7.4.6 Succession

Types of Succession

1. Primary Succession:

• Occurs in areas where there was no previous life (e.g., new land formed after volcanic eruptions).
• Steps involved:

1. Pioneer Species: The first organisms to colonise the area (e.g., lichens, mosses).

• Adapted to survive harsh conditions (e.g., no soil, limited water).

2. Soil Formation: Pioneer species die and decompose, forming humus.

• This creates basic soil that retains water and supports other life forms.

3. Colonisation by Larger Plants: As soil quality improves (richer in minerals), larger plants like grasses and shrubs can grow.
4. Climax Community: The final, stable community is reached, comprising larger trees and complex ecosystems.

• Example: A temperate forest or tropical rainforest.

2. Secondary Succession:

• Happens in areas where a community previously existed but was cleared (e.g., after a forest fire or agricultural abandonment).
• Soil already exists, so the process starts at a later stage than primary succession.
• Progression to a climax community occurs more quickly.

Key Features of Succession

• Biodiversity increases over time as conditions improve (e.g., more soil and nutrients).
• Abiotic factors become less extreme (e.g., more shade, better soil quality).
• Interactions between organisms (e.g., competition and predation) increase, leading to a more stable community.