Emission of greenhouse gases and soil carbon sequestration in a riparian marsh wetland in central Ohio

Wetlands are a C sink, but they also account for a large natural source of greenhouse gases (GHG), particularly methane (CH4). Soils of wetlands play an important role in alleviating the global climate change regardless of the emission of CH4. However, there are uncertainties about the amount of C stored and emitted from wetlands because of the site specific factors. Therefore, the present study was conducted in a temperate riverine flow-through wetland, part of which was covered with emerging macrophyte Typhus latifolia in central Ohio, USA, with the objective to assess emissions of GHGs (CH4, CO2, N2O) and measure C and nitrogen (N) stocks in wetland soil in comparison to a reference upland site. The data revealed that CH4 emission from the open and vegetated wetland ranged from 1.03–0.51 Mg C/ha/y and that of CO2 varied from 1.26–1.51 Mg C/ha/y. In comparison, CH4 emission from reference upland site was negligible (0.01 Mg C/ha/y), but CO2 emission was much higher (3.24 Mg C/ha/y). The stock of C in wetland soil was 85 to 125 Mg C/ha up to 0.3 m depth. The average rate of emission was 2.15 Mg C/ha/y, but the rate of sequestration was calculated as 5.55 Mg C/ha/y. Thus, the wetland was actually a C sink. Emission of N2O was slightly higher in vegetated wetland (0.153 mg N2O-N/m2/h) than the open wetland and the reference site (0.129 mg N2O-N/m2/h). Effect of temperature on emission of GHGs from the systems was also studied.