Stadial–interstadial climate oscillations influence postglacial ecological succession at the southwestern margin of the Fennoscandian Ice Sheet: insights from sedimentary ancient DNA

Palaeoecosystem reconstruction can shed light on postglacial succession and its drivers. Using metabarcoding of the P6 loop and the 16S loci, we have generated a sedimentary ancient DNA ( sed aDNA) record from Lake Dybingen in southwestern Norway. Our record of 139 plants and 16 animals spans the time from the early local retreat of the Fennoscandian Ice Sheet ca. 16,800 to 7200 years ago. The vegetation community turnover peaked at the onset of warm periods, whereas taxonomic diversity stagnates during stadials. However, the immediate establishment of a pioneer high-arctic community after deglaciation indicates rapid dispersal from source regions. Dwarf shrubs establish during the Bølling–Allerød interstadial and survive the Younger Dryas stadial. The main ecological turnover is the boreal forest encroachment ca. 11,000 years ago, and the landscape closing promotes a fern and Ericaceae understorey, while there is a decline of forbs, grasses, and mosses. Rock ptarmigan and reindeer are detected during the Bølling–Allerød interstadial. Reindeer is present again after the Younger Dryas stadial but disappears once trees establish. Our data indicates that the driving force of primary succession and ecosystem development at the southern edge of the Fennoscandian Ice Sheet was climate warming, and the rapid succession suggests a direct dispersal from Doggerland across the Norwegian Channel rather than from the more distant ice-free areas to the east.