Methane emissions from wetlands on the Qinghai-Tibet Plateau

The areal extent of cold freshwater wetlands on the Qinghai-Tibet Plateau (QTP) is estimated at 0.133 x 10(6) km(2), suggesting a significant methane potential. Methane fluxes from wet alpine meadows, peatlands, Hippuris vulgaris mires and secondary marshes were 43.18, 12.96, -0.28 and 45.90 mg.m(-2).d(-1), respectively based on the transect flux studies at the Huashixia Permafrost Station (HPS) from July to August 1996. Average CH4 fluxes in the thaw season were extrapolated at 5.68 g.m(-2) according to the areal percentage of wetland areas in the Huashixia region. The CH4 fluxes at four fixed sites, representative of similar ecosystems, ranged from - 19.384-347.15 mg.m(-2). d(-1), and the average CH4 fluxes varied from 6.54 to 71.97 mg.m(-2).d(-1) at each site during the observation period from April to September 1997. The CH4 emissions at each site during the entire thaw season was estimated from 1.21 to 10.65 g.m(-2), displaying strong spatial variations. Seasonal variations of CH4 fluxes also were observed at four sites: CH4 outbursts occurred upon the spring thaw in May and June, CH4 fluxes increased afterwards with rising soil temperatures. Episodic fluxes were observed in summer, which influenced the average CH4 fluxes considerably. Annual CH4 emissions from cold wetlands on the QTP were estimated at about 0.7-0.9 Tg based on the distribution of wetlands, representative CH4 fluxes, and number of thaw days. The centers of CH4 releasing were located in the sources of the Yangtze and Yellow rivers, and Zoige Peatlands.