Fig. 2. Comparison of simulation performance in calibration,NRMSE (a) and R 2 (b), in which the uncertain parameters in GECROS were calibrated with different upper bounds of the heteroscedasticity parameter \(\sigma_{1}\).W above, aboveground biomass;W grain, grain weight;W leaf, leaf weight;N above, aboveground N content;N grain, grain N content;N leaf, leaf N content in the canopy; and LAI, leaf area index.