a1 Departments of Botany and Soil Science, North Carolina State University, Raleigh, North Carolina 27607, U.S.A.
Spartina alterniflora salt-marsh has been established from seed and transplants on dredged materials and sandy shorelines along the North Carolina coast. Transplants were more successful than seeding over a greater portion of the intertidal range and under more rigorous environmental conditions, but seeding was successful in the upper half of protected sites. Seeding at the rate of 100 viable seeds per square metre from April through May can result in complete vegetational coverage by the end of the first growing-season. At the end of the second growing-season, above-ground biomass accumulation from seeding approached that produced by transplants which had originally been planted on a 0.9-metre centre. Both above-ground and below-ground production of planted marsh compared well with values for these components in natural marshes. There were no differences in production by epiphytes between planted and natural S. alterniflora marsh at two different locations. Faunal production in the upper 13 cm of sediment was significantly less in planted than in natural marsh, and where marsh plants accumulated sediments, faunal numbers and biomass were less in planted than in unplanted areas. Sediment carbon content indicated that 4 to 25 years might be required for a newly-planted marsh to resemble a natural marsh.
Based on our studies, the techniques developed to plant S. alterniflora on dredged material and along sandy shorelines can be employed to initiate new and functional salt-marsh where none existed previously. The length of time required for man-initiated marsh to resemble natural marsh depends upon how closely the new substrate resembles natural marsh in the type of sediment accumulated, in the elevation of the new substrate, in the natural sedimentation rate in the area, and in the relative maturity of the natural marsh system.