Ecological Succession

4-2 What Shapes an Ecosystem?

Ecosystems Change

• Ecosystems are constantly changing in response to natural and human disturbances.

• As an ecosystem changes, older inhabitants die out and new organisms move in. – This is ecological succession.

Primary Succession

• Succession that occurs on surfaces where no soil exists.

• Occurs on the surfaces that are left bare after– Volcanic eruptions – Glaciers melting

• Pioneer species – the first species to populate an area– Often lichens because they can grown on bare

rock

Lichens

Primary Succession

Secondary Succession

• Change in an ecosystem after a disturbance (leaves soil behind)– Examples: after wildfires, clear-cutting a forest,

natural disasters• Ecosystems usually recover from natural

disasters, but may not always recover from long-term human disturbances.

Secondary Succession

Boreal Forest Biome - Succession