Study On Radial Growth Difference And Climate Sensitivity Of Betula Ermanii In Different Slopes And Elevations Of Changbai Mountain

Alpine treeline dynamics are sensitive to climate change.The movement of treeline position has been widely regarded as a representative of climate change which may reflect climate change on a multi-year time scale.However,different from the location movement of treeline,the growth of trees in high-altitude treeline may be more sensitive to the interannual change of climate than that in low-altitude treeline.In mountain ecosystem,the distribution of tree population is always along the altitude gradient,and its radial growth in different slope directions and different altitudes may have different responses to the climate,and even the difference is obvious.Then,are the trees in the Changbai Mountain forest line different in radial growth and sensitivity to climate at different slopes and elevations? If it is different,what kind of law will it behave?Therefore,we collected core samples of Betula ermanii at different altitudes on the northern slope,western slope eastern slope and southern slope of the Changbai Mountain in northeast China,and compared the growth rate of basal area increment(BAI)of Betula ermanii at different altitudes to study the difference in altitude of its radial growth rate.At the same time,the annual ring width index(RWI)was established to analyze the response of radial growth of Betula ermanii at different altitudes to climate,so as to understand whether the relationship between radial growth and climatic factors was affected by altitude.The research results are as follows:(1)Although the position of the forest line was different in different slopes of Changbai Mountain,the radial growth difference of Betula ermanii was not obvious in the middle and low elevations,but was significantly higher than that in the high elevations(near the forest line).At the same time,the radial growth rate at middle altitude was the fastest.(2)The relationship between the radial growth and climate of Betula ermanii is affected by the altitude factor.As the altitude gradient increases,the climate information contained in the annual table of Betula ermanii increases,and the radial growth of Betula ermanii is more restricted by the climate factor,indicating that the growth of trees at high altitude(at the forest line)can be more used as an indicator of climate change.(3)The radial growth of birch in different slopes of Changbai Mountain to different elevations was mainly affected by summer(July)temperature,showing a significant positive correlation.Therefore,in the future,climate warming will further promote the growth of Betula ermanii in Changbai Mountain,and to a certain extent,there is no effect of water stress caused by temperature increase,which also indicates that the change of forest line in Changbai Mountain is mainly driven by temperature.(4)The radial growth of silver Betula ermanii in Changbai Mountain has a weak sensitivity to precipitation but a strong sensitivity to temperature.Betula ermanii can be an important substitute for reconstructing the climate of Changbai Mountain(Northeast Region)over the past few centuries.