Understanding the soil and plant water hydrological cycle in a typical wetland under harsh natural conditions in the Shigatse area of the Tibetan Plateau

In cold alpine regions, ecohydrological feedback to climatic anomalies can provide valuable insights into ecosystem functions in the context of alarming climate change projections. However, the role of vegetation in the hydrological cycle of alpine wetlands remains unclear. We used water stable isotopes (delta O-18 and delta D) supplemented with delta C-13 to investigate wetland soil isotope distributions and plant water uptake patterns. The isotope values of the soil profiles were affected by seasonal factors. During cold and dry periods, the isotopes within the soil profile showed a strong evaporation effect, and during warm and humid periods, the isotopes indicated the mixing of multiple water sources. The isotopes show larger variations in the interior of the wetland than in the periphery. The carbon dioxide and methane released by the wetland may cause a negative shift in the delta O-18 and delta D isotopes of soil water. Rose willow and Sophora moorcroftiana can obtain water from both the surface and deep layers to cope with different water stresses. The dominant water is mainly obtained from the surface layer during cold and dry periods, whereas water from deeper layers can also be abstracted during warm and wet periods for rose willow growth. These findings will provide a better understanding of soil and plant water hydrological cycles under harsh natural conditions in cold alpine regions and could offer guidance to local governments for the conservation of this extreme wetland ecosystem.