Revisiting the role of CH 4 emissions from alpine wetlands on the Tibetan Plateau: Evidence from two in situ measurements at 4758 and 4320 m above sea level

The alpine wetlands on the Tibetan Plateau (TP) constitute 30% of China's wetlands, and previous studies have considered these wetlands to be important sources of CH 4 , based on several swamp measurements from the eastern edges of the plateau. However, the alpine wetlands consist of both swamps (9.5%) and swamp meadows (79.8%). In this study, the CH 4 fluxes of a swamp meadow and a swamp were determined. The results showed that the swamp meadow emitted much less CH 4 (130.8 ± 123.9 µg m −2  h −1 ) than the swamp (2795.2 ± 796.4 µg m −2  h −1 ). The CH 4 fluxes within the swamp meadow showed distinct microscale spatial heterogeneity: the hollow terrain released CH 4 , while the hummocks absorbed CH 4 ; this pattern was explained well by soil moisture. The CH 4 emissions in the swamp meadow were highly sensitive to soil temperature variation ( Q 10  = 3.62), while they were more sensitive to soil moisture in the swamp. By summarizing existing measurements, and considering the differences in CH 4 emissions from swamp meadows and swamps, the emissions of CH 4 from alpine wetlands across the TP were recalculated to range from 0.215 to 0.412 Tg CH 4  a −1 , lower than previous studies. By comparison, the CH 4 uptake by nonwetland ecosystems ranges from −0.68 to −0.53 Tg CH 4  a −1 . Therefore, this study conveys a notion that the alpine wetlands on the TP may not be significant CH 4 sources. However, further studies are needed to reduce the uncertainty regarding CH 4 emissions.