Species diversity and vegetation structure of woody plants in regenerating Juniperus forest replacing Eucalyptus in the conservation area of Gullele Botanic Garden, Addis Ababa, Ethiopia

Abstract

The Gullele Botanic Garden (GBG) adjoins the north-western limit of the city of Addis Ababa, capital of Ethiopia. The floristic composition, species diversity and vegetative structure of the woody plant species in the conservation area of the garden are presented from 81 plots (20 m x 20 m). A total of 104 woody plant species (90% indigenous, the rest planted or naturalised) of 83 genera and 47 families were recorded. The dominant families were Fabaceae and Asteraceae. The number of individuals of the most dominant species, Juniperus procera, decreases with increasing DBH and height class, which indicates a good and healthy reproduction potential of the species in the conservation area. No statistically meaningful plant communities could be identified in the conservation area. Many of the species present in the dry forests of the central Ethiopian plateau occur in GBG. The species richness appears to be relatively high in comparison with what other researchers have found in natural forests on the highland plateau; 87 native woody species (of which 11 are planted) in GBG, 57-97 (cumulatively 127) in Wof-Washa, 32-85 (cumulatively 113) in Menagesha and 41-77 (cumulatively 81) in Chilimo, 34-67 (cumulatively 69) in Entoto, though the definitions for woody species have varied between studies. Clustering on the floristic data gives four partly overlapping clusters with the lowest p-values for indicator species, but the distribution of the plots on clusters changes notably if information on Eucalyptus is in- or excluded. Ordination graphs with partly overlapping groups of species are presented. The findings in this paper can serve as a baseline to follow the regeneration of the conservation area towards natural forest. This is needed for future management and sustainable utilization of the forest species at local and national levels.