Psammosere (Dune Succession)
Refers to AQA A2 Geography
Ecosystems: Change and Challenge Option
- Created by: Bethany
- Created on: 30-04-14 14:51
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- Psammosere (Dune Succession)
- What is a vegetation succession?
- The evolution of plant communities over time from pioneer species to climax vegetation
- At each stage of the plant succession, the plant community alters the soil and micro-climate, allowing other species to establish
- One community of plants is replaced by another as a succession begins to develop
- Pioneer species out competed by plants better adapted to new conditions
- Unless there is human involvement, a climatic climax is reached, where vegetation is in equilibrium with the environment and there are no new species
- Psammoseres
- 5000 ha of partially vegetated sand dunes in Scotland alone
- 500 + vegetation types
- Plants which grow have to adapt to an environment which is dry, salty, mobile and nutrient-poor.
- 5000 ha of partially vegetated sand dunes in Scotland alone
- Requirements for the development of a sand dune
- Plentiful supply of sand
- Strong winds to transport sand particles through saltation
- An obstacle such as a plant to trap the sand
- Why plants are essential to the formation and growth of sand dunes.
- Pioneer Stage
- Seeds blown in by wind or washed in by the sea
- Poor rooting conditions due to drought, strong winds, water immersion and alkaline conditions created by crushed sea shells.
- Wind moves the sand in the dunes, allowing water to drain through rapidly.
- Building Stage
- Plants trap sand as they grow, binding sand together with their roots
- Humus is created by decaying pioneer plants creating more fertile growing conditions. The soil also becomes less alkaline as pioneer plants grow and trap rainwater.
- Less hardy plants can now grow and begin to shade out the pioneers
- As plants colonise, the dunes chage colour from yellow to grey as the sand disappears
- Climax Stage
- Taller plants such as trees and more complex plant species such as moorland heather can now grow
- Plants from earlier stages die out due to compotion for water/ light
- When the water table reaches, or nearly reaches, the surface, dune slacks can occur. Here, water tolerant plants grow.
- Dunes Develop Inland
- New dunes develop on the fore shore (in pioneer stage)
- On older, more sheltered dunes the psammosere is in its building phase
- Furthest inland, on the oldest dunes, the climax stage will be reached
- Embreyo and Fore Dunes
- Plants with waxy leaves to withstand water and wind
- Low plants to avoid strong winds
- Deep tap roots to gain all available water
- High salt tolerance
- e.g. SAND WORT, SEA COUCH
- Yellow Dunes
- Dominant marram grass
- trives on being buried by sand
- In rolled leaves to reduce moisture loss
- Underground rhizomes stabablise sand.
- Dominant marram grass
- Grey Dunes
- High species diversity, mainly perennials, surface lichens give grey appearance, sparse marram,
- What is a vegetation succession?
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