Abstract: The root system of Sabina vulgaris in Mu Us Sandy Land was mainly composed of short roots (diameter < 3 mm) and their weight are 60%~70% of the total amounts. The hairy roots (diameter1 mm) are 30%~65% of the total amounts, and are 3~5 times as the poplar's, and mainly concentrate in the range of 0~20 cm soil layer. The weight of the roots (diameter: 5~7 mm) are the least and only 2.03% of the total amounts. The root vertical distribution can reach up to 2 m in depth, and horizontal distribution can reach up to 1 m in width from the edge of shrub. The weight of the roots in the 0~60 cm soil layer are 60%~70% of the total amounts and distribute decreasely with the depth increasing. The water and nutrients in the 0~60 cm soil layer were mainly used, so the rain is the main source of its water. There is no ground water compensation in the sands except the lowland on inter sand dunes. So the seeds of Sabina vulgaris only regenerated under the Sabina vulgaris and Salix cheilophila shrub on the inter dune lowland with ground water compensation. The roots distributive characteristics of Sabina vulgaris not only verified the strong roots taking but also revealed the obvious restriction of the rainfall against the growth and development. The soil of the main distributive region of Sabina vulgaris in Mu Us Sandy Land were composed of soil particles whose diameter are less than 0.5 mm. In the composition, the fine particles (diameter:0.1~0.3 mm) are 70%~80% of the total particles and the micro particles(diameter0.1 mm) content become higher when the years of sand fixation are more. They could reach up to 4.2%~5.4% of the total particles and the most could be 30%. The soil average unit weight was 1.50 g·cm^-3 and the moisture content was 1.46%~4.20%. The moisture content of the 0~10 cm topsoil was only 0.5%~1.6%, but the moisture content of the inter dune lowland soil was 5.6%~15.37% influenced by smaller ground water depth. The correlation between the root system distribution of Sabina vulgaris and the mechanical composition and moisture content of soil was not obvious, but the moisture content of soil was lower while the soil layer was deeper in the region where the roots were abundant (0~30 cm).

Key words: Sabina vulgaris, weight of root, diameter of root system, distribution of root system, Mu Us Sandy Land