Questions of the day
1. How are forests vital for humans?
2. Why are forests important to PA?
Succession:
Changing Ecosystems
Ecological Succession:
Pond to Forest
Harvested/Disturbed Forest
to Old-growth Forest
Ecological Succession
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The series of changes
in which the original
species are replaced
by new species
Natural “aging” of an
ecosystem
Rate: depends on
climate, impacted by
human activity
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Why do some
organisms flourish
and others disappear?
Conditions of the
environment change
and may become
unsuitable for some
species
Pond to Forest
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Pioneer stagemuddy sandy bottom
Submerged plant
stage-occurs due to
humus that has
accumulated
Emerging plant
stage-cattails,
bulrushes at edge of
pond
Pond to Forest-cont’d
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Marsh-shallow water
with grasses and other
rooted plants
Swamp-organic
matter built up, tree
species, (red cedar,
red maple) seasonally
wet
Beech-maple forestclimax community
Ecological SuccessionWashington State’s
Olympic Peninsula
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Forests- disturbed by fires, landslide, clear
cutting, etc.
Regeneration through succession
Time frame: decades to centuries
Field trip-Pacific Northwest, coastal area
elevation 180 meters, visit over 300 year
development
Site 1
Field trip: Site 1
Describe how the forest
ecosystem has been
disturbed.
What was the fate of the
ecosystem’s
organisms and what
might happen to the
soil?
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If no human
intervention, what
will this site look like
in 15 years?
Site 2
Young Red Adler
Red Adler
Young Douglas Fir
Nitrogen-fixing root
nodules
Site 2
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Characteristics:
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Red alder-restore
nitrogen back to the
soil, with the
nitrogen-fixing
bacteria in nodules
on the roots
Grasses
Young firs-need N
Deer, grazing
species, field mice
Site 3
Douglas Fir
Broadleaf Maple
Young Douglas Fir
Young Red Cedar
Young Western Hemlock
Sword Ferns
Site 3: 60-75 years later, no
human intervention
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What do you notice?
What new tree species are present?
What happen to the previous tree species?
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What does that tell you about the pioneer
species?
Site 4
Western Red Cedar
Western Hemlock
Young Western Hemlock
Sword Ferns
Site 4: 270-300 years, no H.I.
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What are the dominate tree species?
What are the shade-tolerant species?
What would the condition of the soil be?
Climax stage of succession: forest is
mature, ecologically stable
Will it stay this way? What disturbances
can bring it back to site 1?
Review Questions from
yesterday’s activity