Novel multimodel ensemble approach to evaluate the sole effect of elevated CO₂ on winter wheat productivity

Elevated carbon-dioxide concentration [eCO₂] is a key climate change factor affecting plant growth and yield. Conventionally, crop modeling work has evaluated the effect of climatic parameters on crop growth, without considering CO₂. It is conjectured that a novel multimodal ensemble approach may improve the accuracy of modelled responses to eCO₂. To demonstrate the applicability of a multimodel ensemble of crop models to simulation of eCO₂, APSIM, CropSyst, DSSAT, EPIC and STICS were calibrated to observed data for crop phenology, biomass and yield. Significant variability in simulated biomass production was shown among the models particularly at dryland sites (44%) compared to the irrigated site (22%). Increased yield was observed for all models with the highest average yield at dryland site by EPIC (49%) and lowest under irrigated conditions (17%) by APSIM and CropSyst. For the ensemble, maximum yield was 45% for the dryland site and a minimum 22% at the irrigated site. We concluded from our study that process-based crop models have variability in the simulation of crop response to [eCO₂] with greater difference under water-stressed conditions. We recommend the use of ensembles to improve accuracy in modeled responses to [eCO₂].