Establishment of Sarcocornia quinqueflora and Sporobolus virginicus in a created saltmarsh: species-specific responses to topsoil addition and assisted planting

Saltmarsh restoration projects often require the creation of saltmarsh habitat on previously non-tidal areas through excavation of overburden to provide a substrate at an appropriate level within the tidal plane. Such sites may then be covered with topsoil and/or planted with target saltmarsh plant species. However, few such projects in saltmarsh establishment are designed in a way and/or monitored in a manner that would allow for the collection of data that may assess efficacy to guide future restoration projects. A small saltmarsh restoration project in Lake Macquarie, New South Wales, incorporated an experimental design that sought to address the questions as to whether topsoil addition and planting are necessary for the effective establishment of saltmarsh vegetation. Two years post saltmarsh establishment, topsoil addition facilitated the growth (in terms of percentage cover) and recruitment of Sarcocornia quinqueflora, though topsoil provided no appreciable benefit for Sporobolus virginicus. It was further shown that while planting assisted growth for Sarcocornia quinqueflora, it was a necessity for the establishment of Sporobolus virginicus within such time frames. Importantly, this study demonstrated the value of incorporating into a wetland restoration projection an experimental design that tests specific hypotheses.