Forest Structure Analysis in the Oban Division of Cross River National Park, Nigeria

Abstract

Information on forest structure is important for forest management decisions. This is inadequate in many situations, especially where timber is not of primary interest. We analyzed the structure of two forest types in the Oban Division of Cross River National Park, Nigeria. Systematic sampling technique was used to establish two transects measuring 2,000 x 2 m, at 600 m interval in the two forest types in four locations. Four 50 m x 50 m plots were located alternately at 500 m intervals along each transect, constituting 32 plots per forest type and 64 plots in all. Diameters at breast height (DBH), base; middle and top; crown diameter; total height and crown length were measured on all trees with DBH > 10 cm. There were 159 stems/ha in the close-canopy forest and 132 stems/ha in the secondary forest. The mean DBH were 34.5 cm and 33.62 cm respectively. The mean heights were 24.79 m and 23.97 m, respectively. Basal area/ha were 41.59 m2 ha'1 and 27.38 m2 ha'1 for the two forest types. Majority of the trees encountered in the two forest types belonged to the middle stratum which has implication for small mammals’ populations. Emergent trees which are otherwise scarce in other parts of the country were recorded, which also has implications for density thinning and seed supplies