Estimating Tree Height and Volume of Gmelina arborea and Three other Tree Species in Plantations of South-West, Nigeria
This study explores the estimation of stand structure of Gmelina arborea and three other tree species in two plantations, in Ibadan, South West Nigeria, with the primary objective of estimating plot – level mean tree height, merchantable tree height, and volume of Gmelina arborea, Terminalia montalis, Tectona grandis, and Triplochiton scleroxylon. The number of tree species and the volume of wood in the two selected plantations were determined. Random sampling method was adopted in carrying out the assessment of the stand structure. Each plantation was divided into three plots of dimension 32mx32m. Twenty (20) stands were selected randomly in each plot, hence sixty (60) stands in each plantation. Quantitative data were taken on: Diameter at breast height (DBH), Total tree height (TTH), Basal area (BA) and Total volume (of wood) (TVOL). A total of three species were encountered in the two study area; the family Verbenaceae has the highest tree species (75%) in the two plantations. During the assessment of the tree species in both plantations, the results revealed that majority of the trees’ (68%) diameter were within 10-20cm, and the number of tree species in the upper diameter class (>60cm) (20%) were considerably small. Trees in the Gmelina plantation had on average, lower merchantable heights than those in the College Arboretum, despite having higher total tree height, diameter at breast height, basal area, and area volume. Inventory analysis of these plantations will establish a base-line information about the stand, point out possible improvements to the management plan and provide information on the volume of merchantable logs that can be extracted from the stand.
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