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

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 the soil–air gas exchange. In this work, we analyze greenhouse gas fluxes at the soil–air interface measured at the Fonovaya Observatory in 2023 with the use of three chambers, transparent and opaque chambers on soil areas with vegetation and a transparent chamber on soil without vegetation. A stable CO₂ and CH₄ sink throughout the growing season is shown. For carbon dioxide, on the contrary, a weak positive flux was observed. A steady sink of N₂O 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 about zero with the daily average within ± 0.02 mg m⁻² h⁻¹. For CO₂, a nonlinear positive relationship between the increase in vegetation respiration and soil temperature is revealed. Linear temperature dependence is found for methane fluxes in all three chambers, that is, an increase in soil temperature enhances CH₄ absorption. N₂O fluxes show very weak positive dependence on the soil temperature in both transparent chambers (with and without vegetation). The estimates of the contribution of CO₂ fluxes from the soil show that microbial respiration can contribute from 46.7 to 77.9% to the total grassland ecosystem respiration during nighttime. The daily average share of methane absorption by soil due to diffusion and oxidation by methanotrophs not associated with plants varies from 5.3 to 48.3%; it becomes smaller during the daytime and increases at night. The contribution of soil without vegetation to the total N₂O flux can attain 92.3%. The results expand knowledge about the soil–air gas exchange under changing climate conditions.