BUSH ENCROACHMENT CONTROL DEMONSTRATIONS AND MANAGEMENT IMPLICATIONS ON HERBACEOUS SPECIES IN SAVANNAS OF SOUTHERN ETHIOPIA

Abstract

Proper management of bush control methods need to be effectively demonstrated to resource users. In this paper, we evaluated effects of disturbance control (CO) (i.e., government policy approach in the conservation of natural resources), tree cutting and fire (C+F), tree cutting, fire and grazing (C+F+G), the old traditional method of applying fire and grazing (F+G) by herders, grazing with bush cover (GBC) (i.e., current system of land use system by herders in Borana) and tree cutting alone (C) (i.e., Non-governmental Organizations approach in rangeland improvement) on herbaceous species composition, abundance, biomass, basal cover and species diversity in southern Ethiopia. The disturbance control demonstration showed no advantage in terms of biomass and basal cover over other treatments, although herbaceous species richness was improved. Bush removal methods such as tree cutting and fire, tree cutting followed by fire and grazing, fire and grazing, and tree cutting alone improved herbaceous biomass, basal cover and species diversity, while grazing alone greatly reduced herbaceous biomass. Tree cutting and fire treatments seemed superior in terms of herbaceous biomass, while conservation of herbaceous species diversity was improved more by the traditional method of fire and grazing, and tree cutting. With the exception of species richness, protection from disturbance showed no advantage. Only fire and grazing methods can reasonably be applied for the control of bush encroachment with the overall objective of promoting biomass production and species diversity.