ECOLOGICAL SUCCESSION

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ECOLOGICAL SUCCESSION
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Ecological Succession

• Change of environment involving a series of
  species replacements in a community.
• Two types
• Primary
• Secondary

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• Primary succession occurs where there is no
  soil, e.g. after a volcanic eruption or a glacial
  retreat
• pioneer organisms
• Simple plants first no or shallow roots.
• Gradual influx of more complicated and larger
  plants as the habitat changes.
• Ends with a climax community ecosystem
  stays constant, provided there are no changes in
  abiotic influences.

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Primary Succession Sand Dune to Forest
Dune grasses?cottonwoodsshrubs?evergreens?oaks?be
eches maples
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Bare rock

• bare rock?lichens?mosses?grasses?shrubs?trees

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Glacial retreat
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Man-made structures
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• Secondary succession begins in an area where
  soil is already present, (e.g. a once cultivated
  field or after a forest fire.)
• Old field succession
• grasses weeds? taller grasses golden rod?
  small trees (cherries, dogwood, sumac) ? mature
  climax forest (oak, beech-maple, hickory)

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Secondary Succession

• Soil already present.

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Pond Succession

• Abandoned field succession

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Pond?marsh?dry land/grasses ?shrubs?forest
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• Pioneer speciesfirst species to begin a
  succession.
• Climax communitythe final stage in a succession.
  

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Primary vs. Secondary

• No soil
• Pioneer species
• Weathering decomposition
• Humus and sand increase over time
• End climax community

• Soil already exists
• Seeds have suitable soil conditions.
• Occurs much faster
• Climax community.

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Secondary Succession

• After a forest fire

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Hurricane
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Table 53.2 The Pattern of Succession on Moraines
in Glacier Bay
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Figure 53.20 Alders and cottonwoods covering the
hillsides
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Figure 53.20 Spruce coming into the alder and
cottonwood forest
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Figure 53.20 Spruce and hemlock forest
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Figure 53.18x1 Large-scale disturbance Mount
St. Helens
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Figure 53.18x2 Forest fire
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THE END