Dry And Wet Climatic Changes In The West Of Changbai Mountains Over The Last 500 Years Inferred From Multiproxy Peatland Records

As one of the most hot topics in the research of global changes, peat-based climate reconstruction in historical periods has been paid special interest in the recent years. Peatlands are extensively distributed in th northeast of China which is strongly influenced by asia monsoon. Peatland palaeoclimate sequences can sentively document the process of climate variations of monsoon area. In this paper, Hani and Jinchuan peat profiles which are located in the west of Changbai Mountains are selected as the research objects. Based on the analyses of plant macrofossil and humification, mires surface wetness of Hani and Jinchuan peatlands during the last 500 years are reconstructed and the history of precipitation changes in the west of Changbai Mountains in this phase is also preliminarily recurred.The Quadrat and Leaf Count Macrofossil Analyses is used to reveal vegetation assemblages in peat profiles, based on the identification and statistics of plant macrofossils, the plant macrofossil assemblages of Hani core and Jinchuan core are divided into four zones. The result of detrended correspondence analysis (DCA) shows that the ordinations display a clear separation of the wet/dry macrofossil components, and offer strong evidence for a water level gradient along DCA axis 1.Spectroscopic analysis is employed to determine the humification of peat, high humification represents warm and humid paleoclimatic, whereas low humification shows cold and dry paleoclimatic.According to the assemblage of the plant macrofossil, humification and the scores of plant macrofossil DCA axis 1 in the two sites, the dry and wet climatic changes in the west of Changbai Mountains were reconstructed during the last 500 years, the primary conclusions are as follows:1.The correlation analysis of humification and plant macrofossil shows that various climate proxies are significantly correlated at 0.01 level in the two sites. The two proxy records indicate similar dry and wet change, although the bogs are 20 km apart and differ floristically, the results demonstrate parallel responses to climatic forcing, it reflects that climate change in the west of Changbai Mountains are consistent tendency with the change of other places.2. Dry and wet climatic changes of the past 500 years in the west of Changbai Mountains can be divided into 2 different periods:1450-1600AD is a relatively dry climate period, humification in Hani and Jinchuan recorded three precipitation minimums in this phase which indicate three drought stages; since 1600AD, the climate is predominated by humid, but the humification has four peaks in this background which represent four precipitation reduction phases.3.The precipitation variation in 1450-1950AD is similar to the precipitation series from Guliya ice cap by Yao Tandong, the periods of dry and wet changes consist with the environmental evolution based on glacial accumulation, this conclusion proved that the historical period precipitation variation reconstruct by plant macrofossil analysis and humification is reliable and accurate.4.The preliminary study of main forcing factor for the Changbai area climate changes indicates that the variation of precipitation is relevant to solar activity in 1450AD-1950AD, when solar activity is weak, the rainfall is little, when solar activity increases, the rainfall is also rich.This reveals that the solar activities is the major factor which induce the climate changes in short time scale.