GROWTH AND YIELD ESTIMATION OF SOME PRIVATE FOREST PLANTATIONS IN EKITI STATE, NIGERIA

Abstract

This study investigated growth and yield estimation of private forest plantations in Ekiti State. The scientific management of forest resources requires knowledge of growth and yield of various tree species in the forest, which can be achieved through stand growth measurements and assessments. This study was carried out in four purposefully selected local government areas in Ekiti State with the highest concentration of private forest plantations. In each local government area, the dominant plantation tree species was selected for detailed enumeration. Growth data (e.g. dbh, height etc) was taken from three (3) age classes of each dominant species. Each year’s planting of the selected dominant species in each LGA were divided into blocks of one hectare (1 ha), out of which one block was randomly chosen. The 1 ha block was divided into 25 m × 25 m temporary sample plots from which three (3) were randomly selected for detailed enumeration. Various tree growth variables were measured in each sample plot while age of the plantation was obtained from plantation record. Both linear and non-linear regression methods were used in constructing growth and yield model(s) and the best selected based Mean Square Error (MSE), Coefficient of Determination (R2) and residual analysis were used in the selection of the best model among the proposed models. Private forest plantations exist in 12 of the 16 LGAs in Ekiti state, with age ranging from 1 to 46 years. Tectona grandis is the dominant plantation species being established by the private sector in Ekiti state. A total of 1606 ha of private forest plantations has been established in various parts of Ekiti state. Though density of trees was high in all plantations, it was much higher in younger plantations than older ones. Mean dbh of trees ranged from 9.1 to 17.0 cm between the ages of 10 and 40 years while mean tree height varied from 11.1 to of 21.1 m. Mean stand basal area ranged from 13.20 m2/ha to 25.59 m2/ha while stand volume varies from 91.64 m3/ha to 263.72 m3/ha. Several model forms were tried on the