Sediment input into a floating freshwater marsh: effects on soil properties, buoyancy, and plant biomass

Published source details Carpenter K., Sasser C.E., Visser J.M. & DeLaune R.D. (2007) Sediment input into a floating freshwater marsh: effects on soil properties, buoyancy, and plant biomass. Wetlands, 27, 1016-1024.
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This study is summarised as evidence for the following.

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	Add sediment: freshwater marshes Action Link

Add sediment: freshwater marshes

A replicated, randomized, paired, controlled study in 2004 in two floating freshwater marshes in Louisiana, USA (Carpenter et al. 2007) found that adding sediment reduced plant species richness, but had no significant effect on vegetation biomass. After one growing season, plots amended with sediment had lower plant species richness than unamended plots in five of six cases (for which amended: 8–12 species/0.4 m²; unamended: 12–13 species/0.4 m²; statistical significance not assessed). Sediment addition had no significant effect on total, live, above-ground vegetation biomass (amended: 270–660 g/m²; unamended: 320–530 g/m²). Sediment addition typically had no significant effect on the overall biomass of dominant plant species, such as slender spikerush Eleocharis baldwinii and dotted smartweed Polygonum punctatum (see original paper for data). However, in one of two marshes, biomass of frogfruit Phyla lanceolata was greater in amended plots (4–12 g/m²) than unamended plots (<0.1 g/m²). Methods: In spring 2004, thirty-two 1-m² plots were established across two floating marshes. Sediment inputs to the marshes had been reduced by an upstream dam. In each marsh, twelve random plots were amended with sediment collected from a nearby river channel (2 kg/m², 7 kg/m² or 17 kg/m2). The remaining plots received no sediment. All plots were also fenced to exclude nutria Myocastor coypus. In autumn 2004, vegetation was cut from 0.1 m² of each plot then separated by species, dried and weighed.

(Summarised by: Nigel Taylor)