Individual tree growth models for eucalyptus in northern Brazil

Fabrina Bolzan Martins,Gilson Fernandes Da Silva,Carlos Pedro Boechat Soares

doi:10.1590/s0103-90162014000300006

Abstract

The diameter and height growth model is one of three submodels used for simulating individual tree growth. In Brazil, there are few studies on the dimensional growth of individual trees be they native or exotic species, despite their potential. This study aimed to evaluate diameter and height growth models for individual trees for eucalyptus stands and to validate the best fitting model. Tree diameter and height data were obtained from 48 permanent plots of unthinned stands of Eucalyptus grandis × Eucalyptus urophylla hybrid located in northern Brazil. The evaluation of the diameter and height growth models was based on adjusted coefficient of determination, standard error of estimate as a percentage, trend, root mean square error and Akaike Information Criterion. Analysis also included distribution of residual percentage, statistical significance and signs of the coefficients. The Lundqvist-Korf model provided the most accurate estimates for diameter and height growth, in comparison with the other models, providing better statistical values, greater proximity to observed values and better distribution of residual percentages. The use of this type of model is feasible and can result in significant improvements in the accuracy of yield estimates.

Highlights

Dimensional growth in terms of diameter and height is one of the three constituents of an individual tree model and is subject to complex interactions (Andreassen and Tomter, 2003; Soares and Tomé, 2002)
Tree diameter and height data were obtained from 48 permanent plots of unthinned stands of Eucalyptus grandis × Eucalyptus urophylla hybrid located in northern Brazil
All equations referring to the models assessed for the variables diameter and height in all three productivity classes provided values that were very close to each other according to the relevant statistics ( R 2, BIAS, Sy.x%, root mean square error (RMSE) and Akaike Information Criterion (AIC)) (Table 3)

Summary

Introduction

Dimensional growth in terms of diameter and height is one of the three constituents of an individual tree model and is subject to complex interactions (Andreassen and Tomter, 2003; Soares and Tomé, 2002). It is influenced by growth vigor, past growth conditions, microenvironment, genetic traits and competitive status (Tomé and Burkhart, 1989). In models at the level of the individual tree, growth is often estimated via the potential growth function or growth equations (Davis et al, 2005). Growth equations (or functions) use tree attributes (tree size, competition indices, crown ratio, vigor), stand attributes (age, site index, stand basal area) and site characteristics as predictor variables, all combined in a single equation (Uzoh and Oliver, 2006)

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