Environmental Studies(ES)

ENVIRONMENTAL STUDIES

Lesson 11: Energy flow in an ecosystem, ecological succession

Ecological Succession

It is a process through which ecosystems tend to change over a period of time. Succession can be related to seasonal environmental changes, which create changes in the community of plants and animals living in the ecosystem. Succession is a natural process by which different groups or communities colonize the same area over a period of time in a definite sequence. Succession comprises evolution of vegetation from its origin to attainment of climax with several limiting factors in between. One can predict that a cleared or open area will gradually be converted into a grass land, a shrub land and finally a wood land and a forest, if permitted to do so without human interference. Developmental stages in the ecosystem thus consist of a pioneer stage, a series of changes known as serial stages, and finally a climax stage – a tropical forest of the pristine nature.

Primary succession/stage: The succession starts from a primitive substratum
without any life building unliving matter.

Secondary succession/stage: It starts from previously built up substratum with living matter.

Autogenic succession: The existing community as a result of its reaction with the environment, causes its own replacement.

Allogenic succession: The replacement of the existing community takes place due
to the influence of any external force, condition etc.

Successional changes in a pond ecosystem includes a dry terrestrial habitat to the early colonization stage by small aquatic species after the monsoon, which gradually passes through to a mature aquatic ecosystem, and then reverts back to its dry stage in summer when its aquatic life remains dormant.