Ecological SuccessionEcological Succession

Ecological SuccessionEcological Succession

• Ecosystems are constantly changing due to natural and human disturbances

Examples:

• Natural disturbances– Forest fires

• Human disturbances– Clearing a forest for agriculture

Ecological SuccessionEcological Succession

• Succession- orderly, natural changes and species replacements that occur in an ecosystem

– Basically, older organisms die out and new organisms move in, causing further changes in the community

Steps in SuccessionSteps in Succession

1. Grass gets taller and weeds start to grow area looks like a meadow

Steps in SuccessionSteps in Succession

2. Bushes grow, trees appear Different animals enter the area to live

Steps in SuccessionSteps in Succession

3. Less light now reaches the ground Grass slowly disappears

Steps in SuccessionSteps in Succession

4. 30 years later, area will resemble a forest

SuccessionSuccession

• At each stage, different species of plants and animals may be present– Conditions at each stage are suitable for

some, but not others

2 types of Succession2 types of Succession

• Primary and Secondary

• Primary Succession- takes place on land where there are no living organisms– Ex: when lava from a volcano cools and forms

new land

Primary SuccessionPrimary Succession

• Pioneer species- first organisms to occupy new land– Ex: lichens

• Decaying lichens and other pioneer species combine with bits of rock to make soil

Lichen on Lichen on RockRock

Primary SuccessionPrimary Succession

• Seeds move into small patches of soil and begin to grow

Primary SuccessionPrimary Succession

• Primary succession slows down and community becomes stable

• Climax community- a stable, mature community that undergoes little or no species change

Secondary SuccessionSecondary Succession

• Secondary Succession – occurs when community is destroyed or altered but soil is still there– Ex – fire, clear cutting

– Regrows to mature, stable community called climax community

– May take less time than primary succession

Forest Fire RegrowthForest Fire Regrowth