Download wfsc420 lesson04

Ecosystem Responses to Disturbance
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Ecological succession
Disturbance and resilience
Evolving ecosystems
Equilibrium Theory
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Ecosystems are stable environments in
which the biotic interactions among
species determine the structure of the
communities present.
Succession and Disturbance
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Ecological succession: transition between
biotic communities
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Primary: no previous biotic community
Secondary: previously occupied by a
community
Aquatic: transition from pond or lake to
terrestrial community
Primary Succession
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Mosses invade an area and provide a place for
soil to accumulate.
Larger plants germinate in the new soil layer,
resulting in additional soil formation.
Eventually shrubs and trees will invade the area.
Primary Succession
Secondary Succession
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Soil present
Most of the biotic community destroyed
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Human development
Landslides
Fire
Secondary Succession
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Growth of Climax Ecosystem limited
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Erosion of soil
Drought
High temperature
Secondary Succession
Aquatic Succession
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Fresh water aquatic ecosystem develops
into a terrestrial ecosystem
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Sediment and detritus fills in pond or lake
Amount of water decrease
Meadow is often a transitional stage
Climax community  bog or forest
Aquatic Succession
Disturbance and Resilience
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Removes organisms
Reduces populations
Creates opportunities for other species to
colonize
Ground Fire
Fire and Succession
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Fire climax ecosystems: dependent upon
fire for maintenance of existing balance;
e.g., grasslands, pine and redwood forests
Forest management necessary
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Burn off brush and debris on forest floor
Germination of new trees
Reintroduce nutrients into soil