Postglacial changes in the Asian summer monsoon system: a pollen record from the eastern margin of the Tibetan Plateau

A new pollen record constrained by 32 AMS radiocarbon dates from the Hongyuan peatland in the Zoige Basin reveals the long-term dynamics of an alpine wetland ecosystem on the eastern margin of the Tibetan Plateau over the last 13 500 years. Changes in pollen assemblages and influxes suggest that local vegetation has experienced three distinct stages, from alpine coniferous forest-meadow (13 500-11 500 cal. a BP), through alpine coniferous forest (11 500-3000 cal. a BP), back to alpine coniferous forest-meadow (3000 cal. a BP-present). This record reflects an ecosystem response along a transition zone where the South Asian and East Asian monsoon systems may have had different palaeoclimatic influences. A comparison of this record with other pollen records across the Tibetan Plateau shows common features with regard to large-scale Holocene climatic changes, but highlights a pattern of regional temporal and spatial variability that depends on the topography and position relative to the South Asian and East Asian monsoon fronts.