Maarg Manthan · Topic 1.10

Ecological Succession: Types and Process

Environment & Ecology › Basic Concepts of Ecology · Topic 1.10

Ecological succession is the orderly, gradual and predictable change in the species composition of a community over time, leading to a more stable community. It begins with pioneer species that colonise a bare area, followed by a series of seral stages, and ends in a stable climax community. Primary succession starts on a site that has never had life or where all life and soil were lost, such as bare rock, a lava flow or new sand dune, and it is very slow, taking hundreds to thousands of years. Secondary succession starts where an existing community has been removed but soil and seeds remain, such as after a forest fire, flood or abandoned farmland, and it is faster. Succession on rock is a lithosere, on water a hydrosere, on dry land a xerosere, and on salty soil a halosere.

5 min read · UPSC Prelims · Environment & Ecology · Basic Concepts of Ecology

At a Glance

Starts on Bare area (primary)
Starts with soil Secondary
First species Pioneers
Water series Hydrosere
End Climax community
Exam link UPSC Prelims, Environment & Ecology: Basic Concepts of Ecology

Where Does It Fit?

This topic follows the account of periodicity and turnover. Succession is the long term change of a community, and it leads on to the next topic on the climax community. Previous topic: Seasonal and Diurnal Fluctuation, Periodicity, Turnover, Interdependence. Next topic: Climax Community.

What Are the Types and Stages of Succession?

Term	Meaning and examples
Primary succession	Begins on a lifeless surface without soil, such as bare rock, cooled lava, glacial moraine, sand dunes or a newly formed island. Very slow because soil must form first
Secondary succession	Begins on a site where the community has been destroyed but soil and seed bank are present, as after fire, logging, flood, storm or abandoned farms. Faster than primary
Pioneer species	The first colonisers, such as lichens on rock and algae on water, which help in soil formation
Seral stages	The intermediate stages. The whole series is a sere
Autogenic succession	Driven by changes the community itself makes to the habitat
Allogenic succession	Driven by outside forces such as climate change, floods or fire
Autotrophic and heterotrophic	Autotrophic succession is led by green plants, and heterotrophic succession by animals or fungi on dead organic matter

What Are the Steps, Sere Types and Examples?

Nudation: creation of a bare area
Invasion: arrival of species through dispersal, establishing themselves by ecesis
Competition and coaction: species compete and interact
Reaction: organisms modify the habitat, for example by forming soil
Stabilisation: a stable climax community develops
Lithosere: on bare rock: crustose lichens, foliose lichens, mosses, herbs, shrubs, then trees
Hydrosere: in water: phytoplankton, submerged plants, floating plants, reed swamp, sedge meadow, shrubs, then forest. A pond gradually fills and becomes land
Xerosere: on dry areas, a series from lichens to a forest. Psammosere is on sand, halosere on regur) Acidic leached soil Laterite Desert soil Arid soil, sandy Classification…">saline soil

What Else Should You Remember?

Krakatoa: volcano in Indonesia erupted in 1883, wiping out life, and its recolonisation is a classic study of primary succession
Surtsey: an island born in Iceland in 1963
Glacier Bay: Alaska, a famous case of primary succession after glacier retreat
Abandoned field: an old field in India goes from annual weeds to grasses, shrubs and then trees
Eutrophication and succession: nutrient pollution speeds the filling of lakes
Trends of succession: according to Odum: species diversity, biomass and organic matter increase; production to respiration ratio nears one; niches become more specialised
r and K species: early stages have r-strategists, later stages K-strategists
Facilitation: early species make the habitat suitable for later ones
Inhibition and tolerance models: other models of how species replace each other
Lichens: symbiosis of fungus and alga that begins rock weathering
Nitrogen fixers: plants like alder add nitrogen
Succession time: forest on bare rock may take over 1,000 years
Fire succession: fire-dependent forests regenerate after burning
Retrogression: reverse change due to degradation
Management: restoration ecology uses succession to repair land
Link: final stage is in Climax Community
Link to communities: earlier ideas are in Structure and Characteristics of an Ecological Community
Soil formation: lichens and mosses trap dust and produce acids, and their dead matter builds the first thin soil layer
Dispersal: wind, water and animals bring seeds and spores to a bare site
Seed bank: seeds stored in soil allow quick secondary succession
Succession in Sundarbans: new mud banks are colonised by mangroves in a primary series
Succession in glaciers: Himalayan glacier forelands show primary succession on fresh moraines
Role of animals: early animals such as insects and birds add nutrients and disperse seeds
Succession and biodiversity: species richness usually rises through mid stages
Competition: later species shade and outcompete early ones
Exam hint: remember that the type is decided by soil presence, not by the cause of the disturbance

Why Does It Matter for the Exam?

Primary versus secondary: soil presence
Pioneers: lichens, algae
Series: lithosere, hydrosere
Current affairs link: ecological restoration
Common errors: saying secondary succession starts on bare rock or is slower than primary

As an analytical point, knowing succession helps restore degraded land by working with natural processes. Disturbances reset the clock, so forests cleared by fire or farming slowly return through predictable stages if left alone.

Why Is This Topic Important?

Types Primary, secondary
Sere Hydrosere, xerosere
Use Restoration

What Came Next?

The next topic covers the climax community. Next topic: Climax Community.

Key People and Terms

Succession Directional community change
Pioneer First colonist
Sere Series of stages
Seral stage Intermediate stage
Ecesis Establishment of an invader
Climax Stable final community

Exam Corner

Points to Remember

Primary: no soil; secondary: soil present.
Pioneers on rock: lichens.
Krakatoa erupted 1883.
Hydrosere: water to land.
Secondary succession is faster.

Do Not Confuse With

Primary and secondary succession Bare surface versus disturbed site with soil
Autogenic and allogenic Internal versus external cause
Hydrosere and xerosere Water start versus dry start

Memory Hook

Lichens first on rock; water becomes woodland; soil makes it secondary and speedy.

Mains Angle

Questions ask for types, pioneers and sere names. These points help.

Types Two
Stages Sere
Use Restoration

A Question You May Face

An original practice question, not a past paper question.

“Describe ecological succession with examples of primary and secondary succession and explain its importance in ecosystem restoration.”

How to Answer

Define Succession.
Types Primary, secondary.
Stages Seral.
Use Restoration.

GS Relevance

Prelims: types, stages, sere types, examples, pioneer species. GS Paper 3: ecology.

Frequently Asked Questions

What is ecological succession?

Ecological succession is the gradual, orderly and predictable change in the species composition of a community over time, as pioneer species are replaced by other species until a stable community, the climax, is reached. It results from the interaction of organisms with their environment and from external changes.

What is the difference between primary and secondary succession?

Primary succession occurs on a surface with no life and no soil, such as bare rock or new lava, and takes hundreds or thousands of years. Secondary succession occurs where a community was destroyed but soil and seeds remain, such as after a fire or on an abandoned field, and takes much less time.

What is a pioneer species?

A pioneer species is one of the first species to colonise a barren or disturbed area. On bare rock the pioneers are crustose lichens, and in water they are phytoplankton. They tolerate harsh conditions, begin weathering rock and add organic matter, preparing the habitat for later species.

What is a hydrosere?

A hydrosere is the series of stages of succession that begins in water, such as a pond. It goes from phytoplankton and submerged plants to floating plants, reed swamp, sedge meadow, shrubs and finally forest, as the pond fills with silt and organic matter and becomes dry land.

What is autogenic and allogenic succession?

In autogenic succession, the change is driven by the community's own effect on its habitat, such as the formation of soil by plants. In allogenic succession, the change is caused by outside factors such as a shift in climate, floods, volcanic eruption or fire, which alter the habitat from outside.

PYQ Practice — Statement Analysis

1 Secondary succession begins where soil is already present.

True

As after a fire.

2 Lichens are the pioneers in a lithosere.

True

On bare rock.

3 Primary succession is faster than secondary succession.

False

It is much slower.

4 A hydrosere starts on dry land.