Primary vs Secondary Succession

“Succession” is a series of complex processes taking place in the environment due to various driving forces governed by nature. The main causes leading to succession are climatic factors such as erosion, wind, fire, and volcanic activities. The biotic or living forces which drive the process of ecological succession are processes such as migration, aggregation, competition, reaction, etc. that cause changes in the population for short durations.

“Ecological succession” may be classified into various types depending on different parameters. However, the two main types of succession may be grouped as primary succession and secondary succession.

Primary Succession
In any environment, be it terrestrial, marine, or fresh water, primary succession is the first life form that appears on the substratum. In the case of a primary succession, there is no previous living matter of any sort present. The first batches of organisms that establish themselves in that environment are called primary colonizers, primary community, or simply pioneers.

Primary succession occurs where the area is totally devoid of vegetation such as places devastated by volcanic activity or glaciations. Typical examples of primary succession are species such as lichens and algae. They form the base line for other species to sprout up and grow in the area.

Taking an example of volcanic activity, the first living organism to appear on a rock formed on cooled magma are lichens. Due to the activities of these complex organisms, cracking down into the rock takes place which ensures the growth of the next species which are algae and mosses. The cracks in the rocks widen and the formation of soil takes place giving way to grasses and small shrubs which later helps the stabilization of the climax community of conifers.

In a hydrosere, for instance, the primary succession starts with phytoplankton as blue-green algae, diatoms, and bacteria, etc. which later cause the development of rooted, submerged plants, floating plants, reed swamps, sedge meadows, woodlands, and finally forests.

Secondary succession

Secondary succession is another type of ecological succession. This type of succession starts from previously built-up substrata which had the presence of some living matter in the past. This type of succession is forced because the previous population was wiped out due to factors such as sudden steep changes in the climate such as a flood or drought or biotic interventions such as concreting or fire. Due to these factors the area lost the living matter, but the substratum has been modified to sustain living matter and thus the next population developing there is called a secondary succession.

Secondary succession is comparatively faster than a primary succession. Taking the example of a hydrosere where the primary succession has been wiped out due to environmental reasons, a secondary succession ensues in the form of a bog. This moss then results in the growth of higher species.

On a rock where the vegetation has been destroyed by fire, the secondary succession starts with lichens again. The rich, organic matter left over by the fire helps in a quick succession and soon rich conifers are seen in the area.

Summary:

1.Primary succession starts on bare surfaces while secondary succession starts in an area which had been previously inhabited.
2.Primary succession is a slow process; secondary succession is comparatively faster.

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