Post-glacial dynamics of vegetation and tree-lines in the far north of Fennoscandia

摘要: The transitional zone between the boreal forest and northern coastal area of Arctic Ocean in far north Fennoscandia is a globally important ecotone. pollen stratigraphy four lakes, Lakes Hopseidet Ifjord Norway Skaidejavri Rautuselka Finland, was studied to reveal post-glacial dynamics vegetation this These lakes were selected represent different zones within altitudinal changes these zones. Pollen influx concentration determinations used estimate past locations tree-line, although approach partly hampered by effects sediment focusing inwash. results nevertheless show that approx. 11 000-5 500 cal BP birch forests covered most Nordkinn Peninsula. However, pine never reached two tundra lakes. retreat both tree-line started simultaneously rapidly at 5 leading disappearance on plateau Since then species have retreated gradual manner. Late-glacial found only Lake Ifjord, where basal spectra belong Younger Dryas chronozone, being strongly dominated Artemisia (max. > 70 %). earliest Holocene stages characterized very sparse vegetation, suggesting extensive snow-beds moist, open soils. Forest development as established 200-10 000 BP. resembled present submaritime mountain forests, they had dense field layer ferns, lycopods, tall herbs. A major change took place when migration more than 10 It replaced dominant tree over large areas. During later part Holocene, has expanded along with decline and, shown detrended correspondence analysis, zonation become clearer. early-Holocene, mainly flora peaty, moist Pine migrated southwards from areas it 3 y invade Fennoscandia. patterns suggest climate alone did not control but biological factors also played an role environment close limits its ecological tolerance. presence long time-lag gives credence theory early migrations controlled complex set no detailed climatic interpretations should be made basis history single or few species.