Reconstructing Holocene vegetation and climate history of Nam Co area (Tibet), using pollen and other palynomorphs

A drill core (1.8 m; 34 samples) was taken out of a swamp near Nam Co (Tibet, China) for palynological analysis. C14-Dating of the cores sediment at 3 different layers led to an numerical core age of about 8000 BP and the palynomorph content of prepared samples enabled reconstruction of the vegetation and climatic history of Nam Co Area. Pollen of Alpine Steppe elements together with Cyperaceae dominates the palynoflora reflecting the existing vegetation units around the lake throughout the investigated time span. Due to availability of water/precipitation, the different vegetation units extended or had to retreat, and hence the amount of their pollen increased or decreased. The presence of arboreal plants, verified by charcoal particles, suggest the existence of woodlands in the lake's surrounding area until possibly human made fires changed the environment over time. Holocene climate history around Nam Co shows several phases of a strengthening/weakening or even an interruption of monsoonal activity. Changing conditions between dry and humid evolved from 8017 BP until 4800 BP. A mostly humid and relative stable system occurred from 4800 until 700 BP whereas the last 700 years are characterized by drier conditions according to fluctuating monsoonal activity. Humid or arid periods have been different in duration and intensity. The interaction of both parts of the monsoonal system, the South Asian Monsoon and the East Asian Monsoon, influenced the climatic conditions around Nam Co.