Reconstruction of Environmental and Vegetation Changes on the Sanetti Plateau in South Ethiopia, since the Last Deglaciation Based on Biogeochemical Analyses of Sediments

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Addis Ababa Universty


The aim of the study was to contribute to a better understanding of the environmental and vegetation changes of Erica arborea and Erica trimera at the Sanetti plateau community, in the upper Afroalpine vegetation zone of the BMNP (Bale Mountain National Park) South Ethiopia. A sediment core was recovered from a small glacial depression at 3990m altitude in the Bale Mountains of Ethiopia. Accumulation δ13C and δ15N values of the soil organic matter (SOM) in the sediments were analyzed with the objective to get information about environmental changes. The results support hypotheses about climate influences or vegetation changes onδ13C values of SOM during the late Glacial and Holocene δ15N values showed a negative trend with increasing sediment depth, indicating that after deglaciation N cycles were very closed but opened with pronounced fluctuations towards the beginning of the Holocene. δ15N maxima during the Late Glacial and Early Holocene roughly correlate with BC maxima supporting the hypothesis that also fire might influence δ15N values of SOM. If differences in land use history have larger effects on δ13C values than climate fluctuations then δ15N values of SOM may be valuable in conjunction with δ13C analyses for reconstructing aspects of land use and climate variability. Erica shrub and forest decreased in area with increasing altitude and the Afroalpine ecosystem expanded on the plateau. Human impact on the high-altitude Afroalpine and Ericaceous vegetation has been relatively minor, confirming that the endemic biodiversity of the Ethiopian mountains is an inheritance of natural Holocene vegetation change. The aim was to test the potential of Black carbon (BC) analysis in order to make clear the input from grass and wood fires and discuss the potential limitations of the method on sediments of the Garba Guracha. Sediments cover the cultural transition from hunter gatherers to food-producing communities during middle of Holocene. Key words; Bale Mts., Sanetti Plateau, Erica shrubs, fire history, stable isotope (δ13C, δ15N) and BC



Bale Mts, Sanetti Plateau, Erica shrubs, Fire history, Stable isotope (δ13C, δ15N) and BC