?2Hn-alkane and ?18Osugar biomarker proxies from leaves and topsoils of the Bale Mountains, Ethiopia, and implications for paleoclimate reconstructions

Abstract The hydrogen isotopic composition of leaf wax–derived n -alkane (? 2 H ) and oxygen hemicellulose–derived sugar 18 O biomarkers are valuable proxies for paleoclimate reconstructions. Here, we present a calibration study along the Bale Mountains in Ethiopia to evaluate how accurately precisely precipitation is imprinted these biomarkers. -Alkanes sugars were extracted from topsoil samples compound–specific ? values measured using gas chromatograph–thermal conversion–isotope ratio mass spectrometer (GC–TC–IRMS). weighted mean range ? 186 89‰ + 27 46‰, respectively. Degradation root inputs did not appear alter soil analyzed. Yet, show statistically significant species dependence yielded same species–dependent trends. reconstructed water Erica arborea trimera H– O–enriched by 55 ± 5 9 1‰, respectively, compared precipitation. By contrast, Festuca abyssinica reveals most negative least positive values. This can be attributed “signal–dampening” caused basal grass growth. intermediate Alchemilla haumannii Helichrysum splendidum likely explained with plant physiological differences or microclimatic conditions affecting relative humidity (RH) thus RH–dependent isotope enrichment. While actual RH 69 82% (x? = 80 3.4%), based on recently suggested coupled –? (paleo–) hygrometer approach 78 21%. Our findings corroborate (i) that vegetation changes, particularly terms versus non–grassy vegetation, need considered studies records (ii) holds great potential deriving additional paleoclimatic information single approaches.