Mid-late Holocene maar lake-mire transition in northeast China triggered by hydroclimatic variability.

The density of maar lake type peatlands in the Changbai Mountain areas, northeast (NE) China is among the highest in the world. These deposition systems include both peat and limnic deposits, providing valuable sites to study their evolutionary history shaped by their sensitivity to climate-forced state shifts. To investigate the maar lake-mire shift in response to hydroclimatic variability, we examined developmental history of the Jinchuan peatland based on sedimentary facies, grain-size, physical and chemical properites, plant macrofossils and peat basal age. The results indicate that the Jinchuan peatland mainly originated from paludification in a maar lake from approximately 7000 cal. BP. Its water level continuously increased since the Middle Holocene, reaching the peak during the period of 5000–4000 cal. yr BP. The outward expansions of Jinchuan peatland suggest a climate–driven model based on which water level variability superimposes the underlying basin morphology. The hydroclimatic variability and peatland development history can be divided into three periods. From 12 to 7 ka cal. BP, the increasing East Asian summer monsoon (EASM) was the major water vapor source of Jinchuan peatland. The strong evaporation effects induced by the strong Winter Asian winter monsoon (WAWM) and the maximum sea surface temperatures (SSTs) of Japan Sea might have changed the Jinchuan maar lake into dry upland. From 7 to 4 ka cal. BP, the maximum EASM and increasing Westerly jet (WJ) provided water vapor for the peatland. The decreasing EAWM and SSTs of Japan Sea resulted in decreased evaporation effects. The moisture and water level in Jinchuan peatland gradually increased. The peat covered 68.97% of the area during this period. Since 4 ka cal. BP, the decreased EASM and the maximum WJ provided water vapor for the Jinchuan peatland. The weak EAWM and the lower SSTs of Japan Sea induced lower evaporation effects. The moisture and water level in the peatland reached the maximum. Subsequently, peat area further expanded and covered the remaining 31.03% area. This study reveals a remarkable link between the maar lake-mire shift and hydroclimatic variability, which is significant for future prediction of maar lake-mire ecosystem shifts under global climate change. Image 1 • Jinchuan peatland developed from approximately 7 ka cal. BP to present. • Maar lake-mire transition was related to the climate-driven water level variability. • East Asian summer monsoon was the major water vapor source of NE China. • Evaporation effects are more important than precipitation in controlling the moisture changes in NE China. [ABSTRACT FROM AUTHOR]