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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Date
2017-05
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Addis Ababa Universty
Abstract
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
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Keywords
Bale Mts, Sanetti Plateau, Erica shrubs, Fire history, Stable isotope (δ13C, δ15N) and BC