Degradation of wetlands on the Qinghai-Tibetan Plateau causing a loss in soil organic carbon in 1966–2016

Reveal the soil organic carbon (SOC) stock change in the Qinghai-Tibetan Plateau (QTP) alpine wetlands in the past fifty years. The Qinghai-Tibetan Plateau (QTP) has a large area of alpine marshland and wet meadows. Artificial drainage, overgrazing and climate change have caused severe degradation of the alpine wetlands. However, little is known about the effects of wetland degradation on SOC stock, and studies only focused on the Zoige marshland, the biggest marshland of China. Direct SOC observations from the extensively distributed wet meadows remain scarce. SOC in the soil surface layer (0–50 cm) were investigated at four wetland sites where degradation has continued for decades. One site is in marshland, and three are in wet meadows of the QTP. Using datasets from the literature and the field measurements of the present study, we estimated the loss of alpine wetland SOC. Initially, marshland degradation to wet meadows prompted the accumulation of SOC; however, grazing in wet meadows reduced SOC accumulation. Wetland degradation to dried meadows led to a much greater SOC loss than that in the initial degradation stage, and grazing exacerbated the loss of SOC. An exponential decay rate of SOC was found in the grazed dried meadows. The wetlands of the QTP, have lost 141 ± 25 Tg in 1966–2016, representing 15% of the SOC stock.