The Spatial Variations Of Soil Water And Salt Content Under The Populus Euphratica In Jinta And Dingxin Oasis, Gansu Province

Populus euphratica is an unique precious forest resource in desert areas.It playsan important role in stabilizing of the ecological balance of desert river areas, windprevention and sand-fixation, improving oasis weather condition, and preservingfertile soil. In the meantime, populus euphratica is an ancient tree specie, which isimportant in researching the climate change in oasis areas, the river change, theevolution of the plants flora, and the development of ancient economic and culture.Deforestation,land reclamation and river interception project increase thedamagement to the fragile ecosystem. More and more native vegetation weredestroyed. Further more, populus euphratica declined gradually. Soil water andsalinity content are the major factors that affecting the growing of natural vegetation.Given all these considerations, auther choose Jinta and Dingxin Oasis, the typical areain which populus euphratica distribute largely, for study area in this paper, andinvestigated the spatial differentiation of the soil water and salinity in this area. In thispaper, author set7samples (every sample includes18samples) in the study, andmeasured the soil water and salt content of6soil levels (0-20cm,20-40cm,40-60cm,60-80cm,80-100cm,100-120cm).The data is analyzed by Excel、SPSS. Based on theIDW method, author carried on optimal estimation to the soil water and salt of thesesamples which is not measured, and drew the spatial distribution chart of the soilwater and salt content. The result by analyzing is that:(1) Soil water in SCCD decreased with the soil depth increasing. While the soilwater in the other6sample areas in the0-60cm layer decreased. In the60-120cm, thesoil water in HSCD and GBLC layer kept on decreasing, while in DZZC、WXCD、NTWC、XHCD the soil water started to increase. The average soil water in SCCDwas the largest. The average soil water content in each sample in descending order isSCCD＞DZZC＞GBLC＞XHCD＞WXCD＞NTWC＞HSCD, which is from1.33%to14.46%.(2) The general characteristics of soil salt content are higher in the surface layer.The average salt content in the surface soil is up to1.73%. Soil salt content decreasedwith the soil depth increasing, and it reduced to0.77%in100-120cm layer. Soil saltcontent decreased drastically in the upper layers. The average soil salt content in eachsample in descending order is XHCD＞NTWC＞WXCD＞DZZC＞SCCD＞HSCD ＞GBLC,which is from0.43%to1.81%.(3) The coefficient of variation of the soil water was obviously different in eachlayer and became larger with the depth increasing. And the spatial variabilities of thesoil salt content were medium in all layers while it was strong variable in the surfacelayer of DZZC.(4) The soil water and salt content of the study area showed obvious spacedifferences and strong comparability, clearly banded or patchy.The soil water ofhorizontal direction in each layer shared similar characteristics of increasing fromwest to east. It was related with the topographical features of Beida river and Heiheriver basin. The soil water of horizontal direction in each layer decreased with thedistance away from water source. The spatial pattern of soil salt centent in each layergradually decreased from west to east.