Description

Expert-N (since version 5 also XN5) is a comprehensive software package for simulating plant growth and matter fluxes in agroecosystems. The simulation environment consists of modular model components which solve simultaneously partial differential equations for soil water flux (“Richards equation”), soil heat transfer (“Fourier’s heat transfer equation”) and solute transport (“convection-dispersion equation”), coupled to a complex set of ordinary differential equations describing plant phenology and growth as well as carbon-nitrogen turnover in soil (Priesack, 2006). Expert-N is designed as a model library. The modular structure allows alternative or competing model approaches to be implemented and combined for single simulated processes (e.g. nitrogen turnover) or single sub-processes (e.g. mineralisation of soil organic matter). In Expert-N, numerous existing models and process descriptions from the literature have been implemented as well as many own model developments. The development of the Expert-N model system dates back to the 1990s, when a first version was implemented as part of the collaborative project FAM (Forschungsverbund Agrarökosysteme München, a joint project of the Technical University of Munich and the GSF Research Center for Environment and Health in Munich-Neuherberg). Building on this first version, Expert-N has been continuously extended and improved over the last 25 years. During this time, Expert-N has become a comprehensive platform for models and modules on the topic of agroecosystems, which can be combined or interchanged with each other. For example, four different plant growth models have been implemented in Expert-N, as well as several models and alternative process descriptions for soil heat flux, organic matter turnover, or evapotranspiration. In addition, there are modules for grasslands, forest growth, agroforestry systems, and, most recently, agrivoltaics. The large number of alternative process descriptions and submodels offers, among other things, the advantage that the model selection can be adapted to the respective data situation for specific model applications. The inter-changeability of individual process descriptions or entire submodels also favors in-depth model analyses and provides the opportunity to create multi-model ensembles for agroe-cosystems within a single simulation environment. In addition, the modular design of Expert-N favors relatively easy extension of the model system, which, in the first place, made it possible to implement this large number of models and process descriptions. Furthermore, couplings of Expert-N with other model systems have been realized, most important the coupling with the multi-agent simulation software MPMAS. Expert-N is programmed in C/C++ as a model library. Currently, Expert-N is available in the Windows-based version 3.1 and the platform-independent, OpenMP and MPI parallelizable version 5.15 (XN5), for which a Python based Graphical User Interface (GUI) exists. Expert-N offers the possibility for massive parallelized simulations. This option is particularly important for regional simulations (e.g., climate projections at the regional or national scale).

Technical information

Operating systems: Windows (GUI, command line), Linux (command line)