Carbon dioxide balance of subarctic tundra from plot to regional scales

[摘要] We report here the carbon dioxide (CO₂) budget of a 98.6 km²subarctic tundra area in northeast European Russia based on measurements attwo different scales and two independent upscaling approaches. Plot-scalemeasurements (chambers on terrestrial surfaces, gas gradient method andbubble collectors on lakes) were carried out from July 2007 to October 2008.The landscape-scale eddy covariance (EC) measurements covered the snow-freeperiod of 2008. The annual net ecosystem exchange (NEE) of different land covertypes ranged from −251 to 84 g C m⁻². Leaf area index (LAI) was anexcellent predictor of the spatial variability in gross photosynthesis (GP),NEE and ecosystem respiration (ER). The plot-scale CO₂ fluxes were firstscaled up to the EC source area and then to the whole study area using twodata sets: a land cover classification and a LAI map, both based on fielddata and a 2.4 m pixel-sized QuickBird satellite image. The good agreement ofthe CO₂ balances for the EC footprint based on the different measuringtechniques (−105 to −81 g C m⁻² vs. −79 g C m⁻²;growing season 2008) justified the integration of the plot-scale measurementsover the larger area. The regional CO₂ balance based on area-integratedplot-scale measurements was −41 or −79 g C m⁻² yr⁻¹according to the two upscaling methods, the land cover classification andthe LAI map, respectively. Due to the heterogeneity of tundra, the effect ofclimate change on CO₂ uptake will vary strongly according to the landcover type and, moreover, likely changes in their relative coverage in the futurewill have great impact on the regional CO₂ balance.

[学科分类] 地球化学与岩石