Modeling of coversion coefficients of phytomass fractions to determine the biological productivity of stands

Abstract

The purpose of the research is to develop a multidimensional model of conversion coefficients of phytomass fractions for pine forests of the coniferous-deciduous forests of the European part of the Russian Federation. The approved standards are the values of the coefficients averaged over the age groups  of  stands  related  to  different  forest-forming  species  growing  in  the  three  natural  and  climatic zones  of  Russia.  In  contrast  to  the  simplified  approach  to  determining  the  biological  productivity of stands by the values of conversion coefficients averaged in age groups, the most scientifically sound approach  based  on  methods  of  statistical  modeling  of  the  relationship  of  phytomass  fractions  with inventory indicators of stands is shown. The obtained regression models, interconnected with the data of regional tables of the growth course of different authors, made it possible to obtain multidimensional models, and as a result, the most accurate standards for conversion coefficients. The differences between the two methodological approaches are confirmed by the example of pine stands. The results of assessing the accuracy of determining conversion coefficients indicate a significant advantage of an approach that takes into account, along with age, the average height of stands. At the same time, it should be pointed out that the age itself, and even more so the age group, which is the basis of the first approach, is not able to reliably characterize the accuracy of obtaining the values of conversion coefficients (R2 = 0.908) with an error ES = ± 35.4%. As for the influence of the average height of stands on the conversion coefficients, it  is  more  reliable  (R2  =  0.990)  with  an  error  ES  =  ±  11.5%.  The  specified  accuracy  of  the  first  two models is significantly inferior to the combined influence of the predictors indicated in them (R2 = from 0.998 to 0.999) with an error ES = ± 1.76% for trunks, ES = ± 1.34% for roots, ES = ± 2.03% for branches, ES = ± 3.7% for needles, ES = ± 1.19% for bark.