Succession

What is succession?

The process by which ecosystems change over time, with changes in the dominant species

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Why does succession occur?

The changes in the environment due to abiotic factors cause the plant and animal species present to change

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What are the 2 types of succession?

Primary and secondary

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Primary succession

Succession that occurs on a area of land that is newly formed (like bare rock or sand dunes), there is no soil or organic material present

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Secondary succession

Succession that occurs on land where soil is present but contains no plant or animal species because of altered land, e.g. forest fire

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How can primary succession still occur today?

Volcanoes erupt and lava cools forming igneous rock, sand blown by wind creating new sand dunes, glaciers retreat depositing rubble and exposing rock

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What are each of the stages in succession known as?

Seral stages (or sere)

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What are the 3 main seral stages?

1) Pioneer community, 2) Intermediate communities, 3) Climax community

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What is a pioneer community?

The first organisms to colonise an area

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How does the pioneer species arrive?

Seeds or spores in the wind or droppings from birds or animals

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Name a number of adaptations a pioneer species have

Large quantities of seed produced into wind, seeds germinate fast, photosynthesise to produce own energy and have less limiting factors as a result, tolerance to extreme conditions, ability to fix nitrogen from atmosphere

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What is an intermediate community?

New species that come to colonise the area, secondary colonisers, tertiary colonisers and so on

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How do secondary colonisers come about?

Rock erodes forming particles and older generations of pioneer species die & decompose, soil produced with enough organic content to support growth of new plant species, which is the secondary colony

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What is the organic component of the soil from dead plant matter called?

Humus

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Explain how the area then transforms into the final stage

Environmental conditions continue to improve and so more species colonise the area, more organisms die added to humus of soil, soil able to retain more water, abiotic factors more favourable for plants like small trees etc

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What happens to the pioneer species?

Usually they get outcompeted as the conditions are more favourable to the other species, the environment will be a lot more hospitable yet the pioneer species are more adapted to hostile conditions

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What is the climax community?

The final seral stage, the community is in a stable state where very little change will occur, usually there will be a few dominant species

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What does the dominant species depend on?

The conditions of the environment, if it is a warm environment with high water availability, usually large trees will be dominant, in drier conditions shrubs may be the dominant species

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What happens to biodiversity as succession takes place?

Biodiversity increases during succession but the climax community is not always the most biodiverse seral stage, the more successful the dominant species the less diverse the area

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What is defected succession?

When the natural flow of succession is halted by human activities

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When deflected succession occurs, what is the name of the final seral stage?

plagioclimax

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Give 3 examples of how agriculture deflects succession

Grazing and trampling discourages growth, removing existing vegetation to plant crops, burning as a means of forest clearance (secondary succession can occur as a result of this and can lead to increase in biodiversity)

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Succession

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