Results

What worked and what didn’t

Plantings in spring 2005, organized by ACE, involved three species: Spartina alterniflora, Spartina patens, and Juncus roemerianus. Both Spartina species were nursery raised, and came as 2” plugs. Survival of both was high (>80%) with rapid establishment and coalescence in most areas. Juncus was provided as “bare-root” stems (see picture), harvested from wild marsh areas. None of these survived even 1 month after planting. It is recommended that only nursery-raised plants be used in future. They are young plants, so much more capable of responding to new growing conditions than older individuals harvest from the marsh. Nursery-raised plants do not result in the loss of wild marsh habitat, an important consideration in the overall benefit of a restoration project.

Wild harvested Juncus stems did not survive. Not enough roots were left on the stems

The construction of the sand-berm surrounding the site, involved the use of non-degradable plastic-sheets and ground-cloth materials. These were quickly exposed after 3-6 months and persisted as unsightly debris for more than 2 years. Rapid erosion and movement of the sand is demonstrated by the images of a drainage pipe installed in the berm. It is recommended that biodegradable materials like burlap be used to stabilize soils, to minimize undesirable environmental impacts at the site.

Berm construction materials exposed as plastic sheeting (left) and non-degradable ground cloth (center and right) floating about in the intertidal zone.

Exposed pipe that was designed to drain the interior lagoon. The rapid changes in the sand-berm have left this pipe high and dry after less than 2 years.

Supplemental plantings in 2008 - 2009 also involved the same three species of saltmarsh plants. All were grown in the nursery at the Center for Plant Restoration. Spartina alterniflora and Juncus roemerianus were grown from seed, while Spartina patens was grown primarily by vegetative propagation. In addition two species of dune plants were grown by subcontractors in nurseries. These were Uniola paniculata and Panicum amarum. We found that seeds of Panicum did not germinate readily, but vegetative propagation was very successful. To propagate Panicum all one needs to do is cut the stem a few inches below each node, and insert this segment into a peat pellet kept in water. After a few days to one week, the node will produce new roots and leaves. Growth rate of Panicum was the fastest of all 5 species we grew.

Panicum segments after resprouting (left) and Juncus seedlings (mid and right) in the nursery, being grown for later transplanting to Deer Island.

Problems encountered in the transplanting of these included not all plants being put in the ground by the contractor, and planting in inappropriate locations (elevation wrong, or too far from water). Plants grown by subcontractors were grown in pine-bark mulch soil, which did poorly in the restoration zone for two reasons: (1) the root-ball did not stay together on removal from the pot, making planting more difficult, and (2) the mulch is buoyant so many of the transplants simply floated up out of their hole on the first incoming tide! It is recommended that only sand/soil mixtures be used for growing the plants, as this results in a heavy and firm root-ball, aiding in planting in keeping the plants in place during subsequent tidal inundation.

Some plants were left unplanted (left), inappropriate elevation zone (middle), and pine-mulch (right) all resulted in problems that reduced the overall success of the project.

Overall the success of this restoration after 5 years (2010) is medium. Ongoing erosion problems (the reason for the restoration) continue to plague the site. Plants that had established are being lost as the sand-berm erodes into open water. It is likely that more drastic measures, such as construction of a rip-rap rock berm will be needed to protect the northern shoreline, and ensure marsh plants can continue to grow on the created fill.

Erosion is a continuing problem: image of shoreline before restoration (left) and after recent renourishment (right) of sand-berm that eroded rapidly in 3 years.