Diversity of Vascular Epiphytes Along Disturbance Gradient in Yayu Forest, Southwest Oromia, Ethiopia
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Date
2010-07
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Addis Ababa University
Abstract
The change in species diversity and composition of vascular epiphytes along disturbance
gradient was studied in Yayu forest of southwest Ethiopia. Systematic sampling method was
employed in data collection with a line transect was laid out along disturbance gradient of the
forest. Based on their increasing level of disturbance, the forest was divided into three
management zones: natural forest (core zone), semi-forest coffee production system (buffer
zone) and agricultural matrices (transition zone) respectively. A total of thirty-six species of
vascular epiphytes were recorded from thirty-five host (phorophyte) species in the study area.
Each forest zone harbored considerable number of epiphyte species, 31 species in core zone,
32 species in buffer zone and 24 species in transition zone. This indicates the existence of
changes of species diversity along disturbance gradient of the forest due to anthropogenic
disturbance. The species diversity of vascular epiphytes is also greatly influenced by the
phorophyte biophysical factors, such as vertical gradient on individual host plants, host size,
bark texture and elevation. Thus, vertical distribution of vascular epiphytes indicated that
species diversity increases from phorophyte base to the canopy. The larger and older trees of
the same offer more surface than small trees and also have been available for a longer time
than younger hosts for epiphyte colonization. Rough bark texture of the phorophytes has high
water retention capacity and is more convenient for vascular epiphyte species establishment
than smooth ones. The changing forest structure and tree species composition at increasing
altitude provide different quantities and qualities of substrate to epiphytes that resulted in
decreasing number of epiphyte species with increasing elevation. Furthermore, host preference
of vascular epiphytes was apparently exhibited by few species such as: Angraecopsis
infundibulum, Polystachya cultriformis, Vittaria volkensii, Chlorophytum comosum and
Coleochloa abyssinica.
Key words: Disturbance Gradient, Diversity, Phorophyte, Species composition, Species
turnover, Vascular Epiphyte, Yayu Forest.
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Keywords
Disturbance Gradient, Diversity, Phorophyte, Species composition, Speciesturnover, Vascular Epiphyte, Yayu Forest