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We report here the carbon dioxide (CO₂) budget of a 98.6 km² subarctic tundra area in northeast European Russia based on measurements at two different scales and two independent upscaling approaches. Plot-scale measurements (chambers on terrestrial surfaces, gas gradient method and bubble collectors on lakes) were carried out from July 2007 to October 2008. The landscape-scale eddy covariance (EC) measurements covered the snow-free period of 2008. The annual net ecosystem exchange (NEE) of different land cover types ranged from −251 to 84 g C m⁻². Leaf area index (LAI) was an excellent predictor of the spatial variability in gross photosynthesis (GP), NEE and ecosystem respiration (ER). The plot-scale CO₂ fluxes were first scaled up to the EC source area and then to the whole study area using two data sets: a land cover classification and a LAI map, both based on field data and a 2.4 m pixel-sized QuickBird satellite image. The good agreement of the CO₂ balances for the EC footprint based on the different measuring techniques (−105 to −81 g C m⁻² vs. −79 g C m⁻²; growing season 2008) justified the integration of the plot-scale measurements over the larger area. The regional CO₂ balance based on area-integrated plot-scale measurements was −41 or −79 g C m⁻² yr⁻¹ according to the two upscaling methods, the land cover classification and the LAI map, respectively. Due to the heterogeneity of tundra, the effect of climate change on CO₂ uptake will vary strongly according to the land cover type and, moreover, likely changes in their relative coverage in the future will have great impact on the regional CO₂ balance

[1] We studied the carbon dioxide and methane fluxes from early June to mid-September 2001 in the Russian tundra of northeast Europe. Gas fluxes were measured with chamber techniques to determine the seasonal (100 days) carbon gas balance for terrestrial ecosystems representing various vegetation types. Also, the gas balance for aquatic ecosystems in the region was measured. The 2001 fluxes were compared to colder and wetter season fluxes from 1999. The Sphagnum sp. dominated peat plateau fen and Carex sp. and Sphagnum sp. dominated intermediate flarks were carbon sinks of 106 and 110 g C m À2 , respectively. In addition, methane emissions were highest from these sites. Other terrestrial surfaces lost carbon to the atmosphere (28-118 g C m À2 ). The thermokarst lake and the river had seasonal carbon losses of 15 and 34 g C m À2 , respectively. For areal integration, the distributions of the various functional surfaces were classified based on Landsat TM satellite image and on-site validation. This data was used to integrate the carbon fluxes for the entire Lek Vorkuta catchment. The upscaling indicated that the catchment (114 km 2 ) lost 4 (±3.5) Gg C to the atmosphere in summer 2001. The results suggest that predicted warming in the tundra region would induce a substantial loss of carbon. In the warm summer of 2001, the carbon gas released from the whole northeast European tundra (area 205,000 km 2 ) was 8 Tg C when calculated from the Lek Vorkuta data.

[1] Methane (CH 4 ) and carbon dioxide (CO 2 ) fluxes on east European tundra wetland ecosystems (67°23 0 N, 63°22 in a 100 day summer period in WF, IF, WL, IL, and HCK, respectively. The losses of carbon in winter accounted for 23.7%, 5.0%, 3.1%, 2.6%, and 2.3% of the net ecosystem production. CH 4 emissions in summer (and winter) were 7.7 (7.8), 6.6 (0.8), 8.2 (0.4), 0.7 (0.3), and 0.1 (0.2) g C m À2 for WF, IF, WL, IL, and HCK, respectively. The modeled annual carbon balance for grouped microsites shows that dry HCKs were carbon sources À7.5 g C yr À1 while flarks and lawns were carbon sinks ranging from 2.2 to 35.9 g C yr À1 . The results show the importance of WT and vegetation composition on annual flux dynamics in a tundra wetland. CH 4 emissions from arctic peatlands seem to be sensitive to changes in the WT.INDEX TERMS: 1615 Global Change: Biogeochemical processes (4805); KEYWORDS: carbon, Arctic, tundra, Russia, carbon balance, global change Citation: Heikkinen, J. E. P., V. Elsakov, and P. J. Martikainen, Carbon dioxide and methane dynamics and annual carbon balance in tundra wetland in NE Europe, Russia, Global Biogeochem.

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