Sensitivity Analysis of N2O and CH4 Emissions in a Winter Wheat–Rice Double Cropping System

The sensitivity of model outputs to parameter variations is crucial for effective model calibration and application. This study assessed the sensitivity of N2O and CH4 emissions to varying weather conditions and fertilization practices in a winter wheat–rice cropping system. Using the Sobol first-order sensitivity index within the SPACSYS model, key parameters and input variables influencing gas emissions were identified. The results showed that the index effectively detected highly sensitive parameters, particularly those related to soil water content, oxygen dynamics and microbial processes. Both N2O and CH4 emissions were sensitive to carbon availability and soil oxygen levels. For N2O emissions, microbial process parameters and soil water content had substantial impacts, whereas CH4 emissions were more responsive to methane consumption, oxygen levels, and carbon substrates. Fertilization, rainfall and temperature showed high sensitivity for N2O emissions, while temperature emerged as the dominant factor controlling CH4 emissions. The identified parameters offer valuable insights for improving model performance and informing strategies to mitigate greenhouse gas emissions.