Factors influencing CO2 and CH4 fluxes in Tomago wetland

The Tomago wetland, Newcastle, is undergoing wetland rehabilitation by restoring tidal inundation to a previously leveed floodplain. It was hypothesised that the restoration of tidal inundation would convert a methane source into a sink as a consequence of soil salinization. A one year experimental design study was instituted to measure the impact of tidal reinstatement on CO2 and CH4 fluxes. Prior to tidal reinstatement, eddy covariance towers were installed to measure CO2 and CH4 fluxes. Micrometeorological energy balance and environmental variables such as soil water salinity and inundation regime, were undertaken. The highest average diurnal emissions were 2.54 µg m-2 s-1 CH4 during the day and 0.45 mg m-2 s-1 CO2 at night. Monthly average fluxes peaked in February (0.365 µg m-2 s-1 CH4 and 0.137 mg m-2 s-1 CO2).There was a significant negative relationship between CO2 flux and water level (p < 0.001), tidal height (p = 0.02) and positive relationship with water temperature (p = 0.002). CH4 flux showed positive correlation with water level and negative correlation with EC although not statistically significant. Although tidal flooding did not demonstrate clearly carbon sequestration before and after tidal reinstatement, freshwater events (rainfall) were seen to influence the wetland carbon balance.