Environmental Signifcance Based On Tree-Ring δ～(13)C Annual Series And Azimuth Variation In Subtropical Region Of East China

The tree ring has been used widely in the field of global climate change due to its advantage of accurate for cross-dating, well continuity, high-resolution and high sensitivity to the environment. Some academicians have already studied the climate change in the dry area of west and north China by using tree rings. The similar study is relatively lacking in east China especially in the tropic and subtropics region with warm and wet character. Taking Tianmu Mountain, Lushan and Chongshan as the area of case study, we measure the tree ring annual series of δ¹³C and azimuth distribution sampled from these areas by using the tree ring δ¹³C as researching index. We analyze the character of the tree ring annual series of δ¹³C and azimuth distribution and set forth its environmental significance. Moreover, we demonstrate the universality and stability of the existence of azimuth variation of tree ring δ¹³C and analyze the azimuth variation character of δ¹³C and the space and time transferring discipline of extremum, further, probe the mechanism of tree ring δ¹³C changing along with azimuth. The main process and conclusions are as follows:We analyze the correlation of the δ¹³C annual series of the Cryptomeria fortunei(CF) collecting from Tianmu Mountain. The result indicates that there is the similar variation of high frequency and low frequency among the three δ¹³C series and both the factor of climate and factor of atmosphere have influenced together on this variation of CF individuals. There are some differences among the three δ¹³C series, but the individual difference has little influence on the commonness. The individual difference does not make impact on the feasibility of using the δ¹³C as substitutive index on studying climatic changes as well as the reliability and consistency of reconstructing result of historical climate.Based on the correlation test between high-frequency change and climate factor of the tree ring δ¹³C series, we attain the best multivariate regression equation of the δ¹³C and climate factor by using stepwise regression. The correlation coefficient is 0.703 and the explanation rate of variance is 49.4%. Generally, the result shows that the tree ring δ¹³C is restricted by several climatic variable in this area.Through constructing transfer function of information, we reconstruct the history of precipitation from Mar to Sep and the annual mean temperature since 1685 of Tianmu Mountain. The analysis and test illustrate that the result of reconstructing reflects preferably the historical climate variation during the past 300 years in this area. The climatic variation during the 300 years in this area has close correspondence with the climatic variation during the past 500 years of our country and the territorial climate variation reflected by the other geological records in the east region of China. The result proves that the creditability of information of the Little Ice Age existing in the record of tree ring δ¹³C series of Tianmu Mountain.Some important colder, wetter and drier periods recorded in historical materials were confirmed by the reconstructing series. The quasi-periodic oscillations of 58.82 a, 21.28 a, 13.70 a, 3.23 a, 2.63 a, 2.33 a and 2.07 a are involved in the reconstructing series, which show that it has a reasonable record for sunspot and ENSO in the tree ring δ¹³C series of this area.The result reconstructing the change of atmospheric CO₂ concentration in virtue of the three δ¹³C series reflects the long-time changing trend of atmospheric CO₂ concentration during the past 300 years favorably. The conclusion which is educed by the coherence of reconstructing atmospheric CO₂...