荒漠河岸林建群植物的水分利用过程分析

Water Use Process of Constructive Plants in Desert Riparian Forest

荒漠河岸林植物是干旱区生态系统的重要组成部分,研究干旱区荒漠河岸林建群植物水分利用过程,对制定生态保育恢复对策具有重要意义。通过对西北干旱区塔里木河和黑河下游荒漠河岸林植物水分来源、根系水力提升过程的观察和对比分析,解析了不同胁迫环境下胡杨、柽柳等荒漠河岸林主要建群种的水分利用过程。研究结果显示：在塔里木河和黑河下游不同地下水埋深和干旱胁迫环境下,荒漠河岸林植物的水分利用方式和生存策略有较大差别。在水分来源上,胡杨和柽柳主要利用深层土壤水和地下水,但塔里木河下游的植物根系对水资源的利用较黑河下游更加多元化;在水分分配方面,塔里木河下游的胡杨表现出更强的水力提升能力和更显著的水分再分配效应,地下水埋深是造成植物水分利用策略差异的主要原因,地下水位越深（7 m以内）,胡杨受干旱胁迫越大,胡杨根系的水力提升能力亦越强。目前黑河下游的生态已处于平衡维持和发展阶段,而塔里木河下游广大地区的荒漠河岸林植物仍处于严重的干旱胁迫中。

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（ within7 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.