2.1. Study area
The study site was located in the Luanhaizi wetland (37°35′N, 101°20′E, 3250m a.s.l.), which was adjacent to the Haibei Research Station, Chinese Academy of Sciences, in Qinghai Province, China. The region was controlled by the continental monsoon climate of the plateau, with cool summers and cold winters. Based on past monitoring data, the annual average temperature was -1.1℃ and the average minimum (-18.3℃) and maximum (12.6℃) temperature occurred in January and July, respectively. The mean annual precipitation is about 490mm, and precipitation in the growing period accounts for more than 80% of the annual total precipitation. The grass began to photosynthesize and sequester carbon at the end of April. The soil in this study site is a silty clay loam of Mat-Cryic Cambisols, which was rich in organic matter content. The study site has many scattered mounds due to the seasonal freeze-thaw process. The constructive species of the alpine wetland was Carex pamirensis , and the other common species including Carex alrofusca , Hippuris vulgaris , Triglochin palustre , andHeleocharis spp (Song et al., 2015; Wang et al., 2016; Zhao et al., 2010; Zhang et al., 2008).