Changes in Ecosystems:Ecological Succession

Definition:

• Natural, gradual changes in types of species living in area; can be primary or secondary

• Succession based on changes in plant communities over time.

Primary Succession

• Begins in place w/o soil – Sides of volcanoes where lava flow has

occurred.– Landslides– Flooding

• Step 1: Starts w/ arrival of living things (ex: lichens) - do not need soil to survive

• Called PIONEER SPECIES

http://botit.botany.wisc.edu

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

Primary Succession

• Step 2: Soil starts to form

– Weathering & erosion break down rocks into smaller pieces

– Lichens die & decompose - adding small amounts of organic matter (N,P,C) to the rock to make soil

http://www.life.uiuc.edu

Primary Succession

• Step 3: Simple plants (mosses & ferns) grow in the new soil

http://uisstc.georgetown.edu

http://www.uncw.edu

Primary Succession

• 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

• Step 4: Lower plants die, adding more nutrients to the soil

• Step 5: Shrubs and tress can survive now

http://www.rowan.edu

Primary Succession

• Insects, small birds, and mammals have begun to move in

• What was once bare rock now supports a variety of life

http://p2-raw.greenpeace.org

LAVA FLOWS & PRIMARY SUCCESSION

Secondary Succession

• Begins in a place that already has soil and was once the home of living organisms

• Occurs faster because the land doesn’t have to build up the soil.

• has different pioneer species than primary succession

• Very often occurs after natural disasters such as forest fires, volcanic eruptions involving the spewing of ash.

The Cedar Wildfire was the biggest wildfire in California. It was ignited was caused by a hunter when he lit a flammable shrub called chapparral. These fires burned down about 280,000 acres of land.

2 years after the fire…..

Mt. St. HelensWashington1980’s

http://www.geo.arizona.edu

http://www.ux1.eiu.edu

Climax Community

• A stable group of plants and animals that is the end result of the succession process

Climax Community!

http://www.agen.ufl.edu

Climax Communities are NOT always big hardwood trees such as oaks and maples!!!

Desert Climax Community Beach Climax Community

Grasslands Climax Community Taiga Climax Community