Psammoseres & Sand Dunes Flashcards
Definition of Psammosere
Ecological succession that develops in the sands of a coastal environment. They mainly develop in sand dune successions.
How does the coastal environment change as you move inland across a sand dune succession?
The soil pH changes and the sediment that makes up the dunes changes, causing species of plant life and animals to also change.
What conditions are needed in order for sand dunes to develop?
- Large supply of sediment from a large tidal flat.
- An area with a large tidal range (lots of sand exposure)
- Strong continuous wind to move sand grains and transport via saltation.
Conditions of an Embryo dune
Soil pH is high (8.5) as broken down shells made from calcium carbonate mix with the soil.
Species have long roots to enable access to fresh water and help stabilise dune.
How are embryo dunes formed?
Form in the shadow of an obstacle (rock or litter) at strandline. Pioneer species e.g. Prickly Saltwort, colonise and bind sand.
Conditions of a Foredune/Yellow dune
Vegetation has decreased soil pH (7.5) so a wider range of plants can tolerate, e.g. Marram Grass
How are foredunes/yellow dunes formed?
Embryo dunes grow as sediment is trapped in plants. They are also called mobile dunes as the sand is relatively un-compact. Plants further trap sediment, growing dune quite big.
Conditions of a Grey dune
Layers of humus is formed as plant life dies, which is somewhat acidic, lowering the pH.
New species develop but Marram grass remains prevalent.
How are Grey dunes formed?
Marram grass continues to trap and stabilise sediment due to its long thin blades and deep root system. Soil becomes more stable as the humus layer gives it a grey colour (known as fixed dune)
Conditions of Dune Slacks
Fresh water may be exposed in some slacks. More vegetation such as reeds and rushes develop and the humus makes it more hospitable.
How are Dune slacks formed?
They are large depressions often deep enough to expose water table. They are formed by 2 ways.
Dune ridges -> wind is blocked so no deposition and little erosion so rarely water exposed.
Result of blowouts -> trampling reduces stability and so more susceptible to erosion.
Conditions at the Climax
Soil pH is much more acidic as the humus layer becomes thick.
Vegetation such as trees and shrubs grow as they can tolerate the soil pH.
What happens at the Climax of a sand dune succession?
The climax (plagioclimax) marks the end of a succession. Forests may develop as trees are now able to grow. If the climax is brought about by human activity, the end is known as a plagioclimax.
Why do sand dunes need protection?
They are fragile systems susceptible to damage and interference from humans.
Why is it beneficial to make use soft engineering protection methods?
They are low cost, require low technology and work with nature rather than against it.
