Ecological SuccessionEcological Succession

The StandardsThe Standards

• SEV3. Students will describe stability and change in ecosystems.– b. Explain succession in terms of changes in

communities through time to include changes in biomass, diversity, and complexity.

– c. Explain how succession may be altered by traumatic events.

Ecosystems changeEcosystems change

• Ecological Succession– A 100 year old forest was once a lake– A tree falls and opens up space for new life– Mosses, grasses, and small shrubs grow in an

abandoned parking lot.

What is What is ecological successionecological succession??

• Gradual process of change and replacement of some or all of the species in a community.

• May take hundreds or thousands of years

• Each new community makes it harder for the previous community to survive.

2 types2 types

• Primary succession – occurs where no ecosystem previously existed (rocks or sand dunes)

• Secondary succession – occurs after a disturbance where an ecosystem did previously exist. (more common)

Secondary SuccessionSecondary Succession

• Begins after a disturbance like fire, volcano, storms, or human activity– Pioneer species are the first species to

colonize an area.– Each new species makes it easier for the next

species to thrive.– A climax community is a stable community

with little change

Mount St. HelensMount St. Helens

• Right after the eruption in 1980. See figure 17 on p. 138.

• 12 years into secondary succession. See figure 18 on p. 139.

• What has changed? What has stayed the same?

Fire and secondary successionFire and secondary succession

• Important natural cause– Jack pine only germinates after fire– Minor fires can burn out brush and deadwood,

preventing major fires.– Some animals eat plants that appear after a

fire.

• Foresters let minor fires burn when they don’t threaten human life or property.

Old field SuccessionOld field Succession

• Abandoned farmland1. Pioneer grasses and weeds

2. Taller grasses

3. Fast growing pine trees

4. Slow growing oak, hickory, beech, and maple

Primary SuccessionPrimary Succession

• Occurs on new volcanic islands, rock exposed by retreating glacier, or any other surface with no ecosystem.

• Slower than secondary succession

• Hundreds to thousands of years to create fertile soil.

Order of successionOrder of succession

1. Bacteria and lichens

2. Mosses

3. Grasses

4. Shrubs

5. Pine trees

6. Hardwood trees

Other primary successionOther primary succession

• City streets

• Rooftops

• Parking lots