The effects of successive thinnings on the hypsometric function for Pinus oocarpa stands

Abstract

This research aimed to test the hypothesis that successive thinnings mischaracterize the hypsometric function, and that after some thinnings the average height of the plots or of the stand (h) is an unbiased estimate of the remaining tree heights (hi), that is, ĥi = h . The data were obtained from Duraflora S. A. in Agudos, State of São Paulo. This data set came from the measurement of diameters and respective heights of 1,100 trees equitably distributed in 11 different treatments with ages ranging from 5 to 25years, and number of thinnings varying between 0 (zero) and 6. The Stoffels model, previously fitted to all treatments, was used to observe the behavior of the following factors: coefficient of multiple determination (R²), standard error of estimate in percent (Syx %), distribution of residuals, and the significance of the b0 and b1 coefficients in each one of the equations. After tests it was confirmed the hypothesis that average height is a precise estimate of hi for the oldest treatments with more than 4 thinnings. This means low Syx % and unbiased estimates, that is, good distribution of residuals.