Tree Species Diversity and Dominance in Ketumbeine Forest Reserve, Tanzania

Ketumbeine Forest Reserve, an isolated forest on a small protruding hill located in the dry area of northern Tanzania has unknown tree species diversity and dominance. Using a systematic grid of 390 m by 780 m in 77 randomly selected plots of 0.071 ha, located along nine transects, botanical names of tree species, diameter above breast height (dbh), regenerants and key shrub species were recorded in order to determine species diversity index, dominance index, number of shrubs and regenerants, forest stocking and tree basal area, respectively. A total of 26 tree species and 17 shrubs were recorded. The tree species with the highest importance values were Cassipourea malosana (37%), Nuxia congesta (20%), Olea europaea (10%), and Juniperus procera (10%), among others. The Simpson index value ranged between 0.0 and 0.0925 with Cassipourea malosana and Nuxia congesta having the highest index with 0.0925 and 0.0278, respectively. The Shannon index of tree species diversity ranged between 0.0177 and 0.3620 with Cassipourea malosana having the highest index. Forest stocking was 435 stems per ha with a mean species basal area of 30.49 m2 per hectare with Nuxia congesta occupying the highest (259.443 m2 per ha) area and Flacoutia indica the lowest (0.0044 m2 per ha), respectively. The estimated wood volume per hectare was 395.07 m3 . The mean total density of regenerants was 97 ± 30 stems per hectare with Urtica masaica (90), Lippia javonica (30), Rhus vulgaris (20), being the dominant shrubs. In conclusion, the forest has high tree species diversity which is a good stand characteristic of a natural forest. The forest basal area is quite good for the montane forest which normally ranges between 20-60 m2 / ha. However, if unchecked, human disturbance may alter the tree species composition. This survey established a baseline for future monitoring of the forest performance.