Basic Types of Succession

Based on different criteria, there are following kinds of succession:

Primary succession
If an area in any of the basic environments (such as terrestrial, fresh-water or marine) is colonized by organism for the first time, the succession is called primary succession. Thus, primary succession begins on a sterile area (an area not occupied previously by a community), such as newly exposed rock or sand dune where the conditions of existence may not be favorable initially.

Secondary succession
If the area under colonization has been cleared by whatsoever agency (such as burning, grazing, clearing, felling of trees, sudden change in climate factors, etc.) of the previously plants, it is called secondary succession. Usually the rate of secondary succession is faster than that of primary succession because of better nutrient and other conditions in area previously under plant cover.

Autogenic succession
After the succession has begun, in most of the cases, it is the community it self which, as a result of its reactions with the environment, modifies its own environment and, thus, causing its own replacement by new communities. This course of succession is known as autogenic succession

Allogenic succession
In some cases replacement of one community by another is largely due to forces other than the effects of communities on the environment. This is called allogenic succession and it may occur in a highly disturbed or eroded area or in ponds where nutrients and pollutants enter from outside and modify the environment and in turn the communities.

Autotrophic succession
It is characterized by early and continued dominance of autotrophic organism such as green plants. It begins in a predominantly inorganic environments and the energy flow is maintained indefinitely. There is gradual increase in the organic matter content supported by energy flow.

Heterotrophic succession
It is characterized by early dominance of heterotrophic organism such as bacteria, actinomycetes, fungi and animals. It begins in a medium which is rich in organic matter such as small areas of rivers, streams; these are polluted heavily with sewage or in small pools receiving leaf litter in large quantities.

Induced succession
Activities such as overgrazing , frequent scraping , shifting cultivation or industrial pollution may cause deterioration of an ecosystem. Agricultural practices are retrogression of a stable state to a young state by man’s deliberate action.

Retrogressive succession
It means a return to simpler and less dense or even impoverished form of community from an advance or climax community. In most cases, the causes are allogenic, i.e forces from outside the ecosystem become severe and demanding. For example, most of our natural forest stands are regarding into shrubs, savanna or impoverished desert-like stands by the severity of grazing animals brought from surrounding villages. Excessive removal of wood, leaf and twig litter also leads to retrogressive succession.

Cyclic succession
It is of local occurrence within a large community. Here cyclic refers to repeated occurrence of certain stages of succession whenever there is an open condition created within a alarge community.