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Succession – ‘dynamic ecosystems’ ‘Succession is the gradual directional change of a community over time’

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Page 1: Succession – ‘dynamic ecosystems’ ‘Succession is the gradual directional change of a community over time’

Succession – ‘dynamic ecosystems’

‘Succession is the gradual directional change of a community

over time’

Page 2: Succession – ‘dynamic ecosystems’ ‘Succession is the gradual directional change of a community over time’

There are two types of succession:

Primary successionSecondary succession

Here the starting point is bare ground

Here a community is damaged and the soil is left plants then colonise(e.g. a woodland has been felled).

The END POINT of both types of succession is the climax community

Page 3: Succession – ‘dynamic ecosystems’ ‘Succession is the gradual directional change of a community over time’

Succession on sand dunes

Nearest the sea, only a few speciescan colonise the sand. Why?•Sand constantly moves

•High salt concentration

• freely draining ‘soil’

• ‘soil’ has a low nutrient status

Page 4: Succession – ‘dynamic ecosystems’ ‘Succession is the gradual directional change of a community over time’

Succession on sand dunes

Very specialised species live in this area, they are called

PIONEERSThese species are show

xeromorphic & halophytic characteristics

•Sea rocket (Cakile maritima)

•Sea holly (Eryngium maritimum)

Page 5: Succession – ‘dynamic ecosystems’ ‘Succession is the gradual directional change of a community over time’

Sea holly…………..

……………… pioneer species

Latin name: Eryngium maritimum

………of sand dunes

Page 6: Succession – ‘dynamic ecosystems’ ‘Succession is the gradual directional change of a community over time’

These PIONEER species give way to other species as you move in

land

Couch grass (Agropyron junceiforme)

This species has widespread roots, this helps in two ways

•Stabilise the substrate

•Absorb all available water

Page 7: Succession – ‘dynamic ecosystems’ ‘Succession is the gradual directional change of a community over time’

The quality of the substrate improves in two ways as you move

back through the dunes

1. Nutrient levels increase

2.Water retention improves

This is due to: •Death & decay of animals

•Decay of seaweed

•Decay of plant material

A skeletal soil begins to develop

Page 8: Succession – ‘dynamic ecosystems’ ‘Succession is the gradual directional change of a community over time’

These species further improve the edaphic conditions

This makes the substrate more hospitable, encouraging other

species…….

Marram grass (Ammophila arenaria)

These species are still XEROPHYTIC

Page 9: Succession – ‘dynamic ecosystems’ ‘Succession is the gradual directional change of a community over time’

Marram grass (Ammophila arenaria)

Large network of roots, leading to dune developement

Marram produces shoots along its stem, ensuring that it is never

covered with sand

This can lead to large sand dune systems

Page 10: Succession – ‘dynamic ecosystems’ ‘Succession is the gradual directional change of a community over time’

Dunes at this stage are called ‘yellow’ reflecting how little organic matter the substrate

contains

The substrate will turn to ‘grey’ as the levels of dead material

increases

Page 11: Succession – ‘dynamic ecosystems’ ‘Succession is the gradual directional change of a community over time’

The species to follow next in the succession, are N fixers

Restharrow (Ononis repens)

Bird’s foot trefoil (Lotus corniculatus)

These add N to the soil

Page 12: Succession – ‘dynamic ecosystems’ ‘Succession is the gradual directional change of a community over time’

As Nitrogen levels increase, other species become more common

A common one is Red Fescue (Festuca rubra)

These species stabilise the substrate further

Page 13: Succession – ‘dynamic ecosystems’ ‘Succession is the gradual directional change of a community over time’

• http://bcs.whfreeman.com/thelifewire/content/chp55/55020.html

• http://ecoplexity.org/node/219

• www.youtube.com/watch?v=vNHnwHaSolA