Shi Yuan-Zhi, Cui Yuan-Lai, Cai Shuo, Hong Da-Lin, Cheng Jie
State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Nanjing Hydraulic Research Institute, Nanjing 210029, China.
State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan 430072, China.
Huan Jing Ke Xue. 2023 Mar 8;44(3):1572-1582. doi: 10.13227/j.hjkx.202204119.
Paddy fields are complex ecosystems that both emit CH and absorb CO, which plays an important role in the global water-carbon cycle and carbon budget. In this study, the CH fluxes and CO fluxes of double-cropping direct-seeded rice fields in 2020 in the Poyang Lake Plain were obtained using the eddy covariance method, and the variation characteristics, accumulation in the whole growth period, and comprehensive greenhouse effects of two greenhouse gases were quantitatively revealed. The results showed that, the double-cropping direct-seeded rice field in Poyang Lake Plain was the source of CH emission, and the emission during the whole growth period was 52.6 g·m, with an average daily emission of 0.208 g·(m·d). CH emission and daily average emission in the early rice season were 20.7 g·m and 0.188 g·(m·d), respectively, which were lower than the emissions of 31.9 g·m and 0.255 g·(m·d) in the late rice season. CH flux had significant seasonal variation characteristics. The strong emission period (emission peak) of CH was concentrated in the middle growth stage of early rice and the early growth stage of late rice. A total of 85.5% of CH in the early rice season and 92.1% of CH in the late rice season were released during the strong emission periods, and seasonal peak values were 0.638 g·(m·d) and 1.282 g·(m·d), respectively. The diurnal variation characteristics of CH flux showed three types:obvious unimodal type, non-obvious unimodal type, and irregular type. The strong emission period was mainly the unimodal type, and the peak values of 0.453 μmol·(m·s) in the early rice season and 0.977 μmol·(m·s) in the late rice season appeared at 14:00-15:00 and maintained a high emission rate at 12:30-16:00. The CO accumulation in the whole growth period of early rice and late rice was -990.4 g·m and -1156.6 g·m, respectively, and the total was -2147.0 g·m. The comprehensive greenhouse effect of CH emission and CO exchange in the double-cropping paddy field was -673.6 g·m (calculated using the CO equivalent), which showed a cooling effect. Excluding CH emissions when evaluating the greenhouse effect of the paddy field, the CO equivalent emission of 1473.4 g·m would be underestimated, accounting for 68.6% of the net CO absorption. Considering CH emissions, CO exchanges, and carbon emissions caused by rice harvest, the two-season direct seeding paddy field in Poyang Lake Plain was the source of greenhouse gas emissions.
稻田是复杂的生态系统，既排放CH又吸收CO，这在全球水 - 碳循环和碳收支中起着重要作用。本研究采用涡度相关法获取了2020年鄱阳湖平原双季直播稻田的CH通量和CO通量，并定量揭示了两种温室气体的变化特征、全生育期累积量及综合温室效应。结果表明，鄱阳湖平原双季直播稻田是CH排放源，全生育期排放量为52.6 g·m ，日均排放量为0.208 g·(m·d)。早稻季CH排放量和日均排放量分别为20.7 g·m 和0.188 g·(m·d)，低于晚稻季的31.9 g·m 和0.255 g·(m·d)。CH通量具有明显的季节变化特征。CH的强排放期（排放峰值）集中在早稻生育中期和晚稻生育前期。早稻季85.5%的CH和晚稻季92.1%的CH在强排放期释放，季节峰值分别为0.638 g·(m·d)和1.282 g·(m·d)。CH通量的日变化特征表现为明显单峰型、不明显单峰型和不规则型三种类型。强排放期主要为单峰型，早稻季峰值0.453 μmol·(m·s)和晚稻季峰值0.977 μmol·(m·s)分别出现在14:00 - 15:00，并在12:30 - 16:00保持较高排放速率。早稻和晚稻全生育期CO累积量分别为 - 990.4 g·m 和 - 1156.6 g·m ，总量为 - 2147.0 g·m 。双季稻田CH排放和CO交换的综合温室效应为 - 673.6 g·m （以CO当量计算），呈现降温效应。在评估稻田温室效应时排除CH排放，会低估1473.4 g·m 的CO当量排放，占净CO吸收量的68.6%。考虑CH排放、CO交换以及水稻收获引起的碳排放，鄱阳湖平原双季直播稻田是温室气体排放源。
