Re-estimating methane emissions from Chinese paddy fields based on a regional empirical model and high-spatial-resolution data.

Quantifying methane (CH4) emissions from paddy fields is essential for evaluating the environmental risks of the paddy rice production system, and improving the accuracy of CH4 modeling is a key issue that needs to be addressed. Based on a database containing 835 field measurements, both single national and region-specific models were established to estimate CH4 emissions from paddy fields considering different environmental factors and management patterns using 70% of the measurements. The remaining 30% of the measurements were then used for model evaluation. The performance of the region-specific model was better than that of the single national model. The region-specific model could simulate CH4 emissions in an unbiased manner with R2 values of 0.15-0.70 and efficiency values of 11-60%. The paddy rice type, water regime, organic amendment, latitude, and soil characteristics (pH and bulk density) were identified as the main drivers in the models. By inputting the high-resolution spatial data of these drivers into the established model, the CH4 emissions from China's paddy fields were estimated to be 4.75 Tg in 2015, with a 95% confidence interval of 4.19-5.61 Tg. The results indicated that establishing and driving a region-specific model with high-resolution data can improve the estimation accuracy of CH4 emissions from paddy fields.