| As one of the typical stands in the Greater Khingan Mountains,the secondary forest of Betula platyphylla plays an important role in water conservation,soil and water conservation and ecological balance in the Greater Khingan Mountains.In recent years,the Larix gmelinii forest has gradually degraded,and the ecological role of the secondary forest of Betula platyphylla cannot be ignored.Studying the sensitivity of Betula platyphylla to climate change in the Greater Khingan Mountains plays an important role in the study of tree rings in this area.Therefore,this study analyzes the stand structure and radial growth of Betula platyphylla secondary forests in the southern,central and northern parts of Greater Khingan Mountains and the response to climate factors.We Analyze the differences in the stand structure of Betula platyphylla secondary forests at different latitudes,established a standard chronology of Betula platyphylla radial growth at different latitudes,and compared the differences in the response of Betula platyphylla radial growth at different latitudes to climate change,and the difference in the response of radial growth to climate before and after the temperature mutation.The main conclusions are as follows:(1)Under the background of climate warming,the temperature of temperatures at different latitudes in the Greater Khingan Mountains has changed abruptly.After warming up,the temperature has increased by about 1℃approximately 1°C,but the temperature mutation time was different,and the mutation time is occurred later with the increase of increasing latitude.(2)The distribution of Betula platyphylla secondary forest in the southern and central regions is slightly clustered,and the distribution of Betula platyphylla secondary forest in the northern region is random,and the mingling degree increases gradually from south to north.Among the six distribution functions selected,the GAMMA distribution had the best fitting effect on the diameter distribution of Betula platyphylla secondary forest in different regions.LOGISTIC distribution had the best fitting effect on the tree height distribution of Betula platyphylla secondary forest in different regions.(3)Among the four spatial structure indicators,only angular scale and mingling had significant responses to climate factors.Appropriate warming can improve the spatial distribution pattern of trees,but will limit the mingling of birch secondary forests;the increase of precipitation will increase the mingling of the stand.(4)Warming has different effects on the radial growth of birch in different regions,and the effects on the radial growth of birch in different seasons in the same region are also different.After warming,the winter temperature in the previous year had a significant inhibitory effect on the radial growth of Betula platyphylla in the southern part of Greater Khingan Mountains,but had no significant effect on the radial growth of Betula platyphylla in the central and northern parts of Greater Khingan Mountains.Before the growth season,temperature had a weak inhibitory effect on the radial growth of Betula platyphylla in the southern part of Greater Khingan Mountains,a significant inhibitory effect on the radial growth of Betula platyphylla in the central part of Greater Khingan Mountains,and no significant effect on the radial growth of Betula platyphylla in the northern part of Greater Khingan Mountains.In the early growth season,temperature had a certain promoting effect on the radial growth of Betula platyphylla in the southern region of Greater Khingan Mountains,and had a significant inhibitory effect on the radial growth of Betula platyphylla in the central and northern regions.The equilibrium temperature of the hydrothermal conditions in the middle and late growth seasons had no significant effect on the radial growth of birch.After the growing season,temperature had a significant promoting effect on the radial growth of Betula platyphylla at low latitudes,and had a significant inhibitory effect on the radial growth of Betula platyphylla in the central part of Greater Khingan Mountains.In general,after warming,the temperature has a promoting effect on the radial growth of Betula platyphylla in the southern region of Greater Khingan Mountains,and has an inhibitory effect on the radial growth of Betula platyphylla in the central region of Greater Khingan Mountains,and has little effect on the radial growth of Betula platyphylla in the northern region of Greater Khingan Mountains. |
