Water use patterns of riparian Populus euphratica in the Hongyashan Reservoir of Northwest China’s arid region: evidence from water isotope data

Background and aims

In arid areas, the temporal and spatial distribution of water resources is a key factor determining plant growth, and plants’ self-regulated flexible water use patterns are beneficial for the survival of vegetation. This study investigates the impact of reservoirs on ecological forest water use patterns around a plain reservoir.

Methods

We established a systematic monitoring network to study the Populus euphratica forests along the Hongyashan Reservoir in northwest China. Through stable isotope analysis of samples of soil, tree xylem tissue, precipitation, groundwater, and reservoir water, we examined the water use patterns of poplar trees across a distance gradient from the reservoir.

Results

Our findings revealed that: (1) Poplar primarily utilized 0–60 cm soil water and groundwater in areas proximal to the reservoir, and 60–100 cm soil water and groundwater in areas distal from the reservoir. The reservoir’s influence was primarily reflected in the groundwater contribution rate, which decreases with increasing reservoir distance. (2) Water utilization patterns and consumption exhibited significant variations within 2 km of the reservoir, while remaining relatively consistent beyond this distance, indicating that the reservoir’s impact on vegetation growth is predominantly confined to a 2 km radius.

Conclusion

Based on these findings, we recommend that irrigation strategies should be tailored according to the distance from the reservoir. Furthermore, considering the substantial water demand of poplars, careful consideration should be given to the appropriate scale and tree species selection in ecological forest planning.