Ecological succession

Ecological succession refers to the gradual and sequential replacement of one community by another until a more stable community, known as the climax community, is established in the area. This process occurs in an organized and predictable manner.

• The term "ecological succession" was originally introduced by Hult in 1885, during his research on the communities of Southern Sweden.

Features of Ecological Succession-

• It is an orderly process.

• It is the modification of existing community to become stable community with the passage of time.

• It moves from low permanency to High permanency in Nature or in any ecosystem.

Some terms and definitions related to ecological succession

1.Pioneer community-

• The first organisms to become established in an ecosystem undergoing succession are called pioneers and they are unstable in nature.

2.Climax community-

• The final and stable stage of ecological succession, where the community of organisms reaches a state of equilibrium with its environment, is commonly referred to as the climax community.

It has further sub classification or some other definitions

Disclimax -

• Disclimax, also known as disturbance climax or anthropogenic subclimax , refers to a stable community that is sustained by human intervention or the presence of domesticated animals, even though it is not the natural climatic or soil-based climax for the specific site.

Subclimax -

• Subclimax refers to the extended phase in the process of ecological succession that occurs immediately before the climax community is established.

Preclimax -

• In the preclimax stage, it is possible for a community to have life forms that are less developed than what is typically found in the expected climatic climax.

Postclimax -

• Postclimax refers to a community of organisms that exist beyond what would typically be expected in a particular climatic climax.

• These life forms are more advanced or developed than those found in the expected climax community.

3.Seral community –

• The term "seral community" refers to a transitional stage that occurs during ecological succession as an ecosystem progresses towards its ultimate climax community.

4.Sere –

• A sere is the sequence of communities involved in an ecological succession in a particular area.

• The succession may start from grass, then to shrubs, and ultimately to a stable climax community.

• The final stage in the sere is considered the most stable and self-sustaining community.

• Ecological successions may be primary or secondary depending on whether the process starts from an area with no previous ecosystem or from a disturbed ecosystem, respectively.

• The process of sere is essential for the regeneration of ecosystems and can take many years to complete.

5.Seral stage –

• Each of the changes that take place is a seral stage.

6.Serule-

• It is the micro succession of bacteria and fungi on the decaying woods or barks.

• It occurs in the microhabitat and leads to the mesophotic forest.

• It includes both Primary and secondary succession.

Process of Succession-

A.Formation of suitable area

• It is also called as Nudation.

• It is formed by several reasons, such as volcanic eruption , Landslide , flooding , erosion , deposite , fire, disease, or other catastrophic agency.

B.Invasion-

• It is the process of arrival of reproductive bodies in the suitable area and it includes Dispersal of reproductive body.

• Ecesis refers to the process of a migrated plant species thriving and successfully establishing itself in a new environment.

• Collection of aggradations of these bodies in that suitable area is another step.

• And finally, that aggraded part gets further enhanced and turns into a community.

Types of Ecological Succession

1.Primary Succession -

• Primary succession is the natural process of colonization and replacement of species in an environment that is initially devoid of life.

• It begins in areas where there is no soil or where soil has been completely destroyed by volcanic activity, glaciers, or erosion.

• The first organisms to colonize the area are usually lichens, which are capable of growing on bare rock and breaking it down to form soil.

• As soil begins to form, other species such as mosses and ferns can establish themselves, creating a more stable environment for plant life to thrive.

• Eventually, shrubs and trees can take root, forming a complex ecosystem that supports a wide range of plant and animal life.

• Examples. Volcanic eruptions, Rocky Areas etc.

2.Secondary Succession-

• Secondary succession refers to the natural process of ecological change that takes place after an ecosystem has been disturbed, but not destroyed completely.

• This process involves the gradual replacement of plant and animal species over time, starting from the remnants of previously established organisms that have survived the disturbance.

• The damage to the vegetation can occur due to various climatic factors such as flood, fire, or acid rain.

• Unlike primary succession, which occurs on barren land that has never before supported life, secondary succession occurs on land where there was previously some form of vegetation cover.

• As a result, secondary succession tends to occur more quickly than primary succession, as there is already a pre-existing soil base and organic matter to support the growth of new plants.

3.Autogenic Succession-

• Autogenic succession is a natural process of ecological succession driven by biotic components of an ecosystem.

• As the developing plant community changes the condition of a particular area, it may become unsuitable for the original community but creates an environment conducive to the growth of a different community.

• This process involves the alteration of abiotic factors, such as soil nutrients and microclimates, which leads to the emergence of new plant species that are better adapted to the changing conditions.

• Over time, the original plant community may be replaced entirely by the new community, resulting in a more diverse and stable ecosystem.

• Autogenic succession is different from allogenic succession, which is driven by external factors such as disturbances, and occurs more gradually.

4.Allogenic Succession-

• Allogenic succession is a type of succession in an ecosystem that is primarily driven by abiotic factors.

• This is in contrast to autogenic succession, which is primarily driven by biotic factors.

• Allogenic succession occurs when the ecosystem's habitat is altered due to various factors such as volcanic eruption, climate change, comet strike, earthquake, flood, drought, and other natural disasters.

5.Induced Succession-

• It is a man-made process, developed for the benefit of the humankind.

6.Autotrophic Succession-

• When a place is rich in inorganic content & poor in organic matter, the development of succession of plants over that area is called as autotrophic succession.

• In it the energy flow is maintained indefinitely. 

7.Heterotrophic Succession-

• If a succession begins in an area which is rich in organic contents like forest litter, sewage etc , and dominated by saprophytes like fungi , mushrooms etc. is called heterotrophic succession.

• In it there is a progressive decline in the energy content.

8.Retrogressive Succession-

• In certain cases, succession can experience regression instead of progression, as a result of significant biological or biotic interferences.

• Example- Forest community changes to a shrub land or grassland or to a barren land due to deforestation and overgrazing. 

Types of Seres

Hydrosere -

• Succession in aquatic habitat.

Xerosere-

• Succession in dry habitat.

Lithosere -

• Succession on a bare rock surface.

Psammosere -

• Succession initiating on sandy areas.

Halosere -

• Succession starting in saline soil or water.

Senile-

• Succession of microorganism on dead matter.

Eosere -

• Development of vegetation in an era. 

Some remaining concepts in Ecology

Ecotone-

• An ecotone refers to an area of transition between two different biomes with distinct ecosystems.

• It is a zone of junction where two distinct communities meet and integrate with each other.

• Ecotones can occur in both terrestrial and aquatic environments.

• The transitional zone of ecotones often has unique and diverse species of flora and fauna that are different from the adjacent biomes.

• Ecotones are critical for the conservation and management of biodiversity as they provide habitats for a wide range of species that are adapted to living in the transition zone.

Examples-

• Mangrove forests are a unique ecosystem that serves as an interface between marine and terrestrial environments.

• They also act as an ecotone, connecting other ecosystems such as grasslands (between forests and deserts), estuaries (between freshwater and saltwater), and riverbanks or marshlands (between dry and wet environments).

Characteristics of Ecotone

• Ecotone refers to a transitional zone between two adjacent ecosystems with conditions intermediate to both ecosystems, making it a zone of tension.

• Ecotone may vary in width, ranging from narrow (between grassland and forest) to wide (between forest and desert).

• The number and population density of species found in the outgoing community usually decrease as we move away from the community or ecosystem.

• A well-developed ecotone may contain some organisms that are unique and entirely different from the adjoining communities.

Edge effect –

• The edge effect pertains to the changes that occur at the boundary between two distinct biological communities or landscape features.

• This effect is characterized by differences in the population or community structure that occurs at the boundary of two habitats.

• As edge effects increase, the boundary habitat provides more opportunities for greater biodiversity.

• Species that are mainly or abundantly found in this area are referred to as edge species.

Types of Edge Effect-

1.Narrow—

• In this case One habitat abruptly ends and another begins. 

2.Inherent—

• Natural features stabilize the border location. 

3.Induced—

• "Induced edge effect" refers to the phenomenon where both natural and human activities can cause borders to undergo successional changes over time.

• This can be a transient effect, meaning it is not a permanent change, but rather a temporary one.

4.Wide—

• Substantial distance separates border from point where physical conditions and vegetation do not differ from interior of patch.

• It is a type of Ecotone. 

5.Perforated—

• In this case Borders have gaps that host other habitats.

Ecological Niche

• An ecological niche is the functional position and role of an organism in its environment.

• It is determined by the physical and biological conditions that affect the organism's survival and reproductive success.

• A niche is unique to a species, even if many species share the same habitat.

• No two species can occupy the same niche in a habitat because of the competition between them, which often results in the displacement of one species.

Types of Niches -

A. Fundamental niche-

• A fundamental niche refers to the specific ecological niche that an organism occupies when there are no other competitors or predators present in its environment.

B. Realized niche-

• It is referred to as the role an organism actually plays in the community.

• For example, the outcome of inter-specific competition leads to either extinction or the development of differences allowing coexistence.

C. Spatial / habitat niche –

• It represents the physical space occupied by an organism. 

D.Food niche –

• It defines Niche on the basis of what any organism eats or decomposes & what species it competes with. 

Difference between Habitat and Niche-

• A habitat is an area, where a species lives and interact with the other factor sand a niche is an ideology, of how an organisms lives or survive in the provided environmental conditions.

• Habitat consists of numerous niches. Niches does not contain such components.

• Habitat supports numerous species at a time. Niche supports a single species at a time.