Plant SuccessionPlant Succession:Psammoseres:Psammoseres

The Physical CoreThe Physical Core

BiosphereBiosphere

ImportantImportant

Plants are the key to the formation Plants are the key to the formation and character of sand dunes. If there and character of sand dunes. If there were no plants and no plant were no plants and no plant colonisation, there would be no sand colonisation, there would be no sand dunes.dunes.

For pioneer plants however there are several obstacles to overcome

Obstacles for pioneer Obstacles for pioneer speciesspecies

Strong stormy high tides and the use of Strong stormy high tides and the use of beaches by people can destroy plants beaches by people can destroy plants and dunes.and dunes.

Sand is a sterile environment often Sand is a sterile environment often lacking humus and nutrients.lacking humus and nutrients.

Sand can be very dry due to the rapid Sand can be very dry due to the rapid drainage. Drought resistant plants are drainage. Drought resistant plants are classified as classified as xerophyticxerophytic. .

Shelly fragments often create an Shelly fragments often create an alkaline environment.alkaline environment.

Model Sand Model Sand DuneDune

Embryo, fore and mobile Embryo, fore and mobile dunesdunes Plants that occupy this area of a sand Plants that occupy this area of a sand

dune have to be xerophytic.dune have to be xerophytic. They also have to have particular They also have to have particular

growth features.growth features.

Be resistant to salt water during spring

tides

Have foliage to trap the sand, causing it to drift

over them.

As they grow vertically and laterally, they bind the sand and build up embryo and foredunes.

Sea rocket, sea lyme and couch grass

Sea rocket

Couch grass

Sea lyme

Yellow DuneYellow Dune

Once the tops of dunes have grown well Once the tops of dunes have grown well above the highest tide level, above the highest tide level, marram marram grassgrass is able to colonise. is able to colonise.

This is the main pioneering plant.This is the main pioneering plant.

Thanks to Thanks to rhyzomesrhyzomes (long creeping (long creeping underground roots) spreading vertically underground roots) spreading vertically and laterally, the marram very effectively and laterally, the marram very effectively grows with fresh deposits of sand.grows with fresh deposits of sand.

Marram GrassMarram Grass

Marram GrassMarram Grass

Grey dunesGrey dunes On the landward more sheltered side of dunes On the landward more sheltered side of dunes

more plant species establish themselves.more plant species establish themselves.

Such fixed dunes are called grey dunes Such fixed dunes are called grey dunes because of the increased humus content of because of the increased humus content of the soil and the surface growth of lichens.the soil and the surface growth of lichens.

As the distance from the shore increases, sand As the distance from the shore increases, sand no longer accumulates and marram grass no longer accumulates and marram grass cannot compete with new colonising plants.cannot compete with new colonising plants.

Sand sedge, buttercups & dandelions.

Sand sedge buttercups

dandelions

Older grey dunesOlder grey dunes

Further inland, the older grey dunes Further inland, the older grey dunes support bushes such as support bushes such as sea sea blackthornblackthorn but more ‘ordinary’ but more ‘ordinary’ plants are also present – plants are also present – gorsegorse, , broombroom, , heatherheather..

One factor is that the soil is now One factor is that the soil is now more acidic. Any lime from the shells more acidic. Any lime from the shells has been leached (washed out) and has been leached (washed out) and the amount of humus is now greater.the amount of humus is now greater.

broombroom

heatherheather

Dune SlacksDune Slacks

Other ‘ordinary’ species occupy the Other ‘ordinary’ species occupy the dune slacks. These damp, low lying dune slacks. These damp, low lying hollows have a higher water table, hollows have a higher water table, especially in winter.especially in winter.

Hydrophytic (water tolerant) Hydrophytic (water tolerant) vegetation thrives: vegetation thrives: rushesrushes, , willowswillows and and aldersalders are found here. are found here.