PLANT MIGRATION AT THE END OF THE WEICHSELIAN GLACIATION : Macrofossil evidence of early coniferous trees at two northern Swedish sites

• Main Author: Zakrzewski-Sharma, Karan
• Format: Bachelor Thesis
• Language: English
• Published: Umeå universitet, Institutionen för ekologi, miljö och geovetenskap 2019
• Subjects: Scandinavia; Weichselian; plant migration; macrofossils; climate change; Environmental Sciences; Miljövetenskap; Arctic; Climate change; Ice Sheet; Northern Sweden
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-160214

Studies of vegetation history bring a new incentive to our understanding of plant survival and migration in arctic environments. For decades, environmental research was based on palynological data and these studies created a notion that tree species such as larch (Larix sibirica) and Scots pine (Pinus sylvestris) did not grow in northern Scandinavia at the end of Weichselian glaciation. However, findings of macro- and megafossils of these trees dating back to glacial times has been reported in the Swedish mountain range, questioning this view of a late arrival of these trees in Scandinavia. The apparent contrasting views on the composition of the first plants arriving to Scandinavia create uncertainties about the bioclimatic conditions prevailing at the end of the Weichselian glaciation. To improve our understanding about the first vegetation arriving to Scandinavia I probed the macrofossil composition of two novel sedimentary records from northern Sweden. Twelve sediment cores from material underlying Holocene peat deposits were used as archives of early Holocene plants. In these records, I found: I) larch needles dating back to 4.6 and 4.1 calibrated thousand years (cal. kyr) BP; II) pine macrofossils dating back to 9.5 and 8.7 cal. kyr BP; III) fossils from dwarf shrubs (willow and heather) dating back to 9.9 cal. kyr BP; and IV) a birch fossil dating back to 9.5 cal. kyr BP. Also found in the same depth was fragment of a spruce cone. Based on my findings, I concluded that the landscape behind the retreating Weichselian ice-sheet was surpassingly colonised by pine and larch trees, a forest that has no contemporary analogue in Scandinavia. It seems as if this early forest also contained spruce, which is enigmatic as the main spruce invasion is expected to occur across the region during the next millennia. Finally, there is an instigation for future discussion on how our present knowledge of plant behaviour in changing conditions can help minimise the impacts of ever-expanding climate change.