Study

Restoration of saltmarsh vegetation at the Tollesbury managed realignment site in the Blackwater Estuary, Essex, England

  • Published source details Wolters M., Garbutt A., Bekker R.M., Bakker J.P. & Carey P.D. (2008) Restoration of salt-marsh vegetation in relation to site suitability, species pool and dispersal traits. Journal of Applied Ecology, 45, 904-912

Summary

The Tollesbury manged realignment site (21 ha; 51º46’N, 0º51'E) in the Blackwater Estuary (southeast England), historically formed part of the surrounding salt marshes until embankment and conversion to agricultural land in the 18th century. After planned embankment breaching, the process of salt marsh vegetation development was studied, focussing on species establishment and availability of target species propagules at local (adjacent salt marsh) and regional (south-east England) scales.

In August 1995, a 50-m wide breach was made in the embankment, thus connecting the realignment site to the main tidal water channel. A seawall was built on the landward side to reduce the risk of seawater flooding the adjacent agricultural land.

Monitoring: From 1997 (second growing season after breach) to 2001, plant colonization was monitored annually in three 125 m long, 20 m wide transects (subdivided into 1 m² quadrats). These ran from the new seawall towards the breach (i.e. from high to low elevation). In each quadrat, plant species were recorded and percent cover estimated.

Species pools: Close to the realignment site are Old Hall and Tollesbury marshes (vegetation monitored annually since 1994). These marshes were considered to provide the ‘local species pool’ - most salt marsh species disperse only over short distances. The ‘regional species pool’ was derived from NVC salt marsh communities for south-east England, selecting species occurring with a frequency of over 60% in a particular community.

After breaching,  ‘agricultural’ vegetation was quickly killed by tidal seawater inundation. The rate of salt-marsh development and species diversity appeared to be affected mainly by elevation and salt tolerance.

In the first year, three target species established (i.e. <10% of the maximum regional species pool, comprising 34 species). Glassworts Salicornia spp. and annual sea-blite Suaeda maritima colonized first. Perennials (saltmarsh-grass Puccinellia maritima, sea aster Aster tripolium, common cord-grass Spartina anglica, greater sea-spurrey Spergularia media, sea purslane Atriplex portulacoides and sea lavender Limonium vulgare) only started to colonize or increase notably after 3 years.

After 5 years, 9-10 target species were established i.e. within the range of the local species pool (10-14 species). Plant composition at the highest elevation developed from an annual Salicornia community into a Puccinellia marsh which was similar to one of the local marshes. After 8 years, 11 target species had established; the lower elevations were still Salicornia-dominated.


Note: The compilation and addition of this summary was funded by the Journal of Applied Ecology (BES). If using or referring to this published study, please read and quote the original paper, this can be viewed at: http://www3.interscience.wiley.com/cgi-bin/fulltext/119392118/PDFSTART

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