Microbial regulation of greenhouse gas formation in thawing permafrost

Work package 3 investigates the microbial decomposition processes of organic matter in permafrost-affected soils. When currently frozen soils thaw, new sources of organic matter will become accessible to microorganisms, who will decompose the organic matter to carbon dioxide and methane. There are three main foci in work package 3 but the overarching focus of all investigation is on soils, which are particularly vulnerable to warming-induced environmental changes and thermo-erosion.

© J. Walz: Thermo-erosional landscape in Sibiria

The Institute of Soil Science conducts a series of long-term incubations to quantify carbon dioxide and methane production under laboratory conditions. These data are necessary for realistic projections of greenhouse gas fluxes from thawing permafrost, which are modeled in work package 2. Furthermore, greenhouse gas production is quantified under natural field conditions in conjunction with work package 4 in order to upscale these fluxes to the landscape-scale. One central question is the contribution of methane to the total turnover.

Methane production (CH4) in permafrost from Kurungnakh Island was only observed afteractive methanogens were added after 2500 incubation days (Knoblauch et al., Nat. Clim. Change 2018).

The University of Cologne measures 14C-signatures of carbon dioxide and methane in order determine the age of the decomposed organic matter and to identify the main sources of carbon. From these data, conclusion can be drawn about how much the fossil organic matter, which was accumulated hundreds to thousands of years ago, is microbially decomposed.

The German Research Centre for Geosciences in Potsdam examines the microbial communities, which are involved in organic matter decomposition processes. An important aspect hereby is the re-activation of currently dormant microorganisms, which were frozen in the permafrost. A better understanding of microbial functions and the long-term adaptation to warming-induced environmental changes will improve the predictability of the formation and release of climate-relevant greenhouse gases from thawing permafrost.

Goals and milestones:

  • Characterization permafrost-affected soils and sediment properties which are affected by permafrost degradation with varying degree
  • Quantification of carbon dioxide and methane production under laboratory and field conditions
  • Radiocarbon dating of the produced greenhouse gases
  • Quantification of microbial decomposition rates of carbon poos with varying ages
  • Characterization of abundance, diversity, and function of active microorganisms during carbon transformation processes in the seasonally thawed active layer and the permanently frozen permafrost
  • Examination microbial communities adaptations during and after permafrost degradation and their role for the formation of carbon dioxide and methane

German applicants:

  • Dr. Christian Knoblauch (Universität Hamburg)
  • Prof. Dr. Eva-Maria Pfeiffer (Universität Hamburg)
  • Prof. Dr. Janet Rethemeyer (University of Cologne)
  • Prof. Dr. Susanne Liebner (German Centre for Geosciences)

Project employees:

  • Dr. Tim Eckhardt (Universität Hamburg)
  • Scientist (University of Cologne)
  • Scientist (German Centre for Geosciences)

Russian partners:

  • Prof. Dr. Evgeny Abakumov (Saint Petersburg State University)
  • Dr. Pavel A. Barsukov (Institute of Soil Science and Agrochemistry of the Siberian Branch of the Russian Academy of Sciences in Novosibirsk)
  • Dr. Elizaveta Rivkina (Institute of physicochemical and biological problems in soil science of the Russian Academy of Sciences in Pushchino)

News

Publication

The decomposition of eddy covariance-based CO2 fluxes into respiration and photosynthesis was not only applied for the overall footprint as commonly carried out, but instead for each of two vegetation classes. In this way, a differing seasonality in the net uptakes of bushes and sedges could be unveiled. Therefore, the flux decomposition proved to be a useful tool for gaining insights into both the phenological dynamic of individual vegetation classes, plus their respective functional flux to flux driver relationships with the aid of ecophysiologically interpretable parameters (Rößger et al., 2019, Biogeosciences Discuss).

20 Years Lena Expedition

German and Russian scientists, technicians, and students will meet in Saint Petersburg from October 17-19 to celebrate 20 years of successful cooperation in the Lena River Delta and Laptev Sea region. Future expeditions and joint research strategies will also be discussed. The meeting is organized by the Arctic and Antarctic Research Institute in Saint Petersburg, the Alfred Wegener Institute in Potsdam, the Melnikov Permafrost Institute in Yakutsk, and the Institute of Soil Science in Hamburg.

© T. Eckhardt: The "old" research station on Samoylov Island

Publication

Partitioning of CO2 net ecosystem exchange on the microsite scale in the Lena River Delta shows that both polygon centers and polygon rims were sinks for atmospheric CO2 during a growing season, but the sink strengths varied between the two microsites. Furthermore, it was shown that autotrophic and heterotrophic respiration fluxes react differently to changing hydrologic conditions (Eckhardt et al. Biogeoscience Discuss. 2018)

Publication

Greenhouse gas production in degrading ice-rich permafrost deposits in northeast Siberia depends on the climate conditions during deposition. Late Pleistocene Yedoma deposits generally produced more CO2 than Holocene deposits. Thus, organic matter decomposability needs to be interpreted against the paleo-environmental background. However, organic matter decomposability cannot be generalized solely based on the stratigraphic position (Walz et al. Biogeoscience 2018)