Stable Isotopic Characteristics Of Leaves And Groundwater Of Populus Euphratica In Different Habitats

Populus euphratica mainly grows in arid desert areas.It has a certain drought tolerance and plays an important role in ecological balance and sand fixation.The study of stable carbon isotope(δ¹³C)in p.euphratica leaves is helpful to understand the water use efficiency（WUE）of p.euphratica at the same time,the groundwater of p.euphratica forest is the key environmental factor in arid area.The chemical composition of groundwater is important to the survival and regeneration of p.euphratica.The study of chemical composition and hydrogen and oxygen isotopes of groundwater in p.euphratica forest is helpful to evaluate water quality and analyze water sources.The leafδ¹³C,δ¹⁵N,carbon（C）,nitrogen（N）,specific leaf area,hydrogen and oxygen isotope and Hydrochemical Composition of water in p.euphratica forest land were measured in 8 habitats of southern and Northern Xinjiang.The differences ofδ¹³C andδ¹⁵N in different habitats were discussed,which were related to geographical factors（altitude,longitude and latitude）,leaf C,N content,specific leaf area（SLA）the relationship between water use efficiency,and analysis of water sources and different conditions of water quality in iminqak p.euphratica growth situation,the following results:（1）Theδ¹³C values and the contents of carbon and nitrogen elements in the leaves of p.euphratica were significantly different among different habitats（P<0.05）.The meanδ¹³C values in the sapling forest（-27.863‰）were higher than that in the mature forest（-28.230‰）.There was no significant difference in leafδ¹⁵N（P>0.05）,and the mean value ofδ¹⁵N in mature forest（3.651‰）was higher than that in sapling forest（3.259‰）.There was a significant negative and positive correlation between leaf C content and itsδ¹³C andδ¹⁵N values（P<0.01）,while there was a significant positive correlation between leaf C content andδ¹⁵N values in mature forest.（2）Theδ¹³C andδ¹⁵N of sapling forest leaves were significantly positively correlated with altitude（P<0.01）,and theδ¹⁵N of sapling forest leaves was significantly positively correlated with longitude（P<0.05）.Theδ¹³C andδ¹⁵N values of young trees and mature forests were positively correlated with latitude（P<0.01）.The SLA of mature forest was greater than（103.141 cm²/g）and that of sapling forest（91.565 cm²/g）,and the correlation between SLA andδ¹³C was stronger than that ofδ¹⁵N.（3）There were significant differences in leaf water use efficiency between young and mature p.euphratica in different habitats（P<0.01）.The mean value of leaf water use efficiency in young forest（77.618 mol/mol）was higher than that in mature forest（72.463mol/mol）,and there was a significant positive correlation between leafδ¹³C and water use efficiency（P<0.001）.（4）The average values ofδ²H andδ¹⁸O in the groundwater of p.euphratica forest were-55.086‰and-8.656‰.The hydrogen and oxygen isotopic relationship is as follows:δ²H=7.18δ¹⁸O+7.23,R²=0.97.The hydrochemical type of its groundwater is Cl^--HCO₃^--SO₄^2--Na⁺-Mg²⁺,HCO₃^--SO₄^2--Na⁺,SO₄^2--Cl^--HCO₃^--Na⁺-Ca²⁺,Cl^--SO₄^2--HCO₃^--Na⁺-Mg²⁺,HCO₃^--Cl^--SO₄^2--Na⁺-Ca²⁺,SO₄^2--Cl^--HCO₃^--Na⁺-Mg²⁺and Cl^--SO₄^2--HCO₃^--Na⁺-Mg²⁺Such as the main.（5）The survey on the growth of p.euphratica showed that the average height of young p.euphratica（6.8±0.62 m）and mature p.euphratica（22.4±4.13 m）and crown（15.52±1.63 m）in Yutian County（Arix Mazar）and Yutian County（Karki）were higher than those in other sites.