How Ecosystems Change: Ecological Succession

1. How Ecosystems Change: Ecological Succession ES Textbook, Chapter 5 Pages 137-141

2. Ecological Succession • Is a gradual process of change and replacement of some or all of the species in a community. • Can take hundreds or thousands of years • Each new community makes it harder for the previous one to survive.

3. Primary Succession • The type of succession that occurs on a surface where no ecosystem existed before, such as on rocks or sand dunes.

4. Secondary Succession • Is more common than primary succession. • Occurs on a surface where an ecosystem has previously existed. • Occurs in ecosystems that have been disturbed or disrupted by humans or by natural disasters such as storms, floods, earthquakes, and volcanoes.

5. Example of Secondary Succession • 1980 – Mt. St. Helens erupted in Washington State. • It was one of the worst volcanic disasters because more than 44,460 acres of forest were burned and flattened by hot ash and volcanic debris. • Have a look: • http://www.teachersdomain.org/search/?q=mount+st.+Helens&fq_grade=PK&fq_grade=PS

6. Secondary Succession (cont.) • After the eruption, plants began to colonize the volcanic debris. Such plants are called pioneer species. • Pioneer species – the first organisms to colonize any newly available area and begin the process of ecological succession.

7. Secondary Succession (cont.) • Over time, pioneer species will make the new area habitable for other species. Grasses

8. Climax Community • A final and stable community.

9. Fire and Secondary Succession • Natural fires, caused by lightening, are a natural cause of secondary succession. • Jack Pine Tree – a species of tree that can release their seeds only after they have been exposed to the intense heat of fire.

10. Old-field Succession • Another example of secondary succession • Old-field succession occurs when farmland is abandoned. 1 2

11. Old Field Succession 4 3 5

12. Primary Succession • On new islands created by volcanic eruptions, areas exposed when a glacier retreats, or any other surface that has not previously supported life. • Much slower than secondary succession because no soil. • It takes several hundred to several thousands of years to create fertile soil.