Primary Productivity in 20-year Old Created Wetlands in Southwestern Virginia

Thousands of depressional wetlands accidentally formed as a result of pre-1977 contour coal mining in the Appalachian Mountains. Eleven 20-yr old sites were found in a watershed that did not receive acid mine drainage. The purpose of this study was to quantify and model above- and below-ground plant biomass in these created wetlands and to evaluate functional development. Sampling was stratified by weighted average of two plant communities, which corresponded to shallower and deeper water levels, facultative wetland and obligate wetland communities, respectively. In 1994, peak above- ground biomass averaged 473.7 g m(-2) in the facultative wetland community and 409.5 g m(-2) in the obligate wetland community. Scirpus cyperinus exhibited the highest peak above- ground biomass (51.8% of total biomass) and Typha latifolia ranked second. Canonical correspondence analysis detected positive effects of longer soil exposure to the atmosphere and greater sediment depth on above- ground biomass at the site (wetland ecosystem) level. Within communities, forward stepwise regression identified positive association of above-ground biomass with water soluble reactive P, water soluble NH3, decomposition rate over 507 d, live S. cyperinus tissue P content, and sediment depth. When these results are combined with prior studies conducted at the same 20-yr old sites, it appears that both structural and functional development has been arrested at a somewhat immature state resulting primarily from soil and hydrologic factors.