Changes and Vertical Distribution Characteristics of Soil Organic Carbon in Different Land Cover Types in Honghe Wetland of Sanjiang Plain, China

Soil organic carbon (SOC) responds rapidly to changes in land cover types, and changes in SOC provide essential guidance for sustainable utilization of land resources and protection of wetlands. The vertical distribution of SOC under different land cover types in Honghe wetland was analysed through soil samples and remote sensing interpretation. Changes in SOC under different land cover types were assessed in 2002 and 2014. The results showed that wetland and meadow were the primary land cover types in Honghe wetland. The reduction in normalized difference vegetation index from 2002 to 2014 was mainly due to wetland and meadow area changes. The SOC contents under different land cover types followed the order: wetland > meadow > forest land > dry field > paddy field in the 0–15 cm soil layer. With increase in soil depth from 0 to 60 cm, SOC contents tended to decrease. According to preliminary estimations, the SOC stocks of wetland, meadow, forest land, paddy field and dry field in the soil profile from 0 to 60 cm were 4.39 x 10⁴, 2.62 x 10⁴, 2.66 x 10⁴, 2.11 x 10⁴ and 1.98 x 10⁴ t/sq. km respectively. The total amount of SOC declined by about 364.8 Gg C in the 0–30 cm soil layer from 2002 to 2014, which resulted in the emission of 1338.82 Gg CO₂ to the atmosphere.