Variations In Water Use Efficiency Of Mongolian Pinus Sylvestris Var.Mongolica Plantation In Central And South Area Of Northeastern,China

This study is based on the theories and methods of tree chronology,tree-ring climatology,and stable carbon isotope.The central and south area of Northeastern of China(Jilin Province,Liaoning Province)is taken as the research area.The research object is Pinus sylvestris var.mongolica plantation.Selecting 20 sampling sites in the study area to establish chronologies of the tree-ring width of Pinus sylvestris var.mongolica plantation.Then determine the tree-ring stable carbon isotope ratio(?13C)of some Pinus sylvestris var.Mongolica samples and calculate the basal area increment(BAI)and the water use efficiency(WUE)based on the tree-ring stable carbon isotope ratio ?13C.The responses of radial growth(tree-ring width index,BAI),stable carbon isotope and water use efficiency of Pinus sylvestris var.mongolica plantation of each sampling site in the study area to climatic factors(monthly average temperature,monthly precipitation,monthly average relative humidity)were studied.The climatic factors that affect the water use efficiency of Pinus sylvestris var.mongolica plantation against the background of global climate change and the changing laws of water use efficiency are clearly defined,and the relationship between the water use efficiency and radial growth were explored and discussed.The main results of the study are as follows:1.The correlation between tree-ring standard chronology of Pinus sylvestris var.mongolica of each sampling site and climatic factors shows that for Jilin Province,the temperature from November of the previous year to April and October promotes radial growth,and the temperature from May to June inhibits the growth;the precipitation from April to June promotes growth,and the precipitation of January inhibits growth;the effect of relative humidity does not have a good consistency.For Liaoning Province,the temperature of November of the previous year and October promotes radial growth,and the temperature from May to July inhibits growth deeply;the precipitation from February to June promotes growth,and precipitation of January inhibits growth;the relative humidity from April to September promotes growth significantly,and relative humidity from December of the previous year to January inhibits growth.The responses of radial growth of Pinus sylvestris var.mongolica plantation to climatic factors in Liaoning Province are more sensitive than that in Jilin Province.The radial growth of Pinus sylvestris var.mongolica is affected by regional climatic factors synergistically.2.In this study,the basal area increment(BAI)of Pinus sylvestris var.mongolica was used to measure the radial growth of trees.Interannual changes of BAI suggest that the Pinus sylvestris var.mongolica plantation in most sampling sites show extremely significant(p <0.01)growth trends,which indicates the trees were growing well in the radial direction.3.The correlation between the water use efficiency of Pinus sylvestris var.mongolica plantation and climatic factors shows that for Jilin Province,the overall effect of temperature is a more obvious promotion.The temperature of May,June and September promotes the WUE in all sampling sites.The mainly effect of precipitation is inhibition.The relative humidity also suppresses WUE,and inhibition of relative humidity of September was significant.For Liaoning Province,the two main factors that affect WUE are also temperature and relative humidity.May temperature promotes growth significantly,and the temperature of June and September significantly promotes the WUE obviously;The effect of relative humidity is concentrated in the growing season(April-September)of the year,which inhibits the promotion of WUE to a certain extent.4.The relationship between the water use efficiency of Pinus sylvestris var.mongolica plantation and its radial growth(tree-ring width,BAI)reveals that the BAI of Pinus sylvestris var.mongolica in Jilin Province has no obvious response to WUE which is the increase of WUE cannot be translated into radial growth.However,there is a significant correlation between BAI and WUE(p <0.05),and as WUE increases,the radial growth will increase accordingly for Liaoning Province.