Comparison of Non-Linear Height-Diameter Models of Tectona grandis L.f. in a Rainforest Site in Southern Nigeria

Abstract

This study was carried out to select the best model for predicting height for effective management of Tectona grandis stand in the study area. Five 3-parameters well-established non-linear models were used to compare their suitability in predicting height, evaluate and select the best H-D model based on test statistics criteria such as R², RMSE AIC, and BIC. Models with the lowest RMSE, AIC and BIC and highest R² values are judged the best. One hundred (100) trees were enumerated and were subjected for analysis in the study. A plot size of 0.04ha (20m x 20m) with an area of 0.64ha was chosen for this study and 10 sample plots were purposively selected from the study area. The result indicated that schnute model had the highest R² value of 99.9% but it also had the highest RMSE, AIC and BIC values, hence the worst candidate in predicting height in the study area. Weibull model although did not have the largest R² of 97.2% when compared to schnute, had the smallest RMSE, AIC and BIC (1.37596E-14, -832.6836 and -823.9054 respectively) and hence is the best candidate model. The Chapman-Richards, Logistic and Korf models also performed well based on the evaluation criterion. Weibull function with 3-parameters has been confirmed to provide a secure estimate of total tree height for Tectona grandis in the rainforest site of the study area of Southern Nigeria.