succession ib syllabus: 2.3.5 – 2.3.7 ch. 8. syllabus statements 2.1.6: define the terms species,...
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Succession
IB Syllabus: 2.3.5 – 2.3.7
Ch. 8
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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
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Vocabulary
• Climax Community
• Community
• Evolution
• K strategists
• R strategists
• Sere
• Succession
• Zonation
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Community
• A group of populations interacting in a particular area
• The fish community of Ponce Inlet
• The plant community of the scrub habitat
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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
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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
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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
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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
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Time
Small herbsand shrubs
Heath mat
Jack pine,black spruce,
and aspen
Balsam fir,paper birch, and
white spruceclimax community
Exposedrocks
Lichensand mosses
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Pioneer Communities
• Lichens and Mosses• Survive on nutrients in
dust and rock• Start soil formation1. Trap small particles2. Produce organic
material - photosynthesis
3. Chemically weather the rock
4. Patches of soil form
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Seral Stages: Early Successional Plant Species
• Small perennial grasses and herbs colonize, wind blown seeds
1. Grow close to the ground
2. Est. large pop. quickly in harsh conditions
3. Short lived
4. Break down rock
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Seral Stages: Mid to Late Successional Species
• After 100’s of years soil deep enough
• Moisture & nutrients• Also called Seral
Community1. Shrubs then trees
colonize2. Trees create shade3. Shade tolerant
species establish
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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.
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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
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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
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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
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1000Percentage disturbance
Sp
ecie
s d
iver
sity
The intermediate disturbance hypothesis
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Townsend et al, cited in Begon Harper & Townsend, Ecology
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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
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Time
Annualweeds
Perennialweeds and
grasses
ShrubsYoung pine forest
Mature oak-hickory forest
Succession of Abandoned Farmland
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Heliconia Bracts
Tropical Rainforest flower
Newer flowers form at the bottom
As flowers form they fill with waterSupport aquatic communities
Newly formed bracts early succession
Nutrients and organics build up
Over time succession occurs Higher bracts have climax
communities
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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
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3. Gross productivity changes (total photosynthesis)
• 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• # of trophic levels increases over time• Energy lost as heat increases with more transfers
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MidsuccessionalSpecies
ElkMooseDeerRuffled grouseSnowshoe hareBluebird
Late SuccessionalSpecies
TurkeyMartinHammond’s flycatcherGray squirrel
WildernessSpecies
Grizzly bearWolfCaribouBighorn sheepCalifornia condorGreat horned owl
Early SuccessionalSpecies
RabbitQuailRingneck pheasantDoveBobolinkPocket gopher
Ecological succession
© 2004 Brooks/Cole – Thomson Learning
Overview of Successional Changes
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Factors in Succession1. Facilitation
• One species makes an area suitable for another in a different niche
• Legumes add nitrogen so other plants thrive
2. Inhibition• Early species hinder establishment and growth of later
species more disturbance needed to continue• Allelopathy by plants is an example
3. Tolerance• Late successors not affected by earlier ones• Explains mixture of species in Climax Communities
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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
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Aquatic Succession
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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
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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
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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…
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Grizzlybear
NORTHAMERICA
Spottedowl
Black-footedferret
Kemp’sridleyturtle
Californiacondor
Goldentoad
Columbia haslost one-third ofits forest
Black liontamarin
SOUTHAMERICA
More than 60% of thePacific Northwestcoastal forest hasbeen cut down
40% of North America’srange and croplandhas lost productivity
Hawaiianmonk seal
Half of the forestin Honduras andNicaragua hasdisappeared
Mangrovesclearedin Equador for shrimp ponds
SouthernChile’s rainforest isthreatened
Little of Brazil’sAtlantic forestremains
Every year 14,000square kilometers ofrain forest is destroyedin the Amazon Basin
Coral reef destruction
Much of Everglades National Park has dried outand lost 90% of its wading birds
ATLANTICOCEAN
PACIFICOCEAN
Manatee
Chesapeake Bay is overfished and polluted
Fish catch in the north-west Atlantic has fallen42% since its peak in 1973
Humpbackwhale
St. Lawrencebeluga whaleEastern
cougar
Floridapanther
Environmental degradation
Vanishing biodiversity
Endangered species
6.0 or more childrenper woman
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EUROPE
Mediterranean
Liberia
AFRICA
Imperial eagle
640,000 square kilometerssouth of the Sahara haveturned to desert since 1940
Mali
BurkinaFaso
SierraLeone Togo
Sao Tome68% of theCongo’srain forestis slatedfor cleaning
Fish catches inSoutheast Atlantichave dropped by morethan 50% since 1973
Blackrhinoceros
Zambia
Angola
CongoRwandaBurundi
UgandaSomalia
Nigeria
ChadNigerBenin Golden
tamarin
Ethiopia
Eritrea
Madagascar haslost 66% of itstropical forest
Aye-aye
YemenOman
SaudiArabia
Poland is one ofthe world’s mostpolluted countries
Many parts offormer Soviet Unionare polluted withindustrial and radio-active waste
Area ofAral Sea hasShrunk 46%
Central Asia from theMiddle East to Chinahas lost 72% of rangeand cropland
ASIA
Asianelephant
India andSri Lankahave almostno rainforest left
In peninsular Malaysiaalmost all forests havebeen cut
INDIAN OCEAN
Indonesia’scoral reefs arethreatenedandmangroveforestshave beencut in half
Giantpanda
Kouprey
Queen Alexandra’sBirdwing butterfly
Nail-tailedwallaby
AUSTALIA
Much ofAustralia’srange andcroplandhave turnedto desert
90% of the coral reefsare threatened in thePhilippines. All virginforest will be goneby 2010
Deforestation in the Himalayacauses flooding in Bangladesh
Japanese timber importsare responsible for muchof the world’s tropicaldeforestation
Blue whale
ANTARCTICA
A thinning of the ozone layer occursover Antarctica during summer
Snow leopard
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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
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Hydrosere
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Halosere• 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.
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Halosere
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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.
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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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