EGU2020-19009, updated on 09 Jan 2024
EGU General Assembly 2020
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

Greenhouse gas emissions from a Mediterranean floodplain forest: the role of tree emissions under a changing flooding regime.

Sílvia Poblador1, Elisabet Martínez-Sancho2, Mateu Menéndez-Serra3, Emilio O. Casamayor3, Marc Estiarte4,5, Anna Lupon3, Eugènia Martí3, Josep Peñuelas4,5, Santiago Sabaté4,6, and Francesc Sabater4,6
Sílvia Poblador et al.
  • 1Research Group of Plant and Vegetation Ecology, Department of Biology, University of Antwerp, 2610 Wilrijk, Belgium.
  • 2Swiss Federal Institute for Forest Snow and Landscape Research WSL, 8903 Birmensdorf, Switzerland.
  • 3Integrative Freshwater Ecology Group, Centre d’Estudis Avançats de Blanes (CEAB-CSIC), 17300 Blanes, Spain.
  • 4CREAF. Campus de Bellaterra Edifici C, 08193, Cerdanyola del Vallès, Catalonia, Spain.
  • 5CSIC, Global Ecology Unit CREAF-CSIC-UAB, E-08913 Bellaterra, Catalonia, Spain.
  • 6Departament de Biologia Evolutiva, Ecologia i Ciències Ambientals (BEECA), Universitat de Barcelona. Av. Diagonal 643, 08028, Barcelona, Spain.

The increase of greenhouse gas (GHG) emissions into the atmosphere is promoting and accelerating climate warming. Among GHG sources, soils are an important natural source of GHG to the atmosphere through aerobic soil respiration that release carbon dioxide (CO2). However, in riparian areas, soils can also release relevant amounts of methane (CH4) and nitrous oxide (N2O) through anaerobic processes promoted by high groundwater levels or flooded conditions. Recent studies have highlighted the role of trees in CH4 emissions, but little is still known about the origin of these emissions, the processes involved, and their contribution to the global carbon and nitrogen cycles. To shed light on this issue, we measured GHG emissions (i.e. CO2, CH4, and N2O) from the stems of two riparian tree species (Fraxinus agustifolia and Quercus robur) located along a gradient of soil moisture conditions (i.e. from wet to completely flooded soils) in a Mediterranean floodplain forest. Moreover, we also analyzed the isotopic carbon signature of the GHG emitted and the microbial communities inhabiting within tree stems by 16S rRNA gene analysis. Our results showed that CH4 emitted by riparian tree stems was 100-fold higher at the flooded than at wet soil locations, while CO2 and N2O emissions did not vary across moisture conditions. When considering together emissions form soil surface and tree stems under flooded conditions, riparian trees contributed up to 20%, 40% and 60% of the total CH4, CO2, and N2O emissions, respectively. Keeling plots suggested that CO2 emitted through tree stems was produced within the soil compartment and thus transported to the atmosphere through the tree stems, whereas CH4 emissions may have a different origin. However, methanogens were almost absent on the wood microbiome. The substantially higher presence of methanotrophs on the wood than on the soil compartment suggested that, despite CH4 emitted by stems could come from soil microbial activity, the microbial consumption of that CH4 within the tree stem could have changed its isotopic signature. Overall, our findings suggest that the riparian trees growing in this Mediterranean floodplain forest may mainly act as passive transporters of GHG produced in soils instead of being active GHG producers.

How to cite: Poblador, S., Martínez-Sancho, E., Menéndez-Serra, M., Casamayor, E. O., Estiarte, M., Lupon, A., Martí, E., Peñuelas, J., Sabaté, S., and Sabater, F.: Greenhouse gas emissions from a Mediterranean floodplain forest: the role of tree emissions under a changing flooding regime., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19009,, 2020.