Abstract: Water source of Populus euphratica root suckers was investigated through stable isotope analysis, combined with plant water potential and root cutting experiment. Predawn xylem water potential (ψ_pd) 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 recession, 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.

Key words: Populus euphratica, root suckers, δ¹⁸O, water source