2.7 - ecological succession

AP Environmental Science: Unit 2 – The Living World: Biodiversity

Ecological Succession: The process by which an ecosystem or community experiences change over time.
- Climax Community: A stable ecosystem that experiences little to no change under current climate conditions.
  - Example: A forest is often depicted as a climax community, but the Sahara Desert has remained stable for thousands of years.
- Changes in conditions (e.g., increased rainfall in deserts or droughts in rainforests) can trigger a new succession process.

Definition: Occurs after a disaster when only bedrock is present.
- Process:
  - Slow reclamation of the environment (e.g., a parking lot left to grow vegetation).
  - Pioneer Species: Lichens and mosses that break down rock to create soil.
  - Takes hundreds to thousands of years for complex plants (like grasses) to establish.
  - Decomposition of organisms increases soil nutrients, accelerating succession.
  - Eventually leads to larger plants (shrubs and trees) competing for resources.

Definition: Similar to primary succession but occurs in areas where soil remains after a disturbance.
- Process:
  - Triggered by less severe natural disasters (e.g., wildfires, floods).
  - Pioneer species include grasses and weeds (e.g., dandelions).
  - The process follows similar stages as primary succession, leading to competition and ecosystem rebuilding.

Fauna Changes: Animal populations also change during succession.
- Example: Buffalo thrive in grasslands but struggle in redwood forests.

Definition: Species that have a disproportionately large impact on their ecosystem relative to their abundance.
- Example: Wolves in Yellowstone National Park, reintroduced in 1995, significantly altered the park's ecosystem, including river shapes.
- Importance: Keystone species are often undervalued and more prone to extinction due to their critical roles.

Definition: Organisms that reflect the health of an ecosystem.
- Example: Amphibians like frogs indicate the health of both terrestrial and aquatic environments.
- Significance: A decline in indicator species can signal ecological distress or pollution.

Ecological Succession: Gradual change in species composition and community structure over time.
Erosion: The wearing away of soil and rock by natural forces, affecting landscape and soil fertility.
Interspecies Competition: Competition for limited resources among different species, influencing population dynamics.
Lichens: Symbiotic organisms crucial for soil formation and nitrogen fixation.
Pioneer Species: First organisms to colonize disturbed areas, paving the way for other species.
Soil Development: Formation of soil through weathering and organic matter accumulation.
Weathering: Breakdown of rocks and minerals, essential for soil formation and nutrient cycling.