Enhanced Lateral Exchange of Carbon and Nitrogen in a Coastal Wetland With InvasiveSpartina alterniflora

Abstract Lateral movements of materials and energy in coastal wetlands, due mainly to tidal activities, have been recognized as key processes in understanding the biogeochemical cycles of ecosystems. However, our understanding of the roles of lateral movement in shaping ecosystem functions remains limited. Here we quantified the effects of lateral sediment transport on total carbon (C, inorganic + organic) and nitrogen (N) pools in plants and soils in two dominant wetland types: invasiveSpartina alterniflora(Spartina) marshes and nativePhragmites australis(Phragmites) marshes in coastal Shanghai of the Yangtze Estuary. We found that the accreted sediments across the water‐marsh gradients caused by lateral movement resulted in contrasting C and N contents between the two communities. The sediment load and C and N pools in the plants and soils of theSpartinamarshes were significantly higher than those in the adjacentPhragmitesmarshes. The shifts in species composition and community structure not only altered the C and N balance but also enhanced the ecosystem net primary productivity. Our findings highlight the importance of lateral transport in altering ecosystem structure afterSpartinainvasion. The ecosystem C and N pools were significantly higher in the invaded ecosystems than in the native community. Our study also reveals that the plant density and structures can alter tidal hydrodynamics and the lateral transportations of sediments, which in turn influence ecosystem C and N cycle. The C accumulation processes of the native and invaded marshes were further complicated by the contrasting productivities of the ecosystems.