Methane Dynamics of Kettle Holes in a Postglacial Agricultural Landscape –Microbial Ecology and Biogeochemistry (Acronym: MeDKet)

• Applicants: Professorin Dr. Claudia Knief, since 4/2023; Professor Dr. Steffen Kolb
• Subject Area: Soil Sciences
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 465808595

Wetlands represent a major natural source of methane, which is the second most abundant greenhouse gas in the atmosphere. Methane fluxes of wetlands are dynamic in space and time and are linked to the activity of methanotrophic (methane consuming) and methanogenic (methane producing) microorganisms. The activity of these microorganisms is controlled by diverse environmental factors, but this is not well understood, because e.g. the quantitative relevance of anaerobic methanotrophs remains largely unclear. The aim of this project is to study the spatiotemporal variation of net methane fluxes and explain it by distribution patterns and activities of methane-cycling microorganisms in dependence on different environmental factors. We will conduct our studies on kettle holes, as these show a high spatio-temporal variability in methane emissions at small scale. Kettle holes occur frequently in postglacial landscapes and are often surrounded by agricultural land. They are considered as methane source, but the mechanisms driving their dynamic surface methane fluxes are not well understood. Soil profile, soil chemistry, water level, redox conditions, nutrient input and vegetation are anticipated as key environmental factors that influence the abundance, activity and community composition of the methane-cycling microorganisms. To understand the regulatory importance of these factors, MeDKet will combine field studies with laboratory experiments, in which different abiotic factors will be modulated under controlled conditions. The spatial variation of methane formation and consumption as well as the composition of methane-associated microorganisms will be assessed in eight kettle holes, while the impact of the most relevant environmental factors will be studied in detail for one kettle hole. High-resolution gas measurements will be combined with methods of microbial ecology using quantitative PCR, amplicon sequencing, mRNA analysis, stable isotope probing and metagenome analysis to identify and quantify methane-cycling microorganisms, describe their dynamics and distribution, and to resolve their physiological traits. As we aim at a holistic understanding regarding the contribution of methane-cycling microorganisms in kettle holes to methane fluxes, we extent our analyses to aboveground plant parts, a habitat of methanotrophs that has been largely neglected so far. We will use a newly developed approach to measure vertical methane profiles in the atmosphere above the kettle hole and evaluate the presence of methanotrophs on aboveground plant parts. In summary, the results of MeDKet will serve as a valuable basis to (a) understand the regulation of methanotrophy and methanogenesis and thus the high variability of net methane fluxes (b) assess thereby the role of anaerobic methane oxidizers and (c) the role of above-ground methane oxidation in agriculturally impacted wetlands of the Northern hemisphere.

• DFG Programme: Research Grants
• Co-Investigators: Professor Dr. Jürgen Augustin; Dr. Mathias Hoffmann
• Ehemalige Antragstellerin: Dr. Katharina Frindte, until 4/2023