Carbon dioxide balance of subarctic tundra from plot to regional scales

Abstract

We report here the carbon dioxide (CO<sub>2</sub>) budget of a 98.6 km<sup>2</sup> 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<sup>−2</sup>. Leaf area index (LAI) was an excellent predictor of the spatial variability in gross photosynthesis (GP), NEE and ecosystem respiration (ER). The plot-scale CO<sub>2</sub> 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 CO<sub>2</sub> balances for the EC footprint based on the different measuring techniques (−105 to −81 g C m<sup>−2</sup> vs. −79 g C m<sup>−2</sup>; growing season 2008) justified the integration of the plot-scale measurements over the larger area. The regional CO<sub>2</sub> balance based on area-integrated plot-scale measurements was −41 or −79 g C m<sup>−2</sup> yr<sup>−1</sup> 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 CO<sub>2</sub> 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 CO<sub>2</sub> balance

Assessing the spatial variability in peak season CO<sub>2</sub> exchange characteristics across the Arctic tundra using a light response curve parameterization

“…5; Table 3); however, this was based on one single year of data (2008). Though 3-5 • C warmer than the long-term July mean, 2008 July temperatures were lower than 2007 (Marushchak et al, 2013). Thus, we have further examined peak season for sites with available 2008 data (RU-Seid-SA, SE-Stord-SA, NOAndo-SA, US-Anak-LA, RU-Kyt-LA, GL-Nuuk-LA, and GL-Zack-HA) to investigate whether the outlier was the year (2008) or the site (RU-Seid-SA).…”

“…It is imperative that standardized post-processing procedures are used so as to avoid bias introduced by different flux correction approaches (Lund et al, 2010). Details of the EC post-processing corrections are found in the relevant publications for each site: US-Anak-LA , US-Barr-LA and US-Ivot-LA (Kwon et al, 2006), CA-Dar-LA (Lafleur and Humphreys, 2008), FIKaam-SA ), RU-Kyt-LA (Parmentier et al, 2011), NO-Ando-SA, GL-Nuuk-LA and GL-Zack-HA , RU-Sam-LA (Kutzbach et al, 2007;Runkle et al, 2013), RU-Seid-SA (Marushchak et al, 2013), and SE-Stord-SA (Christensen et al, 2012).…”

“…air and soil temperature, soil moisture, vapour pressure deficit (VPD), relative humidity, incoming and outgoing short-wave radiation, net radiation, precipitation and PPFDwere also examined for significant relationship to LRC parameters. Maximum LAI was extracted from referenced literature Laurila et al, 2001;Lund et al, 2010;Marushchak et al, 2013), while NDVI data were retrieved from MODIS Land Product Subsets (http://daac.ornl. gov/MODIS/) as 250 m × 250 m pixels in the dominant wind direction and within the footprint of the flux tower.…”

Methane dynamics in the subarctic tundra: combining stable isotope analyses, plot- and ecosystem-scale flux measurements

“…1) was used to map the distribution of the various land cover types (LCTs) of the study area of 98.6 km 2 (Hugelius et al, 2011;Marushchak et al, 2013). In terms of areal coverage, the tundra heath (58 %) and tundra bog vegetation (24 %) found especially on permanently frozen peat plateaus are the dominant ecosystem types in the region followed by willow stands (9 %), and various fen ecosystems (6 %).…”

“…The CH 4 concentrations in the collected gas samples were analysed within three months from sampling using a gas chromatograph equipped with a flame ionization detector (Agilent 6890N, Agilent Technologies Deutschland, Böblingen, Germany). A leakage test with a high CH 4 concentration (15 ppm) showed that the reduction in gas concentration in the sample vials over 2 months was less than 1 % (data not Marushchak et al (2011Marushchak et al ( , 2013. The adjustment of moss surface to water table fluctuations on willow and fen microsites was monitored in 2008 by a measuring pole pushed through the peat profile down to the mineral soil.…”