Download Unit 1 Chapter 3 Section 3.1 Natural Disturbances and Succession

11/29/2011
Unit 1 Chapter 3
Section 3.1 Natural Disturbances and
Succession
• Ecosystems are always
changing. Sometimes the
change is rapid and
destructive such as this
forest fire.
• Or slow and constuctive
like lichens growing on a
rock.
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• The charred burn zone on
the right represents the
remnants of a once
forested ecosystem.
• What do you think the area
will look like in 5 years?
• 50 years?
• 100 years?
Succession
• All natural areas change over time, whether or
not you do anything to them. This process by
which a biological community changes over
time is called succession.
What do you notice
happening in this burn zone?
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Types of Succession
• Two types of ecological succession are
generally recognized.
• Primary succession which takes place in areas
lacking soil, and as a result the slow process of
soil build-up must take place.
• bare rocks
• sand dunes
• surface mining areas
• cooled
volcanic
lava
Types of Succession - Secondary
• Secondary succession occurs in areas that were
previously inhabited by plant life but where
plantlife is removed by a disturbance. Soil is
already present and as a result secondary
succession occurs much faster than
primary succession.
• abandoned farm land
• burned forests
• polluted areas
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The Driving Force of Succession
• Succession occurs because some living things
simply by existing create an environment more
suitable to other organisms than themselves.
For Example: Black spruce seedlings cannot grow
in the shade of adult black spruce while balsam
fir seedlings can. As a result the black spruce
forest is eventually replaced by balsam fir.
Succession (cont)
• Pioneer species are the first species to inhabit
an ecosystem undergoing succession.
Primary succession The pioneering species are
usually lichens and mosses.
Secondary Succession –
The pioneering species are
weeds and grasses
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Succession (cont.)
• Climax community is the final community in the
process of succession that remains unchanged
for many years. The plantlife finally creates an
environment suitable to itself.
(Succession Stops).
For example, in Newfoundland and
Labrador a Balsam Fir forest
represents the climax community.
Succession (Review)
• Describe the ecosystem changes that occur
during primary & secondary succession with
respect to each of the following factors.
Changes
(i) soil composition
(ii) plant types
(iii) animal types
(iv) amount of light
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Assignment Questions
Complete questions
1-6 & 8-9 on page 73
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