Abstract: Soil water as one of the main restraining factors of the ecological environment in arid and semi-arid area, which study on the dynamic changes of soil moisture under the moving sand dunes and meadows in Horqin Sandy Land contributes to the ecological restoration and desertification governance. Using measured soil parameters and meteorological data from May 25 to October 31, 2018, the applicability of Hydrus-1D model in study region was evaluated and the distribution characteristics of soil moisture in the interfacial area of Horqin sandy dune and meadow were revealed. The dynamic variation rules of soil moisture in the 2m profile of mobile dune and 1m profile of meadow were emphatically analyzed. The results show that: The determination coefficient of soil moisture simulation and measured value of typical land types in the study area is higher than 0.76, and the RMSE is between 0.01-0.02 cm³·cm^-3. There is a clear layered structure on the soil profile that the mobile sand dune is divided into three layers, named dry sand layer (0-20 cm), the active layer (20-120 cm), and the stable layer (120-200 cm), respectively, where 40 cm soil moisture is the most volatile. And the grassland is divided into two layers, that is, the active layer (0-40 cm) and the stable layer (40-80 cm), which is mainly affected by precipitation, evapotranspiration and groundwater level. Furthermore, surface soil moisture in mobile dunes and meadows is significantly correlated with rainfall, which is only positively correlated with groundwater level change in meadows. And during the whole study period, the change of soil moisture storage in mobile dune is 12.6 mm, the actual evaporation of soil is 105.9 mm and the deep leakage of 200 cm is 173.9 mm, accounting for 59.5% of the total rainfall. The change of soil moisture reserve in meadow land is 8 mm. The deep leakage at 80cm soil layer is -27.2 mm (groundwater recharge), the actual soil evaporation is 67 mm, the vegetation transpiration is 244 mm, and the surface runoff is 0 mm.

Key words: mobile dune, meadow land, Hydrus-1D Model, applicability