The Effects of Land Use Change in Desert-Oasis Ecotones by the Gurbantunggut Desert on Soil Properties

In this paper,a comparative study is made on soil properties changes of eight land-use types in desert-oasis ecotone by the Gurbantunggut Desert.It is found that silt content has significant differentiations among various land use types(P0.05).The longer time and greater intensity of cultivation are the higher silt and very find sand content are.On the contrary,fine sand content has a decreasing trend.During the early cultivation period(≤5 years),soil fertility is in inverse proportion to time.After then(5 years),it is proportional to time.Soil fertility of different land use types may be divided into the following four grades: 1) saline-alkali soil with the highest level,2) ecological protection forest land,grassland and natural shrub land,3) farmland of 10 years,farmland of 3 years and vegetable garden of 5 years,4) farmland of 5 years at the lowest level.Human cultivation transforms soil salinity from the(saline-alkali soil) high salt in the upper layer and low salt in the lower layer into low salt in the upper layer and high salt in the lower layer.The saline matter is in inverse proportion to cultivated time.During the process of land use change,soil salinity is proportional to Cl-,SO2-4,Ca2+,Mg2+,K+ and Na+ concentrations and is in inverse proportion to HCO-3 concentration.Soil degradation index of 5-year farming-land(-30.58%) is the highest,1.5~3.9 times of other land-use types.