Reconstructing landscape, climate and human history in semi-arid Mongolia using a multi-proxy biomarker approach

• Applicant: Dr. Marcel Bliedtner
• Subject Area: Physical Geography
• Term: from 2021 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 466655362

Humans have become a major factor during the Anthropocene controlling landscape and environmental changes and especially semi-arid regions are expected to suffer increasingly from human-induced climate and environmental changes during the next decades. Therefore, a better understanding about past climate and anthropogenic influences in such regions is essential and holds particularly true for semi-arid Mongolia, because this region is highly sensitive for the consequences of global warming and strongly increased human activity with accompanied soil erosion and pressure on natural resources.To address those issues, the proposed project aims at reconstructing climate and human-induced landscape changes in semi-arid Mongolia, and to disentangle between both effects by using a multi-proxy biomarker approach on lake sediments. For this, the project will use the very promising ~8.3 ka lake sediments from the high-altitude lake Shireet Naiman Nuur in the central Mongolian Khangai Mountains, an endorheic lake with a small catchment. Beside state of the art sedimentological and geochemical analyzes, a multi-proxy biomarker approach will be carried out and includes the i.) establishment of a robust chronology by compound-specific radiocarbon analyzes (CSRA) of biomarker compounds, ii.) detection of human presence and their livestock by fecal biomarkers, and iii.) consideration of the climatic background signal by compound-specific isotope analyzes (CSIA) of terrestrial and aquatic biomarkers. I will focus on the following specific objectives:• In a first step, extensive effort will be put in 14C-dating of terrestrial macrofossils and CSRA of specific terrestrial and aquatic biomarker compounds to establish the best possible chronology for the Shireet Naiman Nuur sediments. While terrestrial macrofossils become rapidly transported into the lake and should give the timing of sediment deposition in the lake, terrestrial biomarkers from the catchment can be “pre-aged” to a certain degree. 14C-ages of aquatic biomarkers can be stratigraphically consistent or account for possible “hardwater effects”. Occurring age offsets between stratigraphically consistent and inconsistent ages reflect the “mean transfer time” of organic/biomarker material through the catchment and are valuable indicators for soil erosion.• In a second step, the presence of humans and their livestock in the Shireet Naiman Nuur catchment as well as their influence on landscape changes and soil erosion will directly be traced by the analyzes of fecal biomarkers.• In a last step, the paleoclimatic background signal will be reconstructed by CSIA of δ2H on terrestrial and aquatic biomarkers to disentangle climatic and anthropogenic signals in the Shireet Naiman Nuur sediments. Comparing terrestrial with aquatic δ2H has the great advantage to compare both isotope signals, and account for the source water and different degrees of evaporative enrichment in the endorheic Shireet Naiman Nuur.

• DFG Programme: Research Grants