MODELING OF GROWTH AND YIELD OF Eucalyptus STANDS IN LEVEL OF DIAMETER DISTRIBUTION USING SITE INDEX

The prediction of the production of forest stands by diameter class has great importance when it aims to generate timber multiproduct. Keeping this in view, this study aimed to estimate the production of a stand of clones of hybrid Eucalyptus urophylla x Eucalyptus grandis by diameter class using the variable site index (S). The classification of the productive capacity of each plot was taken by site index curves using the methods of the guide curve and the difference equation. Then the Weibull probability density function (p.d.f.) of two parameters was adjusted by the maximum likelihood method. To project the parameters of the p.d.f., a system of equations was used with the inclusion of the variable S. The rating of system adjustment was made by analyzing the residual graphs, and accuracy statistics: adjusted coefficient of determination (R-adjust(2)) and relative standard error of the mean (S-yx%). The adjustment was performed using 80% of the plots and the remaining 20% were used for validation. The classification of productive capacity through site index was efficient by the two evaluated methods, but the guide-curve method was selected due to its simplicity and ease of application. The system of equations with inclusion of local index variable (S) was necessary for modeling the diameter distribution of the analyzed stand. The applicability of the equation system proved quite effective for three consecutive prognoses.