Phenolic Compounds as Unambiguous Chemical Markers for the Identification of Keystone Plant Species in the Bale Mountains, Ethiopia
Bruk Lemma,
Claudius Grehl,
Michael Zech,
Betelhem Mekonnen,
Wolfgang Zech,
Sileshi Nemomissa,
Tamrat Bekele,
Bruno Glaser
Affiliations
Bruk Lemma
Institute of Agronomy and Nutritional Sciences, Soil Biogeochemistry, Martin Luther University Halle–Wittenberg, Von–Seckendorff–Platz 3, D–06120 Halle, Germany
Claudius Grehl
Institute of Agronomy and Nutritional Sciences, Soil Biogeochemistry, Martin Luther University Halle–Wittenberg, Von–Seckendorff–Platz 3, D–06120 Halle, Germany
Michael Zech
Institute of Agronomy and Nutritional Sciences, Soil Biogeochemistry, Martin Luther University Halle–Wittenberg, Von–Seckendorff–Platz 3, D–06120 Halle, Germany
Betelhem Mekonnen
Institute of Agronomy and Nutritional Sciences, Soil Biogeochemistry, Martin Luther University Halle–Wittenberg, Von–Seckendorff–Platz 3, D–06120 Halle, Germany
Wolfgang Zech
Institute of Soil Science and Soil Geography, University of Bayreuth, Universitätsstrasse 30, D–95440 Bayreuth, Germany
Sileshi Nemomissa
Department of Plant Biology and Biodiversity Management, Addis Ababa University, P.O. Box 3434 Addis Ababa, Ethiopia
Tamrat Bekele
Department of Plant Biology and Biodiversity Management, Addis Ababa University, P.O. Box 3434 Addis Ababa, Ethiopia
Bruno Glaser
Institute of Agronomy and Nutritional Sciences, Soil Biogeochemistry, Martin Luther University Halle–Wittenberg, Von–Seckendorff–Platz 3, D–06120 Halle, Germany
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.
