4.1.5 Changes in Ecosystems: Ecological Succession of a Forest Biome

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4.1.5 Changes in EcosystemsEcological
Successionof a Forest Biome
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Assessment Statements

• 4.1.5 Explain the relationships among ecosystem
  stability, diversity, succession and habitat.
• 2.6.5 Describe the concept and processes of
  succession in a named habitat.
• 2.6.6 Explain the changes in energy flow, gross
  and net productivity, diversity and mineral
  cycling in different stages of succession.
• 2.6.7 Describe factors affecting the nature of
  climax communities.

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Questions to think about

• How does diversity change through succession?
• How are habitat diversity and genetic diversity
  related?
• What provides stability in an ecosystem?
• How does human activity modify succession?
• What factors determine if an ecosystem can
  survive change?

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https//www.youtube.com/watch?vjZKIHe2LDP8
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There are two main types of Ecological Succession

• Primary Succession The process of creating life
  in an area where no life previously existed.
• Secondary Succession The process of
  re-stabilization that follows a disturbance in an
  area where life has formed an ecosystem.

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Succession Defined

• Natural, gradual changes in the types of species
  that live in an area
• The gradual replacement of one plant community by
  another through natural processes over time

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Primary Succession

• The development of an ecosystem in an area that
  has never had a community living within it
• Primary succession generally occurs after a
  natural disaster which lead to a major loss in
  diversity
• Volcanic eruption
• Tsunami
• Meteor impact
• Glacial flow

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Primary Succession

• Begins in a place without any soil
• In the beginning there is only rock, sand,
  volcanic ash.
• Since there is no soil, there is no community.
• Why is there no soil?

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In order for there to be soil there must be
nutrients like nitrogen. So why is there no
soil?
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Primary Succession

• .

• Lichens, algae bacteria begin growing on the
  rocks.
• Harsh conditions but limited competition.
• Over many years lichens break down rock into
  sand.
• Weathering and erosion break down rock into sand.
  

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Primary Succession

• Lichens that do not need soil to survive
• Called PIONEER SPECIES (Why?)

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Primary Succession

• Lichens grow larger.
• Some die.
• Decomposers arrive and break down the lichens.
  The dead lichens and waste materials of the
  decomposers enrich the sand.
• Nitrogen cycle begins. Eventually enough
  nutrients enter the sand and it becomes soil.

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Primary Succession

• Seeds/spores are blown in by the wind or carried
  in by animals. Simple plants like mosses and
  ferns can grow in the new soil
• The plants grow and the soil gets enriched as
  plants die..

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Primary Succession

• Herbs and weeds can grow in the thicker, enriched
  soil
• Roots start holding soil in place

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Primary Succession

• The simple plants die, adding more organic
  material
• The soil layer thickens, and grasses,
  wildflowers, and other plants begin to take over
• More shade

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Primary Succession

• Medium sized animals and birds make this their
  habitat.
• The vegetation grows closer together, reducing
  the amount of space available for growing.
• Competition between lichen and shrubs for the
  same space. Eventually one species (lichen) will
  die out (or move) and the
• other species will survive
• (shrubs).

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Primary Succession

• These plants die, and they add more nutrients to
  the soil
• Shrubs and tress can survive now

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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
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Primary Succession

• These plants die, and they add more nutrients to
  the soil
• Now larger trees can grow Beech, Oak, Walnut,
  Maple

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The Climax Community

• A climax community is a mature, stable community
  that is the final stage of ecological succession.
  In an ecosystem with a climax community, the
  conditions continue to be suitable for all the
  members of the community.
• Any particular region has its own set of climax
  species, which are the plants that are best
  adapted for the area and will persist after
  succession has finished, until another
  disturbance clears the area.

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These are Climax Communities
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• Two main physical factors determine the nature of
  the community that develops in an area. These are
  temperature and the amount of rainfall.
• If we place the amount of rainfall on a graphs
  x axis, from 0-10, 10-20,and 20-30 inches and
  the temperature along the y axis from hot,
  moderate, to cold, the various types of
  ecosystems will fit into the graph based on the
  conditions that they require.

Temperature
Cold Cold desert Tundra Taiga
Moderate Temperate forest Grassland Deciduous forest
Hot Hot desert Savanna Tropical forest
Rainfall (inches) 0-10 10-20 20-30
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Primary Succession
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A summary of changes that occur during succession

• Pioneer species colonize a bare or disturbed
  site. Soil building.
• Changes in the physical environment occur (e.g.,
  light, moisture).
• New species of plants displace existing plants
  because their seedlings are better able to become
  established in the changed environment.
• Newly arriving species alter the physical
  conditions, often in ways that enable other
  species to become established.
• Animals come in with or after the plants they
  need to survive.
• Eventually a climax community that is more or
  less stable will become established and have the
  ability to reproduce itself.
• Disturbances will start the process of succession
  again.

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What if?
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What if?

• Ecosystem Fragmentation?

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What if?

• An avalanche?

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What if?

• Deforestation?

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Threats to Climax Communities

• Forest Fires
• Humans building cities and roads (fragmenting
  ecosystem)
• Clearing a community for agricultural purposes
• Deforestation
• Anything that destroys the existing community,
  but much of the soil remains. Sometimes, some of
  the organisms remain as well.

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Secondary Succession
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Secondary Seccession
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Secondary Succession

• Organisms are destroyed but the soil is safe.
• The soil already contains the seeds of weeds,
  grasses, and trees as well as nutrients. More
  seeds are carried to the area by wind and birds.
• Succession begins again but the primary species
  are different.
• Because soil is present, this succession is
  faster.

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Ecological Succession

• N

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Secondary Succession on an Abandoned Cornfield
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Secondary Succession

• 1. Some seeds in the soil begin to grow.

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Secondary Succession

• Larger shrubs move in.

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Secondary Succession

• 3. Fast growing trees (such as pines) move in
• 4. These are followed by slower-growing hardwood
  trees

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http//www.ux1.eiu.edu
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More Succession Resources

• Mt St. Helens after 30 years https//www.youtube.c
  om/watch?v4RsMyVavT2Q
• Succession Song https//www.youtube.com/watch?vrz
  E6BNNLew0