Effects of sediment removal on prairie pothole wetland plant communities in North Dakota

Published source details Smith C., DeKeyser E.S., Dixon C., Kobiela B. & Little A. (2016) Effects of sediment removal on prairie pothole wetland plant communities in North Dakota. Natural Areas Journal, 36, 48-58.
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This study is summarised as evidence for the following.

	Action	Category
	Retain/restore/create vegetation around freshwater marshes Action Link
	Remove surface soil/sediment: freshwater marshes Action Link

Retain/restore/create vegetation around freshwater marshes

A replicated, site comparison study in 2010 of 20 prairie pothole wetlands in North Dakota, USA (Smith et al. 2016) found that potholes amongst restored perennial vegetation contained a different marsh and wet meadow plant community to nearby natural marshes, with greater cattail cover and sometimes greater horizontal vegetation cover. The overall plant community composition in both the marsh and wet meadow zones significantly differed between potholes surrounded by restored perennial upland vegetation and nearby natural potholes (data reported as a graphical analysis). Across both zones, the potholes in restored areas had greater cover of hybrid cattail Typha x glauca (19%) than natural potholes (5%). In the marsh zone – but not the wet meadow zone – visual obstruction was greater in potholes in restored areas than in natural potholes (data reported as a visual obstruction index). Methods: In summer 2010, vegetation was surveyed in the marsh (seasonally flooded) and wet meadow (occasionally flooded) zones of 20 prairie potholes (10 quadrats/zone/pothole). Eleven potholes used to be surrounded by cropland, but this had been restored to perennial vegetation cover (details and dates not reported, but probably around 2–7 years previously). However, these potholes likely contained excess sediment that had washed off the cropland. The other nine potholes were surrounded by land that was not, and had never been, cultivated.

(Summarised by: Nigel Taylor)
Remove surface soil/sediment: freshwater marshes

A replicated, site comparison study in 2010 of 39 prairie pothole wetlands in North Dakota, USA (Smith et al. 2016) found that restoration by excavating excess sediment (and sometimes planting wetland herbs) reduced cover of hybrid cattail Typha x glauca, but that other effects on vegetation depended on the vegetation zone. Across both the marsh and wet meadow zones, restored potholes had lower hybrid cattail cover (6%) unrestored potholes (19%). In the marsh zone, the overall plant community composition significantly differed between restored and unrestored potholes (data reported as a graphical analysis). Restored potholes also had less horizontal vegetation cover (data not reported). In the wet meadow zone, neither the plant community composition nor horizontal vegetation cover significantly differed between restored and unrestored potholes. Compared to natural potholes, the restored potholes had a significantly different plant community in both zones and lower horizontal cover in the marsh zone, but similar horizontal cover in the wet meadow zone and similar hybrid cattail cover (natural: 5%). Methods: In summer 2010, vegetation was surveyed in the marsh (seasonally flooded) and wet meadow (occasionally flooded) zones of 39 prairie potholes (10 quadrats/zone/pothole). Thirty potholes were surrounded by former cropland, converted to perennial vegetation cover. Excess cropland sediment had been removed from 19 of these potholes, 2–7 years previously. Prairie cordgrass Spartina pectinata had also been planted in the wet meadow zone of some excavated potholes (number not reported). The study does not distinguish between the effects of sediment removal and planting on any non-planted vegetation in these potholes. The remaining nine potholes were “natural”, i.e. surrounded by land that had never been cultivated.

(Summarised by: Nigel Taylor)