The structure generator simulates unknown or missing information about individual trees growing in a simulation plot. The simulation plot is a representative sample of a forest stand, usually of a square or a rectangular shape and of various sizes, while a square with an area of 0.25 ha is the most commonly applied plot type. The simulation plot can either be flat, or it can be located in the terrain, which is represented by terrain model in the form of a regular grid. In such a defined simulation plot, individual trees with known characteristics need to be situated. Hence, for each tree the following characteristics need to be determined: tree species, tree diameter at breast height, tree height, parameters describing tree crown (height to crown base, the widest crown diameter, crown shape), horizontal Cartesian coordinates of the tree position within the simulation plot, vertical coordinate of the tree foot, tree quality, tree damage and tree management status (dead tree, living tree marked for thinning, living tree marked as a future crop tree, or living unmarked tree). If any of the mentioned characteristics are unknown, the structure generator is activated. Its task is to generate (i.e. to calculate) missing data using built-in algorithms, while a variety of different data sources can be used as input data differing from one another in the level of information detail. As examples we can name: data obtained from stand description for the whole stand or its part, data gathered within small-scale sample forest inventory in the form of diameter frequencies, and height curve characteristics, or detailed tree data coming from permanent sample plots. Less detail of input data reduces the precision of forest stand structure generation.

This model is used for the spatial visualisation of a forest. The spatial arrangement (configuration, organisation) is of high importance mainly for the competition relationships and thinning systems. The model visualises a forest either in the form of a static schematic plan with basic shift and rotation operations in 3-D view, or in the form of a complex virtual reality, which provides a user with an opportunity of interactive movement in the forest (using the principle of computer games of two types: "first person" and "third person").

This model calculates all important aggregated ouputs at a plot level (mean and per hectare variables): variables characterising production condition of a forest stand (e.g. mean diameter, mean height, stand volume, basal area, stand density); biomass values and the content of chemical elements in wood, bark, roots, and assimilatory organs; different forest biodiversity indices (tree species and structural); revenues arising from a forest in the form of assortment structure of growing stock (expressed both in volume and value); and at last the costs of basic cutting and yarding processes. The results are differentiated between tree species and types of a forest stand component (main, dominant, and secondary crop, mortality, future crop trees).

The task of the mortality model is to select the trees which die in a particular period of the growth simulation naturally. Natural mortality depends on stand density, which should not exceed the maximum possible density, and on susceptibility of individual trees. The susceptibility of each tree is determined on the basis of its tree diameter, and tree basal area increment affected by the competition pressure, tree height-diameter ratio, and the site class, which is modified by site parameters (climate and soil). 

The purpose of this model is to select the trees, which die in individual periods of growth simulations due to the influence of random injurious agents. The model simulates tree mortality caused by wind, snow, icing, bark beetles, timber borers, defoliators, wood-destroying fungi, air pollutants, drought, fire, and illegal cutting. The selection of dead trees (trees that die) is performed on the basis of the disturbance risk and the predicted damage rate. These parameters depend on the number of dead trees left in the stand, on climate anomalies, stand localisation, stand geomorphology, and stand susceptibility determined from a wide scale of stand characteristics. The selection of individual trees is driven by the type of propagation of an injurious agent in a stand (individual - scattered, spotted, local).

This model simulates interventions of a forest manager in a stand. The goal of the model is to select trees for cutting during e.g. thinning treatments. At the same time, if it is required, the model can also select the trees supported by a manager, i.e. crop trees. Various treatment types can be simulated by the model: thinning from below, thinning from above, neutral thinning, method of crop trees, method of target diameter, method of target frequency curve, clear cutting method, and an interactive thinning by list.

This model calculates the competition pressure of the surrounding trees quantified by the competition index. The competition index is three-dimensional and distance-dependent, i.e. this index accounts for the position of individual trees in all directions around the assessed tree. The index is terrain-sensitive as it also considers the character of the terrain under and around the tree. The index is tree-species-sensitive, since it also takes into account tree species composition of the surrounding competitors. In addition, the competition index considers the symmetry or asymmetry of the position of competitors.

This is the main model that determines tree increments of particular variables in a certain simulation period. The model of tree diameter and height increment represents the heart of the growth model, and is based on the reduction of the growth potential. The growth potential is specified by ecological site classification, which is based on climate and soil characteristics. Next, the growth potential is modified by the competition pressure and the tree vitality determined by the tree crown dimension. The model is independent of age, and if the tree age is unknown, it can be derived from the growth potential and the real tree height at the beginning of the growth period. 

This model will simulate natural and artificial forest regeneration. It is the only model that has not been finished yet, and hence, is not activated !!!