DIVERSITY AND DISTRIBUTION OF EPIPHYTIC ORCHIDS IN KIBALE NATIONAL PARK, UGANDA

摘要

The diversity and the distribution of epiphytic orchids in Kibale National Park were investigated. Sampling was by the canopy-based methods that included the Single Rope Technique and a local climber. There were 57 species dominated by genera Polystachya, Bulbophyllum, Tridactyle, Angraecum, and Diaphananthe. There was a weak positive correlation between the orchid's species and basal area of the host trees, but no significant difference in the number of orchid's species between the logged and un-logged forests. Bark inhabitant orchids were characterized by succulence as one of the structural adaptations for water conservation against drought. Most species occurred in the light humus substrate that consisted mainly of bryophyte mats with adequate water retention capacity. Epiphytic orchids were characterized by host preference and not specificity. The most favored phorophytes in un-logged and logged forests were Parinari excelsa, Strombosia scheffleri, Symphonia globulifera, Mitragyna rubrostipulata and Pseudospondias microscarpa. The general pattern of the vertical distribution of epiphytes was that of an increase from the tree base to branch zones and thereafter a decline to the top branch zone. The canopy zones had similar epiphyte communities that were different from that of the host trunk zone.