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Ecosystem ecology

Ecosystem ecology. Definition: an ecosystem consists of all organisms living in a community as well as all abiotic factors with which they interact. Ecosystem framework. Ecosystems are organized into trophic levels: Primary producers, primary consumers, secondary consumers, detritivores

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Ecosystem ecology

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  1. Ecosystem ecology • Definition: an ecosystem consists of all organisms living in a community as well as all abiotic factors with which they interact

  2. Ecosystem framework • Ecosystems are organized into trophic levels: • Primary producers, primary consumers, secondary consumers, detritivores • Laws of physics and chemistry apply to ecosystems • Law of conservation of energy, second law of thermodynamics, conservation of Elements

  3. An overview of ecosystem dynamics

  4. Primary production • Amount of light energy converted to chemical energy (organic compounds) by autotrophs in an ecosystem during a given time period • It is the result of photosynthetic production • Sets the limits for the ecosystem’s energy budget

  5. Components of primaryproduction

  6. Gross and Net primary production • Gross primary production (GPP): total primary production • Net primary production(NPP): gross primary production minus energy used by primary producers for respiration • NPP=GPP-R

  7. Factors limiting primary productivity • Marine/aquatic systems • Light • Nutrients • Terrestrial systems • Temperature • Water (moisture) • Nutrients

  8. Nutrient addition experiments in a Hudson Bay salt marsh

  9. Regional annual net primary production for Earth

  10. Variation in primary production across ecosystems • Most productive per unit area: tropical forests, coral reefs, estuaries • Least productive per unit area: open ocean, tundra, deserts • Highest contribution because of size: open ocean, tropical rain forest

  11. Secondary production • Amount of chemical energy in consumer’s food that is converted to their own new biomass in a given time period • Much of primary production is not used by consumers

  12. Components of secondary production

  13. Production efficiency Production efficiency = net productivity of species n/assimilation of species n Production efficiency is the fraction of food energy that is not used for respiration Production efficiencies: birds and mammals (1-3%), fishes (10%), insects (10-40%). No differences across habitats

  14. Trophic efficiency • Trophic efficiency = net production at trophic level i + 1/ net production at trophic level i • Measures the efficiency of energy transfer across trophic levels • Trophic efficiencies usually range between 5-20% • A consequence of low ecological efficiencies: variation in abundance or biomass across trophic levels

  15. An idealized pyramid of net production

  16. A pyramid of numbers

  17. What limits secondary production? • Primary production • Second law of thermodynamics • Water • Nutrients • Predation • Competition

  18. Food energy available to the human population at different trophic levels

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