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Coastal Deposition Landforms - SAND DUNES

SAND DUNES

Key words

  • Psammosere – another name for a sand dune ecosystem
  • Ecosystem – a collection of plants and animals that adapt and adjust to abiotic and biotic factors in a particular location.
  • Abiotic factors – Sunlight, wind speed and direction, inundation, soil pH, Infiltration rates, rainfall, slope, aspect, soil fertility and humus content
  • Biotic factors – competition, interaction with other plants and animals
  • Human factors – how humans influence an ecosystem
  • Succession – the change in species in an ecosystem over time
  • Zonation – the change in species over space
  • Xerophyte - A plant adapted to living in a dry arid habitat like a sand dune
  • Sand dune - Coastal sand hill above the high tide mark, shaped by wind action, covered with grasses and shrubs.

How sand dunes are created

How sand dunes form

Sand dunes are accumulations of sand and other sized sediments that gather on a beach.  Sand dunes are created around obstacles on the beach, these could be natural such as a rock or human things such as some waste drift wood or a fence.
The sea brings sediment to the beach and then the wind redistributes that sediment.  When the wind encounters the beach obstacles velocity falls and sediment is DEPOSITED.  This makes amount of sand or sediment at the front of the sand dune system, known as an EMBRYO dune.
Over time, tough plants known as PIONEERS such as Marram grass take root on the dune, their root systems helping to stabilise the sand and fix it in place. 
As these plants die off they add nutrients and humus to the sand dune improving the soil, so more complex plants can move in, such as brambles.
Eventually, the climatic climax vegetation is reached, which in the UK would be forest. 

Sand dune profile

How Marram Grass copes in a sand dune environment:
 

Marram grass adaptations
 

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