河源区土壤与河流二氧化碳浓度变化特征及相关性

With the objective to characterize CO₂ dynamics from soil to streams, and to identify relevant influential factors along with temporal evolution patterns, this study established a high-frequency CO₂ concentration monitoring transect with four measuring points in a stream and adjacent soil located in the upper reach of the Hailiutu River Basin in Yulin city, Shannxi province. With the spectrum and wavelet analysis, strong diurnal signals with periods of 0.5 and 1d frequencies are identified based on the CO₂ concentration time series, indicating that the diurnal stream metabolism plays a key role in regulating in-stream CO₂ dynamics. Additionally, variations in hydrological events, i.e. precipitation in the catchment, may lead to prominent changes in CO₂ evasion, which has a significant impact on the carbon cycling between stream and soil. Bivariate wavelet coherence analysis reveals that temperature and soil water content directly control stream and soil CO₂ dynamics, and confirms that soil-stored CO₂ is the main source of the stream CO₂ evasion. Further, the results indicate that groundwater is an important pathway for carbon transport from soil to streams.