APES 2.7 Ecological Succession

Types

Primary Succession

  • Begins with a completely lifeless area
    • Bare rock with no soil
  • A newly formed and uninhabited area is colonized by pioneer species such as lichens
    • They begin to break down rock and form soil
  • Eventually grasses are able to grow
  • The shrubs pop up, then shade intolerant trees like pines, and finally shade tolerant trees like oaks
    • As plant live moves in, so do animals who feed upon those plants
    • Eventually animals further up the food chain move in as well
  • Anthropogenic disruptions include nuclear explosions or mountain top removal
    • This exposes bare rock and begins the succession cycle
  • Natural disruptions include volcanic eruptions and retreating glaciers

Secondary Succession

  • Starts with soil and some grasses but follows the same progression
  • Anthropogenic disruptions can be human-caused forest fires, logging, mining, fossil fuel extraction, clearing land for agriculture, and abandoning fields
  • Natural causes include forest fires often caused by lightning, and storm events

Community Structure

Keystone Species

  • These are species whose activities have a particularly significant role in determining community structure
  • Their role supports many other organisms in the community
  • Like how some predators help control prey populations, which in turn affects quantity of plants and animals in the food chain

Ecosystem Engineers

  • Organisms that create, change, or destroy a habitat
  • For example, beavers take down trees to make their dams
    • This allows for new growth and diverts water, changing and creating wetland habitat

Mutualists

  • Two species that interact for mutual benefit
  • Bees and hummingbirds pollinate flowers and consume nectar
    • Without these pollinators, plants would struggle to reproduce
    • Without the flowers, the pollinators would have no food source

Indicator Species

  • A plant or animal that, by its presence, abundance, scarcity, or chemical composition, demonstrates that some distinctive aspect of an ecosystem is present
  • They typically has a narrow ecological tolerance, like coral

Pioneer Species

  • The species who move into unoccupied habitat and adapt very quickly
  • They are able to outcompete established vegetation that survived the disturbance
  • They have a broad ecological tolerance
  • Being very adaptable, they can pass on beneficial genetic traits quickly