Holocene vegetation dynamics and associated climate changes in the Altai Mountains of the Arid Central Asia

This study reconstructed the vegetation dynamics and associated climate change of the past similar to 4100 years based on the pollen data from a short peat core (i.e., KLSZ-2) in Kelashazi Peat (48.12 degrees N, 88.37 degrees E, 2422 m a.s.l.) in the Altai Mountains. The reconstructed vegetation and climate were then stacked with those from a longer peat core (i.e., KLSZ-1) to evaluate the vegetation dynamics and associated climate change of the entire Holocene and to examine the delta C-13(cellulose)- and delta O-18(cellulose)-based temperature reconstructions in the same peat. This study shows that vegetation in Kelashazi valley was dominated by alpine meadows before -8200 cal. yr BP, by taiga forests at similar to 8200-similar to 5600 cal. yr BP, and by an expansion of alpine meadows since similar to 5600 cal. yr BP. This study also examined the vegetation dynamics and associated climate in the context of the entire Altai Mountains and the surrounding areas. Our examination suggests that the forest expansion in high elevations was initiated when the temperature reached a threshold level during the early Holocene, and the forest expansion in low elevations (i.e., below the down treeline) was initiated when the moisture reached a threshold level during the middle Holocene or even late Holocene. It is also notable that the forest expansion at low elevations appears to have been longitude-dependent, i.e., time transgressive eastward. A possible mechanism to explain the longitude-dependency is that a gradual shrinking trend of the Siberian High linked to the Holocene increase in winter insolation allowed the domination of the water vapor-enriched Westerlies to gradually encroach eastward.