Emission and sink of greenhouse gases in the grassland ecosystem of southern taiga of Western Siberia: estimates of the contribution of soil flux component from observations of 2023
M.Yu. Arshinov, B.D. Belan, D.K. Davydov, A.V. Kozlov, A.V. Fofono
V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Science, Tomsk, Russia
Keywords: atmosphere, air, methane, nitrous oxide, flux, carbon dioxide, emission
Abstract
Modern changes in the global climate are accompanied by rising air and soil temperatures. How do they affect soil respiration and should we expect a change in greenhouse gas emissions? These questions cannot be answered without studying gas exchange between the soil and the atmosphere. In this paper, the analysis of the greenhouse gas fluxes at the soil-atmosphere interface observed at the Fonovaya Observatory in 2023 is presented. A stable CO2 and CH4 uptake throughout the growing season is shown. As for N2O, on the contrary, a weak positive flux was observed. A steady uptake of carbon dioxide from the atmosphere occurred from May to mid-August; its value attained -600 mg × m-2 × h-1 in June and July. The methane flux (sink) attained -0.08 mg × m-2 × h-1. The nitrous oxide flux fluctuated near zero with the daily average being within ± 0.02 mg × m-2 × h-1. For CO2, a nonlinear positive relationship between the increase in respiration of vegetation and soil temperature is revealed. Linear temperature dependences are found for methane fluxes in all three chambers, that is, an increase in soil temperature enhances CH4 uptake. N2O fluxes show very weak positive dependence on the soil temperature in both transparent chambers (with vegetation and without it). The estimates of the contribution of CO2 fluxes from the soil showed that during nighttime, microbial respiration can contribute from 46.7 to 77.9% to the total respiration of the grassland ecosystem. On average, the share of soil methane uptake per day due to diffusion and oxidation by methanotrophs not associated with plants varies from 5.3 to 48.3%. The contribution becomes smaller during the daytime and increases at night. The contribution of soil with removed vegetation to the total N2O emission can attain 92.3%. The results expand knowledge about soil-atmosphere gas exchange under changing climate conditions.
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