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Principles of Ecology
Succession—Notes
(**This note guide does not use Managing Our Natural Resources)
Succession: Changes over time
is the orderly, natural changes and species replacements that take place in the
communities of an ecosystem.
* Succession occurs in stages that are somewhat predictable.
* Succession is difficult to observe because it takes
community succeed from one to another.
to see the
Two types of succession:
1.
is the colonization of new land that is exposed by avalanches,
volcanoes, or glaciers by pioneer organisms. (Starts from rocks)
2.
is the sequence of community changes that take place after a
community is disrupted by natural disasters or human actions. (Start from soil & left over
organisms)
Characteristics of primary succession:
1. The first species to colonize an area in primary succession are
.
2. The final community in succession that is a stable, mature community that undergoes little or
no change in species is called a
.
Characteristics of secondary succession:
1. Secondary succession begins in places that have had communities of organisms exist before.
They also begin with soil instead of rock. This means they take
primary succession.
2. Secondary succession begins with
and ends with a
just like primary succession communities.
Comparing and contrasting primary and secondary succession:
1. Similarities:
2. Differences:
1
time to change than
Causes of plant succession:
1. Plants immigrate by means of
(spread) and then germinate in new
locations.
2. Plants
with each other for light, water, and nutrients. The best “competitor”
wins.
3.
: plants add organic matter to the topsoil which alters the soil.
This in turn changes the plants and animals that live in that site.
4.
Succession “seeks” stability.
: As plants slowly modify the site, this leads to some stable state.
Forces that slow or reverse succession:
*Retrogression can occur in response to fire, overgrazing, introduced species, drought, and other biotic &
abiotic factors.
End-point of succession (climax community):
1. The mature community that will result from
is not always
2. Events such as drought, fire, or grazing during succession may alter the final stable
community.
Ecosystem response to disturbance:
1. Some ecosystems are not easily disturbed—they have high
restoring the ecosystem is difficult—low
2. Other ecosystems have low
.
. But once disturbed,
. (i.e., tropical rainforest)
and high
. (i.e., temperate
grasslands)
3. This affects the impact of humans on ecosystems, in other words, how fragile an ecosystem is.
*Summary of ecosystem function: Living systems have 6 major features.

Interdependences (i.e.,

(i.e., limiting factors and environmental resistance)

Diversity

Unpredictability (i.e.,


)
)
: ability to recover from disturbance
Adaptability: ability to adapt to disturbance (
2
)