Sand dune ecology - AbsoluteAstronomy.com

Sand dune ecology describes the biological and physico-chemical interactions that are a characteristic of sand dunes.

Sand dunes provide a range of habitats for a range of unusual, interesting and characteristic plants that can cope with disturbed

Disturbance

In ecology, a disturbance is a temporary change in average environmental conditions that causes a pronounced change in an ecosystem. Outside disturbance forces often act quickly and with great effect, sometimes resulting in the removal of large amounts of biomass...

habitats. In the UK

United Kingdom

The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

these may include restharrow Ononis repens
Ononis repens
Ononis repens or Common Restharrow is a plant species of the genus Ononis. It is found by the shore and is also common in dry hill pastures in chalk or limestone areas. It is a prostrate woody perennial with small oval leaves. The leaves are covered in glandular hairs which give a resinous smell on...

, sand spurge Euphorbia arenaria and ragwort Senecio vulgaris - such plants are termed ruderals.

Other very specialised plants are adapted to the accretion of sand, surviving the continual burial of their shoots by sending up very rapid vertical growth. Marram grass, Ammophila arenaria
Ammophila arenaria
Ammophila arenaria is a species of grass known by the common names European Marram Grass and European Beachgrass. It is one of two species of the genus Ammophila . It is native to the coastlines of Europe and North Africa where it grows in the sands of beach dunes. It is a perennial grass forming...

specialises in this, and is largely responsible for the formation and stabilisation of many dunes by binding sand grains together. The sand couch-grass Elytrigia juncea also performs this function on the seaward edge of the dunes, and is responsible, with some other pioneers like the sea rocket Cakile maritima
Cakile maritima
Cakile maritima, the European searocket, is a common plant in the mustard family. It is widespread in Europe, especially on coastlines, and it can now be found in other areas of the world where it has been introduced. It is an inhabitant of the west and east coasts of North America, where it has...

, for initiating the process of dune building by trapping wind blown sand.

In accreting situations small mounds of vegetation or tide-washed debris form and tend to enlarge as the wind-speed drops in the lee of the mound, allowing blowing sand (picked up from the off-shore banks) to fall out of the air stream. The pioneering plants are physiologically adapted to withstand the problems of high salt contents in the air and soil, and are good examples of stress tolerators, as well as having some ruderal characteristics.

On the, inland side of dunes conditions are less severe, and links

Links (golf)

A links is the oldest style of golf course, first developed in Scotland. The word "links" comes from the Scots language and refers to an area of coastal sand dunes and sometimes to open parkland. It also retains this more general meaning in the Scottish English dialect...

type grasslands develop with a range of grassland herbs which benefit from the reasonable nutrient status and moderately high pH of the more stable soils, especially when enough humus has accumulated in stabilised soils for water retention to be improved. Species like red fescue and lady's bedstraw are adapted to compete with each other - for nutrients, growing space and light, and are known as CSR plants - i.e. having features of Competitors, Stress tolerators and Ruderals in more or less equal proportions.

There may also be areas in old blow-outs

Blowout (geology)

Blowouts are sandy depressions in a sand dune ecosystem caused by the removal of sediments by wind.Blowouts occur in partially vegetated dunefields or sandhills. A blowout forms when a patch of protective vegetation is lost, allowing strong winds to "blow out" sand and form a depression...

where groundwater

Groundwater

Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock...

is near the surface, and often rises to cause flooding in the winter. Frequent, but intermittent waterlogging of the roots requires adaptations to stress, so the proportions of stress tolerators are increased here.

In nutrient-rich water, however there are some plants with very competitive strategies, like the reed (Phragmites australis). This is an example of a plant which makes rapid growth and suppresses other species by monopolising root and shoot space and shading out the opposition. Even its own seedlings are prevented from establishing within the existing population, but seeds are blown for long distances in copious quantities to start new colonies, whilst mature populations extend by rapid vegetative growth of lateral underground shoots - rhizomes.

Sand dune systems are excellent places for biodiversity, partly because they are not very productive for agriculture, and partly because disturbed, stressful and stable habitats are present in proximity to each other. Many of them are protected as nature reserves, and some are parts of larger conservation areas, incorporating other coastal habitats like salt marches, mud flats, grasslands, scrub and woodland.

See also