EGU21-137
https://doi.org/10.5194/egusphere-egu21-137
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

CH4 and CO2 fluxes at sites with different hydrological patterns in the polygonal tundra of Samoylov Island, Northeastern Siberia

Leonardo de Aro Galera, Christian Knoblauch, Tim Eckhardt, Christian Beer, and Eva-Maria Pfeiffer
Leonardo de Aro Galera et al.
  • Universität Hamburg, Institut für Bodenkunde, Germany (leonardo.galera@uni-hamburg.de)

In the last two decades, there were registered record high permafrost temperatures promoting permafrost thawing and leading to additional CO2 and CH4 emissions. It is crucial to assess the amount of C that is mineralized to CH4, due to its higher global warming potential (GWP) compared to CO2. The role of CH4 in the total C emissions is mainly governed by the hydrological patterns of ecosystems. CH4 oxidation is another critical process and is largely controlled by vegetation. The soil CO2:CH4 production ratio shows the contribution of CH4 to the C emission budget of a determined area. Few studies evaluated in situ CO2:CH4 production ratios. Our objective was to assess CH4 emissions and the heterotrophic CO2:CH4 production ratios in the Siberian tundra during the growing season. To accomplish these goals, we measured CH4 and CO2 fluxes using the chamber technique in the polygonal tundra of Samoylov Island in the Lena River Delta, Northeastern Siberia. The plant-mediated CH4 transport and the heterotrophic respiration (Rh) were determined by comparing plots with and without vegetation through a trenching experiment. To account for the differences between wet and dry tundra, one representative polygon was selected, measurements were made at its water-saturated center and at its drained rim. We also estimated the C budget of the polygonal tundra of Samoylov Island during the measurement period. This is the first study measuring and calculating in situ CO2:CH4 ratios from the Rh of the soil. The CH4 emissions at the polygon center were much higher than the rim and showed evident seasonality. The polygon center median CH4 flux of 26 mg.m-2.d-1 decreased by 80% when the vegetation was removed, indicating the relevance of plant-mediated CH4 transport in these emissions. This was not detected at the polygon rim that had much lower emissions (1.8 mg.m-2.d-1). The heterotrophic CO2:CH4 ratios varied from 1 to 100 at the polygon center, and from 100 to 1000 at the polygon rim, showing the greater importance of CH4 production to the heterotrophic C release at the polygon center. The polygonal tundra on Samoylov Island was a C sink during the measurement period. The wet tundra had a CO2-C sequestration rate (-23 kg CO2-C.ha-1.d-1) more than 3 times higher than the dry tundra (-7 kg CO2-C.ha-1.d-1). Overall, the CH4 emissions represent a decrease of just 5% in the total CO2-e offset of the tundra in Samoylov during the growing season. The CH4 emissions measured in this study were low. However, it is important to point out that only the growing season is considered, and the off-season and winter C emissions might be significant. Our results stress the high microscale variability of emissions of CO2 and CH4, specially related to hydrology, topography, and vegetation.

How to cite: Galera, L. D. A., Knoblauch, C., Eckhardt, T., Beer, C., and Pfeiffer, E.-M.: CH4 and CO2 fluxes at sites with different hydrological patterns in the polygonal tundra of Samoylov Island, Northeastern Siberia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-137, https://doi.org/10.5194/egusphere-egu21-137, 2020.

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