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https://doi.org/10.5194/bg-2019-10
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2019-10
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 19 Feb 2019

Research article | 19 Feb 2019

Review status
This discussion paper is a preprint. A revision of the manuscript is under review for the journal Biogeosciences (BG).

Scaling and balancing carbon dioxide fluxes in a heterogeneous tundra ecosystem of the Lena River Delta

Norman Rößger1, Christian Wille2, David Holl1, Mathias Göckede3, and Lars Kutzbach1 Norman Rößger et al.
  • 1Institute of Soil Science, University of Hamburg, Allende-Platz 2, 20146 Hamburg, Germany
  • 2German Research Centre for Geosciences, Telegrafenberg, 14473 Potsdam, Germany
  • 3Max Planck Institute for Biogeochemistry, Hans-Knöll-Straße 10, 07745 Jena, Germany

Abstract. The current assessments of the carbon turnover in the Arctic tundra are subject to large uncertainties. This problem can (inter alia) be ascribed to both the general shortage of flux data from the vast and sparsely inhabited Arctic region, as well as the typically high spatiotemporal variability of carbon fluxes in tundra ecosystems. Addressing these challenges, carbon dioxide fluxes on an active flood plain situated in the Siberian Lena River Delta were studied during two growing seasons with the eddy covariance method. The footprint exhibited a heterogeneous surface, and the mixed flux signal associated therewith could extensively be decomposed: respiratory loss and photosynthetic gain were not only modelled for the overall footprint, but also for each of two vegetation classes. This downscaling of the observed fluxes unveiled a differing seasonality in the net uptakes of bushes (0.89 μmol m−2 s−1) and sedges (0.38 μmol m−2 s−1) in 2014. That discrepancy, which was concealed in the net signal, resulted from a comparatively warm spring in conjunction with an early snow melt and a varying canopy structure. Thus, the representativeness of footprints may adversely be affected in response to prolonged unusual weather conditions. In 2015, when air temperatures on average corresponded to climatological means, both vegetation class-specific flux rates were of similar magnitude (0.69 μmol m−2 s−1). A comprehensive set of measures (e.g. phenocam) approved the reliability of the partitioned fluxes, and hence confirmed the utility of the flux decomposition for enhanced flux data analysis. This scrutiny encompassed insights into both the phenological dynamic of individual vegetation classes, plus their respective functional flux to flux driver relationships with the aid of ecophysiologically interpretable parameters. For the purpose of comparison with other sites, the decomposed fluxes were employed in a vegetation class area-weighted upscaling that was based on a classified high-resolution orthomosaic of the flood plain. In this way, robust budgets that take the heterogeneous surface characteristics into account were estimated. In relation to the average sink strength of various Arctic flux sites, the flood plain constitutes a distinctly stronger carbon dioxide sink. Roughly 42 % of this net uptake, however, was on average offset by methane emissions lowering the sink strength for greenhouse gases. With growing concern about rising greenhouse gas emissions in high-latitude regions, providing robust carbon budgets from tundra ecosystems is critical in view of the thawing permafrost, whose released carbon can impact the global climate for centuries.

Norman Rößger et al.
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Status: final response (author comments only)
Status: final response (author comments only)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Norman Rößger et al.
Norman Rößger et al.
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