Dynamic Changes in Carbon Fluxes of the Boreal Coniferous Forests of China and Influencing Factor Analysis

The long-term temporal dynamics of carbon fluxes and their influencing factors in this ecosystem investigated by utilizing observational data collected from the Huzhong Positioning Observatory, located at a typical site in boreal coniferous forests in China from 2014 to 2018. The results indicate that the Net Ecosystem Exchange (NEE) in boreal coniferous forests exhibits significant interannual variability, ranging between 2.64 g(C) m⁻² a⁻¹ and 17.63 g(C) m⁻² a⁻¹. This variability is attributed to the interplay of Gross Primary Productivity (GPP) and Ecosystem Respiration (RE). The results also reveal that during the growing season (June–August), GPP exceeds RE, leading to net carbon absorption in the forests. Meanwhile, during the nongrowing season, NEE equals RE, positioning boreal coniferous forests as weak carbon sources. At the daily scale, the trend of NEE variation exhibits an inverted “U” shape, while those of RE and GPP show a “U” shape. The study identifies key factors such as Net Radiation (RN), Relative Humidity (RH), Air Temperature (TA), and Soil Temperature (TS) as primary influencers of daily NEE variations. A regression equation incorporating these environmental factors accounts for 45.19% of the daily NEE variations. At the monthly scale, NEE is primarily influenced by RN, RH, and TA. A regression equation incorporating these environmental factors accounts for 78.42% of the monthly NEE variations.