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Drainage and Elevation as Factors in the Restoration of Salt Marsh in Britain

Authors

  • Stephen Crooks,

    Corresponding author
    1. Department of Marine Science and Coastal Management, University of Newcastle, Newcastle Upon Tyne, NE1 7RU, U.K.
    2. Jackson Environment Institute , University of East Anglia, Norwich NR4 7TJ, U.K.
    3. Centre for Social and Economic Research on the Global Environment (CSERGE) , University of East Anglia, Norwich NR4 7TJ, U.K.
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  • Johan Schutten,

    1. Centre for Ecology , Evolution and Conservation, School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, U.K.
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  • Glenn D. Sheern,

    1. Centre for Ecology , Evolution and Conservation, School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, U.K.
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  • Kenneth Pye,

    1. Surface Processes & Modern Environment Research Group , Department of Geology, Royal Holloway University of London, Egham, Surrey, TW20 0EX, U.K
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  • Anthony J. Davy

    1. Centre for Ecology , Evolution and Conservation, School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, U.K.
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Address correspondence to S. Crooks, s.crooks@uea.ac.uk.

Abstract

Intertidal restoration through realignment of flood defenses has become an important component of the U.K. coastal and estuarine management strategy. Although experimentation with recent deliberate breaches is in progress, the long-term prognosis for salt marsh restoration can be investigated at a number of sites around Essex, southeast England where salt marshes have been reactivated (unmanaged restoration) by storm events over past centuries. These historically reactivated marshes possess higher creek densities than their natural marsh counterparts. Both geomorphology and sedimentology determine the hydrology of natural and restored salt marshes. Elevation relative to the tidal frame is known to be the primary determinant of vegetation colonization and succession. Yet vegetation surveys and geotechnical analysis at a natural marsh, where areas with good drainage exist in close proximity to areas of locally hindered drainage at the same elevation, revealed a significant inverse relationship between water saturation in the root zone and the abundance of Atriplex portulacoides, normally the physiognomic dominant on upper salt marsh in the region. Elsewhere in Essex natural and restored marshes are typified by very high sediment water contents, and this is reflected in low abundance of A. portulacoides. After a century of reestablishment no significant difference could be discerned between the vegetation composition of the storm-reactivated marshes and their natural marsh counterparts. We conclude that vegetation composition may be restored within a century of dike breaching, but this vegetation does not provide a reliable indicator of ecological functions related to creek structure.

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