Summary of saltmarsh succession

The typical view of saltmarsh succession is one where plants colonise tidal mud and sand flats. As sediment deposition takes place (aided by the plants) more mature structurally diverse saltmarsh vegetation develops. Eventually as the height of the marsh increases it is covered by fewer and fewer tides until the oldest marshes become terrestrial habitats which may even support woodland. The typical sequence is illustrated for a rapidly growing marsh in the Dee Estuary in the picture below.

Caption: The creek in the picture opposite shows a typical sequence of vegetation change as the height of the marsh increases away from the tidal creek. This site, on the Dee Estuary, is largely ungrazed and has a sward of tall grasses including red fescue Festuca rubra on the higher marsh levels. Saltmarsh grass Puccinellia maritima is dominant at the lowest levels near the creek bottom. Sea couch Elymus athericus a species intolerant of daily submergence by sea water stretches into the middle distance.

Caution: Many text books depict saltmarsh succession as a straightforward progression from open sand or mudflat, as sediment accumulation and vegetation growth raise the marsh surface resulting, to ever more diverse plant communities and transitions to terrestrial vegetation. This apparently simple picture hides some complex relationships as shown by the plant community classification. Salt pans and creeks can introduce yet more changes into the mosaic and deposits of seaweed on the tide-line may smother the surface vegetation, creating further spatial variation as the strandline deposits rot.