Thermodynamic substantiation of ecological-physiological modeling

Abstract

The forest ecosystem is a classical example of an open system. Its behavior can only be described within the framework of nonequilibrium thermodynamics. The fundamental concept of thermodynamics is the entropy of a system. According to the second law of thermodynamics, the entropy of closed systems takes on the maximum possible value when it reaches an equilibrium state. But in open systems, one can speak of a change in entropy. In ecosystems, the entropies change is represented as the sum of two terms. One term expresses the change in entropy within the system, and the other one is responsible for the connection with the environment. In the work, based on the definition of entropy through the thermodynamic probability of the system (the static weight of the system), a relation was obtained to determine the statistical weight of the forest ecosystem. The statistical weight has determined through the maximum value of biomass achieved during the growth of the stand. As a result, a differential equation has obtained for finding the stand biomass. The analytical solution of the equation is the basis for constructing a basic model of the growth dynamics of a single-species stand. The model was verified for a complete (normal) pine stand of the first five quality classes (1b, 1a, 1, 2, 3). The evaluation of the modeling quality was carried out using the dimensionless Nash-Sutcliffe criterion and showed a very good description of forestry data by the proposed model.