Urban land-use filtering favors herbaceous spontaneous flora and reshapes alien-native composition in a semi-humid inland city.

Urban spontaneous plants record how vegetation responds to land use, disturbance, management, and propagule pressure, but their composition and assembly remain insufficiently studied in semi-humid inland cities. We surveyed 151 urban functional units (UFUs) in Jinan, China, combining field vegetation inventories, high-resolution land-cover interpretation, socioeconomic and management variables, and count-data robustness models to test how urban habitat filters structure spontaneous plant richness and composition. Across all UFUs, 379 vascular plant species were recorded, including 140 spontaneous species. The spontaneous flora was almost entirely herbaceous (138 species, 98.6%), with only two woody species occurring as seedlings and no mature spontaneous trees recorded. Alien species accounted for 74 spontaneous species (52.9%), slightly exceeding native species. Spontaneous richness differed among UFUs, with residential districts supporting the highest mean richness and transportation areas supporting the lowest. Exploratory linear regression identified positive associations of richness with residential land use, fertilization frequency, housing price, and UFU area. After accounting for overdispersed count data, however, negative binomial models retained residential land use and total UFU area as the most stable positive predictors, whereas fertilization and housing price were not significant. These results indicate that spontaneous plant diversity in Jinan is primarily organized by land-use filtering and habitat capacity, while socioeconomic and management gradients provide weaker and model-dependent signals. The study highlights the value of UFU-based analysis for linking urban plant community assembly with practical land-management units in rapidly urbanizing inland cities.