Curvas de crescimento em altura e índice de sítio de povoamentos clonais de Eucalyptus spp. na Chapada do Araripe, Pernambuco

Abstract

At this study were compared the mathematical models adjusted by regression analysis to define the productive capacity using curves site index for hybrid clones of Eucalyptus ssp., In the Araripe, Pernambuco. The study area was located at the Experimental Station of the Agronomic Institute of Pernambuco - IPA, located in the municipality of Araripina, Pernambuco. The data were measured from 45 permanent plots with 15 treatments (clones of Eucalyptus sp.) in three repetitions, with a spacing of 3 x 2 m plot area was 294 m2, with util area of 150 m2, in a block design The first measurement was performed at the time two months after planting to verify the survival, after the planting all plots were measured every six months, with measurements at 2, 6, 12, 18, 24, 30 , 36, 42, 48, 54, 60, 66, 72, 78, 84, 90 months. For each measurement were recorded the tree total height and the diameter at the breast height (DBH) of all trees. However this work did not consider the first four measures, because the plants were still young and therefore had not yet competition and also influence of the treatments were suffering forestry. Three models were to perform the analysis of covariance, Five linear and five nonlinear models were adjusted for the data collected, age and height . The adjusted models were evaluated through the following statistics and precision adjustment: adjusted coefficient of determination (R2aj), coefficient of variation in percentage, and residual graphical analysis in percentage. The differences in slope detected by analysis of covariance indicated, accurately among the fifteen clones tested, indicating the existence of nine groups with different growth patterns. It was considered necessary to adjust the nine sets of site index curves with reference age of 72 months, with an interval of 2 meters among the curves. All equations tested to estimate the growth in height according to age showed a good fit, especially for nonlinear models. For the establishment of the nine sets of site index curves, we selected the Schumacher model, for simplicity and to estimate the heights of trees and with only two parameters and, especially, for having made some better residual graphical distributions.