Comparison of soil and other environmental conditions in constructed and adjacent palustrine reference wetlands

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Wetlands are created to compensate for the loss of natural wetlands as a result of human landuse activities. How well these constructed wetlands mimic natural wetlands is in debate. The goal of this study was to compare soil and other environmental conditions within constructed and adjacent reference wetlands to assess the progress of the constructed wetlands towards a functional wetland. Three constructed wetlands in Virginia, USA, 4 to 7 years old, were paired with adjacent palustrine forested and scrub-shrub reference wetlands to examine differences in topography, hydrology, soil properties, and other environment conditions such as soil temperature and redox potential. Degree of microrelief was greater in reference wetlands than in the associated constructed wetlands. Seasonal fluctuations in water-table levels were similar in both wetland types. Two of the paired wetlands showed considerable differences (15 to 20 cm) in the depth to the water table. Redox potentials were similar in reference and constructed wetlands. Paired wetlands with water-table levels at or near the soil surface throughout the year showed similar soil temperatures. At the site where the summer water levels were 80 to 100 cm below the soil surface, summer temperatures were substantially higher in the poorly shaded, constructed wetland. At the two sites with high water-table levels throughout the year, percent clay and silt, levels of organic C and N, and cation exchange capacity were significantly greater (p <0.05) in the reference wetlands. At the drier site, only 3 of the 16 soil parameters compared were significantly different. In this limited study, observed differences in soil and other environmental conditions between paired wetlands suggest that constructed wetlands may not function in the same capacity as adjacent reference wetlands.