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Ecosystem carbon response of an Arctic peatland to simulated permafrost thaw

Voigt, Carolina; Marushchak, Maija E. LU ; Mastepanov, Mikhail LU ; Lamprecht, Richard E.; Christensen, Torben R. LU ; Dorodnikov, Maxim; Jackowicz-Korczyński, Marcin LU ; Lindgren, Amelie LU ; Lohila, Annalea and Nykänen, Hannu, et al. (2019) In Global Change Biology 25(5). p.1746-1764
Abstract


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... (More)


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.

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publishing date
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Contribution to journal
publication status
published
subject
keywords
climate warming, CO, greenhouse gas, mesocosm, methane oxidation, permafrost-carbon-feedback
in
Global Change Biology
volume
25
issue
5
pages
1746 - 1764
publisher
Wiley-Blackwell
external identifiers
  • scopus:85061985477
ISSN
1354-1013
DOI
10.1111/gcb.14574
language
English
LU publication?
yes
id
d37d8b1f-e680-4506-a6e0-1b80df25a68d
date added to LUP
2019-03-08 08:14:41
date last changed
2019-06-27 14:11:37
@article{d37d8b1f-e680-4506-a6e0-1b80df25a68d,
  abstract     = {<p><br>
                                                         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                             <br>
                            <sub>2</sub><br>
                                                         ) and methane (CH                             <br>
                            <sub>4</sub><br>
                                                         ) 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                             <br>
                            <sub>2</sub><br>
                                                          emissions to the atmosphere (without vegetation: 0.74 ± 0.49 vs. 0.84 ± 0.60 g CO                             <br>
                            <sub>2</sub><br>
                                                         –C m                             <br>
                            <sup>−2</sup><br>
                                                         day                             <br>
                            <sup>−1</sup><br>
                                                         ; with vegetation: 1.20 ± 0.50 vs. 1.32 ± 0.60 g CO                             <br>
                            <sub>2</sub><br>
                                                         –C m                             <br>
                            <sup>−2</sup><br>
                                                         day                             <br>
                            <sup>−1</sup><br>
                                                         , mean ± SD, pre- and post-thaw, respectively). Radiocarbon dating (                             <br>
                            <sup>14</sup><br>
                                                         C) of respired CO                             <br>
                            <sub>2</sub><br>
                                                         , supported by an independent curve-fitting approach, showed a clear contribution (9%–27%) of old carbon to this enhanced post-thaw CO                             <br>
                            <sub>2</sub><br>
                                                          flux. Elevated concentrations of CO                             <br>
                            <sub>2</sub><br>
                                                         , CH                             <br>
                            <sub>4</sub><br>
                                                         , 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                             <br>
                            <sub>4</sub><br>
                                                          in the peat column, however, prevented CH                             <br>
                            <sub>4</sub><br>
                                                          release to the atmosphere. Importantly, we show here that, under dry conditions, peatlands strengthen the permafrost–carbon feedback by adding to the atmospheric CO                             <br>
                            <sub>2</sub><br>
                                                          burden post-thaw. However, as long as the water table remains low, our results reveal a strong CH                             <br>
                            <sub>4</sub><br>
                                                          sink capacity in these types of Arctic ecosystems pre- and post-thaw, with the potential to compensate part of the permafrost CO                             <br>
                            <sub>2</sub><br>
                                                          losses over longer timescales.                         <br>
                        </p>},
  author       = {Voigt, Carolina and Marushchak, Maija E. and Mastepanov, Mikhail and Lamprecht, Richard E. and Christensen, Torben R. and Dorodnikov, Maxim and Jackowicz-Korczyński, Marcin and Lindgren, Amelie and Lohila, Annalea and Nykänen, Hannu and Oinonen, Markku and Oksanen, Timo and Palonen, Vesa and Treat, Claire C. and Martikainen, Pertti J. and Biasi, Christina},
  issn         = {1354-1013},
  keyword      = {climate warming,CO,greenhouse gas,mesocosm,methane oxidation,permafrost-carbon-feedback},
  language     = {eng},
  month        = {01},
  number       = {5},
  pages        = {1746--1764},
  publisher    = {Wiley-Blackwell},
  series       = {Global Change Biology},
  title        = {Ecosystem carbon response of an Arctic peatland to simulated permafrost thaw},
  url          = {http://dx.doi.org/10.1111/gcb.14574},
  volume       = {25},
  year         = {2019},
}