A study of the distribution and diversity of the Family Orchidaceae on some selected lava flows of Mount Cameroon

Abstract

A survey was conducted between December 2005 and November 2006 to determine the diversity and distribution of the family Orchidaceae on three lava flows on Mount Cameroon and to relate species diversity and abundance to altitude, age and soil types. Thirty plots, each of 10 × 10 m were surveyed at low, mid and high altitudes on each lava flow. Forty nine orchid species belonging to 14 genera were identified, with the genera Bulbophyllum and Polystachya being the most represented. One unidentified species was encountered. A rare species, Vanilla sp, was identified in situ. Bulbophyllum porphyrostachys was the most abundant species and grew on the 1959 and 1999 aa lava flows. The least represented species were Ansellia africana and Diphananthe bueae. Diversity and distribution of the orchids depended on altitude, age and climate types of the various lava flows. Diversity was in the order 1922> 1999> 1959. Soil analyses revealed that important chemical parameters change with age and altitude of lava flows. These changes result in changes in diversity. Principal component analyses carried out to determine the orchid safe sites showed that, for any orchid establishment, their ecology, altitude and their association with lower plants (ferns mosses and lichens) are of vital importance.