Radial Growth Of Larix Gmelinii In The Greater Khingan Range And Relationship With Ocean-atmosphere Interaction

Regional climate is generated under the joint influence of multi-layered systems and multi-scale atmospheric processes.Due to the impact of global warming,these processes have shown regional large-scale forcing responses,leading to significant differences in climate change in different regions.Therefore,one important area of current climate change research is the study of regional climate change.The Greater Khingan Range is located in a climate-sensitive area and has unique regional information on climate change,making regional climate research in this area advantageous.This study used Larix gmelinii tree-ring samples collected from Tahe,Xinlin,Huzhong,and Hanjiayuan sites in the northeast of the Greater Khingan Range to establish a Larix gmelinii tree-ring width chronology.By using the standard chronology of each site and principal component analysis,a representative regional principal component chronology was generated.Using the dpl R and treeclim packages in R,a sliding window of 21 years was selected with a 95% confidence interval.The growth of the Larix gmelinii was analyzed at monthly and seasonal scales,and the effects of average minimum temperature and precipitation on the Larix gmelinii in the study area were studied.Using the Larix gmelinii as a proxy for climate,the spatial correlation analysis between sea surface temperature and the PC1 chronology was performed to explore the temporal dynamics between large-scale climate factors and the PC1 chronology,and the relationship between ocean-atmosphere interaction and regional climate was discussed.The main conclusions include:(1)This study uses Larix gmelinii cores collected from the field in the Greater Khingan Range,and first establishes chronologies for individual sample sites.After parameter statistics,it is considered that the chronologies of each sample site are suitable for dendroclimatology research.The cumulative contribution rate of the first principal component of the PC1 chronology established is 49.728%,indicating that climate factors are the main influencing factors on radial growth of Larix gmelinii in the Greater Khingan Range,and their response to climate change is consistent.(2)Analyze the climate information contained in the PC1 chronology.The precipitation and average minimum temperature in August of the current year in the study area have a significant positive correlation with the radial growth of Larix gmelinii,and the warm and humid conditions during the growing season are largely conducive to the growth of Larix gmelinii.The relationship between tree rings and climate is dynamic,and Larix gmelinii is very sensitive to changes in August precipitation of the current year,but its sensitivity has gradually decreased since 2006 and has become insensitive by 2018.In October of the previous year,average minimum temperatures in February and June of the current year had a significant inhibitory effect on the growth of Larix gmelinii.From a seasonal perspective,since 2010,the promoting effect of precipitation during the growing season on the growth of larch has gradually increased.The average minimum temperature showed a significant promoting effect during the previous year’s growing season from 1980 to 2004 and during the current year’s growing season from1990 to 2015.However,it exhibited a significant inhibitory effect during the previous winter from 1978 to 2007.(3)Analyzing the relationship between tree-ring growth and ocean-atmosphere interactions.Both MEI and PDO indices show a trend of changing from positive correlation to negative correlation,then back to positive correlation.The transition periods correspond to the recorded El Ni?o/La Ni?a phenomena during ENSO events and phase transitions of PDO.This indicates that large-scale circulation can affect the growth of Larix gmelinii in extratropical regions,and tree rings can record information about distant ocean-atmosphere interactions.ENSO events represented by MEI that can affect the intensity of temperature and precipitation.The more significant the MEI,the stronger its correlation with climate factors will be.The impact of MEI on average minimum temperature is more significant than that on precipitation.The spatial relationship between December precipitation in the previous year(1988-2009)and lagged sea surface temperatures suggests that ENSO may still have a lag effect on tree-ring growth.(4)Analyzing the response of tree-ring growth to the combined effects of multiple climate factors.When both the MEI and PDO indices showed significant positive correlations with the PC1 chronology,they had a significant positive impact on the radial growth of Larix gmelinii.The MEI not only regulates the negative correlation area in the North Pacific region but also regulates the intensity of the positive correlation area along the western Pacific coast.The MEI and the average minimum temperature in the Greater Khingan Range are connected through ocean-atmosphere interactions,affecting the growth of Larix gmelinii and having leading and lagging effects at the monthly scale.