| Drought resistance, water-consumption characteristics and water use efficiency of Populus albexberolinensis Dipple, Faxinus mandshurica, Betula platyphylla and Ulmus japonica were studied under four soil moisture gradients by the means of pot experiment. Thd paper mainly studied the changes of leaf water potential, water deficiency and wate-holding ability, the water parameters calculated by using Pressure-Volume technique, the effects of water stress on water use efficiency and biomass allocations to seedlings. The results showed as follows. (1) Every species had sensitive reaction to the water stress and carried out osmotic adjustment and water balance by different ways. (2) Continuous-diurnal variations of water consumption fluctuated with the changes of air temperature and humidity and the difference was not remarkable when the degree of water stress was stronger. Soil water content was the biggest one in the all factors which affected the changes of transpiration rate. (3) The abilities of water use efficiency of some seedlings could be increased under suited water stress by their drought exercise. For example, the water use efficiency of Populus albe xberolinensis Dipple in the LW condition was increased by 17.32% compared to CK condition, and so was Ulmus japonica in the MW and WW condition by 12.60% and 7.09% respectively. (4) Although all the four species had the definite abilities of drought adaptability, the adaptive ways were different because of drought tolerance and drought defence operating. Populus albe xberolinensis Dipple adapted drought mainly by drought defence, so did Betula platyphylla and Ulmus japonica by drought tolerance and Faxinus mandshurica by all of them. (5) Through all the above analyze, the ability to resist drought conditon was: Ulmus japonica>Betula platyphylla> Faxinus mandshurica>Populus albe xberolinensis Dipple. It could represent effective information for utilization of water resource and afforestation in arid and semiarid areas.
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