Modeling the effects of crust on rain infiltration in vegetated sand dunesin arid desert

Shapotou Desert Research Station is located at the southeast edge of Tengge r Desert in China. Shapotou sand dunes have been vegetated to stabilize the m. The vegetated dunes have been completely covered by a natural crust. Rai n infiltration was reduced by 36% to 74% on the crusted site while there wa s no reduction of rain infiltration on the sandy site. The infiltration rat e was positively correlated with total rainfall and negatively correlated w ith rain intensity. Runoff on the crusted site provided water for vegetatio n growth in the hollows between sand dunes. The crust significantly impeded increased soil moisture. To increase soil moisture in the surface 40 cm la yer, rainfall had to be above 8.5 mm on the slopes of sand dunes on the cru st site, and increased with rain intensity. In the Shapotou area, the amoun t of rainfall that vegetation on slopes of sand dunes could utilize, was re duced to about 40 mm per year by the crust, although the mean annual precip itation was approximately 180 mm. It is expected that vegetation cover will continuously degrade in the future. To maintain vegetative cover adequate to stabilize the active sand dune, it was necessary to break part of the cr ust at slope of sand dune.