Grazing-Induced Conservative Shift in Water-Use Strategies of Desert Plants: Trait Syndromes from Hydraulic...

Grazing is a pervasive disturbance in arid ecosystems, but its effects on community-level coordination of plant hydraulic and economic traits remain poorly understood. Here, we investigated how long-term grazing alters community-weighted mean hydraulic and leaf economic traits in a desert steppe of Inner Mongolia, and how these shifts affect aboveground biomass (AGB) and water-use efficiency (WUE). Grazing drove a coordinated conservative shift in community hydraulic traits, including more negative osmotic potential at turgor loss point (ψ_tlp), increased cell wall rigidity (ε), and reduced leaf hydraulic conductance (K_leaf). Grazing also restructured trait-function relationships: under grazing, AGB was positively correlated with dehydration tolerance rather than transport efficiency, and WUE was tightly coupled with osmotic adjustment. Variance partitioning showed that hydraulic traits explained 57.4% of AGB variation under grazing, whereas economic traits dominated in the control site (74.5%). Our findings demonstrate that long-term grazing imposes a fundamental reorganization of community-level trait coordination, driving a transition from an efficiency-oriented to a safety-oriented strategy, and highlight the central role of hydraulic traits in mediating ecosystem function under combined stress.