SOME OBSERVATIONS ON THE BIOMASS AND DISTRIBUTION OF CRYPTOGAMIC EPIPHYTES IN THE UPPER MONTANE FOREST OF THE RWENZORI MOUNTAINS, UGANDA

Measurements were made of the percentage cover, biomass and species-ri chness of cryptogamic epiphytes growing upon mature Phillipia phillipi a stands in the ericaceous (upper montane) forest of the Rwenzori Moun tains, Uganda. Macrolichens, especially Usnea spp., dominated the uppe r canopy, while a range of large cushion-forming hepatics (e.g. Chando nanthus, Herbertus, and Plagiochila species) dominated the lower canop y. The distribution of cryptogams was largely controlled by light inte nsity and phorophyte age. Detailed studies of a felled Phillipia revea led twenty-nine epiphyte species (two algae, fourteen bryophytes, elev en lichens and two ferns). The forest appears to be moderately species -rich with a small number of species providing a large proportion of t he cryptogam biomass. Total biomass of the epiphytes was close to 1 to nne ha(-1), representing about 10% of the above-ground standing crop. Concentrations of N, P and K in the epiphytes were estimated as 10, 1, and 3 kg ha(-1) respectively. The lichens and bryophytes contained ab out 2% and 8% respectively of the total above-ground nutrients. Microc limate measurements below the forest canopy demonstrated constant high humidity with suboptimal radiation. Air temperature below the canopy averaged 7.6 degrees C (range 4-9.5 degrees C) during a 10-day period, and increased slightly with canopy height. Evaporation below the fore st canopy showed a significant decline as altitude increased from 2300 to 3600 m.