other wetland types. [ABSTRACT FROM AUTHOR]