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Succession
IB Syllabus: 2.3.5 – 2.3.7
Ch. 8
Syllabus Statements
• 2.1.6: Define the terms species, population,
habitat, niche, community, ecosystem with
reference to a named example
• 2.6.5 – Describe the concept and process of
succession in a named habitat
• 2.6.6 – Explain the changes in energy flow,
gross and net productivity, diversity and mineral
cycling in different stages of succession
• 2.6.7 – Describe the factors affecting the nature
of climax communities
Vocabulary
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Climax Community
Community
Evolution
K strategists
R strategists
Sere
Succession
Zonation
Community
• A group of populations interacting in a
particular area
• The fish community of Ponce Inlet
• The plant community of the scrub habitat
Communities Change
• Ecological Succession: the gradual change in
species composition of a given area over time
• Species do change spatially within an area at
a certain point in time, this is zonation not
succession
• 2 Types depending on start point
– Primary succession: gradual establishment of
biological communities on lifeless ground
– Secondary succession: reestablishment of biotic
communities in an area where they already
existed
Zonation II
• Horizontal bands or zones of animals and
organisms
– Vertical layers in a rainforest
– Differing plant communities as you go up a
mountain
• Created by physical and biological factors
• Change in these factors is called an
environmental gradient
• In a rocky intertidal zone these would be
– Drying (tides), salinity, competition, grazing
So how could you measure changes in
biota along an environmental gradient?
• Biota = living organisms
• Change in benthic (bottom) community of
rocky intertidal with increased depth
• Gradient in moisture or drying
• Use modified quadrat method
– run transect into deeper water
– At set depths place quadrat and sample
organisms
– Do repeated transects along your sample
area
– Calculate differences in communities with
depth
Primary Succession
• Begins in area with no soil on land, no
sediment in water
– Cooled lava, bare rock from erosion, new
ponds, roads
• Must be soil present before producers
consumers and decomposers can exist
Exposed
Lichens
rocks and mosses
Small herbs
and shrubs
Heath mat
Time
Jack pine,
black spruce,
and aspen
Balsam fir,
paper birch, and
white spruce
climax community
Pioneer Communities
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•
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1.
2.
3.
4.
Lichens and Mosses
Survive on nutrients in
dust and rock
Start soil formation
Trap small particles
Produce organic
material photosynthesis
Chemically weather the
rock
Patches of soil form
Seral Stages: Early Successional
Plant Species
•
1.
2.
3.
4.
Small perennial
grasses and herbs
colonize, wind blown
seeds
Grow close to the
ground
Est. large pop. quickly
in harsh conditions
Short lived
Break down rock
Seral Stages: Mid to Late
Successional Species
•
After 100’s of years
soil deep enough
• Moisture & nutrients
• Also called Seral
Community
1. Shrubs then trees
colonize
2. Trees create shade
3. Shade tolerant
species establish
Seral stages
• A seral community (or sere) is an intermediate stage
found in ecological succession in an ecosystem
advancing towards its climax community.
• An example of seral communities in secondary
succession is a recently logged coniferous forest;
– during the first two years, grasses, heaths and herbaceous
plants such as fireweed will be abundant,
– after a few more years shrubs will start to appear
– about six to eight years after clearing, the area is likely to be
crowded with young birches.
• Each of these stages can be referred to as a seral
community.
Climax community
• Characterized by K-selected species
• Determined by
– climate in the area – temperature, weather patterns
– Edaphic factors – saturated wet, mesic, arid
• Climax community structure is in stable
equilibrium for each area
• Humans & other factors may maintain an
equilibrium below climax
– E.g. current warming trends make climax rainforest
communities w/ softer wood, faster growing species
End Result = Complex Community
• Complex community mix of
well established trees shrubs
and a few grasses
• Disturbance may change the
structure
– Fire, Flood, Severe erosion, Tree
cutting, Climate change, Grazing,
habitat destruction
– Natural or Human processes
– Specific successional stage is
dependent on the frequency of
disturbance
Disturbance and Diversity
• Disturbance = any change in conditions
which disrupts ecosystem or community
structure
• Catastrophic or Gradual
• Disturbance eliminates strong competitors
allowing others a chance
• Promotes diversity
• Intermediate disturbance  greatest diversity
Species diversity
The intermediate disturbance hypothesis
0
100
Percentage disturbance
Townsend et al, cited in
Begon Harper & Townsend,
Ecology
Secondary Succession
• Begins when natural community is
disturbed BUT soil & sediment remains
– Abandoned farms, burned forests, polluted
streams
• New vegetation can germinate from the
seed bank
• In both cases succession focuses on
vegetation changes
Mature oak-hickory forest
Young pine forest
Annual
weeds
Perennial
weeds and
grasses
Shrubs
Time
Succession of Abandoned Farmland
Heliconia Bracts
Tropical Rainforest flower
Newer flowers form at the bottom
As flowers form they fill with water
Support aquatic communities
Newly formed bracts early
succession
Nutrients and organics build up
Over time succession occurs
Higher bracts have climax
communities
What changes occur through
Succession?
1. Diversity
• Starts very low in harsh conditions few species
tolerate – r selected species types
• Middle succession mix of various species
types – most diverse (role of disturbance)
• Climax – k selected species strong competitors
dominate
2. Mineral Cycling
• Pioneer, physical breakdown & make
organic, Later processing increase – cycles
expand
3. Gross productivity changes (total
photosynthesis)
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•
Pioneer = Low density of producers at first
Middle & climax = high  lots of producers and
consumers
4. Net Productivity (G – R = N)
•
•
Pioneer = little respiration so Net is large 
system is growing, biomass accumulating
Middle & climax = respiration increases
dramatically  N approaches zero (P:R = 1)
5. Energy flow
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# of trophic levels increases over time
Energy lost as heat increases with more transfers
Overview of Successional Changes
© 2004 Brooks/Cole – Thomson Learning
Early Successional
Species
Midsuccessional
Species
Late Successional
Species
Wilderness
Species
Rabbit
Quail
Ringneck pheasant
Dove
Bobolink
Pocket gopher
Elk
Moose
Deer
Ruffled grouse
Snowshoe hare
Bluebird
Turkey
Martin
Hammond’s
flycatcher
Gray squirrel
Grizzly bear
Wolf
Caribou
Bighorn sheep
California condor
Great horned owl
Ecological succession
Factors in Succession
1. Facilitation
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One species makes an area suitable for another in a
different niche
Legumes add nitrogen so other plants thrive
2. Inhibition
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Early species hinder establishment and growth of later
species  more disturbance needed to continue
Allelopathy by plants is an example
3. Tolerance
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•
Late successors not affected by earlier ones
Explains mixture of species in Climax Communities
Predictability of Succession
• Generally predictable end of succession is
a Climax community
• Only real rules are Continuous change,
Instability, and unpredictability
• Ever changing mosaic of patches in
different successional stages
• No real progression to an end, rather we
see a reflection of an ongoing battle for
resources and reproductive advantage
Aquatic
Succession
Ecological Stability & Sustainability
• Maintained by constant dynamic change
• Positive and Negative feedback systems
• Community may change but you will still
recognize it as a particular type of community
– Inertia = The ability of a living system to resist
disturbance
– Constancy = the ability of a system or population to
keep its numbers within limits imposed by resources
– Resilience = the ability of a system to bounce back
after a disturbance
Diversity vs. Stability
• Once thought that higher diversity = more
stability for a community or ecosystem
• Recent studies by D. Tilman on grasslands
suggest
– More species  higher NPP  more stable
– Population #’s for individual species in diverse
ecosystems fluctuate more widely
• Some level of diversity does provide
insurance against disasters
• Nature is in a continual state of change
The Precautionary Principle
• Human disturbances are disrupting
ecosystem processes
• Our ignorance of long term effects means we
should be cautious
• Thus, “When there is considerable evidence
that and activity threatens human and
ecosystem health, we should take
precautions to minimize harm, even if the
effects are not fully known.”
• Better safe than sorry…
Grizzly
bear
NORTH
AMERICA
More than 60% of the
Pacific Northwest
coastal forest has
been cut down
40% of North America’s
range and cropland
has lost productivity California
condor
Hawaiian
monk seal
Eastern
cougar
Spotted
owl
Blackfooted Florida
ferret panther
Mangroves
cleared
in Equador for
shrimp ponds
Endangered species
6.0 or more children
per woman
Fish catch in the north-west Atlantic has fallen
42% since its peak in 1973
Chesapeake Bay is overfished and polluted
Golden
toad
Coral reef destruction
Every year 14,000
square kilometers of
rain forest is destroyed
in the Amazon Basin
Columbia has
lost one-third of
its forest
PACIFIC
OCEAN
Vanishing biodiversity
Humpback
whale
Manatee
Much of Everglades National Park has dried out
and lost 90% of its wading birds
Kemp’s
ridley
turtle
Half of the forest
in Honduras and
Nicaragua has
disappeared
Environmental degradation
St. Lawrence
beluga whale
Black lion
tamarin
SOUTH
AMERICA
Southern
Chile’s rain
forest is
threatened
Little of Brazil’s
Atlantic forest
remains
ATLANTIC
OCEAN
Poland is one of
the world’s most
polluted countries
Imperial eagle
640,000 square kilometers
south of the Sahara have
turned to desert since 1940
EUROPE
Mediterranean
Many parts of
former Soviet Union
ASIA
are polluted with
industrial and radioactive waste
Central Asia from the
Middle East to China
has lost 72% of range Giant
and cropland
panda
Area of
Aral Sea has
Shrunk 46%
Snow leopard
Japanese timber imports
are responsible for much
of the world’s tropical
deforestation
Saudi
Arabia
Deforestation in the Himalaya
Asian
causes flooding in Bangladesh
Liberia
elephant
Oman
Kouprey
Eritrea
Mali AFRICA
Yemen
90% of the coral reefs
India and
are threatened in the
Burkina Niger
Ethiopia
Sri Lanka
Philippines. All virgin
Faso
Benin Chad Golden
have almost
forest will be gone
Sierra
tamarin
no
rain
Nigeria
by 2010
Leone
forest left
Togo
Congo Uganda
Sao Tome Rwanda
Somalia
In peninsular Malaysia
Queen Alexandra’s
68% of the
Burundi
almost all forests have
Birdwing butterfly
Congo’s
Angola
been cut
rain forest
Indonesia’s
is slated
Zambia
coral reefs are
Nail-tailed
for cleaning
INDIAN OCEAN threatened
wallaby
and
Aye-aye
Fish catches in
mangrove AUSTALIA
Black
Southeast Atlantic
forests
Madagascar has
have dropped by more rhinoceros
Much of
have been
lost 66% of its
than 50% since 1973
Australia’s
cut
in
half
tropical forest
range and
cropland
have turned
to desert
Blue whale
A thinning of the ozone layer occurs
over Antarctica during summer
ANTARCTICA
Hydrosere
• A hydrosere is simply a succession which starts in water.
A wetland, which is a transitional area between open
freshwater and dry land, provides a good example of this
and is an excellent place to see several stages of a
hydrosere at the same time.
• In time, an area of open freshwater such as a lake, will
naturally dry out, ultimately becoming woodland. During
this process, a range of different habitats such as swamp
and marsh will succeed each other.
• This succession from open water to climax woodland is
likely to take at least two hundred years (probably much
longer). Some intermediate stages will last a shorter time
than others. For instance, swamp may change to marsh
within a decade or less. How long it takes will depend
largely on the amount of siltation occurring.
• http://www.countrysideinfo.co.uk/successn/hydro.htm
Hydrosere
Halosere
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The term Halosere is an ecological term which describes succession in a
saline environment. An example of a halosere would be a salt marsh.
In river estuaries, large amounts of silt are deposited by the ebbing tides
and inflowing rivers.
The earliest plant colonizers are algae and eel grass which can tolerate
submergence by the tide for most of the 12-hour cycle and which trap mud,
causing it to accumulate. Two other colonisers are salicornia and spartina
which are halophytes -i.e. plants that can tolerate saline conditions. They
grow on the inter-tidal mudflats with a maximum of 4 hours' and exposure to
air every 12 hours.
Spartina has long roots enabling it to trap more mud than the initial
conlonizing plants and salicornia, and so on. In most places this becomes
dominant vegetation. The initial tidal flats receive new sediments daily, are
waterlogged to the exclusion of oxygen, and have a high pH value.
The sward zone, in contrast, is inhabited by plants that can only tolerate a
maximum of 4 hours submergence everyday (24 hours). The dominant
species here are sea lavender and other numerous types of grasses.
Halosere
Xerosere
• Xerosere is a plant succession which occurs in
conditions limited by water availability or the
different stages in a xerarch succession.
• Xerarch succession of ecological communities
originated in extremely dry situation such as
sand deserts, sand dunes, salt deserts, rock
deserts etc.
• A xerosere may include lithoseres and
psammoseres.
Psammoseres
• In geography, a psammosere is a sand sere - an
environment of sand substratum on which ecological
succession occurs.
• In a typical succession on a sea-coast psammosere, the
organisms closest to the sea will be salt tolerant species
such as littoral algae and glasswort. Progressing inland
the succession is likely to include meadow grass, sea
purslane, and sea lavender eventually grading into a
typical non-maritime terrestrial eco-system.
• www.sanddunes.20m.com/Evolution%20.htm
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