As constituents of one of the vital agricultural ecosystems, paddy fields exert significant influence on the global carbon cycle. Therefore, conducting observations and simulations of CO
2 flux in rice paddy is of significant importance for gaining deeper insights into the functionality of agricultural ecosystems. This study utilized an eddy covariance system to observe and analyze the CO
2 flux in a rice paddy field in Eastern China and also introduced and parameterized the Jarvis multiplicative model to predict the CO
2 flux. Results indicate that throughout the observation period, the range of CO
2 flux in the paddy field was −0.1 to −38.4 μmol/(m
2·s), with a mean of −12.9 μmol/(m
2·s). The highest CO
2 flux occurred during the rice flowering period with peak photosynthetic activity and maximum CO
2 absorption. Diurnal variation in CO
2 flux exhibited a “U”-shaped curve, with flux reaching its peak absorption at 11:30. The CO
2 flux was notably higher in the morning than in the afternoon. The nocturnal CO
2 flux remained relatively stable, primarily originating from respiratory CO
2 emissions. The rice canopy CO
2 flux model was revised using boundary line analysis, elucidating that photosynthetically active radiation, temperature, vapor pressure deficit, phenological stage, time, and concentration are pivotal factors influencing CO
2 flux. The simulation of CO
2 flux using the parameterized model, compared with measured values, reveals the efficacy of the established parameter model in simulating rice CO
2 flux. This study holds significant importance in comprehending the carbon cycling process within paddy ecosystems, furnishing scientific grounds for future climate change and environmental management endeavors.
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