Ecological responses to tidal restorations of two northern New England salt marshes

Published source details Burdick D.M., Dionne M., Boumans R.M. & Short F.T. (1996) Ecological responses to tidal restorations of two northern New England salt marshes. Wetlands Ecology and Management, 4, 129-144.
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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

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

A before-and-after, site comparison study in 1993–1995 in an estuarine marsh in New Hampshire, USA (Burdick et al. 1996) reported that an area in which tidal exchange was improved (by modifying culverts under a road) developed cover of salt marsh vegetation within two years, although total vegetation cover declined. Statistical significance was not assessed. Before intervention, the tidally restricted area was a freshwater wet meadow dominated by grasses (39% cover) and asters Aster spp. (32% cover). Total vegetation cover was 94%. Two years after restoring tidal exchange, the area was dominated by the alga Vaucheria spp. (21% cover) and saltmeadow cordgrass Spartina patens (21% cover), with other salt-tolerant species present at lower abundance (e.g. smooth cordgrass Spartina alterniflora: <1% cover; see original paper for full data). Total vegetation cover was 63%. For comparison, a reference area of marsh downstream contained communities dominated by saltmeadow cordgrass (56% cover) or smooth cordgrass Spartina alterniflora (60% cover) with no algae, and 71–86% total vegetation cover. Methods: A road built across Mill Brook Marsh, in 1970, restricted tidal exchange to part of the marsh through a narrow gated culvert. In 1993, the gate on the old culvert was removed and a new, wider culvert was installed. This restored regular tidal exchange, raised the water table and increased soil salinity in the degraded area. Summer vegetation surveys were carried out, using 1-m² quadrats, before (1993) and after (1995) intervention in the degraded/restored area. The undisturbed marsh below the road was also surveyed.

(Summarised by: Nigel Taylor)