Phenolic Compounds as Unambiguous Chemical Markers for the Identification of Keystone Plant Species in the Bale Mountains, Ethiopia
1
Institute of Agronomy and Nutritional Sciences, Soil Biogeochemistry, Martin Luther University Halle–Wittenberg, Von–Seckendorff–Platz 3, D–06120 Halle, Germany
2
Ethiopian Biodiversity Institute, Forest and Rangeland Biodiversity Directorate, P.O. Box 30726 Addis Ababa, Ethiopia
3
Institute of Computer Science, Bioinformatics, Martin Luther University Halle–Wittenberg, Von Seckendorff-Platz 1, 06120 Halle (Saale), Germany
4
Institute of Geography, Technical University of Dresden, Helmholtzstrasse 10, D–01062 Dresden, Germany
5
Department of Urban Agriculture, Misrak Polytechnic College, P.O. Box 785, Addis Ababa, Ethiopia
6
Institute of Soil Science and Soil Geography, University of Bayreuth, Universitätsstrasse 30, D–95440 Bayreuth, Germany
7
Department of Plant Biology and Biodiversity Management, Addis Ababa University, P.O. Box 3434 Addis Ababa, Ethiopia
*
Author to whom correspondence should be addressed.
Plants 2019, 8(7), 228; https://doi.org/10.3390/plants8070228
Received: 17 June 2019 / Revised: 8 July 2019 / Accepted: 12 July 2019 / Published: 16 July 2019
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.
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Keywords:
paleoclimate; pollen; paleovegetation; oxidation; phenols; Erica; biomarkers; machine learning
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Doi: 10.5281/zenodo.3247691
Description: Figure S1: Comparison of Accuracy (A) and F1 Score (B) of Support Vector Machine (SVM, blue), Random Forest (RF, red) and Recursive Partitioning (RP, grey) algorithm based on the level of relative phenols, in relation to the ratio of tested/total number of samples (n=47) that has been split into test and training datasets, each model has been computed 5 times, the bars indicate the standard derivation between the prediction results of the models; Figure S2: Principal Component Analysis, PCA based on the relative phenol abundance in 47 leaf and twig samples from the Bale Mountains, shown are the first two principal components (PC1 and PC2). Dark red arrows indicate the direction of each vector of feature; Figure S3: Cross-validation of the model used; Table S1: Sum of weighted mean of phenolic compounds of each dominant plant species.
MDPI and ACS Style
Lemma, B.; Grehl, C.; Zech, M.; Mekonnen, B.; Zech, W.; Nemomissa, S.; Bekele, T.; Glaser, B. Phenolic Compounds as Unambiguous Chemical Markers for the Identification of Keystone Plant Species in the Bale Mountains, Ethiopia. Plants 2019, 8, 228. https://doi.org/10.3390/plants8070228
AMA Style
Lemma B, Grehl C, Zech M, Mekonnen B, Zech W, Nemomissa S, Bekele T, Glaser B. Phenolic Compounds as Unambiguous Chemical Markers for the Identification of Keystone Plant Species in the Bale Mountains, Ethiopia. Plants. 2019; 8(7):228. https://doi.org/10.3390/plants8070228
Chicago/Turabian StyleLemma, Bruk; Grehl, Claudius; Zech, Michael; Mekonnen, Betelhem; Zech, Wolfgang; Nemomissa, Sileshi; Bekele, Tamrat; Glaser, Bruno. 2019. "Phenolic Compounds as Unambiguous Chemical Markers for the Identification of Keystone Plant Species in the Bale Mountains, Ethiopia" Plants 8, no. 7: 228. https://doi.org/10.3390/plants8070228
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