Late Weichselian to early Holocene vegetation and bird activity on Andøya, Nordland County : as evidenced primarily by macrofossils

Abstract

This thesis shows that Late Weichselian vegetation on Andøya may have been more diverse than previous studies have revealed. The thorough investigation of macrofossils in four parallel cores provides more reliable evidence for interpreting changes in vegetation cover than reconstructions based on a single core. The botanical macrofossils retrieved in this study largely support previous studies at the northern tip of Andøya. Arctic plant communities, probably dominated by Papaver and several species of Poaceae and Brassicaceae characterized the area. Climatic ameliorations occurred at c. 22 000 – 20 100, 20 100 – 19 500, 19 500 – 19 200, 18 800 – 18 100, 17 500 – 16 800 and 15 100 – 14 500 cal. yr BP, and during these ameliorations, the vegetation may have been more diverse than recorded both in the pollen- and macrofossil material. Macrofossils (bones) of little auk (Alle alle), coupled with other evidence, suggest a longlasting presence of sea birds in the area. Manuring by birds made a considerable impact on the local terrestrial environment, and during the ameliorations in particular, these favorable local habitats may have supported species not found in the present-day Arctic, e.g. Urtica dioica. Sedimentary ancient DNA (sedaDNA) provides evidence that during the ameliorations, Andøya may have hosted small enclaves of boreal conifer trees. Their presence on Andøya has yet to be detected by macrofossil- or pollen analyses, but the DNA evidence provides an important contribution to the debate concerning glacial survival of boreal trees within Scandinavia.