Abstract
In recent years, carbon emission research has been receiving increasing attention. China has put forward the strategic goal of achieving a carbon emission peak by 2030. Hence this research is very important for the measurement of greenhouse gas emissions in China. CO2 and CH4 fluxes from a paddy field in the middle-lower Yangtze Plain in China were analyzed based on the eddy covariance technique. The CO2 flux showed an "U" curve during the observation period, with an average flux of -3.33 μmol·(m2·s)-1, which was a sink. Negative values appeared at the tillering stage, and the minimum was shown at the heading period. The CH4 flux trend was roughly opposite to the that of the CO2 flux, which first increased and then decreased. It raised rapidly during the tillering and jointing stages and then dropped rapidly from the peak to the trough during the booting stage, and only a slight increase was found in the blooming stage. The maximum flux[0.40 μmol·(m2·s)-1] appeared at the beginning of the booting stage and the end of the jointing stage, and the average flux was 0.11 μmol·(m2·s)-1. The CO2 flux was positive at night and negative during the day. It decreased from 07:00 and reached a minimum around 13:00 at -16.01 μmol·(m2·s)-1. The CH4 flux was low at night and high during the daytime. It increased at 06:00 and reached a peak around 14:00, at approximately 0.16 μmol·(m2·s)-1. An exponential correlation was found between air temperature and CH4 flux. The vapor pressure deficit showed a linear correlation with CH4 flux. The response of environmental factors on CO2 fluxes and CH4 fluxes on a diurnal scale was greater than that on a seasonal scale, and the daytime response was greater than that at night. CH4 flux decreased significantly with the increase in CO2 flux on the diurnal scale, but the correlation was not obvious on the seasonal scale. The increased CH4 flux slowed down after fertilizing.
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