Denitrification potentials in restored and natural bottomland hardwood wetlands

Wetland restoration projects are frequently evaluated by their hydrologic roles and vegetation characteristics, but their success in restoring biogeochemical processes, such as denitrification, is less well known. To determine how restoration of structure affects specific ecosystem processes, denitrification potential, soluble organic C (SOC) concentrations, and soil moisture were measured seasonally over a 1-yr period in replicated natural bottomland hardwood (BLH) wetlands (NAT), restored BLH wetlands with hydrology reestablished (RWH), and restored BLH wetlands without hydrology reestablished (RWOH). Denitrification potential was significantly higher in NAT wetlands (657 ng N2O-N g(-1) soil h(-1)) than in RWOH (167 ng N2O-N g(-1) soil h(-1)) (P = 0.07). Soil moisture was highest in NAT wetlands and lowest in RWOH (P = 0.01), but no differences were measured in SOC concentrations in three out of the four seasons sampled. Because RWOH wetlands exhibited denitrification potentials which were significantly lower than NAT wetland sites, these results demonstrate that a BLH wetland restored without the natural hydrologic regime reestablished will not be a replacement for a natural BLH wetland in terms of biogeochemical processes such as denitrification.