Improving leaf area index simulation of IBIS model and its effect on water carbon and energy—A case study in Changbai Mountain broadleaved forest of China

•LAI accuracy has important effects on water, carbon, and energy balance simulation.•LAI estimation of IBIS is modified by combining the advantages of other models.•The modification has evidently improved the performance of IBIS in LAI simulation.•GPP, ET, and soil temperature simulations also improved in the modified model.

Leaf area index (LAI) is a key parameter for the simulation of water and carbon cycle in many ecological and hydrological models. However, it is difficult to estimate the LAI dynamics accurately. In this work, a modified model based on the Logistic Statistical Model and the Mechanistic Model was developed to solve the problem of IBIS (Integrated Biosphere Simulator) in LAI simulation, which noted as IBIS–LAI. Comparison between the primary IBIS, IBIS–LAI, as well as Logistic Statistical Model and the Mechanistic Model are performed in Changbai Mountain broadleaved forest of China. Results show that model performance could be enhanced by modification of LAI simulation, especially in spring and autumn. The relative error of upper canopy LAI simulation by IBIS, IBIS–LAI, Logistic statistical model and mechanistic model is 86.80%, 5.39%, 8.25% and 9.53%, respectively; while the relative error of lower canopy LAI simulation is 80.01%, 18.57%, 33.63% and 20.94%. With the improvement of LAI simulation accuracy, simulation of evapotranspiration (ET), gross primary productivity (GPP) and soil temperature by IBIS–LAI has been improved. It is concluded that the modification of LAI simulation can improve the performance of IBIS on the simulation of land surface processes.