Abstract: In this study four kinds of typical plots, with vegetation cover of 30%, 15%-20%, 10% and <5% respectively, were selected to investigate the spatial variation of soil salinity on Tamarix ramosissima nebkhas and their interdune in Qira oasis-desert ecotone at the southern rim of the Taklimakan desert. Soil samples of 0-10 cm and 10-20 cm layer on T. ramosissima nebkha and interdune in the four plots were collected for analyzing soil pH, and total salinity, Cl^-, Na⁺, K⁺, SO₄^2-, Ca²⁺, Mg²⁺, CO₃^2- and HCO₃^- content from the perspective of Aeolian landform. Results showed that: (1) With the decrease of vegetation cover from plot 1 to plot 4 soil pH, and total salinity, Cl^-, K⁺ and Na⁺ content increased firstly and then decreased in 0-10 cm layer. The maximum values mainly distribute in the plot that the vegetation cover is 30%, the minimum values mainly distribute in the plot that the vegetation cover is 15%-20%, while the maximum values of HCO₃^- content mainly distribute in the plot that the vegetation cover is 15%-20%, and there is no obvious change of Mg²⁺ content. (2) Total salinity, Cl^-, Na⁺, K⁺, SO₄^2-, Ca²⁺ and Mg²⁺ content decreased firstly and then increased from the Under shrub to the Margin of nebkha to the Interdune to the Leeward shadow. However, soil pH and HCO₃^- content increased firstly and then decreased and there was a moderate correlation between soil pH and HCO₃^- content (r=0.644).The maximum values mainly distribute in the ground of Under shrub, while the minimum values mainly distribute in the Interdune. (3) Compared with 0-10 cm soil layer, there was a significant raise of Total salinity, Cl^-, Na⁺ and K⁺ content in 10-20 cm soil layer. However, there was a reduction of SO₄^2-, Ca²⁺ and HCO₃^- content and no obvious change of soil pH. With the decrease of vegetation coverage, the various change of soil salinity content in the two soil layers had a consistent trend. (4) The transpiration, recretion and selective absorption of root of T. ramosissima and soil evaporation make obvious soil salinity enrichment effects around the area of Nebkha. However, with the decrease of the total vegetation cover and the increase of desertification intensity, the non-biological factor of wind erosion begin to play a leading role, and soil salinity enrichment effects of shrubs tend to diminish and disappear gradually.

Key words: oasis-desert ecotone, Tamarix ramosissima Nebkha, soil salinity, spatial heterogeneity