Holocene vegetation history of the Riisitunturi fell area in NE Finland, traced by the palynostratigraphy of two disgenic upland lakes

A palynological study of an upland lake was conducted in NE Finland to assess the timing of post-glacial vegetational phases as accurately as is possible with bulk samples of hard water-free, evenly deposited sediment. The studied lake, Kolmiloukkonen, as a reference site for the Kuusamo region, revealed an age of ca. 10 580 cal. years BP for the beginning of the post-glacial period, ca. 9500-9200 calBP for the appearance of alder, ca. 5700 calBP for spruce by 1% of arboreal pollen, and ca. 3900 calBP for spruce rise. DCA ordination suggested rather stagnant plant communities in the mid-Holocene. Another lake from the mid-Holocene on top of a saddle mire in the oroboreal sparsely wooded heath was of secondary origin. Its sediment types and macrosubfossils showed an uncommon succession from heath forest to mire and finally to a water basin. The age of establishment of nearly open summits could not be pinpointed palynologically, however, some signals suggest a trend towards more open communities nearly 3000 calBP and about a millennium ago.