Modelling Crown-Stem Diameters Relationship for the Management of Tectona grandis Linn f. Plantation in Omo Forest Reserve, Western Nigeria

Abstract

Crown-stem diameter relationship is important for sustainable forest management. Effective forest management requires routine inventory data of tree crops for decision making. Therefore, in this study, crown-stem diameter relationship was modelled for the management of Tectonia grandis L. f. plantation in Nigeria. The dataset consists of 1919 trees measured from 35 sample plots. Three methods including ordinary least square (OLS), quantile regression (QR) and linear mixed model (LMM) were used to model the relationship between crown diameter (CD) and diameter at breast height (DBH). The model was used to estimate the limiting density, growing space and projection area. The result shows that the model from LMM was more suitable than OLS and QR. It explained 0.622 of the variation in CD with root mean squared error of 0.736. The study also shows e.g., that T. grandis trees of 25 cm DBH would occupy an equivalent area 36.32 m2 and to avoid inter-tree competition the stand density should not exceed 275 Nha-1. And if the plantation is to be thinned and clear-felled when mean DBH is 50 cm, density remaining after thinning would be 115 Nha-1 with average growing space of 9.3 m. This information would help in the management of the plantation.

Keywords

• crown diameter
• linear mixed model
• ordinary least square
• quantile regression
• teak.