Ecology 4 Succession Ppt

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Transcript Ecology 4 Succession Ppt

Changing Ecosystems
 Biodiversity is the
variety of organisms
in a given area.
 Physical factors
(abiotic) have a big
influence on
 Ex: Low temp or Low
water = Low
Sahara Desert
Resistance to
Environmental Damage
 The biodiversity of
habitats and ecosystems
varies widely.
 When ecosystems have
high biodiversity, they
are more resistant to
 Systems with low
biodiversity can be
severely damaged
 When we observe
an ecosystem, it
may look like an
unchanging feature
of the landscape.
 However, all
ecosystems change.
 The replacement of
one kind of
community by
another in the same
location is called
Primary Succession
 The arrival of life in
an area where no
previously existed.
 Ex: Volcanic
eruptions of lava
 Rock weathers and
produces soil where
there wasn’t any
Pioneer Species
 The first organisms
to appear in a newly
made habitat.
 Often small, fastgrowing species that
reproduce quickly.
 These change the
habitat in such a way
that other species
can live.
Lichens and mosses are often the first
to colonize a bare area of rock. These
break down rock and help form soil so
that other plants can live.
Secondary Succession
 Occurs in areas that
previously had life.
 Ex: Damage from
severe storms,
plowing with
bulldozers, forest
 Occurs faster than
primary succession
because soil is
already present as
well as seeds from
previous plants.
Secondary Succession
A recently cleared patch of
ground (in Britain).
The same ground 2 years later,
now covered in grasses and low
flowering plants.
 If a major disruption
strikes a community,
many of the
organisms may be
wiped out.
 But the ecosystem
will respond to the
change in such a
way that equilibrium
will be restored.
Forest recovery is more effective when
left to natural processes, as illustrated by
the successful regeneration in
Yellowstone National Park after the fires
in 1989 (left) and nine years later (right).
Climax Community
 Ecologists refer to the
final, highest stage of
ecological development in
an area as the area's
climax community.
 That term refers to a
relatively stable
community that is
environmentally balanced.
 The type of climax
community depends on
the climate
Maintained by Fire
 When fire sweeps through a forest, the fire destroys
just about everything in its path.
 Fire can actually be a good thing for certain
communities, however.
 In fact, fire is important for preserving many plant
communities and the animals that depend on them.
Fire Lovers
 Some plants benefit
from fire.
 Fireweed is one such
 It gets its name
because it quickly
colonizes burned
land without
competition from
other species.
Fire Aides Reproduction of
Certain Species
 The jack pine and
the loblolly pine can
release their seeds
only after they have
been exposed to the
intense heat of a
forest fire.
Jack Pine
Loblolly Pine
Controlled Burns of Forest
 Firefighters often
light fires on
 This firefighter is
setting a controlled
burn fire because
burned vegetation
helps bring nutrients
to the soil.
Fire Used for Forest
 Forest managers
may prescribe a
controlled burn to
reduce the brush
present in the
 Too much
undercover brush
may lead to a more
catastrophic forest
fire later.
Controlled Burns to Reduce
Non-native species Invasion
 Ecologists may also
use a prescribed
burn to reduce the
number of introduced
species in an area.
 This may allow the
native species to
repopulate the land
with less competition.
The goal is to remove non-native
grass thatch and seed and provide a
weed-free planting window for
restoration to diverse, native coastal
bluff scrub vegetation.