Vegetation changes and treeline dynamics in northern Siberia since the last interglacial revealed by sedimentary ancient DNA metabarcoding and organelle genome assembly of modern larches

• Main Author: Zimmermann, Heike H.
• Format: Thesis
• Language: unknown
• Published: University of Potsdam 2017
• Subjects: permafrost; taiga; Tundra; Siberia
• Online Access: https://epic.awi.de/id/eprint/48911/; https://hdl.handle.net/10013/epic.7c396008-a6a2-4aa6-bb88-9caecedcf88b

The arctic-boreal treeline describes the transition zone from taiga to tundra and is a sensitive, climatically driven ecosystem boundary. In Siberia it is formed by deciduous larches as the only representatives of the tree growth form. The recurrent cycles of interglacial and glacial periods throughout the Quaternary resulted in the systematic relocation of the treeline. Awareness of the complex climate-feedback mechanisms of larch forests and their importance for the global carbon cycle is rising. Still, our understanding of genetic variation within and among treeline populations of larches is very limited, as these populations have so far not been focused upon. Patterns of genetic variation in modern populations represent only a snapshot in time, and past climatic changes might have led to a reorganisation of such patterns. Hence, tracing the dynamics of genetic variation in response to climatic changes from the past to the present will improve our perspective on the processes involved in treeline advances and retreats. However, paleobotanic reconstructions rarely date back to the last interglacial (~130-110 kyr BP), as not many locations are known to have preserved suitable deposits. Therefore, our knowledge about the past vegetation and treeline dynamics in northern Siberia predating the Last Glacial Maximum (LGM, ~21-18 kyr BP) is limited. The overall goal of this thesis is to improve our understanding of climatically driven vegetation changes and treeline dynamics since the last interglacial, as well as to provide a baseline for exploring genetic variation in modern and past larch populations from environmental samples. In the scope of this thesis I used sedimentary ancient DNA (sedaDNA) from permafrost sediment cores from the Buor Khaya Peninsula and Bol’shoy Lyakhovsky Island to analyse floristic diversity and composition changes since the last interglacial. In one core, sedaDNA was additionally compared with the pollen record to assess how well sedaDNA reflects past plant community changes. I applied ...