Download Ecological Succession

Ecological Succession
Succession:
• The gradual replacement of one plant
community by another through natural
processes over time
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 soil already is present
Primary Succession
• The development of an
ecosystem in an area that
doesn’t have a
community living within it
and no soil.
• An area in which a
community has never
lived before, would be a
new lava or rock from a
volcano that makes a new
island.
Primary Succession
• Begins in a place without any soil
– In the beginning there is only rock, sand or
volcanic ash.
– Since there is no soil, there is no community.
Why is there no soil? What is soil?
So … why isn’t there any soil?
Primary Succession
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Primary Succession
• Lichens are a mutualistic symbiotic
relationship between a fungus and a
photosynthetic bacteria (cyanobacteria)
• Lichens begin growing on the rocks
(Pioneer Species – First species to
populate the area after the disturbance).
Over many years lichens break down rock
into sand.
Primary Succession
• Lichens grow larger. Some die.
• Decomposers (detritivores) arrive and
break down the lichens.
• The dead lichens and waste materials of
the decomposers enrich the sand to create
“soil.”
Primary Succession
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Primary Succession
• Seeds are blown in by the wind or carried
in by animals. Simple plants like mosses
can grow in the new soil
• The plants grow and the soil gets enriched
as plants die..
Primary Succession
• Herbs and weeds can grow in the thicker,
enriched soil
Primary Succession
• 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
• Insects, small birds, and mammals wait on
plants to move in (need plants to survive)
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Primary Succession
• The plants die, and they add more
nutrients to the soil
• Shrubs and tress can survive now
Primary Succession
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A summary of changes that occur during
succession:
• Pioneer species colonize a bare or disturbed site. Soil building.
• 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.
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.
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
These are Climax Communities
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Threats to Climax Communities
• Forest Fires
• Flooding, Volcanic eruptions
• Human “Development”
What if?
Secondary Seccession
Secondary Succession
• Organisms are destroyed but the soil is
safe.
• The soil already contains the seeds of
weeds, grasses, and trees. More seeds
are carried to the area by wind and birds.
• Because soil is present, this succession is
faster.
Secondary Succession
•N
Secondary Succession
• Some seeds in the
soil begin to grow.
Secondary Succession
• Larger shrubs move in.
Secondary Succession
• Fast growing trees
(such as pines) move
in
• These are followed by
slower-growing
hardwood trees