Taper models to describe the tapering of Pinus taeda in the inhamacari forest in theAdministrative Post of Machipanda

Abstract

The present study aimed to adjust the non-segmented trunk profile equation to estimate the taper of Pinus taeda, from the Inhamacari forest, Manica Province. The data for the present work were collected in the Pinus taeda stand, in a sample of 100 individuals. The total height, commercial and the circumferences of the bole were measured, in the positions at 0.30; 0.50; 0.70; 0.90 1.10; 1.30; 1.50; 1.70; 2.30 m; when greater than 2.30m it was measured approximately, from 1.00 to 1.00 m to the total height. With these data, different trunk profile models were fitted, those of Schöepfer, Hradetzky and Kozak et al. The best equation was selected using the coefficient of determination of fit (R²%), standard error of percentage estimate (Syx%) graphical analysis of the residuals and graphical analysis of the estimated profiles. The Hradetzky and Shöepfer models obtained satisfactory results, with a high coefficient of determination of 99.756 % for the Hradetzky model and 98.394 % for the Shöepfer model, low standard error of the estimate of 6.94 % for Hradetzky and 7.25% for the Shöepfer model and better residue distribution for both models, the model by Kozak et al, obtained unsatisfactory results (95.52% of R²% and 11.50% of Syx%) compared to the others. In the validation of the models, the Chi-square test (X2) was used, where the Hradetzky model that had the best fit was selected, with the same calculated X2 smaller than 0.173835024 than the critical X2 of 15.507, indicating better performance.