Holocene hydroclimate variations in the eastern Tianshan Mountains of northwestern China inferred from a palynological study

Abstract We reconstruct Holocene vegetation dynamics and associated hydroclimate change in the Chaiwopu Basin of the eastern Tianshan Mountains, China. Our study is based on 160 palynological samples from a well-dated peat core. Palynological, assemblages and the associated biome scores show that from ~11.5 to ~9.5 cal. Kyr BP desert vegetation dominated and from ~9.5 to ~7.9 cal. Kyr BP steppe and wetland vegetation expanded. From ~7.9 to ~6.5 cal. Kyr BP wetland continued to be important but coniferous forest also expanded. The period from ~6.5 to ~3.0 cal. Kyr BP was characterized by coniferous forest while wetlands contracted. Further expansion of coniferous forest coverage and contracted desert cover were features of the last 3000 years. The percentage of Picea and changes in the taiga biome indicate a persistent wetting trend during the Holocene. We infer that this was controlled by the increasing frequency of AMO (Atlantic Multi-decadal Oscillations)-like events-linked in Siberian warm-season precipitation. The tundra biome score and the associated percentage of Poaceae+Cyperaceae in the Chaiwopu Basin indicate two major stages of wetland expansion. Wetland expansion can be possibly attributed to i) an increased glacier melt water supply when the ice extent was large, ii) an increase in precipitation when temperature remained more or less constant, or iii) a combined effect of increased precipitation and decreased temperature.