Meteorological responses of carbon dioxide and methane fluxes in the terrestrial and aquatic ecosystems of a subarctic landscape

The subarctic landscape consists of a mosaic of forest, peatland and aquatic ecosystems and their ecotones. The carbon (C) exchange between ecosystems and the atmosphere through carbon dioxide (CO 2 ) and methane (CH 4 ) fluxes varies spatially and temporally among these ecosystems. Our study area in Kaamanen in northern Finland covered 7 km 2 of boreal subarctic landscape with upland forest, open peatland, pine bogs and lakes. We measured the CO 2 and CH 4 fluxes with eddy covariance 15 and chambers between June 2017 and June 2019 and studied the C flux responses to varying meteorological conditions. The landscape area was an annual CO 2 sink of -25.9 ± 65.7 and -41.3 ± 64.9 g C m -2 , and a CH 4 source of 2.4 ± 0.7 and 2.3 ± 0.7 g C m -2 during the first and second study year, respectively. The pine forest had the largest contribution to the landscape-level CO 2 sink, -78.3 ± 50.8 and -118.9 ± 26.8 g C m -2 , and the fen to the CH 4 emissions, 7.0 ± 0.2 and 6.3 ± 0.3 g C m -2 , during the first and second study year, respectively. The lakes within the area acted as CO 2 and CH 4 sources to the atmosphere throughout 20 the measurement period, with an organic sediment lake located downstream