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Based on the morphological analysis techniques developed under the guidance of Yu.P. Pyt'ev, a method for filtering time series is proposed that is capable of detecting an almost cyclic component with a varying cycle length and varying series members within cycles. The effectiveness of the approach is illustrated as applied to decomposition of time series of atmospheric СО2 concentrations. After filtering out the series component responsible for diurnal variability, the series residual becomes stationary, so mathematical statistical methods and Fourier analysis can be used for its further investigation. The results are verified by comparing them with Fourier analysis data. A cyclicity with a period longer than one day is studied using Fourier expansion and wavelet analysis of the original series. [ABSTRACT FROM AUTHOR]

Forest disturbances induced by clear-cutting (CC) lead to the transformation of the natural biogeochemical processes determining the main greenhouse gas fluxes (primarily CO2) between forest ecosystems and the atmosphere. Effects of CC on CO2 exchange substantially vary depending on local environmental and climate conditions. This study focuses on an estimation of the net ecosystem exchange of СО2 (NEE), gross primary production (GPP), and total ecosystem respiration (TER) and soil respiration in the southern taiga in European Russia. The results are based on continuous eddy covariance measurements during two growing seasons (2016 and 2017). The research has shown that CC was a consistent source of CO2 for the atmosphere during the first years following harvest (NEE from May to October is 553.3 gС m–2 in 2016 and 193.3 in 2017). Interannual variability of the cumulative NEE showed increase of GPP (777.5 gС m–2 in 2016 and 1020.5 gС m–2) and decrease of TER (1330.9 gС m–2 in 2016 and 1213.7 gС m–2 in 2017). The results of chamber measurements have shown that soil respiration in the midday hours in summer varied between 3.6 ± 0.7 and 11.8 ± 3.0 μmol m–2 s–1 in 2016 and between 6.0 ± 1.3 and 14.8 ± 3.5 μmol m–2 s–1 in 2017 at the different plots within the clear-cut site. The estimates of the cumulative GPP at the clear-cut in the southern taiga of European Russia exceed the GPP rates obtained previously in the other clear-cut forest ecosystems in boreal and subboreal ecozones. [ABSTRACT FROM AUTHOR]