Multimodal Ensemble Approach to Study Elevated CO2 Effects on Wheat Productivity.

Elevated carbon-dioxide concentration [eCO2] is key climate change factor affecting plant growth and yield. It results to the enhance photosynthesis and biomass production for C3 crops like wheat by increasing water use efficiency. Since most of the earlier crop modeling work was more focused on studying and quantifying the impact of temperature or combined interactive effect of climatic parameters on crop growth, development and yield and very few studies have focused on carbon dioxide alone. We present here novel multimodal ensemble approach to evaluate the performance of different process based crop models under different level of [eCO2] at variable climatic sites in US Pacific Northwest (PNW) which will help to bring/suggest accuracy in the models response to [eCO2]. APSIM ver. 7.7, CropSyst ver.4.19.06, DSSAT ver. 4.5, EPIC ver. 0810 and STICS ver.8.4 were calibrated to observed data for crop phenology, biomass and yield. After calibration, biomass and grain yield of winter wheat was simulated for [eCO2]. The simulated results by all models showed that [eCO2] resulted to the significant variability among models to simulate biomass at three different sites with highest (44%) production at water stress conditions i.e. Lind while under irrigated conditions (Moses Lake) increase in biomass was 22%. Similarly, average yield increase under water stress among all models from ambient CO2 concentration to 1000 µmol mol-1 was 45% comparatively higher than high rainfall site where it was 34% while under irrigated conditions it remained 22% which was almost 50% less then dryland site (Lind). We concluded from our study that process based crop models have variability in the simulation of crop response to elevated CO2 with greater difference under water-stressed conditions which recommend use of ensembles approach to bring accuracy in the models response to elevated CO2.