Changes in Ecosystems:Ecological Succession

Definition:

• Natural, slow changes in the types of species that live in an area; can be primary or secondary

• The slow replacement of one plant community by another through natural processes over time

Primary Succession: Where no plant has gone before!

• Begins in a place without any soil!

Sides of volcanoes, Landslides, Flooding• Starts with the arrival of living things such as lichens that

do not need soil to survive. They are the pioneer species.

• Soil starts to form as lichens and the forces of weather and erosion help break down rocks into smaller pieces

• When lichens die, they decompose, adding small amounts of organic matter to the rock to make soil

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Primary Succession: Step 1

• Bare stone, but a hint of algae on its face and a bird dropping on top. Those, plus weathering, prepare the stone for lichens.

Primary Succession: Step 2

• A community of lichens have started on the stone, which bit by bit dissolve the rock into nutrients.

Primary Succession: Step 3

• Simple plants like mosses and ferns can grow in the new soil

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Primary Succession: Step 4

• The simple plants die, adding more organic material

• The soil layer thickens, and grasses, wildflowers, and other plants begin to take over

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Primary Succession: Step 5

• These plants die, and they add more nutrients to the soil

• Shrubs and tress can survive now

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Primary Succession: Step 6

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

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

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Secondary Succession: Earth’s way to bandage wounds!

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

• Occurs faster and has different pioneer species than primary succession

• Example: after forest fires.

Something Easier to Understand!

• Where land has been scarred by fire or a disturbance such as plowing, it will soon be covered again with green. Secondary succession is incredibly fast compared to primary succession. Soil is already there, with nutrients. Seeds are already there, seeds of earlier occupants, windblown seeds of pioneer species which exploit disturbed soil (living bandages). After a fire, many seeds germinate in the fire's sudden heat that have waited years for the opportunity. Global warming is already changing the mix of species in temperate zones, and will continue.

Secondary Succession

• Nature see bare ground as a wound, and tries to heal this driveway with dandelions.

• This earth was torn up by truck tires six months ago. Pioneers have moved in. Garden weeds are just pioneers

doing their jobs.

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A Climax Community

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

• Does not always mean big trees– Grasses in prairies– Cacti in deserts

What type of succession is this?

• Here is a picture of a pond scene. With your group determine if this is primary or secondary succession.

• Use the details in your response. What evidence proves your thinking.

Homework

• Identify in what ways your ecosystem has undergone succession. It can be an example of primary or secondary succession, but not both.

• Create a poem that explains the succession of your ecosystem.

Resources

• Source: http://www.morning-earth.org/graphic-e/Transf-Success.htm