Download Ecological Succession

Changes in Ecosystems:
Ecological Succession
Definition:
• Natural, gradual changes in the types of
species that live in an area
• The gradual replacement of one plant
community by another through natural
processes over time
Examples:
• A glacier recedes, leaving bare earth.
First lichens colonize the area. They are
eventually replaced by tundra plants and
animals.
• A building is demolished. Mosses, the
grasses, then shrubs, and eventually trees
cover the area.
Types of Succession
• Primary Succession – The sequence of
communities that inhabit a lifeless
environment.
– Sides of volcanoes
Types of Succession
• Primary Succession – The sequence of
communities that inhabit a lifeless
environment.
– Sides of volcanoes
– Receding glacier
Types of Succession
• Primary Succession – The sequence of
communities that inhabit a lifeless
environment.
– Sides of volcanoes
– Receding glacier
– Newly formed island
Types of Succession
• Primary Succession – The sequence of
communities that inhabit a lifeless
environment.
– Sides of volcanoes
– Receding glacier
– Newly formed island
– Abandoned parking lot
Types of Succession
• Primary Succession – The sequence of
communities that inhabit a lifeless
environment.
– Sides of volcanoes
– What happens after the lava cools down??
Primary Succession
• PIONEER SPECIES arrive and colonize
the area.
• Pioneer species are able to survive in
harsh environments. They can survive
without soil.
• Pioneers tend to thrive in areas of intense
sunlight and scarce water.
Primary Succession
• Lichens are a common pioneer.
• Lichens are a mutualistic relationship
between a fungus and an algae.
• The algae is photosynthetic (autotroph)
and the fungus holds water and absorbs
nutrients from the rocks.
• Over time the lichens break down the
rocks.
Primary Succession
• As the water freezes and thaws, it breaks
the rocks up further.
• Lichens die and accumulate in the cracks.
• These lichens decompose and create soil.
• Mosses will begin to grow on the rocks.
Primary Succession
• Mosses grow and die, adding to the soil.
The mosses will shade the lichens, which
will die out.
• Eventually, enough soil will be there to
support grasses and weeds. The grasses
will shade out the mosses.
• The grasses and weeds grow and die,
increasing the depth of the soil.
http://www.life.uiuc.edu
Primary Succession
• Shrubs and bushes will eventually replace
the grasses. The grasses will be shaded
out and die.
• Eventually, the soil will become deep
enough to support larger trees. The tall
trees will shade out the shrubs and
bushes.
Primary Succession
• The point where the ecosystem stops
changing is called a climax community.
• What was once bare rock now supports a
wide variety of
species.
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
– Sawgrass in the Everglades
– Wildflowers and short trees in the tundra
Primary succession can be seen happening
in any lifeless area. If left alone, New York
City would turn into a cement filled
woodland.
Primary Succession
• This is a SLOW process. It may take
hundreds of years for the ecosystem to go
through all of the stages of primary
succession.
• Each community alters its environment.
Those alterations make it possible for the
new community to take over.
Secondary Succession
• Begins in a place that already has soil and
was once the home of living organisms
• Occurs faster and has different pioneer
species than primary succession
• Example: after forest fires
Secondary Succession
• The pioneer would be grasses and weeds.
• The changes in the ecosystem would
follow the same sequence we saw in
primary succession.
• However, the progression from pioneer to
climax community would occur much
faster.
http://www.ux1.eiu.edu
Fires
• Fires are a natural part of many
ecosystems.
– They clear out underbrush, leaving rich ash
behind.
– Some species of trees need fire for their
seeds to germinate.
Slash Pines
Subclimax community
Secondary Succession
• Example:
– after a forest fire
– after a flood
Secondary Succession
• Example:
– after a forest fire
– after a flood
– after a hurricane
Secondary Succession
• Example:
– after a forest fire
– after a flood
– after a hurricane
– An abandoned field or building