1. How Ecosystems Change
April 21, 2009

7. “You could cover the world with asphalt, but sooner or later green grass would break through.” -Ilya Ehrenburg

8. Life Will Find a Way

9. Ecological Succession
Ecosystems are constantly changing in response to natural and human disturbances.
This causes changes in the community because older inhabitants gradually die out and new organisms move in.

10. Ecological Succession
This predictable pattern of changes in a community over time is called ecological succession.

11. 1. Primary Succession
Primary succession is a type of succession that occurs on the surfaces where no soil exists.
Example: on rocks, cliffs, sand dunes, or after volcanic eruption

12. Bare Rock
Bacteria and Lichens
Soil
Decay
Fertile soil for more plants to grow

13. 2. Secondary Succession
Secondary succession occurs on a surface where an ecosystem has previously existed.
It is the more common type of succession.
Example: Trees regrowing after a wildfire.

14. Pioneer Species
These are the first organisms to colonize any newly available area and begin the process of ecological succession.

15. Climax Community
This is the final and stable community which will remain unchanged through time if it is not disturbed.

17. Secondary Succession
Climax
Community
Pioneer
Species

18. Old-field Succession Occurs when farmland is abandoned. 5 yrs later
1 yr later
10 yrs later
2 yrs later
20 yrs later