Rapid Spartina alterniflora removal reshapes bird communities via soil and macrobenthic pathways

The invasion of Spartina alterniflora has caused widespread ecological disruption along coastal wetlands. In response, China launched a large-scale, physical S. alterniflora removal project. Here, we conducted a comprehensive assessment comparing conditions before (absence of removal areas, ARA) and after (removal areas, RA) physical removal. We found that physical removal was associated with significant changes in soil physicochemical properties, including higher pH, total soluble salts, organic carbon, and available phosphorus, and lower total nitrogen and potassium in RA compared with ARA ( p < 0.001). Macrobenthic abundance and richness were significantly lower after removal ( p < 0.001). Bird richness was lower in RA, whereas bird individual numbers were higher. Bayesian phylogenetic structural equation models indicated that soil physicochemical variation was significantly associated with macrobenthic communities (95% CI [−0.36, −0.12]), and that macrobenthic abundance was positively associated with bird individual numbers in RA (95% CI [0.09, 0.29]), while no significant macrobenthos–bird relationship was detected before removal. Direct associations between soil properties and bird metrics were weak or non-significant. Overall, large-scale physical S. alterniflora removal was associated with a transitional ecosystem state characterized by rapid abiotic reorganization, reduced macrobenthic abundance and richness, and restructured cross-trophic relationships. From a management perspective, these results indicate that short-term increases in bird abundance alone may not reliably reflect restoration outcomes. Post-removal evaluation should therefore incorporate both soil physicochemical stabilization and macrobenthic recovery trajectories, and allowing sufficient recovery intervals following physical removal or facilitating macrobenthic recolonization may improve the re-establishment of functional trophic linkages in coastal wetland ecosystems.