Study On Environmental Changes In The Northern Lop Nur Region By Means Of Stable Carbon Isotopes Of The Leaf Litter In Tamarix Cones

Lop Nur is located in the eastern part of Tarim Basin,to the north is Kuluketage mountain belong to Tianshan-odd arteries,to the east is Kumutage desert,to the south is Altun mountain,and to the west is Taklimakan Desert.The climate in Lop Nur region is with larger annual and daily temperature ranges,strong wind speed,less precipitation,more evaporation,frail ecological environment.It is a typical representative of climate environment evolution in arid zone of China.In this paper,taking the sedimentary veins of Tamarix cones as information carries,based on the dating methods of ¹³⁷Cs,²¹⁰Pb and ¹⁴C,to establish the age sequence of sedimentary veins of Tamarix cones,based on the stable carbon isotope values to analyze the relationship between stable carbon isotope values and the each climate elements,and to reconstruct the climate change for recent 240 years in the north region of Lop Nur.The researched results are as follows:(1)By means of the dating methods of ¹³⁷Cs,²¹⁰Pb and ¹⁴C,the reconstructed age sequence is 1832?2019 in the Tamarix well area in the east region of Lop Nur,and1784?2019 in the lower stream of Kongque river in the north of Lop Nur.(2)In Hongliu well region of Lop Nur,the mean stable carbon isotope value is-23.068‰,ranging from-24.747‰to-21.173‰.In the region of lower stream of Kongque river,the mean stable carbon isotope value is-24.335‰,ranging from-25.568‰to-22.882‰.There is larger difference between the stable carbon isotope values in Lop Nur region and in the south of Taklimakan desert,all of which are within the threshold of stable carbon isotopes of C₃plants.(3)The?¹³Ccorr sequence in Tamarix well region has a significant negative correlation to the average temperature of growing season in the same year,and a significant negative correlation to the relative humidity from August to October in the same year,and a significant positive correlation to the sunshine of the same year,and a significant positive correlation to the atmospheric pressure in June of the same year,and a significant positive correlation to annual mean wind speed in the same year.The?¹³Ccorr sequence in region of lower stream of Kongque river has has a significant negative correlation to the average temperature in the same year,and a significant positive correlation to the relative humidity in March of the same year,and and a significant positive correlation to the atmospheric pressure in the same year,nad a significant negative correlation to the sunshine from January to October of the same year,and a significant positive correlation to mean wind speed of every month in the last year.(4)The relative humidity in September,mean atmospheric pressure in January,and mean air temperature in April have significant effects on?¹³Ccorr in Tamarix well region.The mean temperature in June and July of the previous year,the mean wind speed in June,and average temperature in February have significant effects on?¹³Ccorr in the region of lower stream of Kongque river.(5)In the northern region of Lop Nur,the reconstructed temperature sequence based on the average temperature in June and July would be divided into 4 stages:cooler period of 1810?1910,warmer period of 1911?1960,another cooler period of1961?1990,and another warmer period of 1990?2020;the the reconstructed humidity sequence based on the relative humidity in September would be divided into 4 stages:drier period of 1832?1963,wetter period of 1964?1983,another drier period of1984?1993,and another wetter period of 1994?2020.(6)The 3.11a oscillation period of stable carbon isotope may be related to El Nino events,and the 10.75a oscillation period may be related to Sunspot activity.El Nino years also respond to the every lowest values of stable carbon isotopes.