Water transport processes and multiple feedbacks within the groundwater-soil-vegetation-atmosphere (climate) continuum in arid ecosystems is a worldwide frontier hotspot in eco-hydrological field particularly under the global warming. Within, how the deep (fine) roots of desert vegetation with high plasticity response to deep soil water status and groundwater depth when facing excepted increasing available water stress is remain unclear. Focusing on this and using multivariate linear mixing method based on natural ²H isotope, we examined species-specific entire roots water uptake behaviors (stretching the whole unsaturated zone) along the groundwater depth gradient within the critic range of 2 m to 4 m, and tested the performance and suitability of natural water isotopes for quantitatively partitioning vegetation water sources.
   The observations showed that the three desert species investigated physically develop contrasting roots water uptake patterns, making a certain compromise of niche, which allow for their coexistence. The grass species Phragmites prefers to tap GW as well as deep soil moisture and tends to take the lead in launching deeper roots water uptake activities in response to poor available water conditions, while the shrub species favor meteorological water and shallow soil water and do in shallower roots. Among, shrub Kalidium’s ecological plasticity and adaption and environmental tradeoff are the most.
   This study has implications for further disentangling the surface eco-hydrological processes and feedbacks in arid regions, and of raised significance under the global change and the double carbon goal.

Deep roots water uptake,Groundwater,Arid desert ecosystem,Ecological plasticity,Natural water isotope