PRODUCTIVITY DYNAMICS OF STANDS IN CONIFEROUS FORESTS OF MARI TRANS-VOLGA REGION

Abstract

The relevance is conditioned by the need in improvement of sustainability in management of ecological and resource potential of forests achieved with the use of mathematical models of dynamics of productivity of stands. The mathematical models are developed on the regional and typological basis. The goal of the research is to study the regularities of dynamics of productivity of stands in coniferous forests of Mari Trans-Volga region and to reflect them as mathematical models. The forests growing in various hygrotopes of pine forests were the object of this research. E-data base, containing the information about the stands of more than 78 000 stratums with the overall area of 385 184 ha, was the material to analyze. IT solution was used to achieve the targeted task. The IT solution was based on a system statistical analysis of digital information on a personal computer with the use of packages of conventional application software. Results. It is viable to grow pure pine forests in coniferous forests of Mari Trans-Volga region. Pine forests are wide spread and they surpass by far the stands with participation of other species by ecological and economical criteria. The stock of stem wood, its actual stock, and stumpage price increase with the age of stands up to a certain point of time only, then they progressively decline. The functional relation of optimum Y = 100´Х/(а´Х² – b´Х +c), the parameter values of which are unique for each wood species and various hygrotopes, approaches in the best way. In the stands, where the birch prevails, the high point of these valuation indices comes earlier but the value valuation indices is much lower at the moment. The difference between the stands of pine and birch in dry and bogged coniferous forests is very large. The age of technical maturity of stands when mean annual increment of list price for timber is maximum (stands where pine trees predominate) is  65-70 years in fairly moist and moist coniferous forests, 75 years - in dry coniferous forests, 90 years - in damp forests, 120 years - in bogged forests. The figures for birch groves, growing in fairly moist and moist coniferous forests, are much about the same as for pine forests, but there is some difference for the birch groves growing in dry, damp and bogged coniferous forests. Thus, the age of technical maturity of stands when mean annual increment of list price for timber is maximum (birch groves) is 50 years in dry coniferous forests, 65 years - in damp forests, and 80-85 years - in bogged forests. The nature of growth of stands in height and diameter depends to an extent on the density, the influence of which is often polar in different hygrotopes. Altogether, the growth of influence leads to earlier high point of current annual increment, increase of mean height of trees and decrease of their mean diameter. Conclusion: to study the regularities of growth of stands and to solve the managerial tasks, it is desirable to develop the mathematical models, based on the zone-typological basis, not the bonitet one. The revealed regularities of dynamics of productivity of stands confirmed the conclusions of other researchers in full. Besides, they significantly updated them with qualitative economic and ecological data.