Nonlinear yield models for young Tectona grandis L. f. stands in Nnamdi Azikiwe University Awka, Southeastern Nigeria

Yield models are very important to forest management, especially for site quality assessment, subsequent inventories, timber valuation and assessment of stand growth. This study developed yield models for the young Tectona grandis stands in Nnamdi Azikiwe University Awka, Southeastern Nigeria. These models were necessary to the guide forest managers in timber valuation as well as monitoring growth of the stand. Data for this study was collected through complete enumeration method, tree height and stem diameters of the 295 Teak stands were measured. Non-destructive method (Newton’s formula) was used in computing individual tree volumes. The tree growth variables data were subjected to descriptive statistics and used for fitting five nonlinear regression functions. The mean stem height, diameter at breast height and volume were 10.6 m, 8.9 cm, 0.032 m3, respectively. Out of the five yield equations fitted; the generalized combined variable model had the best predictive ability; with the lowest root mean square error (0.0084 m3) and Akaike information criterion (-2809). Therefore, the generalized combined variable model was recommended for yield estimation of Tectona grandis.