Multi-Model Ensemble Crop Growth Simulation by use of the model framework Expert-N

We present an example for the generation of model ensembles by use of the model framework Expert-N. Different crop models are obtained by choosing different sub-models, which represent important processes to determine the dynamics of crop growth. In this way, different sub-models to simulate potential evapotranspiration, actual evaporation, actual transpiration, soil water flow, soil nitrogen transport, soil carbon and nitrogen turnover, crop development, canopy photosynthesis, potential and actual nitrogen uptake and crop growth are combined resulting in different crop models building a model ensemble. The sub-models are based on process descriptions that are included in the crop models CERES, SUCROS, SPASS and GECROS, but also stem from known soil models such as CENTURY, SOIL, SOILN, NCSOIL, LEACHM or HYDRUS.

The generated model ensemble is applied to simulate winter wheat growth at a field site in Southern Germany. We compare simulation results to measurements of crop biomasses and yields, and to soil water and nitrogen contents. It is concluded that model frameworks as the model system Expert-N can help to analyse structural uncertainties which lead to different simulation results between models of a model ensemble.