Transcript Succession - Greensburg

Succession
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Succession- the series of predictable
changes that take place in a community
over a period of time.
Factors that can cause changes:
fire
flood
volcanoes
hurricanes
tornados
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Succession is a change in plants and animals
which occurs periodically in all communities.
An open space or meadow will eventually be
overgrown by a forest which in turn will grow to
a climax forest.
The length of time and kinds of plants involved
in each successional change depends on many
factors.
Disturbances can be human made or natural.
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Primary Succession –the series of changes
that occur in an area where no ecosystem
previously existed.
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Pioneer species- the first species to
populate an area, usually lichens and
mosses that were dispersed by the wind.
They are able to live on bare rock.
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Secondary succession- the series of
changes that occur after a disturbance in
an existing ecosystem.
Lava from Mt. St. Helens
created a barren
landscape, as shown here
near Spirit Lake, on which
succession has begun
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Seral community- an intermediate
community existing in the process of
succession.
Climax community- relatively stable,
almost permanent community.
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Forest ecosystems are always changing. Plants grow
using soil nutrients and eventually die, returning
nutrients to the soil.
Animals feed on plants and leave waste.
Bacteria, fungi and insects thrive on decaying plants,
animals and animal waste, breaking down these
materials and replacing soil nutrients.
These interactions of plants, animals, bacteria, fungi and
insects constantly occur in ecosystems.
1. Forbs stage--------- 0-5 years
A. Certain "pioneer" plants germinate quickly
on exposed soil including mosses, lichens and
small herbaceous plants.
B. Shrub and tree seedlings begin to establish
in the soil.
C. Insects and small rodents feed on grasses,
herbaceous plants and seeds.
D. Songbirds feed on insects and seeds.
Predatory birds feed on small rodents.
2.
Shrub stage---------6-25 years
A. Tree seedlings are established and larger shrubs
shade out many of the herbaceous plants.
B. Shrubs and fallen trees provide abundant nesting
cover for birds, rodents and small mammals.
C. The smaller animals attract larger predators, such
as coyotes, weasels, and bobcats. Deer feed on shrubs
and saplings.
D. Larger predators are also attracted, such as
cougars and bears.
3.
Young forest------- 26-50 years
A. The forest canopy begins to form with deciduous trees being
the dominant species.
B. The diversity and quantity of shrubs and herbaceous plants
decreases.
C. Young evergreens grow up among the shaded forest floor.
D. A reduction of the kinds of food available to some wildlife
species [especially large mammals] reduces the number of wildlife
species.
E. New species enter the area and take advantage of the
resources. Beavers use young trees for food and lodges.
4.
Mature forest------- 51-150 years
A. A few large evergreen species dominate
the ecosystem.
B. Large deciduous trees die and fall leaving
openings in the forest canopy.
C. Shrubs and herbaceous plants take
advantage of the sunlight and attract small
birds and mammals, creating a diverse
ecosystem.
5.
Climax forest 150-300 years
A. Large evergreens, grow in height and diameter.
B. Fewer big trees take up more area so there are fewer trees
per acre.
C. Dead trees, called snags, provide nesting sites for
woodpeckers and other animals.
D. Fallen trees add to the diversity of habitats and provide
additional resources while adding soil nutrients.
E. A climax forest could also be made up of large deciduous trees
such as maple or oak.
In the volcanic
blast around Mt.
St. Helens,
succession has
begun to
replace
destroyed
forests.
Colonizers, such
as this spotted
cat's-ear
(Hypochaeris
radiata) of the
sunflower
family, usually
produce high
numbers of
seeds that are
easily dispersed
over great
distances.
Fireweed is a common
colonizing plant found
in disturbed areas of
Washington.
Pond Succession Animation
http://www2.wwnorton.com/college/biology/discoverbio3/full/content/ch36/animations.asp
Bog Succession Animation
http://www.wiley.com/college/strahler/0471480533/animations/ch23_animations/animation1.html