ecological succession : (important info in blue)
Post on 03-Jan-2016
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Communities in Transition
Ecological Succession – The replacement of one community by another until a climax community is reached
May take hundreds or thousands of years
Each new community makes it harder for the old communities to survive.
New environmental conditions allow one group of species in a community to replace other groups.
All communities change their structure and composition in response to changing environmental conditions.
During succession: Pioneer species arrive first.
(Examples only – Write what will help you) A forest hundreds of years old may have
been a shallow lake thousands of years ago.
A dead tree falls and allow sunlight to reach the forest floor. Sunlight allows seeds to germinate. Wildflowers and shrubs grow.
Moss, shrubs, and small trees cover the concrete of an old city building.
Pioneer Species – The first organisms to colonize any newly available area and begin the process of ecological succession. The pioneer organism will alter the
environment so that a bigger and better organism can move in.
Climax Community – A final and stable community.
A climax community can only be disrupted by a catastrophe.
After the catastrophe it will then rebuild itself back up again.
Primary Succession – Succession that occurs on a surface where an ecosystem did not previously exist
Secondary Succession – Succession that occurs on a surface where an ecosystem had previously existed.
Starting from Scratch
Fig. 7-11, p. 156
Exposed rocks
Lichens and mosses
Small herbs and shrubs
Heath matJack pine,
black spruce,
and aspen
Balsam fir,
paper birch,
and white spruce
forest
community
Time
DEFINITION: Succession that occurs on a surface where an ecosystem did not previously exist Examples: Bare rock, newly cooled lava,
abandoned highway or parking lot
Takes a long time because there is no fertile soil to provide the nutrients needed to establish a plant community.
Begins when pioneer species arrive and attach themselves to bare rock. Examples of pioneer species: Lichens and
mosses
Fig. 7-11, p. 156
Exposed rocks
Lichens and mosses
Small herbs and shrubs
Heath matJack pine,
black spruce,
and aspen
Balsam fir,
paper birch,
and white spruce
forest
community
Time
Starting Over With Some Help
Succession that occurs on a surface where an ecosystem had previously existed. Examples: Abandoned farmland, burned/cut
forests, heavily polluted streams, and land that has been flooded
New vegetation can usually germinate within a few weeks from seeds in the soil and those brought in from nearby plants by wind or by birds and other animals.
Secondary succession occurs in ecosystems that have been disturbed or disrupted by humans, animals, or natural processes.
Fig. 7-12, p. 157
Time
Annual
weeds
Perennial
weeds and
grasses
Shrubs
and pine
seedlings
Young pine forest
with developing
understory of oak
and hickory trees
Mature oak-hickory forest
Secondary Succession: Post-fire
Secondary Succession: Old Field
Secondary Succession: Post-Volcano
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