Paleoclimate history and its influence on ecosystem changes and human occupation/abandonment of East African high mountain ecosystems in Ethiopia

在埃塞俄比亚贝尔山脉的阿弗罗阿尔卑斯山地区，人类占领和遗弃的时期很可能至少部分是由古气候变化引发的。这是从先前项目获得的第一个结果得出的结论。在DFG研究单位2358“山区流放假说”所附的这项后续项目提案中，计划对研究区域的古气候重建作出贡献。这些结果对于补充2358号研究单位“气候-人类-环境相互作用”的全貌至关重要，将与考古学、土壤学、古生态学和冰川学领域的同事们密切合作进行解释。Work Package(WP)1将继续监测现代降水的同位素特征，以更好地了解现代大气环流模式，包括影响贝尔山脉的特定同位素特征。这是合理的，因为东非的同位素记录通常是用“降雨量”来解释的。然而，实际的负责任效应可能更多的是一种“源头效应”。这对于正确解释贝尔山脉的δ2H和δ18O记录以及其他东非古气候同位素记录具有重要意义。WP2旨在建立多代理古气候同位素记录。这里的理由是，迄今为止在加尔巴古拉察湖建立的δ2HN-烷烃和δ180糖记录可能并不明确地归因于水生和陆地来源。为了测试这一点，将对作为明确陆地档案的Hyrax midden(与2358研究单位的P3古生态学子项目密切合作)以及硅藻和水生生物标志物Dinosterol进行调查。最后但并非最不重要的一点是，我们将继续与2358研究组的P2人为土和P3古生态子项目密切合作，调查沉积档案。在WP3中，我们将分析Wergoba山谷、Sanetti高原和Harena森林中已经恢复和确定日期的沉积物和泥炭岩芯，以检查我们的古气候指标信号的时空异质性；在WP4中，我们将调查可能是LGM(最后一次冰川最大值)之前的LGM(最后一次冰川最大值)和Arsi山脉附近的Chereleka湖的LGM岩芯。最后但并非最不重要的是，WP5将以尽可能高的分辨率将重点放在Garba Guracha最顶端的核心部分，其中人类占领/放弃最明显地得到了P1考古学、P2人为土和P3古生态学的证实。

Periods of human occupation and abandonment in the afroalpine region of the Bale Mountains, Ethiopia, were very likely triggered at least partly by paleoclimate changes. This is suggested by first results obtained from a previous project. Within this follow-up project proposal, which accompanies the DFG Research Unit 2358 ‘The Mountain Exile Hypothesis’, it is therefore planned to contribute to the paleoclimate reconstruction of the study area. The results will be essential for complementing the full picture of ‘climate-human-environment interactions’ of the Research Unit 2358 and they will be interpreted in close interdisciplinary cooperation with the colleagues from the fields of archeology, pedology, paleoecology and glaciology.Work Package (WP) 1 will continue monitoring the isotopic signature of modern-day precipitation in order to better understand the modern-day atmospheric circulation patterns including their specific isotopic signatures affecting the Bale Mountains. This is justified given that isotope records in East Africa are usually interpreted in terms of ‘precipitation amount’. The actually responsible effect might, however, rather be a ‘source effect’. This is of utmost importance for the correct paleoclimatic interpretation of δ2H and δ18O records from the Bale Mountains as well as of other East African paleoclimate isotope records. WP2 aims at establishing a multi-proxy paleoclimate isotope record. The rationale here is that the so far established δ2Hn-alkane and δ18Osugar records from Lake Garba Guracha may not be unambiguously attributable to aquatic versus terrestrial sources. In order to test this, hyrax middens as unambiguous terrestrial archives (in close collaboration with Subproject P3 Paleoecology of the Research Unit 2358) as well as diatoms and the aquatic-derived biomarker dinosterol will be investigated. Last but not least, we will continue investigating sedimentary archives in close collaboration with the Subprojects P2 Anthrosols and P3 Paleoecology of the Research Unit 2358. Within WP3 we will analyze already retrieved and dated sediment and peat cores from the Wergoba Valley, the Sanetti Plateau and the Harena Forest in order to check for spatial and temporal heterogeneity of our paleoclimate proxy signals; within WP4 we will investigate presumably pre-LGM (last glacial maximum) and LGM cores from Lake Cheleleka in the close-by Arsi Mountains. Last but not least, WP5 will focus at highest possible resolution on the topmost core sections of Garba Guracha, for which human occupation/abandonment is most obviously confirmed by P1 Archeology, P2 Anthrosols and P3 Paleoecology.