ECOLOGICAL SUCCESSION BHARATHIYAR UNIVERSITY

1. ECOLOGICALECOLOGICAL
SUCCESSIONSUCCESSION

2. What is Ecological Succession?
• Natural areas are subject to
disturbances of many kinds.
Humans and natural disturbances
such as storms and fires,
hurricane, earthquake etc.,
• Such disturbances have existed so long
that animals and plants have adapted
to them and benefit from their
occurrence

3. • If fundamental requirements are
available for life areas on earth without life
are soon filled with living things.
• The Ecosystem undergo series of patterns
of development called ecological
succession.
• There are two types of succession
– Primary succession
– Secondary succession

4. Primary SuccessionPrimary Succession
• The establishment and development of
an ecosystem in an area that was
previously uninhabited
• The establishment and development of
an ecosystem in an area that was
previously uninhabited
Lichens
and
mosses
Grasses
And
small
shrubs
Large
shrubs and
small trees
Large
trees

5. Primary Succession
• Begins in a place without any soil:
»Sides of volcanoes
»Landslides
»Flooding
• First, lichens that do not need soil to
survive grow on rocks
• Next, mosses grow to hold newly
made soil
• Known as PIONEER SPECIES

6. Pioneer Species
Lichens break down rock to
form soil.
Low, growing moss
plants trap moisture
and prevent soil
erosion

8. Mosses on rocks

9. Primary Succession
• 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

11. • Primary succession can
be seen happening on
the sidewalks.
• If left alone, even NYC
would return to a cement
filled woodland.

12. Primary Succession
• Simple plants like mosses and ferns
can grow in the new soil

13. Primary Succession
• The simple plants die, adding more
organic material (nutrients to the soil)
• The soil layer thickens, and grasses,
wildflowers, and other plants begin to
take over

14. Primary Succession
• These plants die, and they add more
nutrients to the soil
• Shrubs and trees can survive now

15. Primary Succession
• Insects, small birds, and mammals
have begun to move into the area
• What was once bare rock, now
supports a variety of life

16. SurtseySurtsey
• The island of Surtsey formed by volcanic
eruption off of the coast of Iceland during
the period from 1963 - 1967

18. Surtsey – Post EruptionSurtsey – Post Eruption

19. Surtsey TodaySurtsey Today

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Primary Succession

21. 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

25. Secondary succession-

26. Secondary SuccessionSecondary Succession
• The recovery of a damaged ecosystem
in an area where the soil was left intact
• The recovery of a damaged ecosystem
in an area where the soil was left intact
FireweedFireweed
Sequoia seedlingSequoia seedling

27. Yellowstone National ParkYellowstone National Park
1988 – Devastating forest fires burn
much of Yellowstone National Park.

28. Yellowstone National ParkYellowstone National Park

29. Yellowstone National ParkYellowstone National Park
1988 – Park map
showing areas
(1.6 million acres)
burned by the
series of fires.

31. 1988 fires – The immediate aftermath.Photo: National Parks Service

32. • One year after the fires
• Note the appearance of
fireweed

33. • Ten years after the fires (1998)

34. Yellowstone National ParkYellowstone National Park
• Twenty years after the fires (2008)

35. ChernobylChernobyl
• In April, 1986, a
nuclear power plant in
the former USSR
experienced a core
meltdown and a
catastrophic release of
radioactivity into the
environment.

36. ChernobylChernobyl
• Surrounding
towns and
villages had to
be immediately,
permanently
abandoned.

40. Chernobyl – Twenty Years LaterChernobyl – Twenty Years Later
Pripyat town square.

41. Chernobyl – Twenty Years LaterChernobyl – Twenty Years Later
Pripyat Soccer Stadium opened in 1986.

42. Chernobyl – Twenty Years LaterChernobyl – Twenty Years Later
A local highway.

43. Pond Succession

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The Circle of Life in
Secondary Succession

46. PATTERNS OF SPECIES CHANGE
DURING SUCCESSION
• THREE PATTERNS OF INTERACTIONS
AMONG EARLIER AND LATER
SPECIES OF SUCCESSION
– Facilitation
– Interference
– Life history difference
CHRONIC PATCHES

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The Climax Community
• A climax community is a mature, stable community that is
the final stage of ecological succession. In an ecosystem
with a climax community, the conditions continue to be
suitable for all the members of the community.
• Any particular region has its own set of climax species,
which are the plants that are best adapted for the area and
will persist after succession has finished, until another
disturbance clears the area.

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These are Climax Communities

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• Two main physical factors determine the nature of the
community that develops in an area.
These are temperature and the amount of rainfall.
• If we place the amount of rainfall on a graph’s “x” axis,
from 0-10, 10-20,and 20-30+ inches and the temperature
along the “y” axis from hot, moderate, to cold, the various
types of ecosystems will fit into the graph based on the
conditions that they require.
Temperature
Cold Cold desert Tundra Taiga
Moderate Temperate forest Grassland Deciduous forest
Hot Hot desert Savanna Tropical forest
Rainfall (inches) 0-10 10-20 20-30+

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• 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.
A summary of changes that occur during
succession:

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Does Ecological Succession
Ever Stop?
• We must recognize that any ecosystem, no
matter how inherently stable and persistent,
could be subject to massive external
disruptive forces (like fires and storms) that
could re-set and re-trigger the success ional
process.
• As long as these random and potentially
catastrophic events are possible, it is not
absolutely accurate to say that succession
has stopped.

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Does Ecological Succession
Ever Stop?
• Also, over long periods of time (“geological
time”) the climate conditions and other
fundamental aspects of an ecosystem
change.
• These geological time scale changes are not
observable in our “ ecological” time, but
their fundamental existence and historical
reality cannot be disputed.
• No ecosystem, then, has existed or will exist
unchanged or unchanging over a geological
time scale.

53. 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

54. Succession Summary
Succession
Creates new
ecosystem
Restores
previous
ecosystem
Example:
New land
created by
volcanic
eruption
Example:
An area
destroyed
by fire
Primary Secondary

55. Forest Ecosystem