APES UNIT 2.7

Ecological Succession

The process of one community replacing another as a result of changing abiotic

and biotic factors, often through a disruption

Primary Succession

The establishment of a community in an area of bare rock that does not have

topsoil.

• Nuclear Explosion

• Mountain top removal for mining

• Volcanic Eruption

• Retreating Glacier

Pioneer Species

The first organisms to appear in an ecosystem

What happens when an ecosystem is in equilibrium?

there is no net change in the number of species.

New species come into the community at about the same rate that others leave the community.

climax community

stable, mature community in which there is little change in the number of species

Secondary Succession

the orderly and predictable change that takes place after a community of organisms has been removed but the soil remains

• Logging, mining, clearing land for agriculture

• Forest fire by lighting 

Keystone Species

species that is not very abundant but has a large effect on an ecological community, significant role.

• ex. Ecosystem Engineers: organisms that create, destroy, or change a habitat –

  Example = beavers. Bees (pollinators).

Indicator Species

A species that demonstrates a particular characteristic of an ecosystem

• ex. Indicator species are often used “to characterize when ecosystems have been

  negatively impacted by humans or when ecosystems are rebounding from some

  harmful impact.”

Typical secondary succession order

1. Pioneer Species: Lichen and Moss secrete acid to break down rock into Soil

   1. They die and add nutrients into ground

2. 1-2 Years: Small weedy, annual plants

3. 3-4 Years: grasses and perennials

4. 5-150 Years: Grasses, shrubs, pines, young oak, hickory

5. 150+: Climax: Mature oak and hickory forest