Modeling nitrous oxide emissions from agricultural soil incubation experiments using CoupModel

[摘要] Efforts to develop effective climate mitigationstrategies for agriculture require methods to estimate nitrous oxide(N 2 O) emissions from soil. Process-based biogeochemical models havebeen often used for field- and large-scale estimates, while the sensitivityand uncertainty of model applications to incubation experiments are lessinvestigated. In this study, a process-oriented model (CoupModel) was usedto simulate N 2 O and CO 2 fluxes and soil mineral nitrogen (N)contents in a short-term (43 d) factorial incubation experiment (16treatments). A global sensitivity analysis (GSA) approach, “Morrisscreening”, was applied to quantify parameter sensitivity. The GSAsuggested that a higher number of sensitive parameters was associated withN 2 O flux estimates and that inter-treatment variations in parametersensitivities were distinguished by soil moisture levels or NO 3 - content and residue types. Important parameters regarding N 2 O fluxestimates were linked to the decomposability of soil organic matter (e.g.,organic C pool sizes) and the denitrification process (e.g., Michaelisconstant and denitrifier respiratory rates). After calibration, the modelbetter captured temporal variations and magnitude of gas fluxes and mineralN in unamended soils than in residue-amended soils. Low-magnitude daily andcumulative N 2 O fluxes were well simulated with mean errors (MEs) closeto zero, but the model tended to underestimate N 2 O fluxes, as observeddaily values increased by over 0.1 g N m −2  d −1 , in which the majormismatch was due to limited success of the model to describe the highemissions during the first few days after crop residue addition. A largeruncertainty was also seen in the magnitude of pulse emissions by theposterior simulations. We also evaluated ancillary variables regarding Ncycling, which indicated that more frequent measurements and additionaltypes of observed data such as soil oxygen content and the microbial sourcesof emitted N 2 O are required to further evaluate model performance andbiases. The major challenges for calibration were associated with highsensitivities of denitrification parameters to initial soil abioticconditions and the instantaneous residue amendment. Model structureuncertainties and improved modeling practices in the context of incubationexperiments were discussed.

[学科分类] 大气科学