Download Secondary Succession

Succession
Ecological Succession
• Natural ecological restoration
– Primary succession – gradual establishment
of biotic communities in lifeless areas where
there is no soil or sediment
– Secondary succession – series of
communities with different species develop in
places containing only soil or bottom
sediment
Primary Succession
• In the beginning…
– No soil = no nutrients
– Over time rock
weathers
Hundreds and thousands of years later…
Primary Succession
• Early pioneer plant
species
– Species arrive and
attach themselves to
inhospitable patches
of weathered rock
• Lichens, mosses
– Help form soil by
trapping wind-blown
soil particles and
detritus
• Add waste and dead
bodies
Hundreds and thousands of years later…
Primary Succession
• Mid-successional
plant species
– Soil becomes deep and
fertile enough to hold
moisture
– Supports the growth of
herbs, grasses, and low
shrubs
– Creates shade which
causes mosses and
lichens to die
– Trees replace grasses
and shrubs
Primary Succession
• Late successional
plant species
– Species that can
tolerate shade
– Bare rock ultimately
becomes a complex
forest
Aquatic Primary Succession
• Newly created small pond
• Influx of nutrients via runoff
Secondary Succession
• Some soil remains in
a terrestrial system or
sediment in an
aquatic system
• Ecosystem has been
– Disturbed
– Removed
– Destroyed
Secondary Succession
• New vegetation can
germinate usually
within a few weeks
– Seeds already in the
soil or imported by
wind, birds, and other
animals
• Climax community –
stability
Similarities
• Primary and secondary succession
– Tend to increase biodiversity
– Increase species richness and interactions
among species
• Primary and secondary succession can be
interrupted by
–
–
–
–
–
Fires
Hurricanes
Clear-cutting of forests
Plowing of grasslands
Invasion by nonnative species
Species Replacement
• Facilitation – one set of species makes an area
suitable for species with different niche
requirements
– Less suitable for itself (mosses and lichens)
• Inhibition – some early species hinder the
establishment and growth of other species
– Pine needles make soil acidic
• Tolerance – late succession plants are largely
unaffected by plants at earlier stages of
succession
Succession Doesn’t Follow a
Predictable Path
• Traditional view
– Balance of nature and a climax community
• Current view
– Ever-changing mosaic of patches of
vegetation
– Mature late-successional ecosystems
• State of continual disturbance and change
Living Systems Are Sustained
through Constant Change
• Inertia, persistence
– Ability of a living system to survive moderate
disturbances
• Resilience
– Ability of a living system to be restored through
secondary succession after a moderate
disturbance
• Tipping point
– Any additional stress can cause the system to
change in an abrupt and usually irreversible way
that often involves collapse