黑河中游临泽地区沙丘植物水分来源的D、^(18)O同位素示踪

Using D and ^(18)O Stable Isotopes to Determine the Water Sources of Sand Dune Plants in Linze,Middle Reaches of Heihe River

基于2008年7月份降雨、地下水、土壤水和植物茎干水的D、18 O同位素观测结果,分析了黑河中游临泽地区沙丘顶、底部不同深度土壤水分的来源,确定了红柳、花棒、梭梭等沙丘植物的吸水层位及其对降雨和地下水的依赖程度,发现:①土壤水δ(D)、δ(18 O)剖面总体呈指数形式,局部受降雨事件入渗过程影响,土壤剖面的上界面受连续蒸发和降雨入渗作用,下界面接受潜水的连续补给;②地表至20～30cm深度内的土壤水由最近的降雨补给,其下至130cm深度内的土壤水由此前1～2周的降雨事件叠加补给,130～150cm深度以下的土壤水主要由潜水补给,偶尔混有前期较大降雨事件的入渗补给;③除沙丘底部的花棒利用较浅层次(120～180cm深度)的土壤水外,其他物种都利用≥185cm深度的土壤水,表明研究点的沙丘植物主要依赖更为稳定的潜水水源,偶尔利用入渗深度较大的降雨。

Using the measured δD and δ18O values of rainfall,groundwater and waters extracted from vegetation and soils,this paper discussed the sources of soil water at different depths at the top and bottom of one sand dune in Linze,middle reaches of Heihe River,and determined the soil layers from which three sand dune plants extract water,and the dependence of these plants on the rainfall and groundwater.The results showed that,when viewed as a whole,δD and δ18O values of soil water declined as a typical exponential function of depth,except that some details of the exponential curve were altered by the infiltration of individual rainfall events.It was indicated that the soil profiles were affected by evaporation and infiltration of rainfall along the top boundary and received recharge from phreatic aquifer through the bottom boundary.Soil water might be recharged by the latest rainfall event for the upmost layer to a depth of 20 cm or 30 cm,by all rainfall events occurring in recent 1-2 weeks for the medium layer from 20 cm or 30 cm to 130 cm in depth,and mainly by phreatic water,accidently mixed with earlier extensive rainfall events,for the bottommost layer under a depth of 130 cm.Hedysarum scoparium extracted soil water from 120 cm to 180 cm in depth at the bottom of the sand dune.Tamarix ramosissima Ledeb and Haloxylon ammodendron,at both the bottom and top of the sand dune,and Hedysarum scoparium at the top of the sand dune,extracted soil water under the depth of 185 cm.It was presumed that the sand dune plants here mainly relied on the more stably available phreatic water,accidently using the rainfall with a large limit depth of infiltration.