How does water conveyance during non-growing seasons affect the water use strategy of lakeshore plants in arid northwestern China？

Within arid and semi-arid ecosystems, water availability is crucial in determining the growth and distribution of plants due to intense evaporation and limited precipitation. Ecological water conveyance has now become an important measure to mitigate the ecological degradation of plants in arid and semi-arid regions. However, different from water conveyance during growing seasons, there has been little research directly exploring the response of water use strategies of plants to ecological water conveyance during the non-growing season. In this context, whether and how non-growing season water conveyance can be used by lakeshore plants in the following growing seasons are interesting issues. Previous studies in regional scale and simple site scale have shown that plant growth can be influenced by ecological water conveyance during non-growing seasons in regional scale and simple site scale. However, the mechanisms of storage and transformation of water conveyed during the non-growing season and the extent and scope of the impact of non-growing season water conveyance are still unclear. To deepen the understanding of plants' adaptation to water conveyance during non-growing seasons, a comprehensive approach of water availability exploration and stable isotope (D, ¹⁸O) tracer model (MixSIAR) was used to analyze the water use strategies of typical plants (Phragmites australis, Nitraria tangutorum, Haloxylon ammodendron, and Peganum harmala L.), and the Qingtu Lake was taken as the study area, which is the terminal lake of the Shiyang River, China. Results indicate that water extraction depths of plants tend to deepen with the increase of the distance from the lake, and for the central areas, Phragmites australis mainly use almost saturated soil water or lake water nearby; for the transitional areas, the depth of water extraction by Phragmites australis, Nitraria tangutorum, and Peganum harmala L. was significantly changed from different depths of soil water during the growing season; for the almost no influence areas, the depths of water extraction by Phragmites australis, Nitraria tangutorum, and Haloxylon ammodendron were more evenly distributed over the whole soil profile, with no significant change during different seasons. Combining the monitoring data of water table depth, soil temperature, volumetric soil water content, and the survey data of soil texture, we realized that: water conveyance during the non-growing season in late summer and early autumn rapidly forms recharge for groundwater and soil water, while the soil texture characteristics of sandy and clay distributed in mutual layers and the seasonal freeze-thaw phenomenon from late November to early April create conditions for the storage of this water, thus providing support for water needs of the plant sprouting in spring and plant growth in summer. Our results provide insight into the storage and transformation mechanisms of non-growing season water conveyance for plant uptake and utilization in arid regions and have practical implications for the scientific management of ecological water conveyance in arid regions.