ECOLOGICAL SUCCESSION

Ecological succession is defined as the observed process of change in the species structure of an ecological community over time. The succession begins with relatively few species called ‘pioneers’, develops through several stages called ‘seral stages’ until it reaches the final stabilized stage called ‘climax community’.

Ecological succession is the gradual process by which ecosystems change and develop over time.

·        Primary Succession: begins on a bare area that has not been previously occupied by any community e.g. newly exposed rock.  

·   Secondary Succession: begins on an area where a community has previously existed but has been destroyed by either natural calamities (landslide, flood, volcanoes) or anthropogenic impacts (deforestation, railway tracks).                    

                                        

Types of succession on the basis of substratum

·        Hydrosere: Succession starts in freshwater

·        Lithosere: Succession starts on rock

·        Psammosere: Succession starts on sand

·        Xerosere: Succession starts in a dry area

·        Halosere: Succession starts in a saline body (e.g. a marsh)

Clement's theory of succession

As per Clement succession involves the following 6 processes:

· Nudation: Succession starts with the formation of a bare area (devoid of vegetation). The process leading to the formation of bare area is called Nudation.

·   Migration: It refers to arrival of propagules (spores, seeds etc.).

·     Ecesis: It involves the establishment of newly arrived propagules and initial growth of vegetation.

· Competition: As newly arrived propagules became well established, grew, and spread, various species began to compete for space, light and nutrients by a process called competition.

·  Reaction: Autogenic changes (changes made by organisms themselves) affect the habitat resulting in replacement of one plant community by another.

·  Stabilization: Reaction phase leads to development of a final community called climax community.