EGU2020-2892, updated on 21 Oct 2023
https://doi.org/10.5194/egusphere-egu2020-2892
EGU General Assembly 2020
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Spruce resins constitute a strong sink for methane (CH4)

Katerina Machacova1, Thomas Schindler1,2, Ülo Mander2, and Kaido Soosaar2
Katerina Machacova et al.
  • 1Department of Ecosystem Trace Gas Exchange, Global Change Research Institute CAS, Brno, Czech Republic (machacova.k@czechglobe.cz)
  • 2Department of Geography, Institute of Ecology & Earth Sciences, University of Tartu, Tartu, Estonia

Woody plants are known to emit methane (CH4) as an important greenhouse gas into the atmosphere. Recent studies show that tree stems might be also sinks for CH4; however, the mechanisms of CH4 uptake and its fate are unknown. Norway spruce (Picea abies) is characterised as negligible CH4 source in boreal forests. Even though spruce trees have been widely planted for its wood in large-scale monocultures in European temperate forests, no studies have focused on their CH4 exchange potential in the temperate zone.

We determined stems of Norway spruce growing in a temperate zone aiming to find out whether the tree stems exchange CH4 with the atmosphere and how they contribute to the forest trace gas exchange.

The measurements were performed at the experimental station of the ‘Kranzberg Forest Roof Experiment’ near Freising, Germany, in June 2019. Fluxes of CH4 in mature tree stems were measured using non-steady-state stem chamber systems (n=32) installed in stem vertical profile approx. two weeks prior to measurements using a portable greenhouse gas analyser. Moreover, resins sampled from spruce stems were investigated for their CH4 exchange potential. Control measurements were performed to ensure that the fluxes do not originate from used chamber materials, in particular silicones used for chamber installation.

Our preliminary results show that the spruce stems can be a strong sink for CH4 (-0.288 ± 0.053 mg CH4 m-2 stem area h-1, mean ± s.e.), even if a small amount of resin is present on the bark. The stems exuded resins to different extent (covering 4.8 ± 1.3% of the stem surface area in chambers), partly as a result of smoothening of rough surface layers of dead bark for chamber installation. However, even spruce stems without obvious “injuries” released small amounts of resins for unknown reasons (response to drought, bark-beetle attack, etc.?). The incubated resin samples consistently consumed CH4 (-12.0 ± 1.7 mg CH4 m-2 resin area h-1). Moreover, the detected stem CH4 uptake negatively correlated with the resin occurrence in the stem chambers (R² = 0.884). After re-calculation of the stem fluxes to resin area, the CH4 consumption rates of stems and resin samples were in the same order of magnitude at median level (-13.2 and -12.0 mg CH4 m-2 resin area h-1, resp.).

Concluded, the spruce resins appear to be a very strong and until now undiscovered sink for CH4. Even one small droplet of resins on bark can turn the known negligible CH4 exchange of intact spruce stems into strong CH4 sinks, having thus severe impact on the overall forest CH4 balance. This consumption potential of fresh resins should be considered by estimation of forest ecosystem CH4 balance especially in areas, where resin bleeding is widely spread or is to be expected (bark-beetle areas, drought events, tree harvest, clear-cutting).

 

Acknowledgement

This research was supported by the Czech Science Foundation (17-18112Y) and National Sustainability Program I (LO1415). We thank Prof. Thorsten Grams for all his kind support, and Jan Hrdlička and Thomas Feuerbach for their technical support.

 

 

How to cite: Machacova, K., Schindler, T., Mander, Ü., and Soosaar, K.: Spruce resins constitute a strong sink for methane (CH4), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2892, https://doi.org/10.5194/egusphere-egu2020-2892, 2020.

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