Specific Methane Fluxes in Upland Soils of Natural and Agricultural Ecosystems of the Forest-Steppe Biome of the European Territory of Russia

Abstract— There is still an obvious lack of field observations of specific methane fluxes in the upland agricultural landscapes of the European territory of Russia (ETR). We compared the rates of specific methane fluxes in soils of different ecosystems in various geographical regions within the forest-steppe biome of the ETR. Four regions located within the biome from southwest to northeast (Kursk, Tula, Ryazan oblasts, and Chuvashia) and seven types of upland ecosystems (croplands, pastures, hayfields, grasslands, forests, stockyards, compost storages) were studied. The research was conducted annually in 2021−2025, during the maximum of growing seasons using the closed-chamber technique and gas chromatography. Stockyards and compost storages are powerful sources of methane to the atmosphere (6.6−57.1 and 11.2−548.4 mg C−CH4/(m2 h), respectively). Pastures can act as both sinks and sources of methane between −0.036 and 0.115 mg C−CH4/(m2 h). Upon cattle grazing pressure of <1 head/ha, and aboveground phytomass >1 t C/ha, they act as net methane sinks from the atmosphere; with a higher pressure, they act as methane sources to the atmosphere. Croplands (−0.026…−0.052 mg C−CH4/(m2 h)), hayfields (−0.025…−0.058), grasslands (−0.026…−0.086), and broadleaved forests (−0.059… −0.120) act as small but permanent CH4 sinks from the atmosphere. Weighed mean rate of methane consumption by upland soils of the forest-steppe biome is −0.046 ± 0.005 mg C−CH4/(m2 h). Methane uptake specific rate is positively dependent on the soil organic carbon and total nitrogen contents (r = 0.543−0.670, p < 0.05). Geographical location (10.0% of total variance), ecosystem type (21.5%) and their interaction (12.3%) significantly affect methane fluxes. Depending on relative area of stockyards and compost storages within a territory, the CH4-budget of the particular agricultural enterprise within the biome can be either a sink or a source to the atmosphere, which provides an opportunity to regulate its local effect on climate.