关键词: 沙坡头土壤水分, 水平衡, 植物

Abstract: Precipitation is the main replenishing source of water supply in the Shapotou area, it accounts for 98.3% of the total water supply source. Compared with precipitation condensation water counts for nothing in water supply although it is good for the annual ephemeral plants. Evapotranspiration of sandy land is the main consumptive term, it constitutes 89.7-92.8% for different afforested structure with different sand-fixing ages. Sometimes, there occur deficits of evaporation, especially in the sand-fixing areas with a onger period. The biological crusts could retain rain water, this will increase evaporation loss, decrease effective infiltration and finally lead to the changes and succession of artificial protective system. Thermal change is the main dynamic condition for water movement in sandy land, while the volumetric heat capacity, heat conductivity and heat diffusivity are the basic parameters of thermodynamic movement in sandy land . All these factors are interacted with soil moisture and dry bulk density. A further study on the coupling movement of heat flow and water flow will contribute to reveal the nature of water movement laws.