Climate And Environmental Changes Since The Late Holocene Recorded From Peat In Changbai Mountains

The late Holocene is the most closely related period to human society.The study of paleoclimate change in this period can provide a reference for understanding the future climate change.Paleoclimate research relies on the establishment of high-resolution environmental and climatic records to a large extent.In this study,we selected peat as the information carrier.This paper takes two typical ombrotrophic bog in Changbai Mountain area as the research objects.First,using AMS¹⁴C dating technique to determine the age data of each depth in two bogs.Then,analysing plant macrofossil,peat decomposition,stable carbon isotope and geochemical characteristic these four proxies of two bogs by synthesis.Reconstructing the surface humidity variation of two bogs to infer historical changes of climate and environment in the Changbai Mountain area during the late Holocene.The possible driving factors of regional climate change are further discussed.The main conclusions of this paper are as follows:(1)Based on the comprehensive analysis of plant macrofossil,peat decomposition degree and stable carbon isotope,the trend of surface humidity variation of is as follows:the surface humidity process of Dongtuling peat profile since 2500 years ago is as follows:dry stage from600 BC to 240 BC,dry to wet stage from 240 BC to 200 AD,dry-wet alternating stage from200 AD to 950 AD,dry to wet stage from 950 AD to 1900 AD,wet stage from 1900 AD up to now.The surface humidity process of Touxi peat profile since 2000 years ago is as follows:wet stage from 60 AD to 460 AD,dry stage from 460 AD to 950 AD,dry-wet alternating stage from950 AD to 1840 AD,wet stage from 1840 AD up to now.The climate variation in Changbai Moutain area instructed by the similar trend of surface humidity variation in two bogs since the late Holocene can be divided into the following periods:dry and warm period from 600 BC to150 AD,wet and warm period from 150 AD to 275 AD,wet and cold period from 275 AD to820 AD,dry and warm period from 820 AD to 1200 AD,dry and cold period from 1200 AD to1480 AD,wet and cold period from 1480 AD to 1900 AD,wet and warm period from 1900 AD up to now.The geological records of long-term climate change in this region have a good correspondence with the previously reported solar activity variation sequence.To sum up,the overall trend of regional climate change revealed by three climate proxies is largely consistent,which proves the reliability of the comprehensive analysis of regional climate change by these three indexes.(2)Geochemical index such as Hg,Ti,Cr and other elements shows obvious high concentration from 930 AD to 970 AD,which indicates the Changbai Mountain area was affected by violent volcanic eruption in this period(about 946 AD)as the history recorded.In addition,the geochemical index of peat also records two volcanic eruptions of 100-150 AD and600 AD accurately.But there is no corresponding record information for other small-scale eruptions.At the same time,it is impossible to review the climate change in the corresponding period.The three climate proxies and geochemical index of the peat profile can not only accurately record the time of volcanic eruption in the period of large volcanic activity,but also indicate a short-term cold and dry climate in the region that volcanic eruption causes.