Impacts of Bush Management on Herbaceous Plant Diversity and Biomass and, Soil Organic Carbon and Nitrogen in Borana Rangelands, Southern Ethiopia

Siraj Kelil Gobelle

doi:10.11648/j.jps.20210902.12

Abstract

Bush thinning or clearing rangeland management practice in Borana rangelands considered to have a high potential to improve rangeland productivities and soil conditions, yet few studies have quantified the impacts of bush management on herbaceous plants species diversity, biomass and soil Organic Carbon and Nitrogen contents. This study was conducted in Yaballo (Hara-woyu Kebele) and Taltale (Sarite kebele) Woreda of Borana zone, to evaluate the impacts of bush management (thinning) on herbaceous plant species composition, diversity, biomass and some selected soil physicochemical properties. Data were collected from bush thinned and bush encroached rangeland management classes at both sites. Sampling plots were placed systematically along the geographic gradient in both of the rangeland management classes at both study sites. Within all plots, herbaceous plants were identified and clipped to the ground, collected and oven-dried to determine biomass. Herbaceous plant species, diversity, biomass and soil organic carbon contents and soil carbon stock were higher under Bush managed (thinned) class compared to bush encroached. However, bush management (thinning) have not shown considerable effects on soil bulk density, pH, nitrogen contents and total nitrogen stock. Thus, understory vegetation and soil organic carbon were influenced by the presence of thinning, but soil bulk density, pH, nitrogen contents were not influenced by thinning in this study. Generally, bush management (thinning) increased the rangeland condition, however; the management is not sustainable in case the thinning practice is not followed recommended procedures because most of the encroacher species are sprout more densely within a short time.

Highlights

Rangeland and savanna ecosystems are characterized by the coexistence of trees, shrubs and grasses
The findings from this study indicated that grass aboveground biomass at the two study sites was not significantly different, but it was significantly different between bush encroached and bush thinned rangeland management class
This paper provides the empirical pieces of evidence on the effects of bush-management on herbaceous plant species diversity and biomass and, soil organic carbon and nitrogen in Borana rangelands, Southern Ethiopia

Summary

Introduction

Rangeland and savanna ecosystems are characterized by the coexistence of trees, shrubs and grasses. The mechanisms permitting the co-existence of trees and grass in Savannas are determined by competition for resources or differential sensitivity to disturbance of the two growth forms [1]. The co-existence of trees and grass is due to the simultaneous influence of rainfall and fire. In the increased rainfall savanna (moist savanna) the co-existence of trees and grasses can only occur in the presence of a high level of fire disturbance [1]. This cohabitation of trees and grass in savanna ecologies provides comprehensive economic and ecological benefits to pastoralist communities [2]. The productivity and long-term economic viability, as well as the ecological integrity of savanna and grasslands are being weakened by increasingly dense thickets of woody vegetation often named as bush encroachments

Methods

Results

Conclusion