Chapter 6: Kinds of Ecosystems

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Chapter 6 Kinds of Ecosystems Communities

• Succession Primary Secondary
• Biomes Terrestrial Aquatic

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Start with bare rock - glacier, volcano fig. 6.2
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Pioneer Organism Lichens fig 6.1Grow right on
rock, break down rock to start forming soil
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Floating Bog figure 6.4Stage 4 in previous
figure. Eventually succeeds to a climax forest
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Soil remains - plowed field, fire fig. 6.5
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Figure 6.6
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Biomes

• Types of Climax Communities Vegetation mainly
  determined by Climate
• Climate mainly determined by temperature
  moisture

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Desert

• Less than 10 inches of rain per year
• Sahara, Atacama, SW US, Kalahari, Australian
• Not necessarily hot - e.g., Gobi, NW US, Poles
• High biodiversity low biomass

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• Gobi Desert

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Grassland Prairie, Steppe

• Fairly dry (10-30 inches of rain)
• Hot summers, mild-cold winters
• Fire or flooding and/or dryness prevent trees
  from establishing

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Grassland Prairie, Steppe

• Good soil for agriculture
• See box on page 118 Grassland succession
• Prairie restoration project at SJC (by Lake Banet)

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Grassland Succession
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Grassland Succession (continued)
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Savanna

• Hot grassland with scattered or patches of trees
• e.g., Serengeti
• Seasonal rainfall Monsoons gt 2 seasons dry,
  wet
• Grades into Tropical Deciduous Forest

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Tropical Rainforest

• Wet and hot all year round
• Near equator in S Central America, Africa, SE
  Asia, Pacific Islands
• Highest biodiversity biomass (more species than
  rest of world combined)

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Tropical Rainforests Farming

• Soil quality is quickly depleted after
  deforestation due to high moisture temps gt
  leaching of nutrients
• Slash Burn agriculture on small scale is only
  sustainable kind
• Read Box on page 121 - Farming
• Conclusion This biome cant support large human
  population!

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Temperate Deciduous Forest

• Sufficient moisture change of seasons (4
  well-defined seasons)
• Fertile soil for agriculture

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Temperate Rainforest

• Pacific NW mild temps, 80 inches rain annually,
  fertile soil
• Many conifers as well as deciduous
• Can have trees up to 800 years old, over 300 feet
  tall
• Over 90 of old-growth forest has been logged

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Boreal Forest Taiga

• Long, cold winters, short cool summers
• Lots of snow
• Conifers
• Grades into tundra at higher latitudes

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Tundra

• Very short summers (or high altitude gt alpine
  tundra)
• Lower layer of soil is permanently frozen gt
  permafrost gt no trees, also lots of swamps,
  ponds
• Insects, migratory birds, hardy mammals

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Aquatic Ecosystems

• Marine (salt water)
• Fresh (Lakes Streams)
• Brackish Estuaries

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Figure 6.19All production (photosynthesis) in
(shallow) euphotic zone true light
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Marine ecosystems

• Most productive in shallow water (few 100 feet)
  gt close to shore
• The most productive marine ecosystem is a coral
  reef fig 6.21 gt
• Needs shallow, warm, clear water
• Very susceptible to sediment pollution (turbidity)

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Open Ocean

• Average ocean depth over 10,000 feet gt no light
  penetrates
• Most of ocean has low productivity, similar to a
  desert

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Estuaries

• Shallow, partially enclosed bays where fresh and
  saltwater mix gt brackish water
• E.g. Chesapeake Bay, Mississippi Delta
• Get lots of nutrients from in-flowing streams
  shallow water (lots of sunlight) gt very
  productive ecosystem (3rd most on earth)
• Susceptible to pollution because of coastal
  cities

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Chesapeake Bay
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Freshwater Ecosystems

• Lakes Streams

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Lakes

• Geologically short-lived features
• Classified by nutrient levels
• Physical measures of health include
• Dissolved oxygen (O2) levels DO
• Organisms cant get oxygen from H2O
• Low DO indicates pollution
• Biological oxygen demand BOD
• nutrients fertilize algae gt algae dies gt
  bacteria decompose algae gt creates higher BOD gt
  depletes dissolved O2 gt Eutrophication
• Very clean lakes have low BOD, but so do dead
  ones

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Causes of Eutrophication

• Sediment from streams carries nutrients,
  especially true in agricultural regions or where
  wastewater not properly treated
• Sediment also makes lake shallower gt ages the
  lake
• Eventually becomes bog then dry land Recall
  secondary succession figure 6.3

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Classification of Lakes

• Oligotrophic
• Deep, cold, nutrient-poor (low productivity)
• High DO, low BOD
• Typical pure, clean mountain lake (young)
• Eutrophic
• Shallow, warm, nutrient-rich (over-fertilized)
• Low DO, high BOD (unless dead)
• Typical scummy farm pond (old)
• Mesotrophic Somewhere in between
• Most recreational lakes lots of fish, but clean
  enough for swimmin (middle-aged)

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Oligotrophic Lake Mmmm...
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Eutrophic Lake yucky...
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Mesotrophic Lake typical...
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Streams

• Flowing water makes them easier to clean up than
  lakes
• Upstream Faster flowing gt Higher DO, lower BOD
• Picks up sediment nutrients downstream water
  flows more slowly gt lower DO