The 3D-CMCC-FEM is constituted by a main matrix subdivided in cells with a variable size ranging from 10m x 10m to 1Km x 1Km (that can be set by user). The model is suitable to simulate uneven-aged, multilayered and mixed species forests thanks to its code architecture which allows aggregating trees into representative classes, each characterized by its variables (e.g. carbon pools, leaf area index, tree height) based on their ages, species-specific and forest structural traits (Collalti et al. 2014, Engel et al. 2021). Simulations run for every cell for different Height classes, each one of them divided in different Dbh (diameter at breast height) classes, each one of them divided in different Age classes and, in turn, different Species classes. The forest could be set as natural type, with two kind of phenotype (evergreen or deciduous), or simulated by management practices. Considering soil characteristics and pools, for each class the model computes daily, monthly and annual values of the variables, such as Gross and Net Primary Production (GPP and NPP), Leaf Area Index (LAI), Soil Water Content (SWC), Evapotranspiration (ET) and the other ones. At the end, the values are cumulated at cell and forest levels.