Secondary Succession

Succession can be defined as the change in composition, structure, or architecture of species and vegetation with respect to time. It can take place in all sorts of vegetation and converts one type of vegetation to another. It has subparts called primary and secondary succession. It is an important part of the biological changes happening day by day.

Examples of Succession

• After ploughing a dirty field, someone left it in the summertime. During the summer season, weeds and wild bushes start growing on that field. After the growth of small weeds and grass, some shrubs start growing as well and take root in the land. After a few years, that area or the particular land becomes densely vegetated with trees growing on it.

• Along the coast, a sand beach has small plants that spread their roots in the land. This makes the plants grow faster by providing them with nutrition. On the other hand, it also promotes soil fertility and leads to the growth of shrubs in that area. After a few years, this coast converts to a forest (because the trees take root in land with time).

Primary and Secondary Succession

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 have 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 floods, and earthquakes.

What is 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 for the following reasons.

• The soil is already present.

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

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.

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.) 

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. 

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

• Flooding Accompanied by Severe Soil Erosion

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

Primary Succession and Secondary Succession Differences

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.

Characteristics of Secondary Succession

• Secondary succession is a systematic process focusing on the species and the change in the structure of species.

• In this succession, the changes in species are described as 'directional' and take place in a particular period of time.

• The secondary succession is caused due to the physical environmental changes and variation in a population of species.

• In secondary succession, scientists predicted the changes based on the knowledge and study they conduct in the forests. Therefore, this process is mainly biologically feasible and self-going.

Causes of Ecological Succession

Ecological succession takes place due to: 

• Due to Climatic Factor - Climate conditions such as fast wind, deposits, erosion, fire can become the cause of secondary erosion.

• Activities are done by the organism in the habitat causing Ecological succession in that area.

• Activities such as migration for safety against outside aggregation can also lead to ecological succession.

• Industrialization and urbanization become a cause of migration, which leads to economic succession.

Succession Mechanism 

Successional processes are not predictable in general. But, Clements predicted some stats in the 1920s which proved to be right in the present time. For example, he predicted the increase in species diversity during the successional age. Similarly, one of the examples of primary succession was presented by William Cooper, William Reiners, and more in the year 1925-1975. Also, the retreating of glacier filling has also been seen Since 1794. 

The invasive species are considered as the natural component of succession. Also, recent research studies have examined secondary succession in-depth but cannot determine the exact statistics about it. Hence, secondary succession can be predictable but not accurately.