| Global warming has damaged the global ecosystem, threatening human survival and development, therefore exploring the effects of climate change to the global ecological environment has become a focus of climate research. Through tree-ring studies, not only can we reconstruct elements of climate change, but also can we forecast the impacts of climate change bringing to the human on the basis of grasping relevant laws and identify coping strategies.In this thesis, Larix chinensis was regarded as sample tree and sampling sites at different direction of slope in different elevations (3100m, 3200m, 3300m, 3400m) were set up. Samples were collected at the height of 1.3m of sample trees and then, drying, polishing and analyzing by Tree-Ring Analysis System—WinDENDROTM 2005a were done to measure the ring width, cross-dating and establishing chronology. Correlation analysis and response analysis were done between tree ring width and average temperature of each month, precipitation of each month, warmth index, coldness index and at last the typical climate was reconstructed. The main results were as below:1. Core samples were measured and cross-dated by using WinDENDROTM 2005a, a software analyzing tree-ring. Through fitting, we found that the correlation coefficient between growth curve of Larix chinensis and polynomial function was the highest than that with other functions. After that, polynomial function was used to normalize core samples to eliminate the effect of the tree-age and the physiological property on the growth of eggplant.2. Standard tree-ring index series of Larix chinensis in each elevation were relatively stable, but compared with other sampling plots, the changing trend of tree-ring at the altitude of 3400m presented a remarkable difference. From the result of chronology test we found that the statistics of tree-ring width series index obtained after standardizing were higher than that of original value and among these statistics, the sensitivity, the variation of the correlation coefficient and signal to noise ratio were more remarkable. Thus, it is visible that theSensitivity of the sample of Larix chinensis to climate change was notable and the sample of Larix chinensis contained a great deal of information,satisfying the requirement of further analysis.3. Correlation analysis was done to chronology in different elevations with climatic factors, the first principal component of chronology and climatic factors and after that the first principal component of chronology was chosen to represent the whole response of Larix chinensis to climatic factors. The result of correlation analysis between the first principal component of chronology and climatic factors per month indicated that there was a remarkable difference between the result of first principal component of chronology and the result of No.4 sampling plot and there was no difference between the result of first principal component of chronology and the result of other sampling plots. There was a positive correlativity between the first principal component and temperature in the early period of growing season in current year, temperature in July, but there was a negative correlativity between the first principal component and temperature in the end of growing season; there was a negative correlativity between chronology of Larix chinensis in the altitude of 3400m and temperature in the early and middle period of growing season in current year and temperature in March obtained the highest correlative coefficient -0.41(P<0.05), but there was a low correlativity between chronology of Larix chinensis and precipitation. There was a high correlativity between No.4 sampling plot and warmth index, coldness index, so as No.3 sampling plot, but the correlative coefficient of No.3 sampling plot was relatively lower than that of No.4 sampling plot; the correlativity of tree-ring width in the whole region was opposite to the correlativity of No.4 sampling plot.4. Chronology was analyzed by using response analysis and the result showed that the response of Chronology four to warmth index during tree growth stages was higher than that of other Chronologies; among all tree growing seasons, the response of Chronology four to temperature in the early and middle of growing seasons were higher than other periods and their fitting functions passed the 95% confidence level test; the result of response analysis of the first principal component to climatic factors per month showed that the response of the first principal component to precipitation in March and April were higher than other months and especially, fitting function of precipitation in March passed 0.01 significance test; on the basis of conclusions above, warmth index, temperature in summer and precipitation in March and April were chosen to be reconstructed climatic factors.5. After climate reconstruction, the curve of fitted predicted value and the curve of measured value were compared and the result indicated that the reconstruction of warmth index, temperature in summer and precipitation in March passed the significance test and their equation were stable; Under the influence of low frequency, the reconstructed values of three climatic factors mentioned above were more stable than that under high frequency. |
