Ecological succession is the orderly process through which ecosystems develop and change over time, ultimately leading to a stable climax community with complex interactions and maximum energy flow. It consists of various stages including pioneer, seral, and climax communities, and can be classified into primary and secondary succession based on the starting conditions. The mechanisms of succession involve a sequence of phases influenced by factors such as nudation, invasion, and competition, with different types of succession depending on environmental conditions.

1. VRINDA VINOD
I MSC BOTANY
SN COLLEGE KOLLAM
ECOLOGICAL SUCCESSION

2. Ecological succession
 Ecological succession is the orderly appearance and
disappearance of communities or ecosystems in an area in
regular succession,until an equilibrium state is attained or
a stable final community is established.
 It is the sequential replacement of communities and it
culminates in a stable climax with high biomass,complex
species interaction and maximum energy flow .
 It is natural ecological as well as evolutionary process by
which an area gets successively colonized by different
communities,until a stable and complex final community
is established

4. Types of Successional communities
 Pioneer communities: it is the first community that develops over a bare
area.It has a very little diversity and takes long time to convert the bare area
suitable for the second or seral communities.
 Seral or transitional communities: These are communities that develop on an
area during biotic succession between pioneer and climax communities.
 Climax communities:it is a stable self perpetuating biotic community with
more complex food webs.

5.  Concept of Climax
 Climax community is the final and the more or less stable
stage of ecological succession.
 Climax community is in steady state or dynamic equilibrium
because it’s net annual organic production,energy level and
density of population are almost kept constant.
 Two kind of climaxes
 Climatic climax ; equilibrium with general climate.
 It is not perfectly stabilized for an indefinitely long period.
 Edaphic Climax : Equilibrium with soil conditions.

6. Mechanism of ecological succession
 Mechanism of ecological succession involves a
continuous, sequential and unidirectional change in
the species composition of a natural community.
 It is completed in three broad phases by the operation
of eight major mechanisms.
 The three phases are ;-
 1.Initiation phase
 2.Continuation phase
 3.Termination phase

7.  The major mechanisms responsible for ecological
succession include;-
 1.NUDATION
 2.INVASION
 3.ECESIS
 4.AGGREGATION
 5.COMPETITION
 6. COACTION
 7.REACTION
 8.STABILISATION/ MATURATION

9. Types of Ecological succession
 1.Primary & Secondary succession (Based on
starting)
 2.Autogenic and Allogenic succesion (Based on
Cause)
 3.Autotrophic and heterotrophic Succession
(Based on community)
 4.Hydrosere and Xerosere( Based on substratum)

10.  PRIMARY SUCCESSION
 . Starts from an area where there was no previous
living matter.
 . Example –succession on bare rock, newly dug out
pond etc
 . First community establishing the new area-
pioneer community (lichen, phytoplankton)
 . Relatively slow and long term process
 . Seral stages of primary succesion are called
primary seres/priseres.

11.  SECONDARY SUCCESSION
 . Starts from a previously built-up substratum(already
existing living matter)
 . Sudden changes causes the disappearance of the existing
community.
 Example –fire, snowfall, biotic interventions
 . Thus the area leaving very few organisms and plenty of
organic matter.
 . Relatively short tern process and faster than primary
succesion because nutrients are already available and
environmental conditions are more favourable.
 The seral stages of secondary succession are called
secondary seres or sub-seres.
 Example –succession on fire destroyed grasslands, cleared
forests etc.

12. Based on Cause :
 Autogenic / Biotic succession
 It is self driven and it involves the interaction
btw organisms and their environment.
 Allogenic succesion
 Replacement of existing community by external
conditions and not by the existing organisms.
 This is common in polluted ponds, areas of
massive soil erosion etc.

13. Based on Community :
 Autotrophic succession
 Mainly green plants are the dominant species.
 Heterotrophic succession
 Detritivorous heterotrophs are the dominant
species (eg:Bacteria, fungi, animals)

14. Based on medium and substratum

 Hydrarch succession(Hydrosere)
 . Ecological succession in stagnant fresh water bodies,
such as pools, ponds, lakes, marshes, swamps etc.
 Starts with the colonisation of the water body by
phytoplanktons which form the pioneer community. From
this stage onwards, succsssion proceeds to climax stage,
represented by large trees or forest.
 Different stages of hydrosere are:-
 Phytoplankton stage Rooted submerged stage Rooted
floating stage Reed-swamp stage sedge-meadow
stage woodland stage forest stage.

16.  XEROSERE (xerarch succession)
 Ecological succession in xeric (dry habitats)such as bare
rocks, wind –blown sand, rocky slopes, etc where there
is an extreme scarcity of water is termed as xerarch
succession.
 It is of two kinds.
 A)lithosere : succession on bare rocks
 b)psammosere : succession in sandy deserts.

18.  Mesosere: succession in moderately moist land regions.
 Halosere : succession in saline water or saline soil.
 Oxylosere: succession in acidic water or soil.