We will now describe the temporal evolution of state variables s, n and now r, of the considered forest.
The growth of a tree depends on its neighbors. There is competition for the resources and the death of a tree, natural or due
to cuttings, implies an increased growth for its neighbors. We make the assumption, that in the course of time, silviculture
makes it possible to maintain the trees uniformly distributed on the area. The model is characterized by the existence of
two levels in the modeling.