Abstract: Desert riparian forest is an important component of the ecosystem in arid area.The study on the water use process of constructive plants in desert riparian forest is of great significance to formulate the countermeasures for ecological conservation and restoration in arid area.In this study,the arid lower reaches of the Tarim and Heihe rivers in northwest China were taken as the study areas to explore the plant water resources and root hydraulic lift process of desert riparian forest plants,and the water use processes of Populus euphratica and Tamarix ramosissima growing under drought stress were analyzed.The results indicated that water use pattern and survival strategy of desert riparian forest plants are various under different groundwater depths and drought stress conditions in the lower reaches of the Tarim and Heihe rivers.In plant water acquiring,P.euphratica and T.ramosissima use mainly deep subsoil water and groundwater,but their water absorption is more diversified in the lower reaches of the Tarim River than in the lower reaches of the Heihe River; In water distribution,P.euphratica growing in the lower reaches of the Tarim River generally has strong hydraulic lift capacity and significant ecological effect on water redistribution.The essential reason for difference in plant water use strategy is groundwater depth,if groundwater level is deep(within 7 m),P.euphratica suffers from serious drought stress,and the hydraulic lift capacity of P.euphratica roots is also strong.The ecology in the lower reaches of the Heihe River has been balanced at the maintenance and development stages,while the desert riparian forest plants in the lower reaches of the Tarim River are still in severe drought stress.

Key words: desert riparian forest, Populus euphratica, Tamarix ramosissima, water use, lower reaches inland river