Autor:innen:
Lisa Kastenholz | University of Bonn, Institute of Crop Science and Resource Conservation (INRES), Molecular Biology of the Rhizosphere | Germany
Danica Kynast | Leibniz Centre for Agricultural Landscape Research (ZALF) | Germany
Prof. Dr. Steffen Kolb | Leibniz Centre for Agricultural Landscape Research (ZALF) | Germany
Prof. Dr. Michael Sommer | Leibniz Centre for Agricultural Landscape Research (ZALF) | Germany
Prof. Dr. Jürgen Augustin | Leibniz Centre for Agricultural Landscape Research (ZALF) | Germany
Prof. Dr. Claudia Knief | University of Bonn, Institute of Crop Science and Resource Conservation (INRES), Molecular Biology of the Rhizosphere | Germany
Dr. Katharina Frindte | University of Bonn, Institute of Crop Science and Resource Conservation (INRES), Molecular Biology of the Rhizosphere | Germany
Climate change is currently one of the greatest challenges facing mankind. Methane is among the most potent greenhouse gases with a 28- to 36-fold stronger global warming potential compared to carbon dioxide. Although the importance of wetlands as sources for atmospheric methane is known, the impact of small wetlands can hardly be estimated as well as their impact on the greenhouse gas budgets of the landscapes in which they are situated. Kettle holes are such small wetlands, mainly located in very hilly young moraine landscapes with intensive agricultural use. The extent of methane emissions and the underlying microbial processes leading to the release or oxidation of atmospheric methane remain largely unknown. We aim to gain insight into landscape related heterogeneities in methane oxidation potential and the corresponding methanotrophic communities. We analyzed soil samples from three transects spanning from agricultural hilltops over slopes down to an ephemerally flooded kettle hole (Christianenhof, Brandenburg). Potential methane oxidation rates at atmospheric methane concentrations and respiration rates were measured in microcosms. Interestingly, the potential atmospheric methane oxidation rates of the hilltop samples were as high as those in the kettle hole, while they tended toward zero in the slope samples. The same trend was found for respiration rates with 3-6 times higher values at hilltops and in the kettle holes compared to slope positions. For methanotrophic community analysis, DNA was extracted and amplicons were generated using the marker gene pmoA to analyze methanotrophic community composition. The communities varied due to topographic position and also between transects. Overall, upland soil cluster alpha was dominating at most sites, but on hilltops also upland soil cluster gamma was found, making the methanotrophic communities of hilltops most distinct from the ones in slope and kettle hole samples. Overall, potential methane oxidation rates and methanotrophic community composition turned out to be more spatially heterogenous in hilly agricultural landscapes than previously thought. Underlying soil traits that may contribute to this heterogeneity are currently under investigation. Overall, our findings indicate that spatial heterogeneity of landscapes should be considered when greenhouse gas budget estimates are performed in hilly landscapes.