Successional development of saltmarsh in two managed realignment areas in se england, and prospects for saltmarsh restoration

Abstract

The primary successions of saltmarsh vegetation in 2 managed realignment sites in the Blackwater estuary (SE England), Tollesbury and Abbotts Hall, began with domination by the opportunistic annual species Salicornia europaea and Suaeda maritima. These species were gradually replaced by perennial species at the higher elevations, and a vertical zonation of dominant species was established in the order Salicornia europaea/Spartina anglica, Puccinellia maritima, Atriplex portulacoides and Elytrigia atherica, from low to high saltmarsh. Suaeda maritima became rarer and patchily distributed. Ordination analysis confirmed that after 12 yr the new saltmarsh at Tollesbury was similar to the adjacent ancient saltmarsh. At Abbotts Hall the broadly similar successional sequence took only 5 yr. These were not facilitated successions-plants increasing the elevation of the sediment-because little sediment had accreted. Instead these were characteristic of tolerancetype successions, with the early opportunistic species having no apparent facilitative or inhibitive effect on the perennial species that arrived later and outcompeted them. If land at the appropriate elevation is provided by coastal realignment, saltmarsh develops to resemble the vegetation structure of ancient saltmarshes rapidly, with positive prospects for saltmarsh restoration. However, the erosion of saltmarsh vegetation that developed in historical realignment sites indicates that this benefit may be relatively short-term. Hence, long-term saltmarsh creation must also account for the processes causing saltmarsh erosion.