INFLUENCE OF TRADITIONAL GRAZING MANAGEMENT PRACTICES ON VEGETATION STRUCTURE AND RANGELAND CARBON STOCK POTENTIALS IN GUJI ZONE, SOUTHEAST ETHIOPIA

Abstract

This study was conducted in the Liben woreda of Oromia regional state, southeastern Ethiopia in May at the end of main rainy season (March-May, 2020). The objective of this study was to determine vegetation structure and carbon stock potential of Guji zone rangelands under the three traditional rangeland management practices i.e., near the village, main grazing land and communal enclosure. A combination of stratification and systematic random sampling was applied to collect the relevant information. Nested plots for collecting tree, shrub, herbaceous, litter and soil data were placed systematically on two parallel lines within each grazing management practice. The tree and/or shrub biomass was estimated using generalized allometric equations and carbon content was measured as 50% of dry biomass, and then converted to tons per hectare. Herbaceous plants were clipped to the ground, collected, oven dried, and their carbon stock was estimated as 50% of oven dried biomass. Litter was manually collected, oven dried and their carbon stock was estimated. A two way ANOVA was used for the data generated from vegetation and 3x3 factorial experiments with Randomized Complete Block Design (RCBD) was used for soil and herbaceous root data using R software. A total of 111 vascular plant species belonging to 40 families were identified. Of which, 61 were herbaceous plant whereas 50 were different tree and/or shrub species. Poaceae and Fabaceae families dominated the study areas. Of 61 herbaceous species identified, 31 (50.8%) were grass while 30 (49.2%) were non-grass species. The highest percentage of less desirable grasses and undesirable non-grass species were recorded in both near village and main grazing land whereas the highest desirable grasses recorded in the communal enclosure. There was significantly (P<0.05) high basal cover, both herbaceous and woody species diversity, species richness and evenness in the enclosure. This study identified that enclosure had the highest plant composition of both herbaceous and woody species than the main grazing and near village. Herbaceous, litter, and tree and/or shrub carbon were significantly higher (P<0.05) in the enclosure. Soil organic carbon showed significantly highest values (P<0.05) in the enclosure and decreased (P<0.05) with increasing depth. It is concluded that communal enclosure had more species diversity, basal cover, desirable herbaceous and woody species, vegetation carbon and soil organic carbon. Therefore, the expansions of communal enclosure with proper management are recommended for better vegetation condition and enhanced soil organic carbon. However, as enclosure needs significant woody thorny plant to be fenced and releases methane per animal unit from slowly degradable fiber of standing hay at the end of dry season. Thus, if life fences will not be used, the author recommends that future studies should consider carbon emissions from the woody plant cut for fences and the trade-off between rescued livestock in face of feed shortage and CH4 emission to unravel the true role of the enclosure in climate change adaptation and mitigationHaramaya