  The hierarchical system of forest ecosystem models based on the theory of
individual-based (structured) models of populations and communities is briefly
described. New self-thinning models are integrated with tree stand models
within a hierarchical system of models, aimed at assessing (quasi-) stable
states of a forest ecosystem under given environment and management. Within the
structural model of succession, the ergodic theorems in biology are proved.
They assert that the areas of biocenoses in a climax state of association
should be proportional to the proper times of their development in a succession
line; the other characteristics of biocenoses should be also proportional to
their own proper regeneration times in a climax state. A simple theoretical
approach to estimating the deviation of the current state of forest ecosystem
from its steady state is derived and applied to data from the Prioksko-Terrasny
Reserve. The results obtained can serve as a theoretical basis in numerical
processing of data on ecological monitoring of undisturbed forest lands.
