Purpose To study the dynamics of carbon sequestration in the paddy ecosystem, providing a basis for formulating and promoting measures of carbon sequestration and emission reduction in cultivated land.
Methods Based on the data of three-year controlled experiments in paddy fields, the denitrification-decomposition (DNDC) model were verified. The carbon sequestration in paddy ecosystems of China during 2018 to 2020 was estimated by DNDC; the spatial and temporal distributions of soil and crop carbon sequestration in paddy ecosystem of China were analysed; the contribution of farmland ecosystems to achieve carbon neutrality was evaluated.
Results The rice yield and soil organic carbon content simulated by DNDC model were in good agreement with the field observations (correlation coefficients were higher than or equal to 0.77, mean absolute error and normalized root mean square error were lower than 13%). The total carbon sequestration of rice paddy in China was 523.29 Tg from 2018 to 2020, and the crop contributed more than 97% of the total carbon sequestration. The regions with higher carbon sequestration for double cropping rice were Jiangxi, Hunan, Guangdong and Guangxi, while the regions with lower carbon sequestration for double cropping rice were Yunnan, Zhejiang and Hainan. The carbon sequestration of single cropping rice was lower in the south and higher in the north, with higher carbon sequestration in Heilongjiang, Jiangsu and Hubei. The carbon sequestration of double cropping rice in Hunan, Fujian, Jiangxi and Guangxi was higher than that of single cropping rice, and the carbon sequestration of double cropping rice accounted for more than 60% of the total carbon sequestration.
Conclusion The DNDC model can be used to simulate carbon budgets in the rice paddy ecosystem. The Chinese paddy fields play an important role in carbon sequestration, with a strong spatial variation.
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