The Dendroclimatological Study On Toutun River Basins And Santun River Basins On The North Slope Of Middle Tianshan Mountains, Xinjiang

It is for the first time to Study on Dendroclimatology of Toutun River and Santun River Basins on the North Slope of Middle Tianshan Mountains. It analyzed the relationship between tree-ring width chronologies in Toutun River Basins and Santun River Basins and climatic information at Xiaoquzi and Daxigou Meteorological Station. Using the method of Sample Function, Correlation calculation indicates that is positive correlation between the lower limit of regional forest chronology and precipitation of Xiaoquzi Meteorological Station from July last year to June current year(R=0.694, Sig.1evel=0.00000002), and showed that there is positive correlation between the upper limit of regional forest chronology and temperature of Daxigou Meteorological Station from February to March current year (R=0.537, Sig.1evel=0.00003).By means of stepwise regression method, using MSZt standardized tree-ring chronology series, the long-term sequence of precipitation was reconstructed from July last year to June current year, with an explained variance of 48.4%; In the same way, using DXZt standardized tree-ring chronology series, the long-term sequence of temperature was reconstructed from February to March current year, with an explained variance of 28.8%. It is verified that the reconstructed precipitation and temperature were reliable. Analyzing the reconstructed series show that:(1)Analysis of relevant function indicated that precipitation was the first limiting factor on the lower limit of regional forest chronology, but temperature was the first limiting factor on the lower limit of the forest chronology. The result that the long-term sequence of recent 146 years'precipitation was reconstructed from July last year to June current year and recent 376 years'temperature was reconstructed from February to March current year has distinct physiological significance. It is widely validated that the reconstructed long-term spring precipitation and temperature is credible.(2) Tree-ring samples were used to develop tree-ring width chronologies by different step size of spline function. Further using image analysis on Influence of different step size of spline function on correlation between tree-ring width chronologies and their climate signals showed: With different step size of spline function, the correlation coefficients curve of Miaoergou Mine and Santun River chronology in the lower limit of forest and precipitation of Xiaoquzi Meteorological Station from July last year to June current year showed the variational form was increase in former part and decline in posterior part, but it had discrepancy in some parts. The respectively best step size was 40 years and 30 years. With different step size of spline function, the correlation coefficients curve of Dongnangou and Xiaoquzi chronology in the upper limit of forest and temperature of Daxigou Meteorological Station from February to March current year showed the smooth logarithmic form was increase in former part and flat in posterior part. The respectively best step size was 220 years and 185 years. After analyzing,it was found that the best step size of spline function had more information than the step size of spline function which based traditional method given and the step size of spline function which based half of tree-ring chronology series.(3) In the 146 years, the precipitation from July last year to June current year had 6 wet periods and 6 dry periods at Xiaoquzi Meteorological Station on the North Slope of Middle Tianshan Mountains. And there were 102 normal years, 20 dryish years, 24 dampish years. The wettest year was 1942 (the mean precipitation was 711.0mm, 28.2% higher than others) ,the driest year was 1945 (the mean precipitation was 339.1mm, 28.0% lower than others).At Daxigou Meteorological Station on the North Slope of Middle Tianshan Mountains, the temperature from February to March current year had 9 warmer periods and 9 colder periods in the 376 years. And there were 208 normal years,56 warmish years,59 coldish years,24 warm years,29 cold years, the longest coldish periods was 1539-1583 (45 years).The warmest year was was 1689 (the mean temperature was -10.5℃, 16.1% higher than other years) ,and the coldest year was 1643 (the mean temperature was -14.4℃, -14.8% lower than others). The long-term change periods of precipitation and temperature are greatly similar to that of the change trend of Xinjiang, the North-west of China, and there are some inherent and intricate relationships and responses between them.(4) The reconstructed precipitation sequence had 2.09and 4.36a changing periods. And the reconstructed temperature diden't has obviousily abrupt change.The reconstructed temperature sequence had 2.03a, 2.05a, 2.8a, 3a and 4a changing periods. And the reconstructed precipitation had abrupt change in 1681a, 1702a, 1726a, 1795a, 1825a, 1850a, 1873a and 1971.