Succession in

Ecosystems

What caused this?

What caused this?

Equilibrium• What did the events do to the earth?

• How did the events do this?

• What part of the earth was affected?

• What differences were there between the two events?

Equilibrium• Ecosystems try to maintain equilibrium

– Equilibrium is a state of balance (similar to homeostasis)

– Major events in an ecosystem can upset the equilibrium• tornado/hurricane• flood• fire• drought • disease

Succession

• Series of predictable changes that occur in a community over time

• Succession allows an area to recover after a catastrophic event– Primary succession– Secondary succession

Succession

• Begins with a pioneer species– can usually perform photosynthesis

• Once equilibrium is reached, it is called a climax community

• Climax communities are different for each area

Primary Succession

• Occurs on an area of newly exposed rock, sand, lava, or any area that has not been occupied by a living (biotic) community.– New island created by volcano– Rock uncovered by glacier

• Takes a very long time

Steps of Primary Succession

1. Pioneer species come ina. Mosses and lichens that help break down

rock to form soil

2. Plant seeds come in on birds, animals, wind, water and begin to grow

3. Eventually, primary succession will lead to a community of organisms in equilibrium

Primary Succession

Example of Primary Succession

Glaciers scrape the Earth as it moves. Some land may have been buried under ice for thousands of years.

Example of Primary Succession

As the glacier melts, rocks are left behind. After about a year, lichens begin to grow on the rock surface. Lichens slowly weather the rock, creating the beginning of soil.

Example of Primary Succession

After the lichens create cracks in the rocks, mosses begin to grow in the cracks. The moss further weathers the rock, forming more soil.

Both lichens and moss are pioneer species

Example of Primary Succession

Once enough soil has been formed, weeds and small shrubs may follow.

Example of Primary Succession

As the soil is built up and enriched by dead plant material, it can support small trees that will mature into a forest.

Primary Succession

Secondary Succession

• Series of changes that occur after a disturbance to an existing ecosystem

• Can be a plowed field, a forest or pasture after a fire etc…

• Occurs faster than primary succession because there is already soil

Secondary Succession

A wildfire goes through a grassland burning all of the plant life. Many of the animals are able to escape by running, flying, or burrowing in the ground.

Example of Secondary Succession

The pioneer community is usually made up of grasses and weeds. Insects, small mammals, and reptiles make their homes there.

Example of Secondary Succession

Small shrubs and trees come in next. Larger mammals sometimes begin moving in to the area.

Example of Secondary Succession

As the shrubs and trees grow taller and begin to reproduce, the ecosystem becomes stable.

Secondary Succession

Yellowstone Fires

http://earthobservatory.nasa.gov/Features/WorldOfChange/yellowstone.php?src=yt