Hydrological And Climatic Changes Recorded By Tree Rings In A Typical Region On The Eastern Margin Of Westerly Winds In Asia

Since the industrial revolution,the global hydrological climate has undergone profound changes,which constantly causes global ecological and environmental problems.Reveal hydrology and climate change rules and characteristics of the long historical period has become the important research content,because the modern apparatus measuring data record is shorter,unable to meet the needs of hydrology and climate change research long historical period,and tree rings has long time series,space,wide distribution,high resolution,in accurate and other characteristics,not only can inversion long sequences of hydrology and climate history,Therefore,it has become an important means to invert the hydrological climate in a long historical period by using tree rings to reveal its laws and characteristics,and it is of great significance to the study of historical hydrological climate change.In this study,elm and juniper were selected as the representative tree species in the typical eastern margin of westerly winds in Asia.The tree-ring standard chronology(STD),difference chronology(RES)and autoregressions chronology(ARS)of elm and juniper were constructed to analyze the response relationship between elm and juniper growth and hydrological and climatic factors.To reconstruct the historical series of annual mean minimum temperature,annual precipitation and annual runoff in the typical region of the eastern margin of westerly winds in Asia in the past 200 years or so,and reveal the regularities and characteristics of the past hydrological and climatic historical changes in this region.The main conclusions are as follows:1.After pretreatment,width measurement and cross determination of 142 sample cores collected in Xilinhot and Wulasshan areas,standard chronology(STD),difference chronology(RES)and autoregressive chronology(ARS)of elm 217 A and juniper 192 A were established by using Arstan software.The mean sensitivity(0.560?0.576),signal-to-noise ratio(8.106?10.507)and mean correlation coefficient(0.488?0.522)of the chronology passed 99% significance test,which indicated that the standardized chronology contained more hydrological and climatic signals and could be used for tree-ring hydroclimatology research.2.Elm trees in Xilinhot and Juniper trees in Wulashan grew rapidly with the decrease of temperature,the increase of runoff and precipitation,and the response to the annual mean minimum temperature was the most sensitive(-0.849?-0.789).Elm,juniper growing season early(April to May),more dependent on temperature.Elm and juniper are most dependent on temperature and precipitation from June to August and from June to July.Elm and juniper grow rapidly from September to October with the decrease of low temperature,the increase of precipitation and the increase of runoff.Elm and juniper are significantly affected by low temperature from November to December.3.Based on the response relationship between the standardized chronology of Elm and Wulashan in Xilinhot and the annual average minimum temperature,annual precipitation and annual runoff,the series of average minimum temperature,annual precipitation and annual runoff in 217 a and 192 a in Xilinhot and 192 a in Wulashan are reconstructed.Correlation coefficients(0.453?0.655),interpretation of variance(18.00%?24.10%),error reduction value(0.236?0.509),efficiency coefficient(0.194?0.421)and product mean value test(3.013?3.908)passed 99% significance test,and the reconstructed equations were stable and reliable.It can be used in the study of hydrological and climatic changes in the historical period of the region.4.During 1825-1859,the temperature fluctuated sharply,and the frequency of cold and warm periods increased.During 1859-1988,the temperature fluctuated weakly,and the frequency of cold and warm periods increased,while the frequency of warm period decreased.The temperature fluctuated sharply from 1825 to 1838,with the frequency of cold period shortening and the frequency of warm period increasing.The temperature fluctuated most gently from 1838 to 1863,and the temperature fluctuated most violently after 1863.The frequency of warm period from 1838 to 1981 was shortened,the frequency of warm period after 1981 was increased,and the frequency of cold period was contrary to the law,both of which had a period of 30 years.5.The precipitation in Xilinhot region fluctuated sharply from 1800 to 1854,the frequency of dry period increased,and the frequency of wet period decreased.The precipitation fluctuation from 1854 to 1988 was the most gentle,and the precipitation fluctuation after 1988 was the most intense,in which the frequency of dry period decreased and the frequency of wet period increased in 1861.During 1825-1871,the precipitation fluctuated slowly,but after 1871,the precipitation fluctuated sharply.In 1825-1889,the frequency of dry period increased,while that of wet period was contrary to the law.In1889,the frequency of dry period shortened,and that of wet period increased.6.The runoff fluctuation in Xilinhot area was the most severe from 1800 to 1834,the most gentle from 1834 to 2002,and the fluctuation was more severe after 2002.From 1800 to 1934,the occurrence frequency of abundant and low periods increased and the duration of continuous abundant periods increased,which was contrary to the rule after 1934.The annual runoff fluctuated gently from 1825 to 1865 in the Wula Mountain region,and the fluctuation was most intense after 1865.From 1825 to 1947,the frequency of partial abundance decreased gradually and the duration of continuous abundance shortened.After1947,it was contrary to the law,and the period of 30 a existed in all cases.7.The annual average minimum temperature in the western part of the study area was higher than that in the eastern part,and the annual precipitation in the western part was lower than that in the eastern part.The hydrological and climatic changes in the west are more intense than those in the east.The duration of cold period in eastern China is shorter than that in western China,and the duration of warm period,dry period,wet period,abundant period and dry period in eastern China is longer than that in western China.