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(Physical) Structure&
Diversity(biological structure)
ofEcosystems
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Apopulation :
a group ofindividualsofthesamespecies
inhabiting thesame area atthesametime.
Important characteristics:
Population Size
Population Density Genetic Diversity
Autecology & Population Ecology
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Kirkwood Lake Pr
plantation planted
in 1928 :notebiological &
physical structure
ofmonoculture
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Communities :
populationsofmanyspecies
living & interacting together
inthesame location
atthesametime.
Similar communitiesoccur undersimilarenvironmental conditions; but
Composition & structure canvary
considerablyfromone locationto another.
Ecotones : Transitions between communities.
Community Ecologyor Synecology
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Physical STRUCTURETerrestrial Ecosystems based primarilyongrowth habitofplants
ground layer (bryophytes & herbs +
dead,downedtrees)
shrubby layer understory canopy
(sometrees suppressed)
overstory canopy
(dominanttrees;may bemorethanone) climbing vines & epiphytes
may beonlyone layer (?)
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Rich understory species &
downed logs / coarse woody
debris
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Greenwood Lake White Pine Stand Diversity
Foreststructure & compositionOverstory: 100% Pw (composition)
Lower canopy: white & black spruce, balsam
fir, white & yellow birch,sugarmapleShrub layer:mountainmaple and beakedhazel
Herbaceous layer
Standing snags and downed logs(coarse woody debris)
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Physical STRUCTURE
Aquatic Ecosystems
(standing orflowing water)
based 1 on chemical propertiesofwater:1. salinity(saltwater,freshwater, brackish)
2. temperature
3. dissolvedoxygen4. Clarity(colour & how well sunlightistransmitted)
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FreshwaterAquatic Ecosystem
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Changesoverspace & time
Ecological succession (time)
& zonation (space)
(See E&FBCh.21; SternCh.25)
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Succession
During succession plantspecies (& otherorganisms) graduallychangetheirenvironment
sothatotherspecies are better adaptedtonew environment;
New specieseventually becomethedominant
plantformsinthat area. Species composition (& communitystructure)
has changed.
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Succession
Primary Succession - Soil Formation
Secondary Succession - Disturbed areas
Pioneering, Transitional & Climaxspecies:
seres
Climax Vegetation - Stable plant associations
(structure & diversityinequilibrium)
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Primary Succession
Xerosere :Primarysuccessionthat begins with bare rocks
and lava thathave beenexposedthrough
glacial orvolcanic activity,orthroughlandslides
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Primary Succession
Hydrosere :Successionin wethabitats.
May be accelerated byeutrophication:
duetoenrichmentfromsedimentorother runoffcomponents
(ie. phosphorousfoundin
fertilizers & detergents)
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Secondary Succession:Fire Ecology
Natural fires,started primarily by lightning,have played a roleinecosystemsfor
thousandsofyears
ie. Western US, growth ringsofPonderosaPinesfire cycle wasofevery 6-7years;
aroundhere, 60-120 typical
specieshavespecific adaptationsto regular
fires;trying toeliminatefiresdisruptsnatural
cycles & ecosystems; can leadto
catastrophic fires.
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Fire Ecology
Fires also play a roleinforestspeciescomposition:
Manytreespecies repeatedly replace
themselves afterfires (fire climax) Firesmaintain grasslands by recycling
deadorganic material, and byeliminating
shrubs and woodyspecies.
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EdaphicClimax
Somesiteshavespecific soil typesthat restrictthespeciesthat can grow there:
dry, acidic & nutrient-poor: jack pine
wet, acidic & nutrient-poor: black spruce
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Diversity
Number & proportionofspecies can beassessed atdifferent levels
plant communityor association
eg.foreststand,meadow watershedor landscape
forest region
biome(E&FBCh. 28 & 29; SternCh. 26)
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Tundra
Primarily abovethe arctic circle Abovetreeline
Precipitation averages < 25 cm annually
Permafrostholds water atornearthesurface
Short growing seasonof2-3months
Hightemperatures rangeto about 27oC Veryfragile
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Taiga
NorthernConifer (Boreal)ForestAdjacentto andsouthofarctic tundra
Dominated by Spruce,Fir, and Pine
Disturbance-drivenecosystems (1 fire) ExtremeClimate:
Temperate Range-50oCto30oC
Annual precipitation rangesfrom 25-100cm,mostlyinthesummer
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Temperate DeciduousForest
Composedofmostly broad-leaved (fall)deciduoustreespecies
Mostlyin continental interiorsofNorthern
Hemisphere
Longer growing season:
Temperatures rangefrom4oCto 20oC
Annual precipitation rangesfrom 50-165 cm;mostlyoccursinsummer
During summer,solid canopy keepsdirect
sunlightfrom reaching theforestfloor
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Algonquin Park
Forest
Authority
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Grassland
Foundininteriorofcontinental massesoftendueto rainshadow effect
Broadleaftrees,butonly around water courses
Mostlyone layerto communitystructure
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Grassland
Warmsummertemperaturesincreasesevaporationrates
Annual precipitation rangesfrom 25-100 cm
Temperatures rangefrom-45oCto45oC
NorthAmerican grasslands (prairies) grew onfertilesoilssupporting largeherdsofmigratory grazingbuffalo
Mediterranean climate receivesmost
precipitationinthe winter,thus grassesdonotgrow astall asthoseofMidwestern prairies
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Desert
Manyofthe worldsmajordeserts are located at30o N and30o S latitude
Plant adaptationsincludethick cuticles, water-
storagetissuesinstems and leaves, andthick
leaves and / or reducedinsize Verydry:
Most receive < 12.5 cm annual precipitation
Low humidity Widedailytemperaturefluctuations
15oC- 35oCon a hotsummerday
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WesternCoastal Forest
TemperateConiferous Rainforests Pacific Northwest
w slopeofmountainous spineinNA
orographic precipitation
-10 Cto +10 Ctemperature range
long growing season
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MountainForests
SubalpineForests portionsofthe RockyMountains andthe
Sierra Nevada Mountains
SimilartoBoreal Forest
Conspicuous altitudinal zonationofspecies
Relativelydrysummers Frequentforestfire regime
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Tropical RainForest
Closeto Equator
Verydiverse communitiesdominated by broad-leavedevergreentrees
Densemulti-layered canopy
Shallow rootsystems
Poorsoils;Nutrientseither uptaken by plantsorleached byheavy rainfall
Annual precipitation rangesfrom 200-400 cm.
Nodryordormantseason Humidity usually > 80%.
Temperatures range between 25oC and35oC.
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