Estimation of tree characteristics as conservation tools in the tropical rainforest ecosystem of Oluwa Forest Reserve, Ondo State, Nigeria

Abstract

This study was carried out in the Oluwa forest reserve describing some forest characteristics as forest inventory results to draw the attention of the forest managers to the declining status of the forest and also showcase the conservation potentials of the tropical rainforest of Oluwa forest reserve, Ondo State, Nigeria. Stratified random sampling was adopted to capture the different land use classes present in the forest reserve with clusters of 115 m x 115 m containing three sample plots of 35 m x 35 representing elbow, north and east plot called parent plots. In each parent plot, three nested plots (2 m x 2 m; 7 m x 7 m; and 25 m x 25 m) were constituted to capture different diameter classes of trees. The data collected were scientific names, DBH, diameter at the base (Db), diameter at the middle (Dm), diameter at the top (Dt) and total height of all live trees. The data were screened and analysed for analysis; basal area, volume, biomass and carbon. The result revealed that the mean diameter at breast height (DBH, 16.20 cm) was far lower than the recommended tree for exploitation as the minimum merchantable size (48 cm) stipulated by the logging policy of South-western Nigeria. The basal area ranged between 140.01 and 170.48 m² ha^–1 and the tree volume ranged between 821.65 and 1,247.46 m³ ha^–1. Also, the above ground biomass of trees ranged between 290.87 and 830.02 Mg ha^–1; and the carbon stock assessed spanned from 145.44 and 415.01 Mg C ha^–1 for different land use classes considered for this study. This study has provided another opportunity for informed decisions on the need for more conservation efforts. The forest managers, policymakers and other stakeholders should prioritise strategies in forest reserve management to include forest services, rather than the only exploitation mechanism.