Geochemical fingerprints of land use and fire regimes in the central Mongolian steppe

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Urbanism has fundamentally changed pastoral nomadism and environment in Mongolia. However, it is not known how the supply of an urban population agglomeration was sustained at the heart of the Mongolian steppe and how this was carried by the surrounding environment. In our project we therefore investigate the history of past land use and fire regimes in the context of paleoclimatic change and the rise and fall of the cities. At local scale, we will evaluate whether and how waste disposal differed between nomadic and urban households at specific time periods. Based on the assumption that we will find evidence for past agriculture, we will analyze colluvial deposits in order to understand regional processes. Finally, when investigating lacustrine sediment-cores, we expect to find information on how urban and non-urban phases correlate with supra-regional fire events and woody plant expansions. To achieve these aims, we conduct nutrient, isotopic, and biomarker analyses with geochemical signals that reside in the environment over long periods of time: in order to localize organic waste, we will examine different P-forms; in addition, sterols and bile acids provide information about their origin, e.g., from humans or animals. For possible evidence of a cultivation of C4 plants, we record the stable isotope composition of soil organic matter; by lignin analyses we differentiate formerly forested and non-forested areas. Black carbon and (methylated) polycyclic aromatic hydrocarbon analyses are performed to reconstruct fire regimes. Overall, we will thus contribute to a better understanding of how the supply of the city was related to environmental and land use conditions.