Deyeuxia angustifolia encroachment alters functional trait patterns of Rhododendron chrysanthum in an alpine tundra

Background and aims Understanding plant encroachment’s impact on functional trait patterns of the plants in alpine tundra is essential for predicting alpine tundra vegetation dynamics under climate change, yet remains underexplored. Methods Along an encroachment gradient of Deyeuxia angustifolia into a Rhododendron chrysanthum -dominated tundra on Changbai Mountain, we measured 47 functional traits of R. chrysanthum to explore changes in trait means, intraspecific variation, and trait integration, and their links to soil properties. Results D. angustifolia encroachment decreased the biomass (~20.76%) and seed mass (~46.89%) of R. chrysanthum , while promoting acquisitive strategies characterized by thinner, larger, nutrient-rich leaves and lower root non-structural carbohydrates contents. Leaf water-use and NSC traits showed greater variability, whereas nutrient traits became more stable. Trait integration intensified, shifting from root- and shoot-centered to leaf-dominated networks, with light-related traits emerging as hubs (edge density increased by 60~100%). Conclusions Overall, trait strategies appeared to shift from high mean values to enhanced plasticity and integration, likely driven by changes in soil temperature, C:N ratio, and nutrient availability. These findings reveal adaptive responses of alpine shrubs to encroachment and offer insights into tundra vegetation dynamics under global change.