Reconstruction Of Precipitation And Runoff In The Source Region Of Datong River Based On Tree Rings

Tree-ring samples have attracted the attention of the majority of scientific researchers due to low difficulty in obtaining,long time scale of samples,high dating accuracy,and ease of carry and preservation.This series of advantages make tree-rings become one of the alternative data to study paleoclimate and hydrological changes.The study of tree-ring and climate change can help scholars understand the variety of paleoclimate and predict the future climate The trend of climate change,the climate and ecological change in Qilian mountain area are the focus of our country in the future.The regional climate change and water conservation capacity will be directly related to the ecological change of the environment.Datong River is located in the inland arid area of Northwest China.It originates from the first tributary of Huangshui River,and is called moele River in Gansu Province and Qinghai Province,The middle part of the river is called Haomen river.Because the Datong River is far away from the ocean,the water vapor in the Pacific Ocean and Indian Ocean is blocked by the vast land,which makes it difficult to reach this area.As a result,the precipitation in this area is scarce,forming a unique Continental monsoon climate.The dominant tree species in this area,such as Picea crassifolia and Sabina przewalskii,are conducive to the study of tree ring.In this paper,the tree ring width chronology of Picea crassifolia collected from the source area of Datong River and the South-North slope of the middle Qilian Mountains is obtained,and its relationship with precipitation,temperature and runoff in the source area of Datong River is analyzed.The main conclusions of this study are as follows:(1)A total of 379 Picea crassifolia tree-ring samples were collected from 7 sampling points(SYK,DC,SMT,HCB,CS,MSW,LDS)in Gansu province and Qinghai province,and they were synthesized based on the cross-correlation of the chronology of the seven sampling points The chronology of 3 regions(QL,QLS,QLN).The samples contain more climate change information and their responses to climate change are relatively consistent.Precipitation in the study area is the main climatic factor restricting the radial growth of Picea crassifolia.Temperature has a negative impact on Picea crassifolia.The influence of spruce radial growth is not obvious,and the difference between the north and south slopes is basically the same.(2)Using the chronology of Picea crassifolia tree ring width in the Qilian Mountain,the total precipitation change in the central Qilian Mountains from 1500 to 2009(509a)from August of the previous year to July of the current year was reconstructed,and the variance explained was56.7%.There were 11 wet periods and 11 dry periods in the study area.The humid periods are:1513-1521,1567-1574,1617-1624,1680-1706,1727-1758,1801-1810,1831-1856,1886-1893,1943-1949,1973-1987 and 1996-2008.The drought periods are: 1504-1512,1522-1566,1575-1616,1625-1679,1707-1726,1759-1800,1811-1831,1857-1885,1894-1942,1950-1972 and1988-1995.There are quasi-periodical changes of 2a,2.3a,3.2-3.4a,5.3a and 6.8a in the precipitation sequence;a significant mutation from less to more occurred in 1712,and a significant mutation from more to less in 1856;The analysis shows that the precipitation reconstruction sequence is greatly representative of the precipitation changes in the central Qilian Mountains.(3)Using the chronology of Picea crassifolia tree ring width in the Qilian Mountains,the total runoff change in the central Qilian Mountains from 1500 to 2009(509a)from August of the previous year to July of the current year was reconstructed,and the variance explained was40.2%.There were 11 wet periods in the study area.And 11 dry periods.The humid periods are:1513-1521,1567-1574,1617-1624,1680-1706,1727-1758,1801-1810,1831-1856,1886-1893,1943-1949,1973-1987 and 1996-2008.The drought periods are: 1504-1512,1522-1566,1575-1616,1625-1679,1707-1726,1759-1800,1811-1831,1857-1885,1894-1942,1950-1972 and1988-1995.There are quasi-periodical changes of 2a,2.3a,3.2-3.4a,5.3a and 6.8a in the runoff sequence;a significant mutation from less to more occurred in 1712,and a significant mutation from more to less in 1856;The analysis shows that the runoff reconstruction sequence is greatly representative of the runoff changes in the central Qilian Mountains.