Sensitivity analysis for models of greenhouse gas emissions at farm level. Case study of N 2O emissions simulated by the CERES-EGC model

Abstract

Modelling complex systems such as farms often requires quantification of a large number of input factors. Sensitivity analyses are useful to reduce the number of input factors that are required to be measured or estimated accurately. Three methods of sensitivity analysis (the Morris method, the rank regression and correlation method and the Extended Fourier Amplitude Sensitivity Test method) were compared in the case of the CERES-EGC model applied to crops of a dairy farm. The qualitative Morris method provided a screening of the input factors. The two other quantitative methods were used to investigate more thoroughly the effects of input factors on output variables. Despite differences in terms of concepts and assumptions, the three methods provided similar results. Among the 44 factors under study, N 2O emissions were mainly sensitive to the fraction of N 2O emitted during denitrification, the maximum rate of nitrification, the soil bulk density and the cropland area.