Psammosere

Strand Line At and behind the strand line, saltwort and sea rocket colonise. It’s a hostile environment (salty, dry, no soil and strong winds) which few plants can tolerate. Flotsam along the strand can cause very small changes to the microclimate, allowing slightly more shelter. Sea rocket can grow here. It has fleshy leaves which allows it to store water and deep tap roots to access moisture. They also have extensive lateral roots and this allows the plant to obtain moisture at the surface. This area is very fragile.

Embryo Dune An embryo dune gradually forms as the vegetation semi-stabilises the sand, encouraging a slight build up of the sand to form a very small dune. Sand couch dominates here. Sand couch will withstand occasional wetting with sea water. Its leaves lie close to the ground so they help to prevent the removal of accumulated sand by the wind. However, sand couch is weakened by vertical growth and so the dunes stay quite small and are easily destroyed by storms.

Fore Dune Sand sedge grass, sea holly and marram grass are found here. The dune is still small but there is a slight increase in humus as plants die out. The humus is sticky and helps to improve water retention. The environment is slightly less salty and hence it becomes more suitable for other plants to grow

Yellow Dune Found 20 m from strand line, this is where marram grass will colonise. It cannot tolerate seawater and can cope with very dry conditions. Its leaves are tightly inrolled to reduce transpiration and it has very long tap roots. It grows very quickly and allows lots of sand to be trapped. In the lee of the dune, where the sand is less mobile, some decomposition of the grass occurs and humus starts to develop. Conditions are now less alkaline. Other plants such as Sand Fescue, Sea Holly and Ragwort grow

Grey (fixed) Dunes When a new range of dunes forms on the seaward side of a range already formed, the latter becomes protected from the wind and the supply of sand is cut-off and the dune ceases to grow. Marram dies off and adds humus to the soil enabling the dune to support other plants such as Dandelions, Clover and Willow Herb. These species eventually stabilise of ‘fix’ the dune.

Dune Slacks In the damp or wet hollows between the dune ridges, where ground water reaches the surface for all or part of the year, dune slacks develop supporting water loving plants such as Cotton Grass, Rushes, Sphagnum Moss and Flag Iris.

Climax Vegetation With increasing distance from the sea, where the age of the dunes may be measured in hundreds of years, a greater proportion of non-maritime species enter the dune community. The most important factor in determining the range of species found is the alkalinity or acidity of the soil. Where dunes have developed on lime rich shell sand, a grassland community will develop. Where the underlying sand is siliceous (few shell fragments), heath vegetation develops such as Heathers and Gorse.