| This research made use of the HR-33T Dew Point Microvoltmeter,the Thermal Dissipation Sap Flow Velocity Probe System,the PRISM Soil Moisture Measurement Instrument,the Li-6400 Portable Photosynthesis System and the Automatic Weather Station were carried on the measurement to the moisture transport index of natural Populus euphratica and influence factors.Based on the data observed in the dry Ejina from 2004 to 2005,the diurnal variation of leaf water potential and root-trunk sap flow of Populus euphratica, the spatial distribution characteristics of roots and influence factors were analyzed. The results showed that:the diurnal variation of leaf water potential wave-form is singular peak, it decreased to 34.58%, in order to strengthen the drink ability of Populus euphratica from soil, vertically ,the fine roots(d<2 mm) of Populus euphratica mainly concentrated at the 60～100cm the wet sand layer soil zone,,this layer soil moisture mainly comes from the river to keep water ,the soil water content in the 60-100 cm decreased to 35.24%,the root fastened to absorb water velocity to lower to 29.60%, thus, it influence the amount of steam, the tree trunk sap flow transfer to descend to 39.37%. The water of the system of plant and root showed:Populus euphratica beard water lack to be worse, to protect it availably for the reasonable, we should value the reasonable allotment of the water resources. Close correlation could be found the variation of leaf water potential has a remarkable correlation to air temperature ,air relative humidity and soil water content;Trunk sap flow has a remarkable correlation to sunny radiation, air temperature and soil water content;Root sap flow has a remarkable correlation to sunny radiation and air temperature.
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