Environmental changes of the Okhotsk-Kolyma divide from glacial lake sediments during the Holocene

Investigations of glacial lake sediments located near the modern altitudinal boundary of a larch forest (between 750-810 m absolute elevation) reveal continuous records of the vegetation and climate changes over the last 12000 years in the area of the Okhotsk-Kolyma divide. For the first time, the pollen accumulation rates (PAR), which are suggestive of pollen productivity, were used as a key indicator to interpret the response of alpine plant communities to climate changes. The palynological data imply that several forest line fluctuations of similar to 100-200 m occurred during the Holocene. A belt of tundra dominated by shrub pine was first established beyond the forest line near 7650 +/- 50 BP. The abrupt appearance of the shrub pine in the studied area is characteristic of a sharp vegetation boundary found in other records from the north of the Far East that corresponds to the Boreal-Atlantic boundary of the Holocene. The birch pollen zone, which occurs in the earlier portions of the records, is characteristic of the transition from the Pleistocene to the Holocene.