Functional trait responses and niche dynamics of native and alien herbaceous plants across urbanization gradients in wastelands

Accelerating urbanization expands urban wastelands, which are increasingly recognized as conservation priorities for sustaining herbaceous plant diversity in cities. Despite the common coexistence of native and alien species in these habitats, it remains unclear how urbanization gradients mediate their functional differences and niche dynamics—a knowledge gap essential to fill for effective urban biodiversity management and alien species mitigation.

We quantified functional trait variation in alien and native herbaceous plants along a gradient of urbanization quantified as degree of impervious surface (500 m × 500 m) within Guiyang's wastelands, measuring functional differences and niche overlap between species groups and identifying their drivers.

Alien plant mean height increased with greater levels of impervious surfaces, while leaf length decreased in both alien and native species. Higher levels of impervious surfaces drove stronger habitat filtering rather than niche differentiation, increasing niche overlap between alien and native plants.

Elevated soil carbon was associated with higher specific leaf area in both groups and reduced leaf dry matter content in alien species, yet it resulted in decreased alien‐native niche overlap. In contrast, increased soil nitrogen levels correlated with greater leaf thickness in both alien and native plants.

Synthesis and applications . This study demonstrates that urbanization intensifies functional niche overlap between alien and native plant species in wastelands, thereby promoting biotic homogenization. Alien plants exhibit greater phenotypic plasticity in response to environmental changes, enabling them to take advantage of urban conditions. To steer plant communities towards the resilience‐oriented goal of functional differentiation while mitigating the competitive advantage of alien plants, habitat management practices such as enhancing soil carbon (e.g. applying organic amendments or retaining plant litter) are recommended for wastelands with high imperviousness.