Ecological Succession

Ecological Succession occurs when a series of communities replace one another due to large scale destruction either natural or man-made. This process continues until a stable & mature community develops.

SPECIES

Pioneer Species: 1st species to invade the bare land, thus they are colonisers.

1. Include bacteria, fungi, mosses, lichens.
2. They show a high rate of growth but short life span.

Successional or seres Species.

1. The diff communities or stage (mosses, herbs, shrubs trees) replace one another during succession & are referred to as seral stages or seral communities — These species are slow-growing and long-lived.
2. A sequence of communities succeeding each other during the course of succession represents the sere.

Climax Community/Species.

1. Climax Community/Species Terminal (final) stage of succession forms community which is called a climax community.
2. They’re stable, mature, more complex & long-lasting.

STAGES of Ecological Succession

Primary Succession

1. Takes place on bare areas like newly formed deltas, emerging volcano island.
2. Area 1st weathered by physical forces so that soil formation is initiated, then inhabited/ colonised by pioneer species like algae, mosses, lichens which further soil-forming process & prov organic matter to the soil once die [Bacteria & Fungi decompose dead pioneer species).
3. Community develop → inc competition & develop a new niche.
4. Invasion of new specie and replace pioneer species.

Intermediate Succession — Seral community

1. Pioneer community after some time gets replaced by another community with different species combination.
2. This transitional community is called stage in succession or seral community or sere.

Secondary Succession.

1. Takes place in the area that was prev occupied by living communities but community wiped out after destructive event like a fire.
2. The area is re-colonised. 
3. Bare farmland 1st invaded by hardy species of grass & eventually develop into forest community.
4. Unlike the primary, SS starts on a well-developed soil, hence relatively faster.

Therefore, the following sequence can be observed in succession

1. Nudation: Bare area without life.
2. Migration
3. Invasion: Pioneer species in the bare area.
4. Competition & Co-action: Sere stage.
5. Reaction
6. Stabilisation (climax).

TYPES OF Ecological Succession

 Autogenic & Allogenic.

1. Autogenic = Succession by living inhabitants.
2. Allogenic = Succession bought by outside forces.

Autotrophic & Heterotrophic.

1. Autotrophic = green plants are greater in quantity.
2. Heterotrophic = heterotroph is greater in quantity.

Other

Hydrarch & Xerarch succession.

1. Hydrarch succession takes place in wetter areas and the successional series progress from hydric to the mesic condition [moist – neither too dry nor too wet].
2. Xerarch succession takes place in dry areas & series progress from xeric to mesic conditions.

• Retrogressive Succession = Forest → Shrubs → Grass by biotic influence (CC effect).
• Serule = ES for micro-org like fungi, bacteria.

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