Shingle foreshore communities

The frequency with which shingle beaches are disturbed by the action of the sea varies according to wave fetch and prevailing meteorological conditions; the resultant vegetation is similarly altered (Randall 1977a). In practice the majority of shingle foreshores are unvegetated or have extremely sparse vegetation cover. Three foreshore stability classes can be seen and related to the vegetation. These are dependent on the length of time over which the shingle is undisturbed by environmental factors, namely:

1. no vegetation - disturbance too frequent to support plant growth: as at the foot of sea-cliffs, distal points of spits, high-energy beaches etc.;
2. summer annuals - beach stable over growing season only: mainly cleavers Galium aparine and orache Atriplex spp. on drift line;
3. short-lived perennials - beach stable for +3 years: considerable strand and foreshore vegetation e.g. yellow horned-poppy Glaucium flavum, curled dock Rumex crispus, sea beat Beta maritima (Scott 1963).

These three stability habitat classes are similar to those identified in relation to the geomorphological types of shingle beaches and may occur at different levels on the same beach. There is considerable variation in the assemblages of species found in shingle foreshore habitats, however, lists compiled from widely separated sites show some floristic pattern. Fringing beaches and the seaward slopes of spits and bars show constancy of several species, in particular scentless mayweed Tripleurospermum maritimum, sea campion Silene maritima, Babington's orache Atriplex glabriuscula, Rumex crispus ssp. littoreus and, in the north, Galium aparine. Other species that are common in this habitat include red fecue Festuca rubra, Beta maritima and sea sandwort Honckenya peploides. Less common, but still locally important are creeping cinquefoil Potentilla anserina, perennial sow-thistle Sonchus arvensis, common sorrel Rumex acetosa, couch grass Elytrigia spp., biting stonecrop Sedum acre and ragwort Senecio spp. It will be noticed from this list of species that the majority, whether annual or perennial, are open ground nitrophiles. Their communities fall within the two Annex 1 habitats of the EU 'Habitats' Directive - the annual vegetation of drift lines and perennial vegetation of stony banks. However, this belies a much more complex sequence of coastal terrestrial shingle vegetation derived from the studies around Britain (Sneddon & Randall 1993a) than this twofold division suggests.The plant communities general fall into the pioneer/secondary pioneer categories in the Great Britain classification.

These three stability habitat classes may occur at different levels on the same beach. For instance at Shingle Street, Suffolk, the exposed foreshore is unvegetated, the lagoon foreshores have drift lines supporting Atriplex spp., whereas the main ridge crest with more stable shingle supports growth of Lathyrus japonicus, Beta maritima and Rumex crispus. On some shingle foreshores as at Cley, Norfolk, mobility of the substrate results in accretion around plants of Suaeda vera. The role that this species, in particular plays in shingle stabilisation has been considered (Chapman 1947) though not since and it is considered further autecological studies might be appropriate. A more detailed description of the relationship between stability and plant colonisation is provided.

References

Chapman, V.J. 1947. Biological Flora of the British Isles: Suaeda fruticosa (vera). Journal of Ecology, 35., 303-310.

Randall, R.E. 1977a. Shingle foreshore. In: The Coastline, ed.Barnes, R.S.K.John Wiley & Sons, Chichester, 49-61.

Scott, G.A.M. 1963. The ecology of shingle beach plants. Journal of Ecology, 51., 517-527.

Sneddon, P. & Randall, R.E. 1993a. Coastal Vegetated Shingle Structures of Great Britain: Main Report. Joint Nature Conservation Committee, Peterborough.