The ecological stoichiometry shifts induced by Ligularia virgaurea invasion in alpine meadows of the Qinghai-Tibetan plateau.

The invasion of alpine meadows on the Qinghai-Tibetan Plateau by Ligularia virgaurea raises serious concerns about its impact on ecosystem functions. This study investigated how its spread influences ecological stoichiometry and nutrient transitions in native plant communities. We investigated four invasion density levels in a typical alpine meadow: no invasion (LN), low (LL), moderate (LM), and high (LH) density. A replicated sampling design was used to assess the C: N:P stoichiometry of different plant functional groups and its correlation with soil nutrients. Our results demonstrate that increasing L. virgaurea density led to a significant decline in plant community nitrogen content and a rise in C: N ratios, mirroring the response of grasses. Phosphorus content in community plants and key groups (legumes, forbs, and L. virgaurea itself) initially increased then slightly decreased, peaking at moderate invasion density. Under high-density invasion, plant organic carbon content decreased significantly. Concurrently, soil inorganic nitrogen declined, while soil available phosphorus, organic carbon, and microbial biomass (C, N, P) increased markedly. These findings suggest that L. virgaurea successfully invades by outcompeting natives for nitrogen and enhancing phosphorus availability via stimulation of the soil microbial pool. Furthermore, different functional groups exhibited distinct stoichiometric strategies; sedges maintained competitiveness through efficient nutrient retention, while grass faced intensified nitrogen limitation. Overall, L. virgaurea invasion induces a fundamental shift in the nutrient cycling of alpine meadows, driven by plant-soil-microbe feedback that reinforces its dominance.