Fitting Linear and Non Linear Growth Models for Selected Plantations in Omo Forest Reserve Southwestern Nigeria

Abstract

This study was conducted to assess the suitability of forest models in Tectona grandis, Pinus caribaea and Nauclea diderrichii stands at Omo forest reserve, Ijebu East, Ogun State, Southwestern Nigeria. Temporary sample plots of equal size (25 m x 25 m) were laid while complete enumeration were carried out in each sampled plot and tree growth variables such as diameter at breast height (dbh), diameter at the top (dt), diameter at the middle (dm) and diameter at the base (db) as well as total height of all trees were measured. Simple linear models and six non linear models were developed and assessed for the selected plantation. The linear model developed _ R-squared ranged from 77% to 93%. The least R- square was obtained in Tectona grandis plantation and the highest was obtained in 93% Pinus caribaea. All the models have high F values ranging from 234.71 to 2965.40. In Tectona grandis plantation, Logistic power model, gave a good fit in describing the relationship between diameter at breast height and volume with AICC values of -2368.92, 0.22 each. The Sigmond models that gave a good fit in describing the relationship between the diameter at breast height and volume in Pinus caribaea were Weibull model (-719.19, 0.09) while Gompertz relation is the best for Nauclea diderrichii, respectively. The various models generated in the study are highly recommended for use in estimating the growth characteristics of the plantation in the future.