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Ecological Succession
Soil
Grass
Shrubs
Small
Trees
Large
Trees
In this presentation you will:
 explore the role of ecological succession
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Introduction
Ecological
Succession is a
gradual, predictable
change to the
plants and animals
in an ecosystem.
It is the process by which an area that is
completely bare of any vegetation could
eventually become a forest.
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Abrupt Changes
Sometimes an abrupt change can occur, that can
cause a drastic change to an ecosystem.
For example forest
fires, floods, wind
storms and volcanic
eruptions.
Events such as these
can destroy whole
ecosystems and leave
the earth bare.
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Ecological Succession
The biotic (living) and abiotic (non-living)
factors of an ecosystem work together in
equilibrium (balance).
The process of ecological
succession can repair
damaged ecosystems to
restore this equilibrium and
enable life to thrive again.
Succession can be
primary or secondary.
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Question 1
“Succession refers to the progressive, predictable and
long term changes to an ecosystem.”
Is this statement true or false?
Answer true or false.
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Question 1
“Succession refers to the progressive, predictable and
long term changes to an ecosystem.”
Is this statement true or false?
Answer true or false.
True
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Primary Succession
Primary succession is the
introduction of organisms
into an area not inhabited
by any organisms.
For example bare rock,
lava after a volcanic
eruption or a sand dune.
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Primary Succession
Bare rock will first be
colonized by a pioneer
species that is able to
tolerate hostile conditions
and make its own food.
Lichen is often the
pioneer species.
They produce acids that
help to break rock
surfaces into small pieces.
Lichen
This helps to create the first soils.
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Stages of Succession
Over many years, the soil gets deeper and
mosses grow.
As they die,
their nutrients
are added to the
soil and so the
soil improves.
Grasses replace
mosses.
Soil
Grass
Shrubs
Small
Trees
Large
Trees
As succession progresses, conditions in the habitat
change and become less suitable for some species
but more suitable for others.
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Stages of Succession
These species thrive and become the next dominant
species.
This continues with the
dominant species being
replaced at each stage.
After hundreds of years
the soil is deep enough
and rich enough to
support a woodland.
Soil
Grass
Shrubs
Small
Trees
Large
Trees
This community remains relatively unchanged and is
called the climax community.
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Question 2
An area of woodland had once been bare rock.
During the process of succession, what would have
been the first species to inhabit the area?
A) Lichen
B) Grass
C) Shrubs
D) Large trees
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Question 2
An area of woodland had once been bare rock.
During the process of succession, what would have
been the first species to inhabit the area?
A) Lichen
B) Grass
C) Shrubs
D) Large trees
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Secondary Succession
An event like a fire may seem
to destroy an ecosystem, but
dead organic matter and any
surviving organisms could be
the beginning of a new
community.
The new community would
change through time until it
reached its climax
community once more.
This is secondary succession.
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Importance of Succession
Ecosystems are constantly
changing.
Fires, floods and
volcanoes frequently
occur all over the world.
Without succession, a disturbed
ecosystem would never recover.
What would our world
be like if ecosystems
could never recover?
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Question 3
Consider a lawn that is constantly being mown. Why
does it never reach the climax community stage?
A) Succession is interrupted each time it is mown
B) Plants cannot grow where grass grows
C) Both of these
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Question 3
Consider a lawn that is constantly being mown. Why
does it never reach the climax community stage?
A) Succession is interrupted each time it is mown
B) Plants cannot grow where grass grows
C) Both of these
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Observing Succession
Succession is not limited to large areas, but occurs
all around us.
A garden cleared of
vegetation and a
concreted area both
have the potential to
turn into a woodland.
You could see this for
yourself by observing a
cleared area of a garden.
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Succession in a Microhabitat
In an area of garden that
is cleared back to soil,
place a series of quadrats
in the area and leave
them there.
Quadrat
If you do not have a
quadrat available, you
could mark out areas
using sticks and string.
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Succession in a Microhabitat
Over the next few months, study the quadrats or
marked areas on a regular basis.
Observe the types of
life that begins to form.
In a journal make a
note of the date and
the plants observed.
Quadrat
You could also monitor the soil
to see if there is any change in
the amount of organic matter
as the plants grow and die.
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Succession in a Microhabitat
A very simple way would be to take a small sample
of soil using a graduated cylinder (or a beaker).
Add water to the sample
and swirl the cylinder to
mix the soil and water.
Left to settle, the
sample will separate
and the organic matter
will float to the surface.
Use the graduations on the side of the cylinder to
observe the amount of organic matter.
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Succession in a Microhabitat
Over the next few months, record the types of
plants that begin to grow there and how the soil
changes.
You would probably
find that the first plants
would be small plants
you would consider to
be weeds.
Eventually these weeds would give way to grasses
and then to larger plants. If you left it long enough
you would see trees.
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Question 4
What type of succession does the investigation
represent?
A) Primary succession
B) Secondary succession
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Question 4
What type of succession does the investigation
represent?
A) Primary succession
B) Secondary succession
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Question 5
Which of the following is not true about ecological
succession?
A) A parking lot could eventually become woodland
B) It enables disturbed or damaged ecosystems to
repair themselves.
C) Succession results in a stable community called
the climax community.
D) The first dominant species will remain throughout
all stages of succession.
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Question 5
Which of the following is not true about ecological
succession?
A) A parking lot could eventually become woodland
B) It enables disturbed or damaged ecosystems to
repair themselves.
C) Succession results in a stable community called
the climax community.
D) The first dominant species will remain throughout
all stages of succession.
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Summary
In this presentation you have seen:
 the role of ecological succession
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