This presentation offers a bird's eye view about community dynamics in general and ecological succession in particular with special reference to Climax vegetation.

1. Dynamics: Succession – Processes, Types; Climax
concepts
By
N. Sannigrahi, Associate Professor
Department of Botany
Nistarini College, Purulia (W.B) India

2. COMMUNITY DYNAMICS
 The word, Dynamics’ always states the continuous change
from one state to another. Community dynamics is the process
and change of development in communities of all living
organisms-including plants, microorganisms and the different
kinds of animals of large or small one. It is also called
biological succession. It also defined as the changes in
community structure and composition over time induced by the
environmental factors. Community with stable structure is said
to be equilibrium. After suffering from the disturbances, it may
or may not bring back the equilibrium state. As the succession
level of community, some species will begin to find that
conditions less suitable for reproduction. Due to degree of
unsuitable conditions, the population declines in number and
even the species may suffer from extinction

3. FEATURES
 1. Models of community dynamics allows species to differ in
their basic ecology and responses to environmental fluctuations
and it may investigate the extent to which the species in a
community differ consistently in abundance because of their
ecology and explores how environmental stochasticity
description of some thing that has a random influence upon
community composition in space and time. 2. The rule of
succession-There is a fundamental rule of succession that
drives all thinking and decision making when dealing with the
natural environment;
 ‘ A species will move into an environment when the conditions
are suitable for its establishment, and will move out of that
environment when the conditions become unsuitable for its
reproduction’.
 3. Succession and stability- In a low succession stability, there
are few species present. It is usual for their populations to
fluctuate widely and often rapidly. These are usually very
unstable.

4. FEATURES
 On the other hand, in high successionally community, many
species with limited numbers may lead to a very stable
populations due to their good relationships with the other.
Biological succession is like a coiled spring; when compressed,
succession is retarded but when the compressive force is
released, spring rapidly move upwards.
 The extent of succession- The ultimate or climax level of
vegetative succession in any environment is governed by both
rainfall and location’s position on the brittleness scale but in
ant location under appropriate management, more species can
be induced to establish. In such condition, rest tends to
decrease succession, leading to ecological stability. On the
other hand, rest applied in the non-brittle environment lead to
increase ecological complexity.

5. SUCCESSION
 Community never stable , but dynamic, changing more or less
regularly over time and space. Environment is always kept on
changing over a period of time due to various climatic and
physiographic factors and the activities of the species around
the communities themselves. The process continues and
successive communities develop on one after another
community at the same place until the terminal community
becomes more or less stable for a period of time. The
occurrence of relatively definite sequence of communities over
a period of time in the same area is known as ecological
succession. Different ecologists have interpreted succession in
different time. Clements (1916) defined succession as ‘ the
natural process by which the same locality becomes
successively colonized by different groups of communities of
plants’.

6. SUCCESSION
 Odum (1971) preferred to call this orderly process as
ecosystem development and defined in his own words as
succession based on the following three parameters:
 1. It is an orderly process of community development that
involves changes in species structure and community process
with time, it is reasonably directional and therefore,
predictable.
 2. It results from modification of the physical environment by
the community, that is, succession is community controlled
even though the physical environment determines the pattern,
the rate of change, and often sets limits as to how far
development can go.
 3. It culminates in a stabilized ecosystem in which maximum
biomass and symbiotic function between organisms are
maintained per unit of ‘available energy flow’.

7. CAUSES OF SUCCESSION
 Succession is more properly a series of complex processes that
may be caused by the following:
 1. Initial or Initiating causes: The climatic factors such as
erosion and deposits, wind, fire , lightning, volcanic activities
and various biotic interactions may initiate the process in bare
areas replacing the old one.
 2. Ecesis or continuing causes- These are the process of
migration, ecesis, aggregation, competition, reaction etc which
causes successive waves of populations as a result of changes
in the edaphic features.
 3. Stabilizing causes- These cause the stabilization of the
community. Climate is the most profound causes of
stabilization along with other secondary factors.

8. FACTORS
 The different factors like site conditions, characters of event
initiating succession( Perturbations), interactions of the species
present and stochastic factors such as availability of colonies or
seeds or weather conditions play a very important role in the
succession. In addition to these, human actions and climate
change along with geology and history of an area, soil type also
play a very important role in this regard. The factors of the
succession are stated below.
 1. The climatic factors-Atmospheric temperature, moisture,
humidity, precipitation, sunlight and the climatic conditions of
the neighborhood region also affect the seasonal development
of vegetation of any particular geographical area.
 2. The biotic factors-Activities of living organisms of plants,
animals and human beings play a very important role.

9. FACTORS
 The Competitions among plants for space, sunlight, water or
energy also play an important role in this regard.
 3. The physiographic factors- Nature of ground. Reliefs (
Mountains, plateaus, plains, faults etc) , altitude, depth, slope
angle etc play a very important role in the cause and
consequences of succession.
 4. succession is also influenced by fire factors which include
both natural forest fires and man-made forest fires. The
vegetation community of a large area can be highly affected by
this kind of consequences and that may have detrimental affect
upon the succession.
 5. the edaphic factors like soil structure and temperature along
with soil nutrients play an important role in this regard.

10. TYPES OF SUCCESSION
 The various type of successions are as follows:
 1. Primary succession-The succession which starts from the
primitive substratum, where there is no previously any sort of
living matter. The first group of organisms are called pioneers,
primary colonizers. Pioneers are lichen, mosses etc. primary
colonizers.
 2. Secondary- It starts from previously built substratum with
already existing living matter. The action of external force like
sudden change in climatic factors, biotic intervention, fire etc
causes the existing community to disappear. The area becomes
devoid of living matter but the substratum build up the area for
another succession called secondary succession.
 3. Autogenic-After the onset of succession, the community
itself modifies its environment and thus causing the
replacement of by new communities.

11. TYPES OF SUCCESSION
 4. Allogenic - Replacement of the existing community is
caused largely by another external condition and not by the
existing organisms. Such course is referred as allogenic
succession.
 On the basis of successive changes in nutritional and energy
contents, succession can be the following types.
 5. Autotrophic succession- It is characterized by early and
continued dominance of autotrophic organisms like green
plants. From the inorganic environment to organic
environment, the autotrophic successions continues its journey.
 6. Heterotrophic succession- Characterized by early dominance
of heterotrophs such as bacteria, actinomycetes, fungi, animals
etc. It starts in a predominantly organic environment and
progressive decline of energy content.

12. PROCESS OF SUCCESSION
 Succession is a slow but steady process in course of the
development of communities from barren land till the climax
stage is achieved. The entire process can be divided under
different stages as follows: 1.Nudation - this is the
development of bare or nude area called nudation. The cause of
the nudation may be topographic soil erosion, landslide,
volcanic activity) climatic and biotic.
 2. Invasion – This is the successful establishment of a species
in a bare area and the species may derive from the other area.
The whole process comprises of the three sub-stages-
 A. Migration-Seeds, spores etc disseminated by air, water etc
reach to the bare area.
 B. Ecesis -It is the process of establishment along with their
urge to establish.
 C. Aggregation- Increase in number of the individual species
and come close to each other.

13. PROCESS OF SUCCESSION
 3. Competition and Coactions-As aggregation enables to
multiply the number, there is a mass competitions both intra as
well as inter-specific occurs for space and nutrition. This is
called competition. But individuals of a species affect each
other’s life in various ways and this is called co-action. To with
stand competition, reproductive capacity and ecological
amplitude are the mist determining factors in this regard.
 4. Reaction- The mechanism of the modification of the
environment through the influence of living organism in it
called reaction. Due to reactions, changes in soil, water,
temperature are noticed. Due to modification of the
environment, the existing community becomes unsuitable and
later replaced by another- seral community. The whole
sequence of the communities changes are called developmental
stages or Sere. The pioneers are likely to have low nutrients ,
more dynamic and take minerals in more complex forms.

14. PROCESS OF SUCCESSION
 5. Stabilization (climax) – It is the final stage of succession.
Climax community is nearly stable and will not change until
the climatic and physiographic conditions changes. When the
final terminal community becomes more or less stabilized for a
longer period of time and it can maintain itself in equilibrium
with the climate of the area.
 Very often, retrogressive succession is also coined in which
continuous biotic influences have some degenerating influence
on the process. Due to destructive effect of the organisms,
sometimes the development of the disturbed communities does
not occur and the process of succession become retrogressive
instead of progressive. Very often, forest may changes into
grassland and this is an example of retrogressive succession.
 Sometimes due to change of local conditions like microclimate,
the climax community are likely to be different

15. PROCESS OF SUCCESSION
 From the presumed climatic climax community. This type of
succession is called deflected succession. Very often, monsoon
feed areas like India, different kinds of communities are
observed in different seasons of the tear .It is called seasonal
succession ( Dudgeon, 1921).The gradual changes of
succession is characterized by the presence of different
communities as known as ‘Seres’. A ‘ Presere’ is a collection of
series making up the development of an area from non-
vegetated surfaces to a climax community. Very often,
succession of micro-organisms including fungi , bacteria
occurring within microhabitat is known as micro-succession.

16. CLIMAX CONCEPT
 The final or stable community in a sere is the climax community or
climax vegetation. It is self perpetuating and in equilibrium with the
physical habitat. There is no net accumulation of organic matter in a
climax community. According to Classical ecological theory of F.E.
Clements (1916), succession steps when the sere has arrived at an
equilibrium or steady state with the physical and biotic environment.
Barring major disturbances, it will persist indefinitely. The end point
of the succession is called climax.
 CHARACTISTICS
 1. It is the vegetation of the tolerant of environmental conditions,
 2. It has a wide diversity of species, a good spatial structure and
complex food chain,
 3. It is the index of the climate of the area. The growth forms
indicate the climatic type.

17. CLIMAX CONCEPT
 4. Individuals in the climax stage are replaced by others of the
same kind. Thus the species composition maintain an
equilibrium.
 5. The climax ecosystem is balanced. There is an equilibrium
between gross primary production and total respiration,
between energy used from sunlight and energy released by
decomposition , between uptake of nutrients from the soil and
the return of nutrient by litter fall to the soil.
 TYPES OF CLIMAX
 Different types of climax are observed as follows:
 1. Climatic climax- If there is a single climax and the
development of climax community is controlled by the climate
of the region, it is termed as climatic complex. Maple-beech
community over moist soil is an good example.

18. CLIMAX CONCEPT
 2. Edaphic climax- When there are more than one climax
communities in the region. Modified by the local conditions of
the substrate as soil moisture, soil nutrients, topography, slope
exposure, fire, animal activity, it is called edaphic complex.
Succession ends with the termination of the aforesaid factors.
 3. Catastrophic climax- Climax community may be vulnerable
to a catastrophic event such as a wildfire. The chaparral
vegetation was removed by the wildfire. A rapid development
of herbaceous vegetation follows until the shrub dominance id
re-established. It is called catastrophic climax.
 4. Disclimax - when a stable community is maintained by man
or any domestic animals, it is designated as disclimax or
disturbance climax or anthropogenic sub-climax. Overgrazing
by stock may produce desert community of bushes and cacti
whereas the local climate would allow grassland for dynamism.

19. CLIMAX CONCEPT
 5. Sub climax - The prolonged stage in succession just
preceding the climatic climax is called sub climax.
 6. Preclmax & post climax- If the community has life forms
lower than those in the expected climatic complex, it is called
preclimax. But the community that has life forms higher than
those in the expected climatic climax is post climax. Preclimax
strips are developed in less moist and hotter areas, whereas
postclimax strands are developed in more moist and cooler
areas than that of the surrounding climate.
 Thus, we see that the different types of climax may develop in
the context of the different regulating factors present in the
community-either the edaphic factors of the anthropogenic
factors.

20. THEORIES OF CLIMAX
 A number of theories have been advocated in order to explain
the cause and consequences of the climax development in a
particular community. Here , mainly four theories have been
put forward to explain it.
 1. Mono-climax or Climatic climax theory: It was proposed by
Clements (1916). It mainly recognizes only one climax and its
characteristics are determined by solely climate. The process of
succession and the modification of environment is overcome
the effects of differences in topography, parent material of soil
and other hidden factors. The whole area now becomes
enriched with uniform plant community Savannahs, Prairies
with grassland climax in Canada, USA are some of the
examples in this regard.

21. THEORIES OF CLIMAX
 2. Polyclimax theory: Advanced by Braun- Blanguet ( 1932)
and Tansley ( 1935), this theory advocates that the climax
vegetation of a region consists of more than one vegetation
climaxes are controlled by soil moisture, soil nutrients,
topography, slope, exposure, fire and animal activity. Thus,
there are different types-climatic complex, edaphic complex
and biotic climax depending upon the situation the climax
vegetation has developed.
 3. Climax pattern theory: It was proposed by Whittaker (1953).
It recognizes a variety of climax governed by responses of
species populations to biotic and abiotic conditions. The total
environment of the ecosystem determines the composition,
species structure and balance of the climax community. The
environment includes the species response to moisture,
temperature and nutrients, their biotic

22. THEORIES OF CLIMAX
 relationships, availability to flora and fauna to colonize the
area, the chance of dispersal of seeds, soil, climate and
disturbance such as fire and wind. The climax community
represents a pattern of populations that corresponds to and
changes with the pattern of environment.
 4. Information theory : According to this model, the community
is considered as thermodynamic unit. In the seral stage, the
dissipation energy less than the input energy. There is more net
production and as the time travels, community grows.
Although, at the initial stage, diversity is low but with the
passage of time, total information in the community increases.
In the climax community, the input energy more or less equal
to or slightly higher than output energy.

23. TIME FACTORS FOR SUCCESSION
 Primary succession on sand dunes-----1000 years
 Secondary succession on abandoned agricultural land- 100
years in tropical climate and 200 years in temperate climate,
 Secondary succession in grass lands- 50-60 years under the
following sub-stages :
 Annual weed stage : 2-5 years
 Short lived grass : 3-10 years
 Perennial grass stage: 10-20 years.
 The climax grassland stage : 20-40 years.
 Succession begins in watery habitat like ponds, marshes and
other standing water is known as hydrach and the different
stages of succession called hydrosere and in sand like desert
areas called xerosere.

24. IMPORTANCE OF SUCCESSION
 1. The ecological succession conveys the importance of seral
stages productivity although comparatively less stable. The
climax community is mature and stable with greater biological
diversity, larger in number and energy flow.
 2. The climax community is very important as far as
productivity considering it as multiple use system. Here, the
P/R ratio in such community is one and there is least for NPP
harvesting.
 The early succssional stages act as source of food for
heterotrophy.
 The secondary succession can male the road for renovation of
devastated area to be a climax one.
 The conversion of spoil to soil enhanced by the journey of
succession.

25. THANKS FOR Your visit
 ACKNOWLEDGEMENT
 1.Google for images
 2.Different WebPages for content
 3.Ecology & environment- P.D.Sharma
 4.Ecology & Environmental Biology- T.K.saha
 5. A text book of Ecology- S. Chand & Company.
 6. Plant Ecology & Phytogeography - Arun Chandra Sahu
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