Bush Encroachment And Its Impacts On Plant Biodiversity In The Borana Rangelands

Until few decades ago the Borana rangeland was considered as one of the finestrngrazing areas in East Africa. However, the pastoral system has recently shownrnsymptoms of destabilization because of the shift in the natural balance betweenrntrees and grasses, and bush-tree cover has become dominant in the rangeland. Inrnorder to assess the major encroaching woody plant species and their advancementrnunder three land use units (Kalo, Worra & Foora); the impact on plant biodiversity; asrnwell as possible causes of the encroachment and their challenges to the pastoralrncommunity; a comprehensive vegetation and household survey was conducted. Thernresults of the study revealed that the density of woody species in the study area isrn4185 ha ̄ ¹, which is far beyond the critical limit. Species such as Acaciarndrepanolobium, A. mellifera, A. bussi, A. bresvispica, and A. senegal were found tornbe the major encroaching species. The mean density of total woody speciesrnsignificantly differed across the land use units (P < 0.05). Relatively higher densitiesrnof woody plants occurred at Kalos that might associate with reduced grazingrnpressure in Kalos compared to other land use units provide suitable environment forrnseeds to germinate. Diversity of herbaceous grass species negatively correlated withrnwoody density(r=-0.520, p

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