Distribution Characteristics Of Earlywood And Latewood And Climatic Sensitivity Of Larix Gmelinii In The Northern Of Great Xing'an Mountains

Located in the high latitude and cold region,the Great Xing'an Mountains forest zone is one of the most significantly affected areas in the world by the climate.The rising temperature makes the local forest ecosystem more vulnerable.Larix gmelinii,as a local species,is widely distributed in the Great Xing'an Mountains permafrost region and its tree-ring growth is highly sensitive to climate change.In order to reveal the influence of climate change on the radial growth of Larix gmelinii and predict the growth of Larix gmelinii on the regional scale,in this paper,the changes of Larix gmelinii 's earlywood width,latewood width and ratio of earlywood to latewood and the correlation between them and climate factors was analyzed,based on the Larix gmelinii as the research object in the north of Great Mountains,using the method of dendrochronology,establishing total tree-ring width chronologies,earlywood width chronologies and latewood width chronologies.The response of earlywood width,latewood width and annual rings(total treering width)to climate change and the law of distribution variation in earlywood and latewood width were discussed.The main results are as follows:(1)When Larix gmelinii was under 40 years old,the earlywood proportion increased significantly.Between 41 and 80 years old,the latewood proportion began to increase significantly.During the period of 81-140 years old,Larix gmelinii the earlywood proportion increased year by year(p > 0.05),but the increase was much less than that between 1-80 years old,almost negligible(k = 0.0001).Larix gmelinii after 140 years old,the ratio between earlywood and latewood width tended to be stable and the earlywood proportion and latewood proportion fluctuate around 0.7 and 0.3 respectively.(2)There is no significant change in earlywood proportion and latewood proportion with the increase of altitude(p > 0.05),while earlywood proportion decreased with the increase of latitude,but the change range was small(p > 0.05).(3)The total tree-ring index of most sample sites are positively correlated with the monthly average temperature from April to September of the current year(p < 0.05).The effect of the precipitation on total tree-ring width was mainly concentrated in November of last year to January of the same year.SPEI index effect on the radial growth of Larix gmelinii is mainly concentrated from November to march of the previous year.(4)The correlation between the earlywood width chronologies and meteorological factors is lower than the total tree-ring width chronologies no matter the value of the correlation coefficient or the number of months reaching significant correlation,and the latewood width chronologies is higher than the total width chronologies.After eliminating the correlation between the earlywood width and latewood width,the adjusted latewood chronologies(LWa)were obtained.LWa enhanced the correlation between the temperature and the chronologies in April of that year.Except for HML1,all sites in the study area were positively correlated with the monthly average temperature in April of that year,and the correlation coefficient was relatively high.Temperature is the main limiting factor for the radial growth of Larix gmelinii in the study area,but environmental factors such as temperature,altitude and latitude do not affect the distribution ratio of earlywood and latewood width in the same year.The distribution of earlywood and latewood width is mainly affected by the age of Larix gmelinii.For the Larix gmelinii before 140 years,the distribution of earlywood and latewood width is related to age,while after 140 years,the earlywood and latewood rate of Larix gmelinii is stable at 70% and 30% respectively.