EGU22-7493, updated on 21 Oct 2023
https://doi.org/10.5194/egusphere-egu22-7493
EGU General Assembly 2022
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Greenhouse Gas Dynamics in a Drained Peatland Forest: Annual CH4 and N2O Fluxes from Tree Stems and Soil

Reti Ranniku1, Thomas Schindler1,2, Jordi Escuer-Gatius3, Ülo Mander1,2, Katerina Machacova2, and Kaido Soosaar1,2
Reti Ranniku et al.
  • 1University of Tartu, Faculty of Science and Technology, Institute of Ecology and Earth Sciences, Tartu, Estonia (reti.ranniku@ut.ee)
  • 2Global Change Research Institute of the Czech Academy of Sciences, Brno, Czech Republic
  • 3Institute of Agricultural and Environmental Sciences, Estonian University of Life Sciences, Tartu, Estonia

Peatland soils are considered the dominating source of methane (CH4) and nitrous oxide (N2O) to the atmosphere. However, there are high spatio-temporal uncertainties regarding the soil greenhouse gas (GHG) fluxes due to complex dynamics between the soil chemical, physical and biological variables. Although GHG fluxes from peatland soils are relatively well studied, tree stem fluxes have received far less attention and are often overlooked in GHG models and assessments. Moreover, simultaneous year-long measurements of soil and tree stem CH4 and N2O fluxes in peatland forests are missing, as previous studies have primarily focused on the growing season. We aim to determine the seasonal dynamics of CH4 and N2O fluxes in drained peatland forests, as drainage can lead to release of the large amounts of carbon and nitrogen stored in peat into the atmosphere as GHGs.

Our research focuses on tree stems and soil GHG fluxes in the Agali Drained Peatland Forest Research Station in Estonia, dominated by Downy Birch (Betula pubescens) and Norway Spruce (Picea abies) trees. During the weekly sampling campaigns (November 2020–December 2021), we used manual static stem chambers to collect gas samples, which were later analysed for CH4 and N2O in the laboratory using Shimadzu GC-2014 gas chromatography. We measured soil CH4 and N2O fluxes using an automated dynamic soil chamber system connected to a Picarro G2508 analyser.

Preliminary results show that on average, birch stem GHG fluxes were greater than spruce stem fluxes. Birch trees were a net annual source of both CH4 (0.38 ± 0.09 µg C m-2 stem area h-1, mean ± SE) and N2O (0.94 ± 0.32 µg N m-2 h-1). Spruce trees were a net source of CH4 (0.08 ± 0.05 µg C m-2 h-1) but a net sink of N2O (–0.08 ± 0.02 µg N m-2 h-1). Temporal dynamics of birch stem CH4 emissions were characterised by significant emission peaks in November and June. During the rest of the year smaller fluxes with fluctuations between emissions and uptake were observed. Spruce stem CH4 fluxes followed a roughly similar pattern as birch fluxes. However, during the birch emission peak in June, spruce stems showed uptake of CH4. Birch stem N2O emissions remained very small for most of the year, with increased emissions in autumn months and March. Spruce stem N2O fluxes remained very low throughout the year.

Soils were a net annual sink of CH4 (–6.44 ± 0.76 µg C m-2 ground area h-1) and source of N2O (41.68 ± 3.15 µg N m-2 h-1). CH4 was taken up by the soil most of the year, however occasional emissions occurred. A substantial increase in CH4 uptake was observed in June, peaking at –49.53 µg C m-2 h-1 at the end of July, and diminishing towards the end of summer. Hot moments – notably higher daily average emissions compared to the period average – characterised the temporal dynamics of soil N2O emissions.

Further results on soil meteorological and biogeochemical properties will help determine the possible drivers of stem and soil fluxes’ dynamics and their origin.

How to cite: Ranniku, R., Schindler, T., Escuer-Gatius, J., Mander, Ü., Machacova, K., and Soosaar, K.: Greenhouse Gas Dynamics in a Drained Peatland Forest: Annual CH4 and N2O Fluxes from Tree Stems and Soil, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7493, https://doi.org/10.5194/egusphere-egu22-7493, 2022.

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