The Tree-ring Based Study On Response Of Pinus Tabuliformis On The South And North Slope Of The Central Qinling Mountains To Climate And Regional Climate Reconstruction

Qinling is the east-west direction of the mountains and the watershed between the Yellow River and the Yangtze River,the middle of which is located in Shaanxi.The Qinling Mountains-Huaihe River is an important geographical north-south demarcation line,800 mm isohyet and January 0? isotherm,which is a sensitive area of climate change and important for the study of climate change in the area.In Muwang National Forest Park on the south slope of Qinling Mountains and Nanwutai on the north slope,We collected sample cores of the Pinus tabuliformis tree rings,after some experimental treatments,using LINTAB to measure ring-widths.The crossdating result of tree ring-widths data was tested with COFECHA software,then the growth trend of Pinus tabuliformis ring-widths was determined by ARSTAN software after cross dating with the negative exponential function or the spline function,the standardized chronologies of Pinus tabuliformis at two sampling sites was obtained.Using the DENDROCLIM 2002 software and SPSS 22.0 to analysis the correlation relationship and Moving correlation relationship between the standardization chronologies of two sampling sites with climatic factors.Finally,based on Linear regression analysis,we reconstructed the March-April average maximum temperature of Zhen'an from 1853 to 2017,and used wavelet analysis to analyze the periodicity of the reconstructed sequence.The results showed that:(1)The annual average temperature,annual average maximum temperature and annual minimum temperature recorded by Zhen'an Meteorological Station and Chang'an Meteorological Station both showed significant increases in varying degrees,and there was no significant increase or decrease in precipitation.(2)The response of the radial growth of Pinus tabuliformis in Muwang National Forest Park on the south slope of the central Qinling Mountains and in Nanwutai on the north slope to climatic factors had certain differences.Temperature had a certain lag effect on the growth of Pinus tabuliformis on the north and south slopes of the Qinling Mountains,and the correlations between the tree-ring width index and the restrictive monthly temperature in the previous year is positive on the south slope,while negative on the north slope.The radial growth of Pinus tabuliformis in Nanwutai was mainly restricted by the temperature in August and October of the previous year,while in Muwang National Forest Park was mainly limited by the temperature of June-July,September and November of the previous year.In current year,the radial growth of Pinus tabuliformis in Nanwutai was mainly limited by the temperature in October and November,while in the Muwang National Forest Park was mainly affected by the temperature in January-May,June-July,September,November,and the correlations between the chronology of Pinus tabuliformis and the restrictive monthly temperature in the current year were positive.The response of the radial growth of Pinus tabuliformis in Muwang National Forest Park and Nanwutai to the precipitation was not very strong.The chronology of Pinus tabuliformis in Muwang National Forest Park was only significantly positively related to the precipitation in February,while in Nanwutai was only significantly positively related to the precipitation in May and June of the current year.(3)With the development of climate warming,the response sensitivity of the radial growth of Pinus tabuliformis in Muwang National Forest Park on the south slope of the central Qinling Mountains and in Nanwutai on the north slope to climatic factors of the two sampling sites had changed to some degree,and there were certain differences.The sensitivity of the radial growth of Pinus tabuliformis in Muwang National Forest Park responsing to the monthly mean temperature(June-July of the previous year,and JanuaryApril,June-July,September of the current year),the monthly mean minimum temperature(March-April,July,September of the current year),the mean maximum temperature(JuneJuly,September,November of the previous year,and February-July,September,November of the current year)and the precipitation(February of the current year)had increased,and the response sensitivity to the monthly mean minimum temperature(January-February,May of the current year)and the precipitation(July of the current year)has weakened.The sensitivity of the radial growth of Pinus tabuliformis in Nanwutai responsing to the monthly mean temperature(August,October of the previous year and November of the current year),and the monthly mean minimum temperature(October,November of the current year),the mean maximum temperature(August of the previous year and October of the current year)and the precipitation(August of the previous year,October of the current year)had weakened,and the response sensitivity to the September monthly mean temperature of the previous year,the May monthly mean minimum temperature of the current year,the May monthly mean maximum temperature of the current year and the precipitation in May and June of the current year had increased.(4)Temperature fluctuated obviously in the reconstruction sequence of March-April average maximum temperature of Zhen'an,and there were two colder periods and four warmer periods.The warm years were more accompanied by flood events,and the cold years were with more drought events.The obvious periodic variations of 2-7,8-15,18-28,75-96,and 100-125 years were found in the reconstruction sequence,in which the quasi-113,88,and 22 years were the first,second and third main periods,respectively.