Ecology Chapter on Succession

Summary of Succession

• Succession is the change a community goes through as it ages.
• A predictable series of plant and animal species fill roles and then disappear in each biome.
• Succession starts with pioneer species and ends with a climax species.
• Communities are named by their climax species (e.g., aspen forest).

Types of Succession

• Primary Succession: Begins on bare rock (e.g., after a volcanic eruption).

  • Lichen and moss colonize rock surfaces, breaking it into soil.
  • Larger plant species grow after enough soil is formed.
  • Suitable species survive due to changing habitats.

• Secondary Succession: Begins on existing soil (e.g., after a fire or deforestation).

  • Requires less time because soil already exists.
  • Pioneer species (small plants) appear quickly and are replaced by larger plants.
  • Eventually, a stable forest community forms.

Causes of Succession

• Natural events (e.g., fires, floods, volcanic eruptions)
• Human disturbances (e.g., deforestation, farming)

Pioneer Species

• First species to colonize an area
• Often small, fast-growing species (e.g., lichen, mosses)
• Help build soil.

Climax Species

• The final and stable species in a succession.
• Usually large trees and other complex plants.
• Give the community its name (e.g., aspen forest).

Why Succession Occurs

• Species changing the habitat and resources available.
• Harsh conditions initially select for species that can tolerate those conditions.
• More hospitable conditions allow less tolerant species to move in and outcompete others.
• Communities become more diverse over time.
• Eventually, stable climax species dominate.