Equation systems used in the construction of density management diagram of teak stocks

Abstract

The aim objective of study was to evaluate the system of equations used at the construction of density management diagrams. The data was collected at clonal stands of teak in the southern-central region of Mato Grosso state, Brazil. The ages of the stand varied between one and eight years, where the measures were taken in circular plots. The plots had areas varying from 359 to 616 m². The diameter at breast height and total height were measured from the trees that composed the plots. The volume was calculated in 827 trees by the Smalian’s method. Two systems of equation were used to carry this study out and the evaluation of the fit was made by the statistics: root mean square error (RMSE), percentage of root mean square error (RMSE (%)), coefficient of determination (R²) represented by the squared correlation coefficient ( ), residuals in the percentage scale (residual (%)), and graphical analysis of the parameter fittings. The system of equation that obtain the best results was the proposed by Dean and Baldwin, with the statistic R² between 0,9942 - 0,9994, and RMSE (%) 2,88 - 1,84, regarding the other system that presented 0,9558 - 0,9539 and 13,94 -7,99 to the statistics R² and RMSE (%), respectively.  The distribution of residues from the Dean and Baldwin system were also superior, corroborating the results of the statistical analyzes. The results of this work allow us to infer that the system of equations proposed by Dean and Baldwin is more accurate, and, therefore, the one indicated in the development of population density management diagrams in clonal teak stands.