Preprints
https://doi.org/10.5194/egusphere-2024-934
https://doi.org/10.5194/egusphere-2024-934
30 Apr 2024
 | 30 Apr 2024
Status: this preprint is open for discussion.

Carbon balance and emissions of methane and nitrous oxide during four years of moderate rewetting of a cultivated peat soil site

Kristiina Lång, Henri Honkanen, Jaakko Heikkinen, Sanna Saarnio, Tuula Larmola, and Hanna Kekkonen

Abstract. We experimented a gradual water table rise at a highly degraded agricultural peat soil site with plots of willow, forage and mixed vegetation (set-aside) in southern Finland. We measured the emissions of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) for four years. The mean annual ground water table depth was about 80, 40, 40 and 30 cm in 2019–2022, respectively. The results indicated that a 10 cm raise in the water table depth was able to slow down annual CO2 emissions from soil respiration by 0.87 Mg CO2-C ha-1. CH4 fluxes changed from uptake to emissions with a raise in the water table depth, and the maximum mean annual emission rate was 11 kg CH4-C. Nitrous oxide emissions ranged from 2 to 33 kg N2O-N ha-1 year; they were high from bare soil in the beginning of the experiment but decreased towards the end of the experiment. Short rotation cropping of willow reached net sequestration of carbon before harvest, but all treatments and years showed net loss of carbon based on the net ecosystem carbon balance. Overall, the short rotation coppice of willow had the most favourable carbon and greenhouse gas balance over the years (10 Mg CO2 eq. on the average over four years). The total greenhouse gas balance of the forage and set-aside treatments did not go under 27 Mg CO2 eq. ha-1 year-1 highlighting the challenge in curbing peat decomposition in highly degraded cultivated peatlands.

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Kristiina Lång, Henri Honkanen, Jaakko Heikkinen, Sanna Saarnio, Tuula Larmola, and Hanna Kekkonen

Status: open (until 15 Jun 2024)

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Kristiina Lång, Henri Honkanen, Jaakko Heikkinen, Sanna Saarnio, Tuula Larmola, and Hanna Kekkonen
Kristiina Lång, Henri Honkanen, Jaakko Heikkinen, Sanna Saarnio, Tuula Larmola, and Hanna Kekkonen

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Short summary
We studied greenhouse gas fluxes at an agricultural peat soil site with willow, forage and set-aside. The mean annual water table raised from 80 to 30 cm in 2019–2022. Raising the water table slowed down annual CO2 emissions. CH4 fluxes changed from uptake to emissions, and nitrous oxide emissions decreased towards the end of the experiment. The total greenhouse gas balance was relatively high, highlighting the challenge in mitigating emissions from cultivated peatlands.