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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-2019-432
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2019-432
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 28 Nov 2019

Submitted as: research article | 28 Nov 2019

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

Comparison of eddy covariance CO2 and CH4 fluxes from mined and recently rewetted sections in a NW German cutover bog

David Holl, Eva-Maria Pfeiffer, and Lars Kutzbach David Holl et al.
  • Institute of Soil Science, Center for Earth System Research and Sustainability (CEN), Universität Hamburg, Hamburg, Germany

Abstract. With respect to their role in the global carbon cycle, natural peatlands are characterized by their ability to sequester atmospheric carbon. This trait is strongly connected to the water regime of these ecosystems. Large parts of the soil profile in natural peatlands are water-saturated, leading to anoxic conditions and to a diminished decomposition of plant litter. In functioning peatlands, the rate of carbon fixation by plant photosynthesis is larger than the decomposition rate of dead organic material. Over time, the amount of carbon that remains in the soil and is not converted back to carbon dioxide grows. Land use of peatlands often goes along with water level manipulations and thereby with alterations of carbon flux dynamics. In this study, carbon dioxide (CO2) and methane (CH4) flux measurements from a bog site in NW Germany that has been heavily degraded by peat mining are presented. Two contrasting types of management have been implemented at the site: (1) drainage during ongoing peat-harvesting on one half of the central bog area and (2) rewetting on the other half that had been taken out of use shortly before measurements commenced. The presented two-year data set was collected with an eddy covariance (EC) system set up on a central railroad dam that divides the two halves of the (former) peat harvesting area. We used footprint analysis to split the obtained CO2 and CH4 flux time series into data characterizing the gas exchange dynamics of both contrasting land use types individually. The time series gaps resulting from data division were filled using the response of artificial neural networks (ANNs) to environmental variables, footprint variability and fuzzy transformations of seasonal and diurnal cyclicity. We used the gap-filled gas flux time series from two consecutive years to evaluate the impact of rewetting on the annual vertical carbon balances of the cutover bog. Rewetting had a considerable effect on the annual carbon fluxes and led to increased CH4 and decreased CO2 release.

The larger relative difference between cumulative CO2 fluxes from the rewetted (22 ± 7 mol m−2 a−1) and drained (13 ± 6 mol m−2 a−1) section occurred in the second observed year when rewetting apparently reduced CO2 emissions by 40 %. The absolute difference in annual CH4 flux sums was more similar between both years while the relative difference of CH4 release between the rewetted (0.83 ± 0.15 mol m−2 a−1) and drained (0.45 ± 0.11 mol m−2 a−1) section was larger in the first observed year indicating a maximum increase of annual CH4 release of 84 % caused by rewetting; at this particular site during the study period.

David Holl et al.
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David Holl et al.
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Short summary
We measured greenhous gas (GHG) fluxes at a bog site in NW Germany that has been heavily degraded by peat mining. During the two-year investigation period, half of the bog area was still mined whereas the remaining half had been rewetted shortly before. We could therefore estimate the impact of bog-rewetting on the GHG flux dynamics. Rewetting had a considerable effect on the annual GHG balances and led to increased (up to 84 %) methane and decreased (up to 40 %) carbon dioxide release.
We measured greenhous gas (GHG) fluxes at a bog site in NW Germany that has been heavily...
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