EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Mosses as biofilters for ditch methane emissions from forestry drained peatlands

Tuula Larmola1, Antti J. Rissanen1,2, Paavo Ojanen1,3, Leena Stenberg1, Lukas Kohl4, and Raisa Mäkipää1
Tuula Larmola et al.
  • 1Natural Resources Institute Finland, Natural Resources, Helsinki, Finland (
  • 2Faculty of Engineering and Natural Sciences, Bio and Circular Economy research group, Tampere University, Tampere, Finland
  • 3Department of Forest Sciences,University of Helsinki, Helsinki, Finland
  • 4Department of Environmental and Biological Sciences, University of Eastern Finland, Kuopio, Finland

In drained peatland forests, drainage ditches cover ca. 3% of the area, but contribute to up to 100% of methane (CH4) emission. The drained peat soils, in contrast, can act as a CH4 sink especially under efficient drainage. Therefore, emissions from ditches will impact whether drained peatland is a net CH4 sink or source. The net CH4 flux is likely to be impacted by the conditions in the ditches such as the extent and type of plant cover and the time since drainage. In order to provide more accurate ditch CH4 emission factors for national greenhouse gas (GHG) inventory, we examined the fluxes and the underlying CH4 cycling processes in a nutrient rich peatland forest in Ränskälänkorpi, Southern Finland during May-October 2021. We compared the ecosystem-atmosphere CH4 fluxes and their δ13C values from moss dominated and open water ditches. We determined CH4 and CO2 mixing ratios and their δ13C values in water and in sediment by gas chromatography and cavity ring-down spectroscopy (Picarro G2201-i), respectively. We also assessed the role of CH4 as a carbon source for Sphagnum mosses growing in ditches by analyzing δ13C values in submerged and partly submerged Sphagnum using elemental analysis - isotope ratio mass spectrometry. We found that mean seasonal CH4 emissions from moss dominated ditches were 90% lower than from open water surfaces. In this dry summer, moss-dominated ditches were occasionally net sinks of atmospheric CH4. These results can be explained by CH4 consuming microbes inhabiting surface water, moss layer or sediment below the moss layer and using CH4 as a source of carbon and energy. Isotopic mass balance calculations accounting for the measured δ13C values of Sphagnum moss, dissolved CO2 and CH4 as well as fractionation against 13C during (mass-transfer-limited) moss CO2 fixation indicated that 10-28% of carbon in ditch Sphagnum mosses potentially originated from oxidized CH4. Ditch network maintenance, including removing mosses, is likely to decrease along with changing peatland forest management, e.g., continuous cover forestry. Our results suggest that ditches overgrown by mosses have potential to reduce CH4 emissions from drained peatland forests and could serve as an additional GHG mitigation measure to management practices that maintain a continuous forest cover, attenuate the changes in water table level and thus reduce CH4 emissions from peat soils.


How to cite: Larmola, T., Rissanen, A. J., Ojanen, P., Stenberg, L., Kohl, L., and Mäkipää, R.: Mosses as biofilters for ditch methane emissions from forestry drained peatlands, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-1382,, 2023.