The Response Of Multi-point Tree Ring Sequence To Climate Change In The Greater Khingan Range

In the context of global warming,the response relationship between tree annual rings width and climate change has gradually entered the view of researchers.The Greater Khingan Range is located in a climate-sensitive area of Eurasia,with a relatively fragile ecological environment and a perennial permafrost layer underneath,it is one of the regions with the highest latitude and fastest warming in China.Therefore,The Greater Khingan Range has a unique regional variation to climate,and it is more meaningful to use this region as the study area in the study of the response of tree annual rings width to climate change.In this study,we applied the theory and method of dendroclimatology to analyze the response relationship between tree annual rotation and climate change by principal component analysis,correlation analysis,time sliding analysis,and spatial correlation analysis.The main conclusions include :（1）In this study,three chronologies（STD,RES,ARS）of Larch tree-ring width were established for five sampling sites,and statistical parameters of the chronologies were analysed,all of which were applicable to the study of dendroclimatology.（2）The correlation between Larch growth and temperature and precipitation was analysed using month-by-month and season-by-season climatic data.The results showed that the width of the Larch tree-ring in Tahe was significantly negatively correlated with the mean maximum temperature in the growing season of the current year,including a highly significant negative correlation with the mean maximum temperature in June of the current year,indicating that the temperature in June of the current year was the main factor affecting the radial growth of Larch during the growing season;the width of the Larch tree-ring in Xinlin was significantly positively correlated with the mean minimum temperature of the previous growing season and with the mean maximum temperature of the current growing season;the width of the Larch tree-ring in Hanjiayuan was significantly positively correlated with the mean maximum temperature in July of the previous year and negatively correlated with the minimum temperature in July of the current year;the width of the Larch tree-ring in Amuer was significantly positively correlated with the mean temperature in the growth season of the previous year,and significantly positively correlated with the mean maximum temperature,including a highly significant positively correlation with the mean maximum temperature in August of the previous year,indicating that the temperature in August of the previous year is the main factor affecting the radial growth of Larch in the growth season of the previous year;the width of the Larch tree-ring in Huzhong was significantly positively correlated with the mean and mean maximum temperatures of the previous and current growing season,the mean minimum temperature was highly significantly positively correlated with the maximum temperature in the begin of growing season,with a highly significant positive correlation with the mean and mean maximum temperature in May of the current year,indicating that the temperature in May of the current year was the main factor influencing the radial growth of Larch in the begin of growing season.The results show that the effect of growing season temperature on the radial growth of Larch is not invariable and that the sensitivity of Larch changes with certain conditions,such as high altitude,high latitude and high precipitation,thus promoting or inhibiting Larch growth.（3）The principal component analysis method is used to extract the regional principal component chronology of tree ring data at four sampling points,which can better represent the common characteristics of tree ring change in the Greater Khingan Range,the cumulative contribution rate of variance of the first principal component PC1 chronology is 49.73%.A time-slip correlation analysis was conducted between the mean monthly and seasonal observed climate data from the four stations and the regional-scale information reflected in the PC1 chronology to provide a basis for further analysis of the spatial and temporal dynamic response of Larch radial growth to climate change in the region.（4）The radial growth of Larch and climate change in the region were analysed in both temporal and spatial dimensions,and an attempt was made to reflect the changing patterns of the general characteristics of precipitation in the late summer（August）in the Greater Khingan Range of China through the PC1 chronology.The results indicate that the spatial correlation between the PC1 chronology and the August precipitation field in the Greater Khingan Range was once shifted to the southeast in a gradual weakening process,a trend that may be related to the change in the extent of the East Asian summer winds and the warming and drying of the regional climate.