Two-parameters single equation stem taper models of Pinus sibirica in Siberia, Russia

Abstract

A large number of studies have been devoted to the cedar forests in Russia, but studies of the conicity of trunks remain limited. The main goal of this study was to analyze two-parameter single equation stem tapper models for Siberian cedar trees, which will serve as guidelines for future research. The study tested six two-parameter models of one equation for the conicity of the trunk of Siberian cedar trees. For this, data from 1805 measurements of diameters in 193 felled trees were used. The data were collected in natural pure and mixed Siberian pine stands in Irkutsk region (Southern Siberia) and Tyumen region (Western Siberia), Russia. Our analysis showed that for our data set, the Reed and Green model turned out to be the best model. The model is characterized by the smallest average absolute error percentage, the square root of the root mean square error, and the largest coefficient of determination. The residuals of this model are independent and characterized by constant variance. The analysis performed showed that two-parameter single equation models have a good fit in the central part of the trunk, therefore, forestry management in cedar forests should be used with caution. For the purposes of forestry management in cedar forests, it is recommended to develop and put into practice more complex models.