Long-term measurements gases fluxes from the wetland ecosystems (Plotnikovo field station, Bakchar Bog)

The use of automated systems when studying greenhouse gases (GHG) fluxes allows accurate measurements at minimal disturbance of the soil surface to be carried out and high resolution datasets for extended periods of time to be obtained. Due to the above advantages, chamber measurements play an important role while establishing long-term observations in the framework of such research infrastructures as Integrated Carbon Observation System (ICOS). CO2 and CH4 fluxes from Bakchar bog nearby Plotnikovo, West Siberia, were measured by means of a solar powered automated system (Flux-NIES) consisted of six static chambers installed along the transect and connected to the LI-820 NDIR analyzer and modified commercial methane sensor TGS-842, respectively. The water vapor can significantly affect the measurement accuracy of most gas-analyzers. It is recommended the ambient air to be completely or moderately dehumidified before supplying it to a measurement cell. We used a three-stage drying unit before supplying the air sample to the analyzers: an auto drain water trap, the Nafion dryer, and the chemical desiccants. The least square adjustment method with determining the linearity of the process by the pair correlation coefficient R was applied with the purpose of the most accurate determination of the gases fluxes value when processing changes in the output signals of the gas-analyzers in the closed chamber mode. The width of the data filtering window was determined by the maximum value of R² which corresponded to the highest values of the detected emission / uptake of the studied GHG at the soil - atmosphere boundary. Observations were carried out during the growing season (from May to October) in 2016-2020 at the hollow-ridge complex (O-site) oligotrophic bog. Correlation analysis made it possible to derive the dependences of CO2 and CH4 fluxes on the local hydrometeorological conditions of the surface. The seasonally integrated net СО2 uptake shows that Siberian wetland ecosystems are a strong sink of atmospheric carbon. Gases fluxes were correlated spatially: higher net uptake CO2 and lower CH4 emissions are observed at forested ridge with higher photosynthesis and respiration rates and drier surface conditions; lower net uptake CO2 and higher CH4 emissions were observed into wet hollow landscape. Constant high emission for CO2 and CH4 were observed on the surface tiny bog lake.

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