Hydraulic redistribution of soil water in Populus euphratica Oliv. in a central Asian desert riparian forest

Hydraulic redistribution has been widely confirmed to occur in the arid and semi‐arid ecosystems. However, no research has documented the existence of such a water use/sharing mechanism in the desert riparian forests of the lower reaches of the Tarim River. The current study continuously monitored the sap velocity of roots, micro‐meteorological factors and volumetric soil water content at different soil depths and different distances from the trunk to verify whether Populus euphratica Oliv., the dominant species of the riparian forest, has a hydraulic redistribution mechanism and to document its influence factors and ecological effects. We also sampled the stable isotope δ18O in both soil and plant samples. On the basis of this data, the magnitude of hydraulic redistribution, its driving factors and ecological effects were estimated statistically. The results demonstrate that P. euphratica possesses clear hydraulic lift properties, and the effect of hydraulic lift was distinct at depths of 60–120 cm in the soil within a distance of 4 m from the trunk. This soil moisture spatial variation was attributed to the spatial distribution of the root system. Furthermore, hydraulic lift can improve soil moisture, providing approximately 10–20% of daily water used in the upper soil layers (0–120 cm). By increasing the availability of water in the upper soil water, hydraulic lift can facilitate the existence of some herb species in the Populus community. For the first time, we have estimated the extent of hydraulic redistribution in these ecosystems, and the data indicate that hydraulic lift is an important process in the desert riparian forests in the extremely arid regions of Central Asia.