Abstract

(Introduction):  A new site classification system for Tectona grandis L.F. is presented based on information collected during more than 30 years of research.

(Objective):  To construct an updated family of site index curves for teak plantations for the pacific coast of Costa Rica.

(Methodology):  The data came from the stem analysis of 55 dominant trees with ages between 6 and 40 years, selected in different locations of the Pacific slope. These were combined with dominant height data from 38 permanent plots that were part of 6 formal growth and yield trials remeasured between 10 and 32 years old. Growth models were fitted by mixed effects nonlinear regression, considering that trees and plots were remeasured annually. Six mathematical models were used: Richards, Gompertz, Logistic, Korf, Mitscherlich and Weibull. The models were re-parameterized according to the observed dominant height (S) at the base age of 16 years, associating it with a random effect. The best model was chosen according to the information criteria and goodness-of-fit statistics.

(Results):  The Akaike and Bayesian information criteria indicate that Korf's model was superior to the others, both in the anamorphic and polymorphic variant; the goodness-of-fit statistics confirmed this appreciation. The residual analysis showed a better fit for this model when describing growth in dominant height with age. Although the polymorphic model was superior, the observed trends seem to rule out the existence of a common asymptote for teak plantations growing in the different site qualities.

(Conclusions):  The results showed that the data from stem analysis and permanent plots show similar pattern trends, which are adequately represented by the Korf's model.

Keywords: Mixed effects; permanent plots; polymorphic curves; random effects stem analysis; site quality; teak