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Ecological Succession… …the Eternal Living Braid…


Ecological Succession the Eternal Living Braid by Nicolette, Leslie and Joel Ecological Succession is The observed process of change in the species ... – PowerPoint PPT presentation

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Title: Ecological Succession… …the Eternal Living Braid…

Ecological Succession the Eternal Living
  • by
  • Nicolette, Leslie and Joel

Ecological Succession is
  • The observed process of change in the species
    structure of an ecological community over time.
  • The community begins with relatively few
    pioneering plants and animals and develops
    through increasing complexity until it becomes
    stable or self-perpetuating as a climax
  • Succession occurs in all natural environments.
    Each environment has a particular name that
    expresses the nature of their ecological
    succession Primary and Secondary

Ecological Succession

There are two main types of Ecological Succession
  • Primary Succession The process of creating life
    in an area where no life previously existed.
  • Secondary Succession The process of
    re-stabilization that follows a disturbance in an
    area where life has formed an ecosystem.

Examples of Succession Primary
Primary Succession
  • The development of an ecosystem in an area that
    has never had a community living within it occurs
    by a process called PRIMARY SUCCESSION.
  • An example of an area in which a community has
    never lived before, would be a new lava or rock
    from a volcano that makes a new island.

Primary Succession
Secondary Succession
  • SECONDARY SUCCESSION begins in habitats where
    communities were entirely or partially destroyed
    by some kind of damaging event.
  • When an existing community has been cleared by a
    disturbance such as a fire, tornado, etc...and
    the soil remains intact, the area begins to
    return to its natural community. Because these
    habitats previously supported life, secondary
    succession, unlike primary succession, begins on
    substrates that already bear soil. In addition,
    the soil contains a native seed bank.
  • Since the soil is already in place, secondary
    succession can take place five to ten times
    faster than primary succession.

The Circle of Life in Secondary Succession
Why Does Ecological Succession Occur?
  • Because it is the process of life for plants,
    soil and other living organisms.
  • Because organisms alter soil structure,
    chemistry, and microclimates, the species
    composition of ecological communities constantly
    changes over time.
  • Succession will continue until the environment
    reaches its final stagethe Climax Community.

The Climax Community
  • A climax community is a mature, stable community
    that is the final stage of ecological succession.
    In an ecosystem with a climax community, the
    conditions continue to be suitable for all the
    members of the community.
  • Any particular region has its own set of climax
    species, which are the plants that are best
    adapted for the area and will persist after
    succession has finished, until another
    disturbance clears the area.

These are Climax Communities
  • Two main physical factors determine the nature of
    the community that develops in an area. These are
    temperature and the amount of rainfall.
  • If we place the amount of rainfall on a graphs
    x axis, from 0-10, 10-20,and 20-30 inches and
    the temperature along the y axis from hot,
    moderate, to cold, the various types of
    ecosystems will fit into the graph based on the
    conditions that they require.

A summary of changes that occur during succession
  • Pioneer species colonize a bare or disturbed
    site. Soil building.
  • Changes in the physical environment occur (e.g.,
    light, moisture).
  • New species of plants displace existing plants
    because their seedlings are better able to become
    established in the changed environment.
  • Newly arriving species alter the physical
    conditions, often in ways that enable other
    species to become established.
  • Animals come in with or after the plants they
    need to survive.
  • Eventually a climax community that is more or
    less stable will become established and have the
    ability to reproduce itself.
  • Disturbances will start the process of succession

Threats to Succession
  • The grasses that move in as pioneer species are
    often thought of as weeds.
  • The subsequent growth of shrubs are considered
    undesirable "brush".

  • Without these intermediate stages, the disturbed
    habitat can't return to a natural forest.
  • The fragility and stability of the ecological
    community are dependent upon several factors.
  • For example, in temperate forests, if the shrubs
    are not allowed to grow, insect pests begin to
    feed on young trees instead. This has happened in
    many places where trees are replanted after an
    area is clear-cut. Large quantities of pesticides
    are then brought in, polluting the soil and water
    and altering the natural ecosystem even further.

How Do Humans Affect Ecological Succession?
  • Clearing the land for the garden and preparing
    the soil for planting represents a major external
    event that radically re-structures and disrupts a
    previously stabilized ecosystem. The disturbed
    ecosystem will immediately begin a process of
    ecological succession.
  • Plant species that adapt to the sunny conditions
    and the broken soil will rapidly invade the site
    and will become quickly and densely established.
    These invading plants are what we call "weeds in
    which we consider a nuisance or invaders.

How Do Humans Affect Ecological Succession?
  • A gardener's only course of action is to spend a
    great deal of time and energy weeding the garden
    or using chemicals to infringe upon the weeds and
    the ecosystem around it.
  • The farmers and gardeners who are growing our
    foods incur an immense cost in terms of time,
    fuel, herbicides and pesticides that humans pay
    every growing season because of the force of
    ecological succession.

Does Ecological Succession Ever Stop?
  • We must recognize that any ecosystem, no matter
    how inherently stable and persistent, could be
    subject to massive external disruptive forces
    (like fires and storms) that could re-set and
    re-trigger the success ional process.
  • As long as these random and potentially
    catastrophic events are possible, it is not
    absolutely accurate to say that succession has

Does Ecological Succession Ever Stop?
  • Also, over long periods of time (geological
    time) the climate conditions and other
    fundamental aspects of an ecosystem change.
  • These geological time scale changes are not
    observable in our ecological time, but their
    fundamental existence and historical reality
    cannot be disputed.
  • No ecosystem, then, has existed or will exist
    unchanged or unchanging over a geological time

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