The Surface-to-Atmosphere GHG Fluxes in Rewetted and Permanently Flooded Former Peat Extraction Areas Compared to Pristine Peatland in Hemiboreal Latvia

When it comes to greenhouse gas (GHG) reduction, the role of water tables in former peat extraction areas has received considerable interest in recent decades. This study analysed the carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) surface-to-atmosphere fluxes from a rewetted and permanently flooded former peat extraction areas in comparison to pristine peatland in hemiboreal Latvia. Measurements of GHG fluxes combined gas sampling using a closed-chamber (opaque) method with the gas chromatography detection method. Among the studied land-use types, the highest annualised CO2 fluxes (soil heterotrophic and autotrophic respiration) were recorded in rewetted former peat extraction areas with restored vegetation and in undisturbed peatland (4.10 +/- 0.21 and 3.45 +/- 0.21 t CO2-C ha(-1) yr(-1), respectively), with the lowest in flooded former peat extraction areas (0.55 +/- 0.05 t CO2-C ha(-1) yr(-1)); temperature and groundwater level were found to be significant influencing factors. The highest annualised CH4 fluxes were recorded in undisturbed peatland (562.4 +/- 155.8 kg CH4-C ha(-1) yr(-1)), followed by about two-fold and similar to 20-fold smaller CH4 fluxes in flooded and rewetted areas, respectively. N2O fluxes were negligible in all the studied landuse types, with the highest N2O fluxes in undisturbed peatland (0.66 +/- 0.41 kg N2O-N ha(-1) yr(-)1).