Ecology Chapter: Succession

Succession

• Succession is the gradual change in a community's species composition over time.
• It's a predictable process for a biome or micro-environment.
• Species fill roles and then disappear, starting with pioneer species and ending with a stable 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 volcanic eruptions or landslides).

  • Pioneer species, like lichen and moss, break down rock into soil.
  • Small plants then colonize, followed by larger species.
  • Eventually, a stable community develops.

• Secondary succession: Begins on pre-existing soil.

  • Happens after a disturbance (e.g., fire, deforestation) removes some but not all organisms.
  • Soil remains, making the process faster than primary succession.
  • Pioneer species rapidly colonize.

Climax Species

• The final species in a community's succession.
• It's named after the climax species (e.g., aspen forest).

Why Succession Occurs

• Species change the habitat.
• Species change the available resources.
• Initially, only species tolerant of harsh conditions can survive.
• As the environment becomes more hospitable, other species can invade.

Biodiversity During Succession

• Biodiversity is higher at the climax of succession.
• A greater number of species can survive at later stages.

Forest Fires and Succession

• Forest fires can be positive and negative in nature.
• Positive effects include nutrient return to soil, seed germination.
• Negative effects include organism destruction, succession termination.
• Controlled burns mimic natural processes, often used in National Parks.

Traditional Uses of Fire

• First Nations people in Alberta historically used purposeful prairie fires in spring to begin secondary succession.
• Fireweed, a pioneer species, had traditional uses for food, medicine, etc.

Consumer Species Succession

• Producer species succession affects consumer species.
• Consumer species adapt to the changing food sources.

Factors Affecting Biodiversity in Succession

• Effect of time on biodiversity—increased biodiversity in later stages.
• Low biodiversity at the start of succession, due to harsh conditions.
• Gradually more species adapt to changing ecosystems.