Assessment of Stand Density and Growth Rate of Three Tree Species in an Arboretum within the University of Uyo, Nigeria

Abstract

Plots of Gmelina arborea, Nauclea diderrichii and Tectona grandis at the arboretum of the Department of Forestry and Wildlife, University of Uyo, were assessed for stand density and diameter growth rates of the tree species. All the trees in the three plots were counted and their diameters at breast height (dbh) measured. Diameter tape was used in measuring dbh. Density of each plot was determined by calculating the number of trees and basal area per hectare of the plot. Gmelina arborea stand had the highest density of 300 treesha^-1 and a basal area of 36.68m²ha^-1, followed by Nauclea diderrichii stand with a density of 168 treesha^-1 and a basal area of 19.37m²ha^-1. Tectona grandis had the lowest stand density of 86 treesha and a basal area of 9.05m²ha^-1. The diameter growth rates of the species were determined by calculating their mean annual increments (MAIs) in DBH. Gmelina arborea and Nauclea diderrichii had an average DBH of 38cm each and mean annual increments (MAIs) of 2.21cmyr^-1 and 2.36cmyr^-1, respectively, while Tectona grandis had an average DBH of 36cm and MAI of 2.37cmyr^-1. Mean annual increment generally increased with decline in stand density. It was recommended that the stock density in Gmelina arborea plot should be reduced while that of the Tectona grandis should be increased, all to 45% of their initial stockings.

Key Words: Stand density, growth rate, tree Species, arboretum, Nigeria