Project W7

Preliminary work

Lipid biomarkers, e.g. leaf waxes and sterols, are preserved in lake sediments and are increasingly used for paleoenvironmental and climate reconstructions. Leaf wax dD is a particularly valuable paleohydrological proxy, and first studies have been conducted at Nam Co and on the Tibetan Plateau (Mügler et al. 2010; Günther et al. 2015). However, it remains challenging to disentangle changes in the isotopic composition of past precipitation and other influencing factors such as evapotranspirative enrichment. It has been suggested that coupling leaf wax dD and sugar d¹⁸O analyses solves this issue, because evapotranspirative enrichment affects both isotopes differently (Hepp et al. 2015; Hepp et al. 2019). Moreover, leaf waxes can also be targeted for compound-specific d¹³C (Diefendorf and Freimuth 2017; Struck et al. 2020) and radiocarbon analyses (Häggi et al. 2014; Gierga et al. 2016).  

Steroid biomarkers are increasingly used in geoarcheological studies to infer the past presence of various animals (Prost et al. 2017; Harrault et al. 2019). While detecting and distinguishing human versus herbivore faeces as well as phytosterols is relatively straight-forward, more recent studies suggest that focusing on bile acids and 5β-stanol compounds holds great promise to detect and distinguish a wide range of animals such as pigs, dogs, cows, horses, goats and sheep.

Research objectives

1. Evaluation and calibration of the coupled leaf wax dD and sugar d¹⁸O isotope approach, as well as leaf wax d¹³C, using plant and topsoil samples near Nam Co.
2. Reconstruction of past climate and environmental changes during the last 2000 years using compound-specific isotope analyses (leaf wax dD, d¹³C and radiocarbon, as well as sugar d¹⁸O) in sediment cores.
3. Investigation of the abundance of steroid biomarkers in topsoils near Nam Co.
4. Reconstruction of the environmental and land-use history at Nam Co during the last 2000 years using steroid biomarkers in sediment cores.

Cooperation within TransTiP

• S1, S5, S6, C1: The translocation of the leaf waxes, plant sugars and steroid biomarkers from the catchment into the lake shall be compared to other carbon pools and to sediment translocation.
• W2, W3: Paleoenvironmental and particularily -hydrological reconstructions based on various approaches (e.g. diatoms, invertebrates and their isotope composition) shall be checked against each other.

Sino-German complementarity of research

The Chinese partners analyze lipid biomarkers and their compound-specific isotopic composition in river and core top sediments in order to (i) track the translocation of the proxy signals from the catchment into the lake and (ii) investigate the spatial distribution of the biomarker and isotope signals in the lake. Moreover, long sediment cores complement our 2k paleo-reconstructions. 

Supervisors:

Prof. Dr. Roland Zech, FSU Jena
Prof. Dr. Antje Schwalb, TU Braunschweig
Prof. Dr. Liping Zhu, ITP-CAS