Spatial patterns of salt marsh biomass and their geomorphic controls: evidence from central China’s tidal wetlands

Salt marsh vegetation plays a critical role in regulating hydrodynamics, sediment transport, and eco-geomorphic evolution in coastal wetlands. While biomass–elevation relationships have been widely investigated in temporal frameworks, the spatial organization of biomass across marsh platforms and its local geomorphic controls remain insufficiently understood.

In this study, we investigate the spatial distribution patterns of aboveground biomass of Spartina alterniflora across two salt marshes along the central Jiangsu coast, China. By combining multi-year satellite remote sensing data processed on Google Earth Engine with field-based vegetation sampling and surface elevation measurements, we quantify biomass variability along multiple cross-shore transects spanning marsh front edges, tidal creek networks, and interior zones.

Our results reveal that aboveground biomass consistently follows a parabolic spatial pattern along transects, with maximum biomass occurring at intermediate distances between the marsh front and interior. However, this general pattern is locally modified by tidal creeks, microtopography, and anthropogenic disturbances, leading to site-specific linear or segmented biomass–distance and biomass–elevation relationships. Transects intersecting tidal creek networks exhibit pronounced spatial heterogeneity, highlighting the organizing role of creek-induced elevation gradients and drainage conditions.

Temporal analysis further demonstrates that optimal biomass locations migrate synchronously with marsh front dynamics, indicating a strong coupling between vegetation growth and geomorphic evolution at decadal scales. These findings emphasize that spatial biomass patterns cannot be directly inferred from temporal biomass–elevation relationships alone.

Overall, this contribution highlights the importance of spatial heterogeneity and tidal creek systems in controlling salt marsh biomass distribution and provides empirical constraints for eco-geomorphic models that incorporate vegetation–topography feedbacks. The results are relevant for improving process-based simulations of salt marsh evolution under environmental change.