中文摘要：

利用稳定同位素技术结合水势观测及断根试验，研究胡杨（Populus euphratica）根蘖苗的水分来源。结果表明：淹没前胡杨根蘖苗清晨水势显著低于母株，水分主要源于60cm以下土壤水；退水后浅层土壤水的δ18O值贫化，根蘖苗木质部水的δ18O值相应贫化，清晨水势显著高于母株，水分主要源于浅层土壤水（0～60cm）。样方调查表明：胡杨根蘖苗萌发于母株浅于30cm根系上，根蘖苗发生部位不产生不定根，切断母株近端根（萌发点至母株端）和远端根（萌发点至根末端）后枯死，说明维持根蘖苗生长的水分主要源于母株。综合分析表明：胡杨根蘖苗的水分主要源于母株浅层根系远端根，对土壤水的利用取决于浅层根系对水分的吸收。

英文摘要：

Water source of Populus euphratica root suckers was investigated through stable isotope analysis, com- bined with plant water potential and root cutting experiment. Predawn xylem water potential （ψpd） of root suckers was significantly lower than that of parents, and the water used by root suckers was mainly from soils water 60 cm below the ground under the condition of that there was soil water in shallow layers prior to inundation. After the re- cession,δ18O of the upper layer soil water was depleted, associated with the δ18O of xylem water of root suckers. At the same time, water used by root suckers was mainly from soil water in shallow layers （0 -60 cm）, and the root suckers presented a significant higher ψpd than their parents. Excavation indicated that root suckers developed from parental root within 30 cm depth, without tap root. Further experiments showed that root suckers died from cutting their proximal （between sucker and parents） and distal （from root sucker to end） roots of the spacers, which suggested that the water maintaining root sucker growth was primarily from the parents. Our results suggested that P. euphratica root suckers obtained water primarily from parents＇ distal roots of which the water absorption by shallow roots＂ determines the soil water using patterns for root suckers.