notes on succession

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  • Created on: 16-04-12 08:51
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7.3 Describing one example of primary succession resulting in a climax community: sand dunes
Any change in a community of organisms can cause a change in their habitat. Any change in a habitat can also cause a
change in the make-up of the community. These ideas can help to explain why gradual directional changes happen in a
community over time. Such a process of directional change is called succession.
The island of Surtsey (Iceland) was created by a volcanic eruption,
and is now home to a community of plants. Development of such
communities from bare ground is known as primary succession,
and comes about as follows:
- algae and lichens begin to live on the bare rock (these make the
pioneer community)
- erosion of the rock, and a build-up of the dead and rotting
organisms produces enough soil for larger plants, mosses and
ferns, to grow, which replace (or succeed) the algae and lichens
- in a similar way, larger plants succeed these plants until a final,
stable community called the climax community is reached
Succession does not have to happen in such a way from bare ground, it can occur on previously colonised (but disturbed
or damaged) habitat. This is called secondary succession.
Sand dunes
Sand dunes are interesting because they display all the same
stages of succession in one place at the same time. Looking at
the beach and sand dunes, you see different sections. Sand is
deposited on the beach by the sea, and so we know that the
areas of sand closest to the shore are more recent than the ones
further inland.
This means that the sand just above the high tide mark is just
starting its process of succession, whereas areas more inland
have already reached their climax communities.
a `mini dune' forms and other plants
nutrients collect, and more stability and colonies over
pioneer plants like sea bigger plants such as accumulation of time, and further
rocket and prickly sea couch grass and nutrients allows for the inland larger
sandwort colonise the marram grass grow growth of species such plants may grow
sand just above the as Bird's foot trefoil
high water mark
further inland
young sand dunes
beach old sand dunes

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Eventually, a dune's community may develop into a grassland community, and then a woodland community (as shown in
the final stage of the diagram on the previous page), although this takes much longer and is usually a fair bit inland. This is
representative of the UK as a whole, as most climax communities in the UK are grassland ecosystems.…read more


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