Soil Organic Carbon Stocks across Hydrologic Schemes in Freshwater Wetlands of the Chi River Basin, Northeast Thailand

The role of freshwater wetlands as soil organic carbon (SOC) stocks has been well documented for temperate regions but less is well known in tropical regions. In this study, SOC stocks were compared within three different hydrologic schemes in six freshwater wetlands of the Chi River Basin in tropical Northeast Thailand. The SOC concentration exhibited a decrease with increased depth and significantly differed among the hydrologic schemes (9.15 +/- 0.84, 8.66 +/- 0.67, and 5.53 +/- 0.49 g C kg(-1) for the intermittently flooded zone, saturated zone, and permanently flooded zone, respectively). The SOC stocks at 50 cm depth were significantly highest in the intermittently flooded zone (69.05 +/- 10.86 Mg C ha(-1)), followed by the saturated zone and the permanently flooded zone (66.06 +/- 7.75 and 43.39 +/- 5.83 Mg C ha(-1), respectively). Total SOC stocks among wetlands ranged from 123.30 to 291.29 Mg C ha(-1). These differences indicate the spatial variability of SOC within wetland locations and among wetlands. The study demonstrates an important ecosystem service of these wetlands as carbon stocks, and it will be useful for management and policy planning of the wetlands in the Chi River Basin.