Height-diameter Relationship Models for Teak (Tectona grandis) Plantation in Nimbia Forest Reserve, Nigeria

Abstract

The study on height-diameter modelling was carried out on Teak (Tectona grandis) plantation in Nimbia Forest Reserve. Two fit methods (Chapman-Richards and Weibull) were used to model height-diameter relationship. The teak plantation is divided into four forest beats as management unit, therefore, stratified random sampling was employed to select five plots of 20 x 20 m from each forest beat (as stratum), thereby having a total of 20 plots. Stump diameter (Dst), diameter at breast height (Dbh), diameter at middle and top positions (Dm and Dt) of trees, and tree height for all the selected trees were measured. Average Dbh measured 15.00 cm and the mean tree height was 6.77 m. Pseudo coefficient of determination (Pseudo R2) and residual mean square error (RMSE), goodness-of-fit statistics were considered as model selection criteria. Chapman-Richards function produced the best goodness-of-fit statistics for Teak height-diameter modelling. The height-diameter models require additional site factors for better models; hence the need for establishing permanent sample plots (PSP) in order to get additional information from re-measurements of the plots.