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Ecosystem carbon response of an Arctic peatland to simulated permafrost thaw

Author:
  • Carolina Voigt
  • Maija E. Marushchak
  • Mikhail Mastepanov
  • Richard E. Lamprecht
  • Torben R. Christensen
  • Maxim Dorodnikov
  • Marcin Jackowicz-Korczyński
  • Amelie Lindgren
  • Annalea Lohila
  • Hannu Nykänen
  • Markku Oinonen
  • Timo Oksanen
  • Vesa Palonen
  • Claire C. Treat
  • Pertti J. Martikainen
  • Christina Biasi
Publishing year: 2019-01-25
Language: English
Pages: 1746-1764
Publication/Series: Global Change Biology
Volume: 25
Issue: 5
Document type: Journal article
Publisher: Wiley-Blackwell

Abstract english


Permafrost peatlands are biogeochemical hot spots in the Arctic as they store vast amounts of carbon. Permafrost thaw could release part of these long-term immobile carbon stocks as the greenhouse gases (GHGs) carbon dioxide (CO
2
) and methane (CH
4
) to the atmosphere, but how much, at which time-span and as which gaseous carbon species is still highly uncertain. Here we assess the effect of permafrost thaw on GHG dynamics under different moisture and vegetation scenarios in a permafrost peatland. A novel experimental approach using intact plant–soil systems (mesocosms) allowed us to simulate permafrost thaw under near-natural conditions. We monitored GHG flux dynamics via high-resolution flow-through gas measurements, combined with detailed monitoring of soil GHG concentration dynamics, yielding insights into GHG production and consumption potential of individual soil layers. Thawing the upper 10–15 cm of permafrost under dry conditions increased CO
2
emissions to the atmosphere (without vegetation: 0.74 ± 0.49 vs. 0.84 ± 0.60 g CO
2
–C m
−2
day
−1
; with vegetation: 1.20 ± 0.50 vs. 1.32 ± 0.60 g CO
2
–C m
−2
day
−1
, mean ± SD, pre- and post-thaw, respectively). Radiocarbon dating (
14
C) of respired CO
2
, supported by an independent curve-fitting approach, showed a clear contribution (9%–27%) of old carbon to this enhanced post-thaw CO
2
flux. Elevated concentrations of CO
2
, CH
4
, and dissolved organic carbon at depth indicated not just pulse emissions during the thawing process, but sustained decomposition and GHG production from thawed permafrost. Oxidation of CH
4
in the peat column, however, prevented CH
4
release to the atmosphere. Importantly, we show here that, under dry conditions, peatlands strengthen the permafrost–carbon feedback by adding to the atmospheric CO
2
burden post-thaw. However, as long as the water table remains low, our results reveal a strong CH
4
sink capacity in these types of Arctic ecosystems pre- and post-thaw, with the potential to compensate part of the permafrost CO
2
losses over longer timescales.

Keywords

  • Climate Research
  • climate warming
  • CO
  • greenhouse gas
  • mesocosm
  • methane oxidation
  • permafrost-carbon-feedback

Other

Published
  • ISSN: 1354-1013
E-mail: mikhail [dot] mastepanov [at] nateko [dot] lu [dot] se

Researcher

Dept of Physical Geography and Ecosystem Science

+46 46 222 39 75

+46 73 936 09 67

473

16

Department of Physical Geography and Ecosystem Science
Lund University
Sölvegatan 12
S-223 62 Lund
Sweden

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