Abstract: The study area is located in the hinterland of the Taklimakan Desert where the annual and monthly average temperature in July (the hottest month) and December (the coldest month) are $12.4^{\circ}\mathrm{C}$ , $28.2^{\circ}\mathrm{C}$ and $-8.1^{\circ}\mathrm{C}$ , the extremely maximum and minimum temperatures are $45.6^{\circ}\mathrm{C}$ and $-22.2^{\circ}\mathrm{C}$ , respectively. The annual accumulated temperature ( $\geq 10^{\circ}\mathrm{C}$ ) is $4621.8^{\circ}\mathrm{C}$ ; the frost-free period is about 283 days, the annual sunshine duration is about 2571.3 hours; and the annual precipitation and evaporation are $36.6\mathrm{mm}$ and $3638.6\mathrm{mm}$ respectively. The strong winds and dust weathers occur frequently. In this paper, the spatial density distributions of effective root length and weight of Tamarix ramosissima and Haloxylon ammodendron seeding were analyzed under drip irrigation by means of dig methods from left to right and from up to down, respectively. The results indicated that the mean density of effective roots of H. ammodendron seeding was three times as high as that of T. ramosissima. In the vertical direction, the density distribution of effective roots was varied with the different of species. The density distribution of effective roots of T. ramosissima seeding was decreased at an exponent function with the increase of the soil depth while that of H. ammodendron seeding demonstrated a single peak curve. In the horizontal direction, the density distribution of effective roots of two species all decreased at an exponent function with the increase of the distance from the stem. Regression estimation of non-linear parameters showed that model RD = $\mathrm{e}^{\mathrm{A} + \mathrm{BX} + \mathrm{CZ}}$ could preferably reflect spatial distribution of effective root density of T. ramosissima seeding under drip irrigation. The soil moisture of surface layer about two species was relatively low. With the increase of soil depth, the soil moisture was both remain basically stable at $2^{\circ}$ percent. But H. ammodendron soil moisture of every layer was lower than that of T. ramosissima.

Key words: effective roots density, Tam arix ram osissina, Haloxylon ammodendron, Taklinakan Desert