Ecological Succession and its types and details

ECOLOGICAL SUCCESSION
Online Lecture
Dr. AMIT MITTAL
Department of Allied Sciences, GEHU, Bhimtal Campus
Email: amitforestry26@gmail.com

CONTENTS
• Ecological succession –Introduction.
• Characters of succession.
• Process of ecological succession.
• Primary succession.
• Secondary succession.
• Factors affecting ecological succession.
• Characteristics of climax community.

What is Ecological Succession?
 Succession means when one thing is replaced by the other and
the process is continued till a final stage is reached.
 The term Succession was firstly used by Hult.
 He was the first to recognize that a relatively large number
of pioneer plant communities give way to a comparatively
small number of relatively stable communities (climax
community).
 Is the process of change in the species structure of an
ecological community over time.
 The time scale can be decades or even millions of years after a
mass extinction due to some disturbances.

 Succession may be initiated some of the disturbances such as
from a lava flow or a severe landslide , or by some form of
disturbance of a community, such as from a fire, severe wind
throw.
 The community begins with relatively few pioneering plants or
animals and develops through increasing complexity until it
becomes stable or self-perpetuating as a climax community.

PROCESS OF SUCCESSION
For succession new sites are
needed. In India such new sites are
available for colonization on :
Alluvial deposits:- These include
deposits of sand, gravel and silt by
flowing rivers and rivulets.
Sand dunes :- These are huge
deposits of sand that occur along
the sea shore, banks of rivers and
lakes and in the desert areas of the
world.

Land-slips: These sites are formed by land slides and are very
good sites for succession because the soil contains humus and
mineral nutrients and water is also available.
Screes : These are found in cold mountainous places and rarely
form good sites.
Erosion : Bare areas are also produced by erosion and such sites
are abundantly available all over India for secondary succession.

Volcanic action and Fire : These two natural catastrophes
destroy vegetation and create bare areas that become available
for recolonization or secondary succession.
Glaciers also create new sites. but such areas are rare in
India.

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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
 » 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

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

Pioneer Species
Lichens break down rock
to form soil
Low, growing moss plants

• 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.

• Simple plants like mosses and ferns can grow in the new soil

• 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 .

• These plants die, and they add more nutrients to the
soil
• Shrubs and trees starts growing in that area.

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

• The island of Surtsey formed by volcanic eruption off of the
coast of Iceland during the period from 1963 - 1967
Examples of primary succession

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:

• 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.
• The recovery of a damaged ecosystem in an area where the
soil was left intact.
Secondary Succession

examples of Secondary Succession
1988 – Devastating forest fires at Yellowstone
National Park.
• The Yellowstone fires of 1988 was the largest
wildfire in the recorded history of Yellowstone National
Park in the United States.
• Starting as many smaller individual fires, the flames quickly
spread out of control with increasing winds and drought
and combined into one large fire.
• Only the arrival of cool and moist weather in the late autumn
brought the fires to an end.
• A total of 793,880 acres (3,213 km2) of the park was affected
by the wildfires.

forest fire at Yellowstone National
Park.

One year after the fires
Note the appearance of weed

Ten years after the fires (1998)

Twenty years after the fires (2008)

Difference between primary and
secondary succession

Factors affecting ecological succession
• It includes both biotic and abiotic factors
Abiotic factors:-
1.topography:- Landslides and mudslides are examples of
this type of factor because they cause a massive reformation
of the landscape.
2.soil:- soil type, ph and moisture affect plant that are going
to arise in that area.
Eg; dry condition, moist soils
3.Climate:- Rainfal and temperature, wind play major role
in ecological succesion.

Biotic factors:-
1.Species interaction and competition:-
• pioneer species.
• As diversity increases competition increases dominant
species
only sustain remaining species will die.

Stages of Succession
As soon as the suitable bare site for succession is available
the process involves the following stages :-
1. Colonization :-
• This process involves the invasion of a bare area by the
seeds (seed plants) and spores (cryptogams) of plants
growing in the neighboring communities or from far off
places through the agency of wind, water and animals.

Colonization includes following steps
a. Migration
This is the arrival of reproductive bodies such as seeds, spores and
propagules of plants from other places.
This is affected by wind, water and animals.
The nature of the bare area determines the type of plants that can
grow there.
e.g. the bare area is a pond the seeds of water plants can germinate. In
case the bare area is a desert the seeds of xerophytes will germinate.
So the condition of the bare area determines the type of initial vegetation it
can afford.

b. Ecesis
• This process involves the establishment of the initial plants
on a bare area i.e. the germination of the reproductive
bodies and the growth of the plant to maturity.
• This process is dependent upon the climatic, edaphic
and biotic factors.
• The success of plant depends upon some of the adaptations to
withstand the unfavorable conditions which includes both
biotic and abiotic conditions e.g. dormancy.

c.Aggregation
• It follows ecesis i.e. as the species become established in
an area, they flower, fruit and produce seeds.
• The seeds germinate and the members of the species increase
in number.
• This increase in number of the species is called
aggregation.

d.Competition
• This phenomenon involves struggle for existence between two
or more individuals growing in an area, that make excessive
demands, that are similar in nature on the soil.
• Such a struggle is usually between plants of the same
kind that have similar demands.
e.g. between different types of lichens or between trees, or
shrubs, or herbs, but never between a tree and a lichen or a
tree and a herb.
The competition may be interspecific (or) intraspecific
As a result of competition the weak individuals are eliminated
and stronger ones are retained.

e.Reaction
• This includes the effect of plant growth on the habitat.
• The plants alter habitat conditions.
e.g. they draw raw materials from the environment in large
amounts, and return metabolic wastes.
These wastes accumulate in large amounts and differ from the
original raw materials, thus altering the environments.
The effect of plants on the environment was divided into
two:-
1. On aerial environment (above ground).
2. On soil (below ground).

(c) Divergence in the later stages of succession:
• At early stages number of species will be less and uniform
at later stages the habitat changes the divergence will be
observed in the species.
3.Climax forest
Is the last stage in the process of succession and consists in the
establishment of a definite community which does not undergo
any more durational change.
By this time the environmental conditions also become more or
less uniform.

4.Secondary succession
It take place when a climax forest developed as a result of
primary succession is destroyed by man or as a result of
natural agencies like fire and diseases.

The vegetation is tolerant of environmental
conditions
It has a wide diversity of specie and complex
food
chains.
Individuals in the climax stage are replaced by others
of the same kind. Thus the species composition
maintains equilibrium.
It is an index of the climate of the area. The life or
Characteristics of climax community

REFERENCES
• https://en.wikipedia.org/wiki/Ecological succession
• http://sciencing.com/factors-ecological-succession
• Plant ecology and applied ecology by Vasishta and
Gill.

Ecological Succession and its types and details

Ecological Succession and its types and details

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