Height-Diameter Models for Prediction of Teak Stand in Western Nigeria

Abstract

The Diameter-height relationship has proven to be an important part in growth and yield models which describe stand changes. Ten existing nonlinear height-diameter models were used to fit and evaluate Tectona grandis stand in Oluwa forest reserve (Nigeria) in this study. Three hundred and ninety-seven (397) trees were measured for their stand variables of which diameter at breast height (Dbh) and height (Ht) were paramount. All functions were fitted using weighted nonlinear least square regression (NLLSR), considering hetroscadasticity of variance. Model performance were evaluated using three fit statistics such as root mean squared error (RMSE), Akaike Information Criterion (AIC) and Bayesian Information Criterion (BIC). Logistic 3-parameters H-D function as the best fit based on the model’s evaluation statistics and its predictive ability with values of RMSE, AIC and BIC as 2.8925, 1974 and 1990, respectively. Gompertz, Weibull, Chapman-Richards and Michaelis-Menten models also provided good fit results comparable to the observed height-diameter relationship. Logistic function with 3-parameters has been confirmed to provide a secure estimate of total tree height for Tectona grandis in Oluwa Forest Reserve.