Succession in Ecosystems

​Primary succession begins when bare rock forms.

* Bare rock forms due to a volcano eruption or due to glacier retreat.

* These rocks do not have organic material from dead animals or plants.

There is no nutrient-rich soil for plant growth.

​The first species that

settle and grow on new rock formations are called pioneer species.

Pioneers are often lichens.

* Lichens are composite organisms made of algae and fungi that grow together as one.

It obtains water and nutrients from the atmosphere and the algae produces carbohydrates through photosynthesis.

​Soil forms as lichens break down rock into smaller particles.

Organic material from dead organisms

​increases in the soil.

​Early colonizing plants are often nitrogen-fixing species that increase the nitrogen content of the soil.

* With soil, grasses, ferns, and herbs can now grow, which provide a habitat for insects and small animals

Once the soil has more organic material (that builds up with decomposing material from other dead organisms), larger plants like shrubs and trees can grow in the area.​

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More animals are attracted to the area. Once a steady state in the ecosystem is established, scientists say a climax community has been reached.

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Secondary Succession begins after an event that reduces an established ecosystem to a smaller population, on an already established soil.

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* These events could be a hurricane, a forest fire, or

land that was farmed but then abandoned to grow wild again

* Larger trees begin to grow again and a climax community is reached.

The community remains relatively stable until another disturbance (disaster or fire) occurs.

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​Secondary succession can take up to 300 years for the ecosystem to recover back to a steady climax community state