Changes in soil organic carbon stocks of wetlands on China's Zoige plateau from 1980 to 2010

Abstract China's Zoige Plateau, located in the northeastern part of the Qinghai-Tibet plateau, has the largest alpine peat wetland in the world. However, little is known about how the soil organic carbon (SOC) stock of these wetlands has been influenced by human activities. In this study, we quantified the changes in the SOC stock in two counties (i.e., Hongyuan and Ruoergai) in the Zoige Plateau wetlands between 1980 and 2010 in response to progressive drainage of the wetlands and increased grazing intensity using the Environmental Policy Integrated Climate (EPIC) model. The results indicate that wetlands accumulate large amounts of SOC (>300 t C ha −1 ) in the upper 1 m of the soil in the study area. Wetland soils sequestered ∼0.25 t C ha −1  yr −1 despite the degradation that has occurred due to drainage and grazing. Drainage was one of the main driving factors for SOC loss in the wetlands. Conversion of wetlands to grassland via drainage since 1980 led to a loss of approximately 4 t C ha −1 from the SOC stock. On the other hand, grazing might have positive impact on root biomass accumulation, thus enhancing the SOC stock. As estimated by EPIC, more intensive grazing slightly increased the SOC stock. However, grazing is also a reason why wetlands were drained with all the negative effects on the SOC pool. The potential SOC sequestration of intensive grazing was offseted by the negative effect of drainage. The outcomes suggest not only to limit drainage and restore wetland, but also to control grazing which will in turn decrease drainages to sustain the ecosystem service of carbon sequestration provided by the Zoige wetlands.