obtained under conditions of a passive experiment with strong correlation of input
variables and distortions in the estimates of regression coefficients.
For mathematical description of the deterministic component of the time series of
forest growth, different functions are used. These are parabolas of 2-3 orders of
magnitude, the equations proposed by F. Korsun, Bakman’s model of logarithmic type,
etc. [18].
M. Prodan and E. Assman [19] indicate two main features of the growth curves
of trees and forest stands:
➢
Growth curves have an asymptote with unlimited increase in age – a straight
line parallel to the abscissa;
➢
The current increment of the growth curve increases and reaches a maximum
at the bend point of the curve, and then decreases and slowly falls to zero, that is, until
the forest stand is completely disintegrated.
The maximum increment depends on the tree species and growth conditions. If
these principles of plantation growth process are met by a mathematical model, then
such a model is quite suitable for modeling the productivity of forest stands.
The number of growth functions proposed by researchers at various times
amounts to several dozens and is increasing every year. The technique for calculating
the parameters of growth functions is described in the book by M. Prodan [20]. All the
formulas can be divided into two groups: those obtained by formal mathematical
constructions or constructed on the basis of energy concepts.
The mathematical models of protective plantations growth allow calculating the
process of phytomass formation within such limits which provide photosynthesis
sufficient for growth and optimal functioning of CPE. To do this, methods are used to
calculate the growth and productivity of plantations based on changes in weight and
area of the assimilation apparatus for a certain period of time.
Periodic determination of the weight of plants (W) and the area of the assimilation
apparatus (A) allows obtaining the following indicators: absolute and relative
increments, absolute and relative growth rate, net assimilation value, ratio of leaf area
to plant weight [16].
Depending on the values of the parameters that characterize the external and
internal CPE environment, different mathematical models can be used.
Since we consider mathematical models that allow for transparent physical,
chemical and biological interpretation, this makes it possible to substantiate the
requirements of the normative support for CPE functioning.
To describe the growth of the tree as a starting point, Kolobov [21] used the model
of free growth of the tree, proposed in the work by Poletaev [22]. The model is based
on the following hypotheses:
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