Abstract:

Based on the National Agricultural Environment Observation and Experiment Station of Xining ( Xining Station), the instantaneous CO₂ flux of farmland ecosystem in Qinghai Province was obtained by using eddy covariance technique. The data were processed by Eddypro, Tovi and other software to explore the variation characteristics and influencing factors of instantaneous carbon flux at different scales of farmland ecosystem. The results showed that the daily average values of instantaneous net ecosystem carbon flux NEE during crop growth period (April 1 to August 10) in Xining station of Qinghai-Tibet Plateau in 2022 and 2023 were −2.78µmol·m⁻²·s⁻¹ and −3.12µmol·m⁻²·s⁻¹, respectively. The cumulative net ecosystem carbon flux during the growth period was −1396.07g·m⁻² and −1564.79g·m⁻², respectively. The carbon sink in 2022 increased by 150.73g·m⁻² compared with that in 2023. The air temperature (TA), wind speed (WS), photosynthetically active radiation (PPFD) and net ecosystem carbon flux (NEE) were significantly correlated during the crop growth period in Xining station of Qinghai-Tibet Plateau from 2022 to 2023, and the correlation coefficients were all above 0.4. The order of correlation coefficients was air temperature (TA)>photosynthetically active radiation (PPFD)>wind speed (WS). Among them, photosynthetically active radiation ( PPFD ) had a promoting effect on carbon absorption; with the increase of temperature ( TA ), the absorption was promoted first and then inhibited. Wind speed (WS) had an inhibitory effect on carbon absorption. In summary, the net ecosystem of farmland in the wheat−rape rotation system in Qinghai Province from 2022 to 2023 was a carbon sink. Photosynthetically active radiation, air temperature and wind speed are the main influencing factors of the net ecosystem carbon flux of farmland in the wheat−rape rotation system in Qinghai province.

Key words: Net ecosystem carbon exchange, Carbon source, Carbon sink