| The Holocene period of global climate change, is one of the most important research content of the international global change programme.The reconstruction of high resolution Holocen-e climate records, change rule, for understanding the climate system to cope with the current face severe climate and environmental situation, forecasts the trend of future climate change which has a crucial important significance.Currently Holocene climate evolution of the gradual deepening of the drive mechanism on climate change during the Holocene, although still controversial, but made some achievements, laid the foundation for further study of Holocene climate change.The stalagmite compares with loess, ice cores, tree ring, lake sediments, pollen and other climate proxies for reconstruction, with precise dating, high resolution, preserving climatic and environmental records,widely distributed, the sample is easy to get and low cost advantage, and has become one of the current research of paleoclimate records of the main force.This paper is based on Chongqing Qingmuguan as the study area,which is the upper reaches of Yangtze River.The use of 25 230Th dating data and 315 stable oxygen and carbon isotope data of Stalagmite QM09 from Shizishan Cave in Chongqing area to establishing stalagmite oxygen and carbon isotope time series of high resolution time period during 0-9.4kaBP,combined with other stalagmite record which is belonging to the Asian monsoon region, analysis the responsible relationship between the stalagmite oxygen and carbon isotope, and with the Holocene climate, further more, we talk about the change of climate fluctuation in the inner Holocene;The use of stalagmite carbon isotope try to analyse the relationship between vegetation changes at the time of climate changes, and then analyze the response relationship exists between human activities and climate in the Holocene, the relationship between man and natural environment of the Holocene period,the main focus of the study focused on the natural environment the impact of change on human activities, especially since the "4.2Ka event" to study the impact of human activities on the natural environment is more a lack of in-depth study the effects of human activity and innovation is the key point of this paper, by exploring the following conclusions:(1) the lion cave stalagmites QM09 high-resolution oxygen isotopic records show that:the lion cave of regional climate change and other parts of the Asian monsoon region of chongqing climate change trends of basic consistent, stalagmite record has repeatability, shows the lion cave stalagmites basic not influenced by regional factors, study area during the kaBP of 6.0～9.4, the delta 18 o value range is 9.483‰～11.187‰, average of 10.435‰, the changing rate of 1.704‰, overall is in a state of partial negative oxygen isotope, show that the phase monsoon overall strong stage, abundant precipitation; During 4.2～6.0 kaBP, stalagmite 18 o delta value range is 8.874‰-10.762‰, average of 9.776‰, the changing rate was 1.888‰, stalagmites delta 18 o value was beginning to show, but overall is in negative state, show that the phase monsoon the overall state of a strong, abundant precipitation, within monsoon fluctuation, strengthening and weakening the monsoon events appear alternately. Stalagmites delta since 4.2 kaBP,18 o value range is 7.132‰～9.921‰, average of 8.538‰, the changing rate was 2.789‰, the delta 18 o values show has already begun in the polarized state, suggests that the monsoon overall began to abate, precipitation gradually reduce.(2) the lion cave stalagmites QM09 high-resolution carbon isotope records show that:the lion cave stalagmites QM09 carbon isotope.During 4.5～9.4 kaBP, carbon isotope value range to 14.555 ‰-13.341‰, the changing rate of 1.214‰, the average of 13.911‰, it can be seen that carbon isotope values basic fluctuating in-14‰, overall in negative state, to indicate the chongqing region vegetation coverage rate is higher, vegetation type C3 vegetation as the main vegetation types, relatively few C4 vegetation; Since 4.2 kaBP, carbon isotope value range is 14.403‰～5.848‰, the changing rate of 8.555‰, the average of 11.260‰, strong fluctuations in carbon isotope value, whole tend to be polarized state, indicating C3 vegetation coverage decreased obviously, and the natural ecological environment deteriorated.(3)Since 4.2ka BP, especially in the last 2000 years, the size of the Chongqing area of human activity significantly increased and significantly expanded the scope, impact on the natural vegetation to further expand and change the surface of the plant types, the indirect effects of soil organic matter and biomass, soil organic matter reduce and reduce biomass stalagmite formation of the intermediate links, especially carbon isotope stalagmite produce changes to gradually emphasis is demonstrated through the transformation of human activity vegetation types, will have influence on the natural environment. |
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