Lemma, B.; Mekonnen, B.; Glaser, B.; Zech, W.; Nemomissa, S.; Bekele, T.; Bittner, L. & Zech, M. (2019): <b>Chemotaxonomic patterns of vegetation and soils along altitudinal transects of the Bale Mountains, Ethiopia, and implications for paleovegetation reconstructions – Part II: lignin-derived phenols and </b>. <i>E&G Quaternary Science Journal</i> <b>68</b>, 189-200.
Resource Description
Title:
Chemotaxonomic patterns of vegetation and soils along altitudinal transects of the Bale Mountains, Ethiopia, and implications for paleovegetation reconstructions – Part II: lignin-derived phenols and
FOR816dw ID:
134
Publication Date:
2019-09-04
License and Usage Rights:
Resource Owner(s):
Individual:
Bruk Lemma
Contact:
email:
bruk_lemma <at> yahoo.com
06110 Halle(Saale)
Heinrich-Schütz Straße 7
Germany
Erica is a dominant vegetation type in many sub-afroalpine ecosystems, such as the Bale Mountains<br/>
in Ethiopia. However, the past extent of Erica is not well known and climate versus anthropogenic<br/>
influence on altitudinal shifts are difficult to assign unambiguously, especially during the Holocene.<br/>
The main objective of the present study is to chemotaxonomically characterize the dominant plant<br/>
species occurring in the Bale Mountains using lignin phenols and n-alkane biomarkers and to examine<br/>
the potential of those biomarkers for reconstructing vegetation history. Fresh plant material,<br/>
organic layer and mineral topsoil samples were collected along a northeastern and a southwestern altitudinal<br/>
transect (4134–3870 and 4377–2550ma.s.l., respectively). Lignin-derived vanillyl, syringyl<br/>
and cinnamyl phenols were analyzed using the cupric oxide oxidation method. Leaf-wax-derived n-<br/>
alkanes were extracted and purified using Soxhlet and aminopropyl columns. Individual lignin phenols<br/>
and n-alkanes were separated by gas-chromatography and detected by mass spectrometry and flame<br/>
ionization detection, respectively.<br/>
We found that the relative contributions of vanillyl, syringyl and cinnamyl phenols allow us to<br/>
chemotaxonomically distinguish contemporary plant species of the Bale Mountains. Erica in particular<br/>
is characterized by relatively high cinnamyl contributions of > 40 %. However, litter degradation<br/>
strongly decreases the lignin phenol concentrations and completely changes the lignin phenol pat-<br/>
terns. Relative cinnamyl contributions in soils under Erica were < 40 %, while soils that developed<br/>
under Poaceae (Festuca abyssinica) exhibited relative cinnamyl contributions of > 40 %.<br/>
Similarly, long-chain n-alkanes extracted from the leaf waxes allowed for differentiation between<br/>
Erica versus Festuca abyssinica and Alchemilla, based on lower C31 =C29 ratios in Erica. However,<br/>
this characteristic plant pattern was also lost due to degradation in the respective O layers and Ah horizons.<br/>
In conclusion, although in modern-day plant samples a chemotaxonomic differentiation is possible,<br/>
soil degradation processes seem to render the proxies unusable for the reconstruction of the past<br/>
extent of Erica on the Sanetti Plateau, Bale Mountains, Ethiopia. This finding is of high relevance<br/>
beyond our case study.
