Salt marsh restoration with sediment-slurry amendments following a drought-induced large-scale disturbance

Published source details Schrift A.M., Mendelssohn I.A. & Materne M.D. (2008) Salt marsh restoration with sediment-slurry amendments following a drought-induced large-scale disturbance. Wetlands, 28, 1071-1085.
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This study is summarised as evidence for the following.

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Add sediment: brackish/salt marshes

A replicated, site comparison study in 2007 of eight tidal salt marshes in Louisiana, USA (Schrift et al. 2008) found that marshes amended with sediment to counteract subsidence typically had greater vegetation cover and species richness than degraded marshes, and similar cover and richness to natural marshes, after two years. Vegetation cover in amended marshes was greater than in degraded marshes and similar to natural marshes in three of five cases (for which amended: 85–100%; degraded: 8%; natural: 93%). Similarly, total plant species richness was greater than in degraded marshes and similar to natural marshes in three of five cases (for which amended: 1.3–2.4; degraded: 0.1; natural: 1.4 species/unit; units not clearly reported). Additionally, the relative abundance of smooth cordgrass Spartina alterniflora in amended marshes was greater than in degraded marshes in four of five cases, but similar to natural marshes in only two cases (data reported as importance values). In the other cases, cover (12–30%), richness (0.4–0.8 species/unit) and cordgrass relative abundance in amended marshes remained similar to degraded marshes and typically lower than in natural marshes. These comparisons generally involved amendments with large amounts of sediment on initially bare areas. Methods: In 2002, sediment slurry was pumped onto four degraded salt marshes (subsided after most plants were killed by drought in 2000). The marsh surface was raised 13–36 cm above natural marshes. Between autumn 2003 and 2004, vegetation was surveyed along transects in the four restored marshes, two adjacent degraded (subsided) marshes and two adjacent natural marshes. This study was based on the same experimental set-up as (5).

(Summarised by: Nigel Taylor)