Holocene history of alpine vegetation and forestline on Pyhäkero mountain, northern Finland

Paleoecological analyses were carried out from two sediment cores from lake sites at the alpine treeline on Pyhäkero mountain, the northernmost peak of an isolated mountain range, Pallastunturi-Ounastunturi, south of the polar forestline in western Finnish Lapland. Plant macrofossils, supported by pollen data, show presence of pine (Pinus sylvestris) and birch (Betula pubescens) on the top of the mountain from 9500 cal yr BP (birch) and 8300 cal yr BP (pine) up to 2000 cal yr BP (pine) and 1500 cal yr BP (birch). However, the major floristic elements of the modern alpine vegetation, as evidenced by plant macrofossils of a number of typical alpine taxa, including Salix cf. polaris, show persistence through the warmer periods of the Holocene, and indicate that the scattered pine-birch forest never completely replaced the low-alpine plant communities. The current low-alpine vegetation on the mountain top has therefore long continuity from the time of regional deglaciation. Dispersal of these alpine species took place primarily during the deglaciation phase and it is unnecessary to invoke dispersal of the arctic-alpine plants from the arctic regions of Fennoscandia during the mid- or late-Holocene to explain the origin of the alpine flora of the mountain range.