Water sources of Salix matsudana and its response to the water level of the Yellow River in the riparian of Ulan Buh desert

To explore the water sources of riparian forests and their response to the water level of the Yellow River in the Ulan Buh desert section of the Yellow River basin, reveal the water use strategies of Salix matsudana, understand their adaptability under drought conditions, and to provide a theoretical basis for ecological protection and restoration in the desert area of the Yellow River basin.

Salix matsudana was selected from the river bank of the Ulan Buh desert of Yellow River “Jizi bend”. In the growing season of 2022-2023, plant stems were collected, as well as forest soil, groundwater, Yellow River water and other potential water sources of plants. Water was extracted from plant and soil samples by a freeze-vacuum water extraction device, and the stable hydrogen and oxygen isotopes of each water sample were determined and analyzed. The contribution ratio of different potential water sources to plants was calculated using MixSIAR model.

The water source of Salix matsudana had obvious seasonal changes. In May 2022, Salix matsudana mainly absorbed deep soil water, accounting for 84.1%. In June, July, August and September, the absorption proportion of deep soil water decreased (44.6%, 36.9%, 26.0%, 54.1%). Concurrently, the proportion of water absorbed from the middle soil increased by 24.3%, 13.7%, 8.6% and 7.2%, respectively. Additionally, the proportion of groundwater absorption increased by 6.9%, 21.5%, 38.3% and 19.1% respectively during these months. From May to September 2023, Salix matsudana mainly absorbed deep soil water and groundwater. The proportion of deep soil water absorption was 65.6%, 38.9%, 63.3%, 52.3% and 30.2%, and the proportion of groundwater absorption was 14.3%, 31.6%, 18.6%, 29.1% and 48.2%, respectively. There was no significant difference between 2022 and 2023 in the contribution ratio of different potential water sources (P>0.05). The proportion of groundwater absorbed by Salix matsudana increased with the water level of the Yellow River, and the proportion of Yellow River water to the water source of Salix matsudana decreased.

The main water source of Salix matsudana is relatively reliable deep soil water and groundwater. The water level of the Yellow River will affect the water source of Salix matsudana to a certain extent, especially the absorption ratio of groundwater and Yellow River water, which reflects the adaptability of Salix matsudana to drought.