Ecological Succession
Both the biotic or living and the abiotic or
non- living components of an ecosystem
change over time.
• Will this landscape of rocks remain this
way forever?
The answer is, “NO!”
• Over the years, one kind of community
is replaced by another kind of
community until eventually, a stable
community develops.
• The gradual change in a community is
known as succession.
Two Types of Succession
• Primary Succession: The process of
creating life in an area where no life or soil
previously existed.
• Secondary Succession: The process of rerebuilding a previously existing community
after being destroyed by some disaster
like fire. Soil exists.
Primary succession
• The development of an ecosystem in an
area that has never had a community
living within it occurs by a process
called PRIMARY SUCCESSION.
• An example of an area in which a
community has never lived before,
would be a new lava or rock from a
volcano that makes a new island.
Primary Succession
• Begins in a place without any soil
– Sides of volcanoes
– Receding Glaciers
• Starts with the arrival of living things such
as lichens that do not need soil to survive.
• Called PIONEER SPECIES
• Lichen is a classic Pioneer species
Pioneer Organisms
• Primary succession on land begins in an area
where there are no living things and no soil.
• The first plants or plant-like organisms that arrive
are called pioneer organisms.
• They can grow on bare rock without soil
eventually breaking it up and helping soil to
form. These include lichens and algae.
Modification of the environment
• Soil starts to form as lichens and the forces of weather
and erosion help break down rocks into smaller pieces.
• When lichens die, they decompose, adding small
amounts of organic matter to the rock to make soil
Creation of New Soil
• Creation of soil allows plants to grow.
Primary Succession
• Simple plants like mosses and ferns can
grow in the new soil
Primary Succession
• The simple plants die, adding more
organic material.
• The soil layer thickens, and grasses,
wildflowers, and other plants begin to take
over.
• Then These plants die, and they add more
nutrients to the soil.
• Shrubs and tress can now survive now.
Primary Succession
• Insects, small birds, and mammals have
begun to move in.
• What was once bare rock now supports a
variety of life.
How does the change of the plants
determine the types of animals in
the community?
• Since plants are the basic source of food
for a community, the types of plants that
are present determine the animals that live
there and eat those plants. Thus, as the
plant populations change, so too do the
animal populations.
Pictures of Succession
• One sequence of plant succession in New
Jersey might be lichens----then----grasses--shrubs----conifers (pine trees)---deciduous forests(beech and maple trees).
Climax Community
• Succession ends with the development of
a climax community. Here, the plants and
animals exist in balance with each other
and the environment. For example, in New
Jersey a hemlock-beech-maple forest is a
climax community. Animals that reside
here include, chipmunks, deer, bear,
turkeys, rabbits, squirrels, fox, birds, to
name a few!
Typical New Jersey State forest
Animals in a hemlock, beech,
maple forest
Animals found in a TYPICAL New
Jersey State forest
Climax communities are stable
• The climax community will exist indefinitely
without further change, unless something
catastrophic occurs. A volcanic eruption or
a forest fire, will alter and possibly destroy
the climax community. Then, ecological
succession begins again and after many
years, a new climax community will
develop.
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
• SECONDARY SUCCESSION begins in habitats where
communities were entirely or partially destroyed by some kind
of damaging event.
• When an existing community has been cleared by a
disturbance such as a fire, tornado, etc...and the soil remains
intact, the area begins to return to its natural community.
Because these habitats previously supported life, secondary
succession, unlike primary succession, begins on substrates
that already bear soil. In addition, the soil contains a native
seed bank.
• Since the soil is already in place, secondary succession can
take place five to ten times faster than primary succession.
Why Does Ecological
Succession Occur?
• Organisms alter their environment
• Organisms become less suitable for
environment
• New organisms better adapted to changes
in the environment come in and out
compete original organisms
A Summary of Changes That occur
During Succession
• Pioneer species colonize a bare or disturbed site. Soil building.
• Changes in the physical environment occur (e.g., light,
moisture).
• New species of plants displace existing plants because their
seedlings are better able to become established in the changed
environment.
• Newly arriving species alter the physical conditions, often in
ways that enable other species to become established.
• Animals come in with or after the plants they need to survive.
• Eventually a climax community that is more or less stable will
become established and have the ability to reproduce itself.
• Disturbances will start the process of succession again.
Does Ecological Succession
Ever Stop?
• No
• Do Humans Affect
Ecological Succession?