TREE VOLUME AND STEM TAPER EQUATIONS FOR TEAK(Tectona grandish L.F)PLANTATIONS IN ARAMOKO FOREST RESERVE, EKITI STATE,NIGERIA

Abstract

The effective scientific management of forest resources requires knowledge of growth and yield of various trees species in the forest. This can be achieved through stand growth measurement and assessment. The study examined the growth and yield characteristics, generates tree volume and stem taper equations for Tectona grandis plantations in Aramoko Forest Reserve, Ekiti State, Nigeria. Six (6) age series were selected for this study. Enumeration of tree growth parameters was conducted within the sample plots of 20m x 20m in each one hectare block from which 3 sample plots were randomly selected per each age series. The data were subjected to linear, non linear, multiple regression analysis, scattered diagram showing growth and yield models developed, growth and yield characteristics. Regression analysis was done with the use of Statistical Package for Social Scientists (SPSS) to generate equations relating tree volume and tree diameter; tree diameter at any height. Eight (8) individual tree volume models and four (4) taper equations were generated for four diameter classes (10-20 cm, 20-30 cm, 30-40 cm and 40-50 cm) and were all assessed using F-ratio, Root Mean Square of Error (RMSE), Adjusted R-Square (R2adj). The models were validated using t-test to compare the observed and predicted volume. Linear model 𝑉=−0.457+0.034𝑑𝑏ℎ was selected as the best tree volume equation to predict volume of Tectona grandis in the study area. Taper equations generated for the diameter classes are 𝑑2=𝐷2(1.784(ℎ𝐻−1)−20.978(ℎ2𝐻2−1)), 𝑑2=𝐷2(10.264(ℎ𝐻−1)−34.239(ℎ2𝐻2−1)), 𝑑2=𝐷2(10.916(ℎ𝐻−1)−46.935(ℎ2𝐻2−1)), 𝑑2=𝐷2(−13.296(ℎ𝐻−1)−27.513(ℎ2𝐻2−1)) for trees in 10-20 cm, 20-30 cm, 30-40 cm and 40-50 cm diameter class respectively. The equations developed met the criteria for appropriateness, were biological plausible and thus recommended for use for Tectona grandis plantation in the study area.