Starter: Discuss with a partner!

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Starter Discuss with a partner!

• In Meaghers Grant youll find populations of
  both wild rabbits and fox. Explain why there are
  usually more rabbits than fox (there are many
  reasons, how many can you come up with?).

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• The following food web is an example of the
  interactions you can find in the Bay of Fundy.
  Herring is a popular fish to catch in this
  particular area. How would the overfishing of
  herring cause an increase in the population of
  sea urchins? Explain.

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Which is density -independent population
regulation?

• Hurricane Juan
• The eruption of Mount Vesuvius
• Gang violence
• Shortage of food
• The Eastern shore of Nova Scotia being flooded in
  April
• STDs

4
Which of the following are examples of
intraspecific competition?

• Shirley and Maria fighting over who gets to take
  Bob to the prom
• The development of a swamp ecosystem for new
  condominiums in Gaetz Brook
• My dog Toby growling at a cat over a place to sit
• Children in war-torn Libya fighting over food

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Which of the following are examples of biotic
factors affecting a deer population?

• The amount of grass in the forest
• The amount of hunters in the forest
• The amount of sunlight in the forest
• The season (winter, summer, etc)
• How much snow there is
• The number of rivers in the forest

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Ecology Chapter 1.4 Productivity
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Think About It

• Picture a field of vegetables growing in Nova
  Scotia, and a tropical rainforest in Guatemala.
• Do you think a hectare of a Canadian field and a
  hectare of a tropical forest produce the same
  amount of biomass during a given period of time?
• If not, what might make their production
  different?

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Productivity of Ecosystems

• Productivity the average amounts of new plant
  biomass produced each year on a given area
  (kJ/m2/yr)
• Different ecosystems have different productivities

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Example 1 Estuary (where a river meets the sea)
40 000 kJ/m2/yr
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Example 2 Tropical Rainforest 40 000 kJ/m2/yr
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Example 3 Savanna (groves of trees with a grassy
understory) 13 000 kJ/m2/yr
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Example 4 Desert Scrub 2 000 kJ/m2/yr
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Ecosystem Productivity Levels (See table, p. 25)

• Estuary 40 000 kJ/m2/yr
• Swamp/Marsh 40 000 kJ/m2/yr
• Tropical Rainforest 40 000 kJ/m2/yr
• Temperate Forest 25 000 kJ/m2/yr
• Northern Coniferous Forest 15 000 kJ/m2/yr
• Savanna 13 000 kJ/m2/yr
• Agricultural Land 12 500 kJ/m2/yr
• Woodland and Shrubland 12 000 kJ/m2/yr
• Temperate Grassland 10 000 kJ/m2/yr
• Lakes and Streams 10 000 kJ/m2/yr
• Continental Shelf 7 000 kJ/m2/yr
• Open Ocean 5 000 kJ/m2/yr
• Tundra 3 500 kJ/m2/yr
• Desert Scrub 2 000 kJ/m2/yr
• Extreme Desert 1 000 kJ/m2/yr

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Productivity of different ecosystems
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Plant Productivity and Climate

• Plant growth (and therefore land productivity)
  depends on
• Sunlight
• Water (precipitation)
• Carbon Dioxide
• Nutrients such as nitrogen and phosphorus in the
  soil
• Temperature
• So, whats the best climate for growth?

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The Best Productivity

• Warm temperature and wet areas highest levels
  of productivity
• Cooler temperature and little water low levels
  of productivity
• So why cant we just irrigate a desert or clear a
  rainforest to grow crops?

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• Replacing ecosystems can cause the loss of
  habitats for plants and animals, and a decrease
  in species diversity. This changes the energy
  flow if the ecosystem, change soil composition
  and cycling of water.

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• It would be extremely costly to irrigate a desert
  and there would be many political issues as to
  where the water was coming from and which
  countries they would have to bring it from.

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• Due to its high productivity, nutrients that are
  recycled back into the soil of a rainforest by
  the decomposers are used up as fast as they are
  replaced. As a result, if the rainforest is cut
  down and replaced by a less productive crop
  field, the very thin soil would soon be eroded
  away.

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Desertification

• One of the most serious problems facing people
  today is desertification.
• It results from human activities that degrade the
  land and cause deserts to expand.
• How much of Earths land surface do you think is
  affected by desertification? How many people are
  threatened by it?
• What kinds of human activities contribute to
  desertification?
• How can is be prevented?
• Are there any regions in Canada that may be
  affected by this?