Preprints
https://doi.org/10.5194/bg-2022-5
https://doi.org/10.5194/bg-2022-5
 
26 Jan 2022
26 Jan 2022
Status: a revised version of this preprint was accepted for the journal BG and is expected to appear here in due course.

Variation in CO2 and CH4 Fluxes Among Land Cover Types in Heterogeneous Arctic Tundra in Northeastern Siberia

Sari Juutinen1,2, Mika Aurela1, Juha-Pekka Tuovinen1, Viktor Ivakhov3, Maiju Linkosalmi1, Aleksi Räsänen4,5, Tarmo Virtanen4, Juha Mikola4,5, Johanna Nyman1, Emmi Vähä1, Marina Loskutova6, Alexander Makshtas6, and Tuomas Laurila1 Sari Juutinen et al.
  • 1Finnish Meteorological Institute, Erik Palménin aukio 1, 00560 Helsinki, Finland
  • 2Department of Geographical and Historical Studies, University of Eastern Finland, Yliopistokatu 2, FI-80100 Joensuu, Finland (P.O. Box 111, FI-80101 Joensuu, Finland)
  • 3Voeikov Main Geophysical Observatory, Ulitsa Karbysheva, 7, St Petersburg, 194021, Russia
  • 4Ecosystems and Environment Research Programme, University of Helsinki, Viikinkaari 1, 00790 Helsinki, Finland
  • 5Natural Resources Institute Finland (LUKE), Latokartanonkaari 9, 00790 Helsinki, Finland
  • 6Arctic and Antarctic Research Institute, Bering str., 38, St Petersburg, 199397, Russia

Abstract. Arctic tundra is facing unprecedented warming, resulting in shifts in the vegetation, thaw regimes, and potentially in the ecosystem-atmosphere exchange of carbon (C). The estimates of regional carbon dioxide (CO2) and methane (CH4) budgets, however, are highly uncertain. We measured CO2 and CH4 fluxes, vegetation composition and leaf area index (LAI), thaw depth, and soil wetness in Tiksi (71° N, 128° E), a heterogeneous site located within the prostrate dwarf-shrub tundra zone in northeastern Siberia. Using the closed chamber method, we determined net ecosystem exchange (NEE) of CO2, dark ecosystem respiration (ER), ecosystem gross photosynthesis (Pg), and CH4 fluxes during the growing season. We applied a previously developed high-spatial-resolution land-cover map over an m area of 35.8 km2. Among the land-cover types varying from barrens to dwarf-shrub tundra and tundra wetlands, the light-saturated NEE and Pg scaled with the LAI of vascular plants. Thus, the graminoid-dominated tundra wetlands, with high LAI and the deepest thaw depth, had the highest light-saturated NEE and Pg (up to −21 (uptake) and 28 mmol m−2 h−1, respectively) and were disproportionately important for the summertime CO2 sequestration on a landscape scale. Dry tundra, including the dwarf-shrub-dominated vegetation and only sparsely vegetated lichen tundra, had only small CO2 exchange rates. While tundra wetlands were sources of CH4, lichen tundra, including bare ground habitats, consumed atmospheric CH4 at a substantial rate. On a landscape scale, the consumption by lichen tundra and barrens could offset ca. 10 % of the CH4 emissions. We acknowledge the uncertainty involved in spatial extrapolations due to a small number of replicates per land-cover type. This study, however, highlights the need for distinguishing different land-cover types including the dry tundra habitats to account for their consumption of the atmospheric CH4 when estimating tundra C-exchange on a larger spatial scale.

Sari Juutinen et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'reviewer comment on bg-2022-5', Anonymous Referee #1, 16 Feb 2022
    • AC1: 'Reply on RC1', Sari Juutinen, 30 Mar 2022
  • RC2: 'Comment on bg-2022-5', Anonymous Referee #2, 21 Feb 2022
    • AC2: 'Reply on RC2', Sari Juutinen, 30 Mar 2022

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'reviewer comment on bg-2022-5', Anonymous Referee #1, 16 Feb 2022
    • AC1: 'Reply on RC1', Sari Juutinen, 30 Mar 2022
  • RC2: 'Comment on bg-2022-5', Anonymous Referee #2, 21 Feb 2022
    • AC2: 'Reply on RC2', Sari Juutinen, 30 Mar 2022

Sari Juutinen et al.

Sari Juutinen et al.

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Short summary
We measured CO2 and CH4 fluxes in arctic tundra with heterogeneous land cover and extrapolated the land-cover specific fluxes for a larger area. We found that tundra wetlands with sedge and grass vegetation contributed disproportionately as the sites of ecosystem CO2 uptake and CH4 emissions to the atmosphere. In contrast, we observed high CH4 consumption in dry tundra, particularly in barrens, offsetting part of the CH4 emissions from the wetlands.
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