Study

Floristic development patterns in a restored Elk River estuarine marsh, Grays Harbor, Washington

  • Published source details Thom R.M., Zeigler R. & Borde A.B. (2002) Floristic development patterns in a restored Elk River estuarine marsh, Grays Harbor, Washington. Restoration Ecology, 10, 487-496

Actions

This study is summarised as evidence for the following.

Action Category

Facilitate tidal exchange to restore/create brackish/salt marshes from other land uses

Action Link
Marsh and Swamp Conservation
  1. Facilitate tidal exchange to restore/create brackish/salt marshes from other land uses

    A site comparison study in 1987–1998 of two estuarine marshes in Washington, USA (Thom et al. 2002) reported that after breaching a dyke to restore tidal influx to one marsh, its plant community became more similar to an adjacent natural marsh. Statistical significance was not assessed. The restored marsh progressed through four key phases. Before breaching, it was dominated by freshwater wetland plant species (not quantified). In the first two years after breaching, the most abundant plant species was reed canary grass Phalaris arundinacea (in 43–57% of quadrats). After 4–5 years, the dominant species was pickleweed Salicornia virginica (52–53% cover). After 8–11 years, the dominant species were saltgrass Distichlis spicata (36–48% cover), arrowgrass Triglochin maritima (12–23% cover) and pickleweed (7–16% cover). Meanwhile, an adjacent natural marsh was dominated by saltgrass (24–47% cover), tufted hairgrass Dechampsia cespitosa (18–42% cover) and pickleweed (6–14% cover). Overall, the plant community composition in the restored marsh became more similar to the natural marsh over time (32–42% similarity after 4 years; 58–68% after 8 years; 48–80% after 11 years). After 4–11 years, total plant species richness was similar in both marshes (restored: 8–12 species/36 m2; natural: 9–14 species/30 m2; 14 species recorded in each marsh over all surveys). Methods: In early 1987, tidal exchange was restored to 23 ha of coastal land by breaching a dyke that had been built in the early 1900s. This area had subsided whilst dyked, and had a higher salinity than adjacent estuarine water after restoration. Vegetation was surveyed most summers in 1987–1998: initially species presence in seven 1-m2 quadrats in the restored marsh, but from 1991 presence and cover in 30–37 quadrats in the restored marsh and an adjacent natural marsh.

    (Summarised by: Nigel Taylor)

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