Download Succession of an Ecosystem

Succession
Where the changing of species composition
occurs over a period of time.
Two main types:
Primary succession: starting from scratch.
Where there is no living organisms, and
soil formation is starting.
Secondary succession: starting over. Where
there is soil and previous organisms that
will be brought by wind, or lay dormant until
conditions are right to start growing again.
Primary succession
Primary succession (Prisere):
It starts with a lifeless abiotic area. Soil being deposited
and the colonization of organisms slowly appearing.
Succession goes through stages called seral stages.
A sere is a set of communities that succeed one after the
other.
i.e.:
Lithosere – bare rock to woodland community.
Hydrosere – build up of vegetation in a lake/pond turning
into a forest.
Plagiosere – human activity stops a natural succession
from occurring into climax or subclimax community.
Primary Succession
Types of Primary succession communities:
 New volcanic land
 Retreat of a glacier
 Build up of vegetation from a deep pond or lake.
Stages of succession:
 Bare/inorganic surface – lifeless abiotic
environment, ready for soil deposits to form from wind
sediment and erosion.
 Seral 1 (colonization) – first species to colonize
(pioneer species) usually small in size, short life
cycles, rapid growth and maturity with many offspring.
 Seral 2 (establishment) – Species diversity begins.
New species move in either to prey or colonize.
Invertebrates appear in soil. Humus (organic matter)
increases in amount.
Primary Succession
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Seral 3 (competition) – climate continues to change
with addition of new species. Larger plants appear
and increase cover and shelter are provided for
newer and more diverse species to inhabit area.
Less temperature extremes.
Seral 4 (Stabilization) – fewer new species,
colonizers are established or slowing fading out of
the area. More complex food webs are seen and
more specialized niches are found. Larger less
productive organism are establishing.
Seral 5 (Climax) – Final stage. Climax community.
The area is stable and has reached a dynamic
equilibrium.
Primary Succession
Pioneer communities:
 Consists of a group of species that are
rapidly growing/reproducing.
 Well adapted to extreme climates
 Examples:
 Microorganisms (bacteria, phytoplankton),
mosses, lichen, insects
Secondary Succession
Gradual replacement of one community of
organisms by another in a slow predictable
manner in an area where life has already
started.
Causes of:
 Catastrophic event – major earth/natural
event that has caused disruption in the
natural succession of the environment.
 Ex: forest fire, flood, hurricane, tornado,
rock/mud slide.
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Succession of a Water Source
Hydroseres:
o In primary succession:
o Only bacteria, phytoplankton or simple organisms move in
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and live. – Pioneer species
Organic material settles to the bottom of a river, lake, pond
etc.
Buildup of these organic materials along with deposited
seeds from birds and wind cause plants, algae, grasses and
reeds to grow at the edges or bottom of the water source. –
A marsh is formed
As the plant bases and animal species move in more and
larger organisms move in – such as trees and shrubs, fish,
turtles, amphibians, insects.
Then the sediment will build up and the marsh becomes a
bog – where soil and plants take over the top layer of the
water and sediments build up from the bottom.
Succession of a Water Source
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Secondary Succession:
 When a disaster such as pollution, flooding,
hurricanes etc, change a water source the
changes to find equilibrium are considered
secondary.
 The organisms either die or move out from the
disaster
 Then simple plant and animal species will
readapt and grow
 Once pioneer species move back in and
sediments are reestablished then larger
organisms will move in.