Ecosystem

Ecological succession


  • Every community undergo a series of changes until a group of organisms is established which can live and reproduce most successfully in the area. This is called as biotic or ecological succession.
  • A biotic community is influenced by biotic factors physio - chemical changes factors and geographical factors.
  • Types of successional community
    Pioneer community → 1st community which appears on an area. Eg: lichens on rocks
    Serial community → pioneer community is followed by specific orderly sequence of series of plant communities. Eg: Bryophytes herbs, shrubs in xerophytes
  • Climax community is the last community. (mostly depends on climate. Eg: Forests, it is relatively stable).
  • Ecological succession is of two types 1° and 2° succession (depends on type of nudity of the area)
  • 1° succession occurs on biologically sterile area which has no record of any previous vegetation. eg: Newly created pond, new exposed rock area, soul dunes, igneous rocks
  • 2° succession occurs on an area which was previously occupied by vegetation, that was later destroyed by fire, deforestation, over graxing, volcanic eruptions and floods etc so it takes 100-200 years to complete.
  • Autogenic and allogenic succession : when a community replaces the other due to modification of the environment by the community itself, the succession is said to be allogenic when a community replaces the other largely due to the forces other than the effects of communities on the environment.
  • Autotrophic succession is characterized by early dominance of heterotrophs and beings in predominantly inorganic environment.
  • Heterotrophic succession is characterized by early dominance by heterotrophs and beings in a predominantly organic environment.
  • Contents of ecological succession.
    Hydrosene (succession on pond)
    (i) Plankton stage: eg: diatoms, bacteria etc. (pioneer stage)
    (ii) submerged stage: eg: Hydrilla, vallisneria, Najas
    (iii) Floating stage: eg: Nymphaca, Azolla, Lemna, etc.
    (iv) Reed swamp: eg: sagittaria, typha, scirpus etc.
    (v) Marsh/sedge meadow: eg: Juncus, cyperas.
    (vi) Woodland: eg: salix, populus, etc
    (vii) Climax: eg: Acer, quercus etc.

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