On the afroalpine vegetation of the Ruwenzori Mountains, Uganda
Schmitt, K.; Beck, E.
The afroalpine vegetation of the Butawu valley (Ruwenzori Mountains, Uganda) was analysed in 1984 in an area of c. 2.5 km2 between 3800 and 4500 m asl. This area is characterised by high precipitation, regular nocturnal frost and the prevalence of well-drained Leptosols. Fifteen plant communities comprising twenty-seven subcommunities and two types were described. Two of these communities were interpreted as series comprising seven subcommunities or stages. Tussock grassland is the pioneer vegetation on sites which allow the accumulation of soil matter and on the upper parts of recent scree fields. At its lower limits this grassland is invaded by the most widespread community in the valley, Helichrysum bush. This bush commonly forms a transition zone to the spectacular Senecio woodland, which obviously represents the climax community and favours well-drained and wind-sheltered sites on the valley floor. Another woodland, dominated by Hypericum bequaertii, is described for the first time for the Ruwenzori Mountains. Erica excelsa bush borders the Carex bogs of the lower alpine zone, i.e. the zone where afroalpine plant communities grow together with Erica bush. Here small patches of Alchemilla shrub are found on gently-sloping sites with moderately-drained topsoils. Mosses and lichens are dominant and typical of the upper alpine zone. The differences in vegetation growing on the two sides of the Central Ruwenzori, resulting from varying environmental factors, are discussed.