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Secondary Succession

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Primary and Secondary Succession

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Primary succession is the succession that can be defined as the process of growth of the community in the area that was previously inhabited, barren, unoccupied and there was no initial vegetation found. On other hand, secondary succession is the succession that can be defined as the growth of the community in such areas that were previously occupied, inhabited, and that has primary vegetation but got disturbed or impaired due to some external or internal factors. 

The example of primary sessions is the newly formed bare rocks, desert areas, and sand dunes, etc. whereas an example of secondary succession is the area covered under deforestation or affected by natural calamities such as flood, and earthquake.


Secondary Ecological Succession

The secondary session is one of the two types of ecological succession. In contrast to the primary succession, secondary succession definition states that it is the process started by an event (forest fire, harvesting, hurricane, etc) that minimizes an already settled ecosystem (i.e wheat field or a forest) to a smaller population of species, and as such secondary session occurs on already existing soil whereas primary succession occurs on a place lacking soil. The factors that occur in secondary succession are tropical interaction, initial composition, and competition colonization trade-offs. The factors that prevent an increase in an abundance of species during succession may be identified mainly by microclimate, seed production and dispersal, bulk density, ph, soil textures (sand and clay, etc.) 


Define Secondary Succession

Secondary succession is an ecological succession that comes about after the initial succession has been disrupted and some plants and animals still exist. The secondary succession is usually faster than the primary succession because of the following reasons:

  • The soil is already present

  • Seeds, roots, and underground vegetative organs may still exist in the soil.


Secondary Succession Stages

Following are the steps of secondary succession stages:

  • An area of growth.

  • A disturbance such as fire begins. 

  • The fire destroyed the vegetation.

  • The fire leaves behind empty but does not destroy the soil.

  • Grasses and other herbaceous plants grow back first.

  • Small bushes and trees started to colonize the public area.

  • Fastest growing evergreen tree and bamboo tree develops completely, while shade-tolerant trees develop in the understory.

  • The shorter-lived and shade-intolerant evergreen tree dies as the large deciduous trees overtop them. This ecosystem is not back to the stage where it started. 


Secondary Succession Pioneer Species

Secondary succession occurs in formerly inhabited areas that were disturbed.  The disturbance could be fire, flood, or human activities such as farming. This type of succession is rapid because the soil is already in place. The pioneer species in secondary succession are plants such as grasses, birch trees, and fireweed. Organic matters from secondary succession pioneer species improve the soil. This enables other plants to move into the areas. An example of secondary succession is shown in the figure given below:


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In the above secondary succession figure, two months after a forest fire, the plants that are new are already sprouting or budding the charred logs.


What is Primary Succession?

Primary succession is defined as a change in vegetation that takes place on previously unvegetated terrain.  A few examples where primary succession comes about include the formation of new islands, new volcanic rock, and on land formed from glacier retreats. The initial conditions in primary succession are often harsh, with little or no soil present. The site condition changes slowly in response to the vegetation as soil grows. 

The problem here is that primary succession occurs only on previously unvegetated terrain. However, if the soil continuously develops throughout time and there is a relation between vegetation and soil development, the primary succession never ends.


Primary Succession Examples

Primary succession can occur after the different events. This includes:

  • Retreat of Glaciers

  • Volcanic Eruptions

  • Landslides

  • Nuclear Explosion

  • Oil Spills 

  • Flooding Accompanied by Severe Soil Erosion


Secondary Succession Examples

Some examples of secondary succession slides:

  • A classic example of human-induced secondary succession is an abandonment of cropland.

  • Fire

  • Oak and hickory forests cleared by wildfire is a renowned example of secondary succession.

Following are the key differences between primary succession and secondary succession.


Primary Succession and Secondary Succession Differences

Key Differences

Primary Succession

Secondary Succession

Occurs

It occurs in areas that are lifeless or barren

It occurs in areas that were previously inhabited or recently denuded

Time to Complete

It takes around 1000 or more years to complete 

It takes around 50- 200 years to complete

Humus

Humus is absent in starting as there is no soil

The presence of humus in secondary succession is due to the previous occupants and their decomposition 

Solubility

It dissolves in warm water

It does not dissolve in water 

Soil

Absence of soil in the initial process

The soil is present along with the other organisms

Environment

The environment is unfavourable since beginning 

The environment is favourable since beginning

Seral Community

Many intermediary seral communities are there in primary succession 

Less intermediary seral communities  are there in secondary succession in comparison to the primary succession

Previous Community

No previous community is found in the environment prior to the  primary succession 

Previous communities are present  in the environment prior to the secondary succession

Example

Ponds, desert, bare rocks etc

These are affected by natural calamities, covered under deforestation, etc.


Primary And Secondary Ecological Succession Facts

  • Primary succession is a series of community changes that occurs in an entirely new habitat and has never been colonized before. A  newly quarried rock face or dunes is an example of primary succession.

  • Secondary succession occurs in an area that is previously colonized but disturbed or damaged habitat.  For example, after falling a tree in the woods, land clearance, or a fire.

  • Succession will not move further than the climax community. This is the final stage of succession.

  • The most renowned example of succession deals with plant succession. It is worth remembering that as the plant community changes so will the associated microorganisms, fungus, and animal species. Succession includes the whole community rather than just the plant community.

FAQ (Frequently Asked Questions)

1. What is Ecological Succession?

Ans. Ecological succession is the process of changing the structure of the species of an ecological community over time. These changes result in some species becoming more abundant while others may go into decline. The time duration of ecological succession can be decades (for example, after a wildfire) or even millions of years after the mass extinction. There are two types of ecological succession namely primary succession and secondary succession

2. What are Known as Pioneer Species?

Ans. A pioneer species is the first one to colonize a barren system. These hardy plants and microbial species are the first to return to the environment that has been disturbed by deforestation and wildfires. Once they arrive, pioneer species begin the recovery of the ecosystem by making it more hospitable for the species. This can be processed through nutrition enrichment, soil stabilization, minimization of light availability and wind exposure, and temperature moderation.

3.  What is a Seral Community?

Ans. A seral community is nothing but an intermediate phase of ecological succession progressing towards the climax community.  A seral community is replaced by a subsequent community. It consists of simple food webs and food chains and exhibits a very low degree of diversity. Depending on the substratum and climatic conditions, a seral community can be the following:


Hydrosere - Community on Water

Lithosere - Community on rock

Psammosere - Community on sand

Xerosere - Community on dry areas

Halosere-  Community in saline area.