Littoraria irrorata growth and survival in a sediment-restored salt marsh

Published source details Stagg C.L. & Mendelssohn I.A. (2012) Littoraria irrorata growth and survival in a sediment-restored salt marsh. Wetlands, 32, 643-652.
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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 in eight tidal salt marshes in Louisiana, USA (Stagg & Mendelssohn 2012) found that marshes amended with sediment to counteract subsidence typically had greater smooth cordgrass Spartina alterniflora cover than degraded marshes, and sometimes had similar cover to natural marshes. After five years, total smooth cordgrass cover was greater in amended than degraded marshes in three of four comparisons (for which amended: 16–42%; degraded: 2%). Natural marshes had 49% smooth cordgrass cover. This was not significantly different from amended marshes in two of four comparisons (where small amounts of sediment had been added or cordgrass rhizomes persisted before amendment; cover: 29–42%) but was lower in amended marshes in the other two comparisons (where higher amounts of sediment had been added to bare marsh; cover: 16–19%). Live cordgrass cover was 8–12% in amended marshes (24–59% of total), 2% in degraded marshes (100% of total), and 15% in natural marshes (30% of total; statistical significance of differences not assessed). Methods: In 2002, sediment slurry was pumped onto four degraded salt marshes. These had subsided after plants were killed by drought in 2000, but retained some patches of cordgrass rhizomes (underground horizontal stems). The marshes were raised to 3–15 cm above mean sea level. In summer 2007, vegetation was surveyed in 0.25-m² quadrats 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 (4).

(Summarised by: Nigel Taylor)