Ecological sucssion,SUCESSION,HYDROXERE,ECOLOGY,ENVIORNMENT,

1. ECOLOGICAL SUCCESSION
Submitted To- Dr. Ashun
Submitted By – UDAYPAL
Roll. No. – CUHP20PLS30
MSc. Plant Science

2. ECOLOGICAL SUCCESSION
• Ecological succession is a gradual and orderly process of change in an ecosystem brought about
by the progressive replacement of one community by another until a stable climax is establish.
• Each succession begins by a few hardy
invaders called pioneers. Succession ends with
a diverse and relatively stable climax community.
• The entire sequence of communities that
successively change in a given area is called sere.
The individual transitional communities are termed
as seral stages or seral communities .

3. Characteristics of Ecological Succession
• Succession has the following characteristics:
1. It is a systematic process which involves change in species structure.
2. The changes are directional and take place as a function of time.
3. The succession occurs due to the changes in physical environment and
population of species.
4. The changes are predictable and the process of succession is self going.

4. Types of Succession
• Xerach Succession: The succession initiated in extremely dry situations
such as bare land , sand, etc. The different stages in this succession are
called Xerosere.
It can be subdivided ; Lithosere (Xerosere which originates on rock
surface) and Psamosere (xerosere which origin on sand).
• Hydrach Succession: The term refers to succession beginning in water, or in
pond, lake, marshes, etc. The various stages of this succession are called
Hydrosere.
• The succession occurs on saline water is called halosere whereas the
succession that occurs on acidic bog is called oxylosere.

5. • Primary Succession: It is an ecological succession of plant life occurring on sites
which have previously no living organisms (these could be areas where no living
organisms ever existed vegetation) .
The areas where the primary succession takes place are bare rock, cooled lava,
newly created pond or sand or clear glacial . The establishment of a new biotic
community is generally slow. There must be soil before establishment of a biotic
community of diverse organisms. The formation of soil depends mostly on the climate
and it takes several hundred to several thousand years to produce fertile soil on bare
rock.
• Secondary Succession: It is the series of community changes that take place on an
area that somehow, lost all the living organisms that existed there. Secondary
succession begins in the areas where natural biotic communities have been
destroyed such as in abandoned farm lands burned or cut forests, lands that have
been flooded. Since some soil or sediment is present, succession is faster than
primary succession.

6. • Autotrophic Succession: It is characterized by early and continued
dominance of autotrophic organisms like green plants. It begins in a
predominantly inorganic environment.
• Heterotrophic Succession: It is also known as micro-succession. This
involves the succession of micro organisms. It begins in
predominantly organic environment and there is a progressive decline
in the energy content.

7. • Autogenic Succession: The succession in which organisms themselves bring
change in the environment during succession is called autogenic succession.
For example, larger species like trees produce shade on to the developing forest
floor. It destroys the light-requiring species, whereas the shade-tolerant species
in the area get established.
• Allogenic Succession: The succession in which external environmental factors
cause change in the environment during succession is called allogenic
succession. Soil erosion, leaching or the deposition of silt can change the soil.
Animals also play an important role in the allogenic changes. They act as
pollinators, seed dispersers . They can also increase the nutrient content of the
soil in certain areas.

8. • Retrogressive Succession: It is defined as the reversion to some earlier stage of
succession consequent on the introduction of an adverse factor-like excessive
population of herbivores , overgrazing by cattle, felling of tree etc.
• Induced Succession: The climax community has low productivity as compared
to the initial communities. The respiration almost balances the production of
organic matter in climax community. Hence, a very little is left for men to
harvest. Man has controlled succession to obtain a managed steady state to get
maximum amount of organic matter. It is known as induced succession, e.g.
agriculture.

9. General Process Of Ecological Succession:
• Nudation : It is the creation of bare area without any life form. This formation can
be due to landslide, volcanic eruption and soil erosion (topographic factor), or due
to drought, hail, and fire (climatic factor) or due to overgrazing, cutting of trees,
industry, agriculture, housing a disease outbreak, etc. (biological factor). These all
factors cause destruction of existing vegetation and make an area bare of
vegetation.
• Invasion: This is the successful establishment of a species in a bare area. The species
in arrive at this new site from any other area. This whole process is completed in
the following succession stage:
Migration : It starts with migration where some seeds, spores from the nearby
localised reach the bare area through air, water etc. in the form of propagules.
Propagules are a vegetative structure.
Migration is controlled by four factors - agent, distance, mobility and topography.
The first arrival in the bare area is known a pioneer and the occupation of bare area
by these pioneers is called colonization

10. Ecesis: After migration, successful establishment of the species is known as
ecesis. It is no necessary that all the migrated propagules must stabilize.
The stabilization process depends great on the conditions prevailing in that
area, and only those species establish which adjust with the existing
condition.
Aggregation; Number of species increases due to reproduction and they
come to close each other. It may be simple (increase numbers of pioneer
only) or mixed (increase in numbers of pioneer and other invaders).

11. Invasion : New species continue to reach the area after the establishment of
the pioneer. These new species also establish in new area and the process is
known as invasion and the species a known as invader. Only those invaders
establish which adjust with the existing condition.
Competition : After aggregation of a large number of individuals of the different
species at the limited place, there develops a competition.
The competition develop among the individuals of different species
(interspecific) or among the individuals of the same species (intraspecific).
The competition occurs for space, food, light, minerals and water .
Intraspecific is an in competition is more severe because these individuals
require same kind of habitat and nutrition.

12. Reaction: This is the most important stage in succession and it includes method of the
modification of the environment through the influence of living organism on it. Once
the number of different species increases, they have a strong influence on the physical
environment and the mechanism of the modification the environment through the
influence of living organism on it, known as reaction.
Most of the changes occur in soil, water, temperature and light conditions etc. Due to
all these reaction, the environment is modified, (becoming unsuitable for the existing
community which is replaced by another seral community. The whole process of
replacement of one community by other community in the given area in a definite
sequence is known as a sere, and various communities constituting the sere as seral
communities.
Stabilization (Climax): This is the final stage of development and known as climax
community. Climax community is nearly stable and will not change so long as the
climate and physiographic factors remain the same.

13. Hydrosere
• This type of succession starts in a
water bodies like pond and ends in a
climax community as a forest. As
succession continues in such areas,
the environment gradually becomes
drier.
• The hydrosere succession is primary
succession .

14. There are seven stages in the Hydrosere Succession :
• Phytoplankton Stage: The phytoplankton
(phyto-plant, plankton-floating) are the
pioneer community in hydrosere.
• Unicellular floating algae such as diatoms,
blue green algae and bacteria are pioneer
species in a water body. The
phytoplanktons are followed by
zooplanktons. They settle down to the
bottom of the water body after their death
and decay and add organic matter and
nutrients. The organic matter mixes with
the silt and forms a soft mud at the bottom.
As soil builds up, the pond becomes
shallower and favours the growth of the
next seral stage.

15. • Submerged Stage: Some rooted submerged (under the surface) species become
established as the water body becomes shallower. The submerged aquatic
vegetation grows in the regions of ponds and lakes where the water depth is
about 10 feet or more and light can penetrate up to the bottom.
• Once submerged species colonize, the successional changes become more rapid
as organic matter accumulates at the bottom. Consequently, the pond or lake
becomes sufficiently shallow (2-5 ft) due to more humus formation because of
the death and decay of older and buried parts of the submerged plants.
• This changed habitat becomes less suitable for the rooted submerged plants but
becomes more suitable for the growth of floating species.

17. • Floating Stage: The floating species become established in shallow waters of
water bodies. The floating species are rooted in the mud, but some or all of their
leaves float on the surface of the water.
• The floating hydrophytes Azolla, Lemna , Pistia , Salvinia and Wolffia .
• The large and broad leaves of the floating plants shade the water surface and
conditions become unsuitable for growth of submerged species. The plants decay
to form organic mud which makes the pond shallow. This modified environment
becomes suitable for the establishment of reed swamp stage.

18. • . Reed Swamp Stage: This stage is also known as the amphibious stage. When
the water depth is 1 to 3 feet. the pond is invaded by plants that are rooted
with most of their shoots exposed to the air.
• Important plant species of this stage are Phragmites (reed-grasses), Typha
(cattail), and Sagittaria. The foliage leaves of such plants are exposed above
the surface of water and roots are generally either anchored in mud or
submerged in water.

19. • The foliage leaves form a cover over the submerged and the floating plants
which devoid them changes of light. Neither the submerged nor the floating
plants can survive under such conditions of Transpiration, deposition of soil and
plant debris at the bottom of water bodies reduce the depth of water and make
the habitat less suitable for the pre-existing plant species.
• The secondary species such as Polygonum , Sagittaria, etc. start appearing.
Later, these plants also bring about some which make the habitat more suitable
for the next stage of plants.

20. • Sedge Meadow Stage: The successive decrease in
water level finally results in a marshy so which may
be too dry for the plants of pre-existing
communities. Now, the plants well adapted to new
habitat begin to appear in the pre-existing
community in a mixed state.
• The members of Cyperaceae and Graminae families
are well suited to the marshy habitat. The
prominent species of this stage are sedges
(members of the Cyperaceae like Cyperus, Carex,
Juncus, etc.), Mentha, etc.
• As these plants grow in the marshes, they modify
the habitats in numerous ways. They absorb and
transpire large quantity of water and also add to
the accumulating soil at the base. This results in a
dry habitat, totally unfit for the growth of normal
hydrophytes. Gradually, the mesophytes start
appearing, which replace the sedge vegetation later
on.

21. • Woodland Stage; The soil gets dry in due course of time and becomes suitable for
development of wet woodland species.
• It is invaded by Shrubs in the beginning but medium size trees also appear in the later
stages. These plants provide more shade and absorb & transpire large quantity of
water. Thus, they make the habitat drier. Shade loving herbs may also grow under the
trees and shrubs.
• The important plants of woodland community are species of Alnus, Acacia , Cassia,
Terminalia, etc.
• The changed habitat becomes suitable for the growth of final climax stage.

22. • Forest Stage : The woodland stage may lead to the development climax
vegetation in the last stage. The habitat becomes drier and well aerated due to
the raised level of above the water level by progressive accumulation of humus
and soil particles. The stable uniform plant community consisting mostly of
woody trees (i.e. all trees, shrubs ).

23. Thankyou