Project Database

Abstract:

Despite the fact that the vegetation pattern and history of the Bale Mountains in Ethiopia were reconstructed using pollen, little is known about the former extent of Erica species. The main objective of the present study is to identify unambiguous chemical proxies from plant-derived phenolic compounds to characterize Erica and other keystone species. Mild alkaline CuO oxidation has been used to extract sixteen phenolic compounds. After removal of undesired impurities, individual phenols were separated by gas chromatography and were detected by mass spectrometry. While conventional phenol ratios such as syringyl vs. vanillyl and cinnamyl vs. vanillyl and hierarchical cluster analysis of phenols failed for unambiguous Erica identification, the relative abundance of coumaryl phenols (>0.20) and benzoic acids (0.05—0.12) can be used as a proxy to distinguish Erica from other plant species. Moreover, a Random Forest decision tree based on syringyl phenols, benzoic acids (>0.06), coumaryl phenols (<0.21), hydroxybenzoic acids, and vanillyl phenols (>0.3) could be established for unambiguous Erica identification. In conclusion, serious caution should be given before interpreting this calibration study in paleovegetation reconstruction in respect of degradation and underground inputs of soil organic matter.

Abstract:

Fire plays a critical role shaping both the distribution and composition of the Afroalpine and Afromontane communities. Some plant communities are resilient to certain fire regimes, presenting post-fire traits such as resprouting, as is evident in the sub-Alpine Ericaceous zone, while others lacking these strategies are more fire-prone. The fire regime concept includes the biological role in fire occurrence because some of the parameters driving fire regimes – frequency, type or intensity - are often regulated by the vegetation through its structure, flammability and connectivity.

Abstract:

Garba Guracha is a cirque lake located at 3950 m altitude in the Bale Mountains National Park, Ethiopia, at the boundary between the Afro-alpine and sub-alpine Ericaceous vegetation belts. Jean-Jacques Tiercelin and Mohammed Umer cored its sediments in about 2002, leading to publication of one of the longest, best-dated, and most continuous Late Pleistocene-Holocene palaeoenvironmental records from above 3000 m in Africa. Their 2007 and 2008 papers document the vegetation and deglaciation history of the Bale Mountain plateau, which supports the most extensive area of Afro-alpine vegetation on the planet, and an exceptionally rich endemic biodiversity. However, those publications revealed little about human exploitation of the Bale Mountain environment. We again cored Garba Guracha (‘Black Lake’ in the Oromo language) in February 2017, as part of a major DFG-funded research unit (“The Mountain Exile Hypothesis - How humans benefited from and re-shaped African high altitude ecosystems during Quaternary climate changes”) that aims to test the hypothesis that human settlement of the Bale Mountains dates from at least the late Pleistocene. We also drilled cores from seven other sites in the area in early 2018, in partnership with archaeological, glacial geological and pedological investigations. Here we attempt an early synthesis of the results of ?XRF geochemistry, stable isotope, biomarker, pollen and charcoal analyses of the Garba Guracha sediments with a new age model based on radiocarbon and 210Pb ages, and suggest an initial interpretation of anthropogenic impact on the Bale Mountains.