Response Of Tree Rings To Climatic Factors In The Source Region Of Aksu Rive

Studying the changes of historical climate elements is of great significance for a better understanding of past climate change,providing an effective reference for the development of ecological protection work in the study area,and laying a solid foundation for the development of regional climate change research.This study analyzes the response of radial growth of snow-covered spruce to climate through tree ring technology and mathematical statistics method,and reconstructs the average temperature of the Aksu River source area from July to August by using the single-year table to reconstruct the regional average climate.The extreme maximum temperature in February and February and the average relative humidity in May-June were analyzed by the reconstruction sequence to analyze the characteristics of climate change in the historical period and to analyze the possible impact factors of climate change in the historical period of the study area.(1)Through the field survey and sampling,the snow-capped spruce tree annual ring cores were collected in the source area of the Aksu River,and a set of width samples were formed.After the previous processing and measurement operations,the design of the three chronologies was completed: STD year Table,RES chronology and ARS chronology.Because the STD chronology can combine both high and low frequency signals,it was chosen for climate response and reconstruction analysis.Setting the EPS value to 0.85 or higher also determines the initial year of the chronology record.(2)Combination of monthly average temperature,monthly average maximum temperature,monthly average minimum temperature,extreme maximum temperature,extreme minimum temperature,monthly precipitation,sc PDSI,relative humidity and five standardized width chronologies of the source area of Aksu River Correlation analysis found that the relative humidity of May-June was well correlated with the STD chronology,the highest correlation was 0.635;the average temperature of July-August was the highest correlation with the STD chronology of-0.529.Considering the correlation between the five chronologies and the temperature,precipitation,sc PDSI and average relative humidity,the average temperature from July to August and the average relative humidity from May to June are reconstructed.The cross-validation results prove that the conversion equation is highly reliable.Sex and stability,the reconstructed value has a good correspondence with the measured value.(3)The average temperature sequence of reconstruction from July to August has four warm periods: 1897-1907,1922-1936,1938-1954,2013-2016;5 cold periods1890-1896,1959-1978,1980-1985,1987-2006,2010-2012.There are 9 wet periods in the average relative humidity of the reconstruction from May to June: 1890-1895,1911-1916,1921-1924,1936-1942,1953-1968,1973-1977,1981-1983,1988-1998,2003-2005;9 dry periods 1896-1910,1917-1920,1925-1935,1943-1952,1969-1972,1978-1980,1984-1987,1999-2002,2006-2016.(4)The average temperature sequence of the reconstructed Aksu River source area from July to August has three main periods of 39,56 and 27 years.The average relative humidity of May-June is 4 main cycles of 57 years,37 years,27 years and 12 years.(5)The AMO index may be an important driving factor for temperature changes in the source area of the Aksu River from 1890 to 2016.