Stage-dependent shifts in native and invasive traits mediate community invasibility in subtropical urban ecosystems.

Biological invasions threaten biodiversity and ecosystem stability through stage-dependent functional trait mediation. However, the mechanistic linkages between invasion intensity and multidimensional functional traits remain inadequately characterized. To address this gap, we analyzed eight multidimensional functional traits across 290 subtropical herbaceous plots in Jinhua, China. By integrating invasion level, we evaluated how native and invasive species traits differentially regulate community invasibility, a metric quantifying a community's susceptibility to biological invasion. Functional and taxonomic diversity exhibited hump-shaped patterns, peaking at moderate invasion before declining sharply under heavy invasion, while community invasibility increased markedly with invasion level. Native communities resisted invasion through persistent suppression of canopy height and stage-adaptive strategies: Leaf thickness emerged as a critical resistance trait under heavy invasion, counteracting invasive dominance. In contrast, invasive species initially prioritized rapid canopy occupation via height-mediated advantages, subsequently shifting toward stress tolerance (e.g., thickened leaves) and resource reallocation (e.g., root-shoot ratio adjustments) to consolidate dominance. Native abundance universally suppressed invasibility across all invasion stages, whereas invasive abundance amplified success only at advanced stages. Resistance was governed by stage-dependent trait trade-offs: Native leaf dry weight enhanced invasibility under light invasion but became ineffective as competition intensified. Conversely, invasive aboveground biomass and root-shoot ratio consistently promoted invasibility, reflecting prioritization of rapid resource acquisition. Our findings demonstrate that invasion outcomes depend on the spatiotemporal coordination of multidimensional functional traits. We propose an adaptive management framework for urban ecosystems emphasizing structural preservation (e.g., maintaining native canopy height) combined with stage-specific trait optimization of resistance traits to mitigate invasibility.