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A B S T R A C T CO 2 and CH 4 fluxes were measured from three small wetland lakes located in the middle taiga and forest tundra zones on West Siberian Lowlands (WSL), the world's largest wetland area. Fluxes were measured during summer 2005 using floating chambers and were validated against the thin boundary layer model based on the relationship between gas exchange and wind speed. All studied lakes were supersaturated with CO 2 and CH 4 , and acted on a seasonal basis as sources of these greenhouse gases to the atmosphere. Daily mean CO 2 fluxes measured with chambers ranged from near the zero to 3.1 g CO 2 m −2 d −1 and corresponding CH 4 fluxes from 1.1 to 120 mg CH 4 m −2 d −1 . CH 4 ebullition (0.65-11 mg CH 4 m −2 d −1 ) was detected in two of the lakes. Total carbon evasion from the studied lakes during the active season was 23-66 g C m −2 , of which more than 90% was released as CO 2 -C. The carbon loss per unit area from the studied lakes was of similar magnitude as previously reported values of net carbon uptake of Siberian peatlands. This emphasizes the importance of small water-bodies in the carbon balance of West Siberian landscape.

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