Salt marsh wetlands in the Yellow River Delta are highly sensitive to changes in riverine water and sediment supply, which are increasingly influenced by large-scale river regulation and coastal environmental change. Understanding how marsh ecosystems respond to sediment decline is therefore critical for sustainable coastal management and wetland restoration. This study integrates long-term satellite-derived vegetation data (1999–2020) with sediment discharge records from the Lijin hydrological station to examine how declining sediment supply influences salt marsh vegetation and landscape organization in the Yellow River Delta. By combining landscape metrics, generalized additive models (GAM), change-point detection, and spatial hotspot analysis, we quantified nonlinear vegetation-sediment relationships and identified potential ecological thresholds in marsh landscape dynamics. The results show that salt marsh vegetation underwent substantial reorganization during the study period. Native Suaeda salsa declined markedly, Phragmites australis increased overall, and invasive Spartina alterniflora expanded rapidly after 2008. Several landscape metrics exhibited significant nonlinear responses to sediment discharge, typically displaying U-shaped or inverted-U patterns. A coherent transition in landscape structure occurred around 2014–2016, corresponding to a critical sediment threshold of approximately 1.2–1.6 × 10 8 t. Spatial hotspot analysis further indicates that vegetation changes were concentrated within the active delta lobe and in areas outside the nature reserve, highlighting the importance of geomorphic conditions and management regimes in shaping marsh landscape dynamics. These findings provide new insights into how sediment reduction associated with river regulation influences the stability and spatial organization of deltaic marsh ecosystems. The identification of sediment thresholds and spatially heterogeneous vegetation responses offers valuable guidance for adaptive water–sediment regulation, invasive species control, and coastal wetland management in sediment-limited delta systems. • Long-term satellite data reveal landscape reorganization in Yellow River Delta marshes. • Salt marsh landscapes show nonlinear responses to declining sediment supply. • A critical sediment threshold (∼1.2–1.6 × 10 8 t) indicates potential regime shift. • Spartina alterniflora expansion reshapes coastal wetland landscape patterns. • Findings support adaptive water–sediment regulation and wetland management.
Xiaolong et al. (Thu,) studied this question.