Rice paddies play a crucial role in the global carbon cycle by sequestering or releasing carbon dioxide (CO₂) into the atmosphere. However, the effects of net CO₂ exchange in paddy fields under elevated CO₂ concentrations (e[CO₂]) have rarely been assessed in previous literature. In this study, a four-year field experiment (2018‒2021) was conducted to understand the effects of e[CO₂] on the CO₂ flux in paddy fields. The experimental treatments included environmental [CO₂] (CK) and 200 µmol mol^–1 above the environmental [CO₂] (T). A static chamber and a laser greenhouse gas analyzer were used to measure the net CO₂ uptake and ecosystem respiration. Moreover, the relationships between CO₂ flux and environmental variables, plants, and soil factors were analyzed during the rice-growing season. The results showed that the T treatment did not change the diurnal and seasonal dynamics of CO₂ flux in paddy fields compared with CK. However, T treatment significantly promoted net CO₂ uptake, where the seasonal cumulative amount of net CO₂ exchange (CAC) of the T treatment was 1.13‒1.25 times that of CK treatment over the four-year rice growth period. Net CO₂ exchange was significantly correlated with photosynthetically active radiation (PAR), relative humidity, air temperature (Ta), soil temperature, and soil water content, and path analysis indicated that net CO₂ exchange variations were mainly controlled by PAR and Ta. Furthermore, e[CO₂] increased CH₄–C/CO₂-C over the four rice-growing seasons. Overall, our findings revealed that e[CO₂] had a positive impact on net CO₂ exchange, enhanced the capability of paddy fields as a net carbon sink, and also promoted carbon emission to the atmosphere in the form of CH₄ from paddy fields.

稻田通过封存或释放二氧化碳(CO ₂ )到大气中，在全球碳循环中发挥着至关重要的作用。然而，以往的文献很少评估高CO ₂浓度(e[CO ₂ ])下稻田净CO ₂交换的影响。_{本研究通过为期四年（2018-2021）的田间试验来了解e[CO 2} ]对稻田CO ₂通量的影响。实验处理包括环境 [CO ₂ ] (CK) 和高于环境 [CO _{2 ] 200 µmol mol} ^–1]（T）。使用静态室和激光温室气体分析仪来测量净CO ₂吸收和生态系统呼吸。此外，还分析了水稻生长季节CO ₂通量与环境变量、植物和土壤因子之间的关系。结果表明，与CK相比，T处理没有改变稻田CO _{2通量的日和季节动态。}而T处理显着促进了CO ₂净吸收，在水稻四年生育期内，T处理的季节性累积净CO ₂交换量（CAC）是CK处理的1.13~1.25倍。净CO ₂交换与光合有效辐射(PAR)、相对湿度、气温(Ta)、土壤温度和土壤含水量显着相关，通径分析表明净CO 2 交换变化主要受_PAR和Ta控制。此外，e[CO ₂ ]在四个水稻生长季节增加了 CH ₄ –C/CO _{2 -C。}总体而言，我们的研究结果表明，e[CO _{2 ]对CO 2}净交换具有积极影响，增强了稻田作为净碳汇的能力，并促进了稻田以CH 4 形式向大气排放碳_。。