The grassland model intercomparison of the MACSUR (Modelling European Agriculture with Climate Change for Food Security) European knowledge hub

The grassland model intercomparison of the FACCE MACSUR knowledge hub involves nine modelling approaches. Grassland-specific approaches (AnnuGrow, PaSim, SPACSYS) are compared to the approaches mainly conceived to simulate crops (ARMOSA, EPIC, STICS) and biomes (BiomeBGC MuSo, CARAIB, LPJmL). The model intercomparison exercise is run over nine grassland sites across Europe and peri-Mediterranean regions where data were collected from at least five, up to 31 years, with focus on biomass production and carbon exchanges. The protocol for model intercomparison, derived from AgMIP Agricultural Model Intercomparison and Improvement Project, includes sensitivity tests, as well as blind and calibrated simulations. A fuzzy-logic based indicator for model assessment was developed providing insights into agreement between simulations and observations, complexity of model structure and robustness of simulation results over a variety of conditions. Some results are anticipated and show the limitations of the modelling undertaken thus far with current parameterization to simulate grassland dry matter and C exchanges across the Euro-Mediterranean region. The study also suggests that the regional calibration can accommodate model discrepancies. However, areas in the model structures have been identified that require further improvements to reduce uncertainties and increase reliability of model results in impact studies.