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Biogeosciences An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/bg-2020-215
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2020-215
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

  10 Jul 2020

10 Jul 2020

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This preprint is currently under review for the journal BG.

Drought years in peatland rewetting: Rapid vegetation succession can maintain the net CO2 sink function

Florian Beyer1,, Florian Jansen2, Gerald Jurasinski2, Marian Koch3,, Birgit Schröder2, and Franziska Koebsch2, Florian Beyer et al.
  • 1Geodesy and Geoinformatics, Faculty for Agricultural and Environmental Sciences, Rostock University, 18059 Rostock, Germany
  • 2Landscape Ecology, Faculty for Agricultural and Environmental Sciences, Rostock University, 18059 Rostock, Germany
  • 3Soil Physics, Faculty for Agricultural and Environmental Sciences, Rostock University, 18059 Rostock, Germany
  • deceased, 15 April 2020
  • These authors contributed equally to this work.

Abstract. Rewetting is a necessary measure to stop CO2 emissions of degraded peatlands and to restore their natural habitat and C accumulation function. Although the severity and frequency of droughts is predicted to increase as a consequence of climate change, it is not well understood whether such extreme events can jeopardize rewetting measures. The goal of this study was to better understand drought effects on peatland restoration measures. Based on long-term reference records, we investigated anomalies in vegetation dynamics and CO2 exchange, including ecosystem respiration (Reco) and gross ecosystem productivity (GEP), in a rewetted fen during the extreme European summer drought 2018. Drought-induced vegetation dynamics were derived from remotely sensed data.

Since flooding in 2010, the fen was characterized by a patchy mosaic of open water surfaces and vegetated areas. After years of stagnant vegetation development, drought acted as a trigger event for pioneer species such as Tephroseris palustris and Ranunculus sceleratus to rapidly close persistent vegetation gaps. The massive spread of vegetation assimilated substantial amounts of CO2. In 2018, the annual GEP budget increased by 20 % in comparison to average years (2010–2017). Reco increased even by 40 %, but enhanced photosynthetic CO2 sequestration could compensate for half of the drought-induced increase in respiratory CO2 release. Altogether, the restored fen remained a net CO2 sink in the year of drought, though net CO2 sequestration was lower than in other years.

Our study reveals an important regulatory mechanism of restored fens to maintain their net CO2 sink function even in extremely dry years. Even in times of more frequent climate extremes, fen restoration can create ecosystems resilient to drought. However, further research needs to focus on the long-term effects of such extreme events beyond the actual drought period.

Florian Beyer et al.

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Florian Beyer et al.

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Short summary
Increasing drought frequency can jeopardize the restoration of the CO2 sink function in degraded peatlands. We explored the effect of the summer drought 2018 on vegetation development and CO2 exchange in a rewetted fen. Drought triggered a rapid spread of new vegetation, whose CO2 assimilation could partially outweigh the drought-related rise in respiratory CO2 loss. Our study shows important regulatory mechanisms of a rewetted fen to maintain its net CO2 sink function even in a very dry year.
Increasing drought frequency can jeopardize the restoration of the CO2 sink function in degraded...
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