Tree species distribution in forests of the Albertine Rift, Wesern Uganda

Abstract

The distribution of trees of diameter ≥ 10 cm was assessed in twelve 1-ha (20 · 500 m) plots of Bwindi Impenetrable National Park (BINP), Kasyoha-Kitomi Forest Reserve (KKFR), Kibale National Park (KNP) and Budongo Forest Reserve (BFR) in the Albertine Rift, western Uganda. Distribution was analysed at three spatial scales: local (1 ha plots), within individual forests (>300 km2 each) and regional (>56,000 km2). The aim was to classify tree species into Rabinowitz’s seven forms of rarity. We recorded 5747 trees in 53 families, 159 genera, and 212 species. Twenty two families had one species each while the rest had between two and 25 species. Number of species was highest in the family Euphorbiaceae (25 species) followed by Meliaceae and Rubiaceae with sixteen species each. Based on Rabinowitz’s forms of rarity, 93% of the species were geographically widespread, 47% were restricted to a single forest type, while 41% occurred at densities of <1 individual ha)1. Ubiquitous common species with high frequency and high local abundance occurred in the Meliaceae, Flacourtiaceae, Moraceae and Apocynaceae families. Conservation of geographically widespread species should focus on landscape rather than site specific approaches. The rarest species would benefit from species-specific strategies.