Morfométria como estimador da porcentagem de cerne em Cordia trichotoma (Vell.) Arráb. Ex Steud. na região central do Rio Grande do Sul – Brasil

Abstract

This work aimed to predict the heartwood proportion (PCE) in Cordia trichotoma (Vell.) Arráb. Ex Steud, free and submitted to competition. The study was carried out in the central region of the state of Rio Grande do Sul, in the city of Santa Maria. The wood samples used in this study belong to the collection of the Forest Management Laboratory at DCFL-UFSM. These come from data collection for practical classes, course completion works, dissertation and thesis, between the years 2005 and 2015. The following variables were measured: diameter at breast height (DBH), total height (H), morphological inversion height (HIM), crown diameter (CD) and crown length (CC), as well as information on growth and competition conditions, health and vitality. Aiming to equalize the samples for statistical purposes, 24 trees under competition (UC) and 23 trees free from competitors (FC) were selected. For these two groups were identified for the dendrometric and morphometric variables of the trees, their minimum and maximum values, as well as the means and statistics, used to compare and identify their similarities and differences. The growth condition of the sampled trees does not differ in dendrometric and morphometric characteristics. UC have higher mean and minimum values of diameter at breast height (DBH) while having the lowest maximum value for this variable. The diameter of the UC has a negligible influence on the width of the sapwood (WS) with an average of 16.25mm, ranging from 9.1 to 25.3mm. UC showed a slight tendency to have fewer growth rings (NR) as a function of DHB. FC, on the other hand, did not show a regression trend. The dendrometric and morphometric variables have little or no influence on the WS and NR variables, therefore, it is understood that none of the evaluated variables can explain the NR and WS for free and competitive Cordia trichotona trees. The PHP presented a linear relationship with the statistically unsatisfactory dendromorphometric variables, not meeting the conditions for analysis of variance and covariance, needing to transform to the neperian logarithm. The transformation of the variables brought about a marked reduction in the autocorrelation of the residuals, estimated by the Durbin-Watson statistic, however, the normality of the distribution of the residuals was poorly met. Tree growth conditions were not shown to be influential as a classification variable, thus, a unique model was adjusted for each independent variable, regardless of the competition condition to which the trees are submitted. The PHP can be estimated disregarding the competition condition of the trees, as a function of the Neperian logarithm (NL) of the DHB variables: PHP = 41.7943 + 12.5273 * NLD; H: PHP = 45.3556 + 14.6508 * NLH and CD: PHP = 57.8098 + 13.872 * NLCD.