Abstract
As the extinction risk of plants increases globally, there is need to prioritize areas with high floristic richness and diversity to inform the design of evidence-based conservation interventions. As such, this study aimed to; (i) determine the floristic richness and diversity in six central forest reserves of north eastern Uganda and (ii) evaluate the similarity and complementarity of floristic composition. Data was collected from nested quadrats (20 x 20 m for trees, 10 x 10 m for shrubs and 5 x 5 m for herbaceous climbers, forbs and grasses) placed at intervals of 100 m along a transect of 1000–1500 m. Species richness, diversity and evenness were determined for each forest reserve. Binary similarity coefficients were computed because only presence/absence data of plant species was recorded. A sum of 417 plant species in 76 families were recorded representing 8.7% of known vascular plants reported in Uganda. All the CFRs had high diversity indices ranging from 4.2 in Kano CFR to 4.47 in Bululu hill CFR. In terms of floristic similarity, the CFRs clustered into two groups namely Onyurut and Ogera hills cluster and Akur, Kano, Bululu hills and Mount Moroto cluster. The CFRs complement one another by supporting plant species not recorded elsewhere. Notably, three CFRs (Bululu hills, Mount Moroto and Onyurut) account for 81.53% of the plant taxa. Addition of the fourth (Ogera hills) accommodates nearly 90% of the species and the fifth (Akur CFR) accounts for more than 95% of the species. The highest threat level on taxa in these CFRs is Vulnerable (4 species) and Near Threatened (4 species) with 137 Least Concern and 270 Not Evaluated. The CFRs in NE Uganda have richness and floristic diversity with up to 8.7% of the known plants in Uganda present. The two similarity clusters depict variation in altitudinal, proximity and climatic conditions. Five CFRs are required to conserve 95% of the species recorded. There is need to assess the population of the threatened species, and investigate the edaphic factors which influence plant distribution.