Ecological Succession Notes

Changes in Ecosystems:

Ecological Succession

Changes in Ecosystems:

Ecological Succession

Definition:

• Natural, gradual changes in the types of

species that live in an area

• Can be primary or secondary.
• It is the gradual replacement of one plant

community by another through natural
processes over time.

Primary Succession

• Begins in a place without any soil.

– Sides of volcanoes
– Landslides

• Starts with the arrival of pioneer species

called lichen.

• Lichen do not need soil to survive

http://botit.botany.wisc.edu

http://www.saguaro-juniper.com/

Primary Succession(Stage 1)

• Soil starts to form as lichens and

the forces of weather and erosion
help break down rocks into smaller
pieces

• When the lichens die, they

decompose, adding small amounts
of organic matter to the rock to
make soil.

http://www.life.uiuc.edu

Primary Succession(Stage 2)

• Simple plants like mosses and ferns can

grow in the new soil

http://uisstc.georgetow

n.edu

http://www.uncw.edu

Primary Succession(Stage 3)

• The simple plants die, adding more

organic material

• The soil layer thickens, and grasses,

wildflowers, and other plants begin to take
over

http://www.cwrl.utexas.edu

Primary Succession(Stage 4)

• These plants die, and they add more

nutrients to the soil

• Shrubs and tress can survive now

http://www.rowan.edu

Primary Succession(Stage 5)

• Insects, small birds, and mammals now

move into the area and what was once
bare rock now supports a variety of life.

http://p2-raw.greenpeace.org

Secondary Succession

• Begins in a place that already has soil.
• It was once the home of living organisms.
• Occurs faster than primary succession.
• Examples:

• after forest fires.
• Floods
• Logging operations

http://www.geo.arizona.edu

http://www.ux1.eiu.edu

http://www.agen.ufl.edu

Draw

Directions:  Below are descriptions of the steps of primary succession that occurred in Crater Lake after Mt. Mazama erupted.  Read each description and decide the order of the events.  Type in numbers 1-4 in the right column to indicate the correct sequence of events.

During the years following the explosion of Mt. Mazama, the 4,000 ft deep crater began to fill with water from precipitation.  Eventually, a bird or group of birds landed on the lake.  Their feet would have had any number of algae or phytoplankton attached to them.  These algae cells survived and spread out across the lake.

Primary Succession in Crater Lake

Secondary Succession

• Begins in a place that already has soil.
• It was once the home of living organisms.
• Occurs faster than primary succession.
• Examples:

• after forest fires.
• Floods
• Logging operations

http://www.geo.arizona.edu

http://www.ux1.eiu.edu

http://www.agen.ufl.edu

Climax Community

• A stable group of plants and animals that

is the end result of the succession
process.

• This does not always mean big trees.
• Cacti in desert and grasses in prairies are

not big trees however they are part of a
climax community.

Draw

Directions:  Below are descriptions of the steps of secondary succession that have occurred after a wildland fire.  Read each description and decide the order of the events.  Type in numbers 1-4 in the right column to indicate the correct sequence of events.

Secondary Succession in Crater Lake

Other than volcanic activity, wildland fire is the most powerful and significant natural process that has shaped Crater Lake National Park.  Virtually all vegetation communities show evidence of fire dependence or tolerance.  Research from ecologists show that several forest types in the park have been shaped by the return of frequent fires ranging.  An average of 16.1 fires occur per year within Crater Lake National Park, most are ignited by lightning but 1-2 per year are human caused.