Diversity And Ecology Of Vascular Epiphytes In Harenna Afromontane Forestbale Ethiopia

The Ecology and Diversity of vascular epiphytes were studied in Harenna Afromontane Forest in southeastern Ethiopia atrnan altitude of 2000 -3000m. Fifty-five species of vascular epiphytes (i.e.22 holoeiphytes, 3 hemiepiphytes and 30rnopportunistic/humus/ epiphytes) were recorded. At all altitudinal levels, pteridophytes were the species rich group. ThernShannon-Weiner index (H/ = 1.62) of alpha diversity of the epiphyte community in the study area is low. The speciesrndiversity of vascular epiphyte is greatly influenced by the host tree biophysical factors, such as vertical gradient of hostrntree and size as well as the altitude. The regression correlation test showed that the number of species of vascularrnepiphytes and the size of host tree are positively correlated (R2 = 0.34, p = 0.0001) but non-linear correlation existsrnbetween the species number and bark and humus pH. The altitudinal distribution of species of epiphytes was higherrntowards the lower altitudes (for holoepiphytes and hemiepiphytes) but humus/edaphic epiphytes don’t exhibit clear patternrnof distribution. The altitudinal distribution of epiphytes may be influenced by altitudinal factors like temperature andrnmoisture. The vertical distribution of vascular epiphytes (holoepiphytes and hemiepiphytes) along the vertical gradient ofrnthe host trees indicated that most species were localized at the intermediate height, except humus epiphytes, which arernmostly restricted to the base and below first branches of the host trees. The vertical ecological gradients (i.e. solarrnradiation and humidity differences from the forest floor to the canopy) may be relevant for the distribution of epiphyternfloras. Majority of the species of epiphyte occurred in a wider range of both humus and bark pH (pH = 5.0 - 6.0 for barkrnand pH = 6.0 to 7.0 for humus) but few species were restricted to narrow range of pH. However, the pH values of humusrnand the barks utilized by specific species of vascular epiphytes were almost corresponds to each other. The host treernpreference of vascular epiphytes was exhibited by few species such as Aerangis brachycarpa, hosted on Vernoniarnamygdalina and Liparis deistelii, on Schefflera volkensii and Erythrina brucei.rnKey words: Disturbance, Holoepiphyte, Hemiepiphyte, Phorophyte, and Diversity, Bark pH, Humus pH.

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