| Summary: | Upland forest ecosystems are recognized as net sinks for atmospheric methane (CH<sub>4</sub>), one of the most impactful greenhouse gases. Biological methane uptake in these ecosystems occurs due to the activity of aerobic methanotrophic bacteria. Russia hosts one-fifth of the global forest area, with the most extensive forest landscapes located in West Siberia. Here, we report seasonal CH<sub>4</sub> flux measurements conducted in 2018 in three types of stands in West Siberian middle taiga–Siberian pine, Aspen, and mixed forests. High rates of methane uptake of up to −0.184 mg CH<sub>4</sub> m<sup>−2</sup> h<sup>−1</sup> were measured by a static chamber method, with an estimated total growing season consumption of 4.5 ± 0.5 kg CH<sub>4</sub> ha<sup>−1</sup>. Forest type had little to no effect on methane fluxes within each season. Soil methane oxidation rate ranged from 0 to 8.1 ng CH<sub>4</sub> g<sub>DW</sub><sup>−1</sup> h<sup>−1</sup> and was negatively related to water-filled pore space. The microbial soil communities were dominated by the <i>Alpha</i>- and <i>Gammaproteobacteria</i>, <i>Acidobacteriota</i> and <i>Actinobacteriota</i>. The major group of 16S rRNA gene reads from methanotrophs belonged to uncultivated <i>Beijerinckiaceae</i> bacteria. Molecular identification of methanotrophs based on retrieval of the <i>pmoA</i> gene confirmed that Upland Soil Cluster Alpha was the major bacterial group responsible for CH<sub>4</sub> oxidation.
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