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Interdependent Relationships in Ecosystem- Ecological Succession

Class 8
May 19, 2023


The study of ecosystems is called ecology. The establishment and evolution of communities across time fascinate ecologists or people who study ecology.

Ecologists have spent much time looking at how complex communities like forests arise from naked rock or bare soil.

Henry Chandler Cowles was a botanist and environmental pioneer from the United States.

He was the first to study ecological succession in the Indiana Dunes of Northwest Indiana as a professor at the University of Chicago.

Ecologist Henry Chandler Cowles

Ecological succession is a series of changes that leads to the formation of a relatively stable climax community.


The first life to colonize an area is known as the pioneer community, and the final stage of succession is known as the climax community.

The process leading to the climax community is the successional stages or series.

Increasing production, nutrient shifts from reservoirs, increased diversity of creatures with increased niche formation, and the progressive increase in complexity of food webs are all characteristics of this period.

Pioneer community
Climax community


Primary and secondary succession has been identified as two distinct types of succession.

Primary succession occurs in essentially lifeless areas where the soil is incapable of supporting life due to factors such as lava flows, newly formed dunes, or glacier-retreated rocks.


Secondary succession happens when a previously existing community is destroyed, characterized by smaller-scale disturbances that do not entirely wipe all life and nutrients from the environment.

Land after a volcanic eruption
Small land ecosystem

Primary Succession:

Where there has previously been no community, primary succession occurs.

The new site is first colonized by a few hardy pioneer species, usually microorganisms, lichens, and mosses, in a terrestrial location.

Rock outcrops, newly created deltas, and dunes are examples of such regions; nascent volcanoes are lands and lava flows, glacial moraines (muddy areas exposed by a retreating glacier), and so on.

The pioneers change the ecosystem circumstances by growing and developing over several generations.

The pioneers die, and later, their decomposition leaves patches of organic debris where little animals can survive.

During decomposition, the organic matter produced by these pioneer species has organic acids that dissolve and etch the substratum, releasing nutrients.

Organic detritus collects in cracks and crevices, giving soil for seeds to lodge in and flourish.

Different organisms may be able to establish themselves under the new conditions if they arrive at the spot later.

As the community of organisms grows, it gets more diversified, and competition increases, but new niche opportunities emerge simultaneously.

As environmental circumstances change and new species invade, the pioneer species vanish, replacing the previous community.

Primary succession

Secondary succession:

The progressive growth of biotic communities after the entire or partial destruction of the current society is known as secondary succession.

Natural catastrophes such as floods, droughts, fires, or storms, as well as human interventions like deforestation, agriculture, overgrazing, and other factors, can destroy a mature or intermediate community.

Hardy grasses that can thrive on bare, sunbaked soil are the first to invade this abandoned territory.

Tall grasses and herbaceous plants could soon be joining these grasslands. Mice, rabbits, insects, and seed-eating birds have all dominated the ecology for several years.

Some trees will eventually sprout in this location, with seeds carried by the wind or animals.

A woodland community emerges over time. As a result, an abandoned piece of land becomes overrun with trees and transforms into a forest.

Unlike the primary series, the secondary succession begins on well-developed soil previously formed at the site. As a result, the secondary line moves more quickly.

Secondary succession

Autogenic succession:

Ecological succession driven by biotic components of the environment is known as autogenic succession.

Living creatures cause changes in the composition of an ecological community. For example, when a vast tree matures, its branches cast shade across a large ground area.

The shade-tolerant plant species flourish in that environment.

Furthermore, organic matter deposited in the soil as a result of dead plant and animal matter alters soil nutrients, microbes, pH, and other factors.

Autogenic succession occurs as a result of soil changes. The secondary line begins with the autogenic line.

Shade-tolerant plants
Dead trees
carcass of animal

Allogenic succession:

The ecosystem’s abiotic components (fire, flood) cause allogenic succession.

Grasses have a clever way of monopolizing space. During the dry season, the grasses dry up, causing fires that harm other plant species and their seeds. However, grasslands also flourish where plant development is impossible due to a lack of rainfall.

In most ecosystems, trees are the climax community; however, grasses are the climax community in the grassland environment because of the fire and the lack of water.

Once deforestation in water-scarce places gives way to grasslands, the process is almost irreversible.

Burning Forest
Forest flood
Ecological Succession


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