Multi-Proxy Study On Hydrologic And Climatic Changes From The Laolike Peatland,Changbai Mountains

Since the industrial revolution,human activities have increased and the damage to nature has become increasingly serious,which has exacerbated the global climate change characterized by warming.In recent years,climate change has gradually evolved into a key issue facing the whole world,which has attracted the attention of many scholars.Therefore,the reconstruction of the paleoenvironment has great reference significance for modern environmental change research.In the study of peatland paleoenvironment,the combination of multiple proxy indicators can improve our understanding of the feedback mechanism of peatland and the causes of change.In this study,two peat profiles LLK1901 and LLK1902were collected from the Laolike peatland in Changbai Mountains area.Through AMS¹⁴C dating method and ²¹⁰Pb/¹³⁷Cs dating method,the age-depth model of the two profiles was established,and the identification of testate amoebae and the determination of stable isotopes were carried out on the peat profile.The environmental change history of Laolike peatland in Changbai Mountains was reconstructed,and combined with meteorological data,the effects of temperature and precipitation on the depth of water table of the peatland quantitatively reconstructed by testate amoebae and the carbon and oxygen isotopes of Sphagnum cellulose were analyzed.The main conclusions of this paper are as follows:（1）Using AMS¹⁴C and ²¹⁰Pb/¹³⁷Cs dating methods,a high-resolution age depth model of the Laolike peatland was established.The bottom age of the LLK1901 peat profile is 1490AD,and the bottom age of the LLK1902 peat profile is 1360 AD.（2）An optical microscope was used to identify the species of testate amoebae from two peat profiles of Laolike.The LLK1901 peat profile identifies a total of 52 species and 12544 shells of testate amoebae.The main species are mainly dry species,such as Assulina mucorum,Nebela militaris,Trinema compatum,Euglypha rotunda,and Pharyganella acropodia.The LLK1902 peat profile identifies a total of 55 species and 14159 shells of testate amoebae.The main species are mainly humid species and moderately humid species,such as Centropyx aerophila type,Centropyx aculeata type,Difflugia rubescens,Centropyx platystoma type,and Pharyganella acropodia.（3）Based on the species composition of testate amoebae from two peat profiles,a transfer function was used to quantitatively reconstruct depth of water table changes in the Laolike peatland.In the past 30 years,the LLK1901 peat profile has experienced a change from humid to arid,then humid,and finally arid,which can be divided into three stages.The first stage was 1990-1997 AD,and the peatland was in the wettest stage,indicating that there were rich species in the humid area.The second stage was 1997-2007 AD,where species indicating wetness gradually decreased or even disappeared,while species indicating drought show a gradual increase trend,indicating a transition from wetness to drought during this stage.The third stage is 2007-2019 AD.The peatland has experienced the most arid stage of peatland,from wet to dry,then to wet,and finally to dry,indicating the decrease of wet species and the increase of dry species.Over the past 600 years,the overall environment of the LLK1902 peat profile has been slightly humid,and it has rapidly dried out in recent times,which is divided into five stages.The first stage is 1476-1661 AD,the peatland is in a medium humid environment,and humid species coexist with dry species.The second stage is 1661-1863 AD,the peatland is in the wet stage,and the testate amoebae are mainly wet species.The third stage is 1863-1935 AD,where the depth of water table shows a trend of first decreasing and then increasing,indicating frequent occurrences of moist species and a decrease in species indicating drought.The fourth stage is 1935-1990 AD,the peatland is in the wet stage,with more species indicating wet and fewer species indicating drought.The fifth stage is 1990-2019 AD,and peatland is in the driest stage,indicating the disappearance of wet species and the emergence of a large number of dry species.（4）The DWT（Depth of Water Table）reconstructed from the testate amoebae was compared with the isotope values of Sphagnum cellulose at LLK1901 peat profile.The DWT was significantly correlated with theδ¹³C andδ¹⁸O values of Sphagnum cellulose.In the second stage,the variation ofδ¹³C value is controlled by the water film of Sphagnum,and the DWT is consistent with the information transmitted by isotope signals.In the third stage,the trend of DWT andδ¹⁸O value is still consistent,but theδ¹³C signal may be affected by dissolved inorganic carbon and methane,showing an opposite trend.（5）The Laolike peatland is greatly influenced by climate factors.The overall performance is that the temperature is low,the evaporation of the peatland is weakened,the atmospheric precipitation increases more,and the depth of water table of the peatland is higher,and vice versa.However,some stages of detachment from the control of climate factors may be related to the own process of peatland development.