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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.