The ecosystem 2.5 2.6 2.7

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The ecosystem 2.5 2.6 2.7

  1. 1. DP Environmental systems and societies Topic 2 The ecosystem
  2. 2. 2.5 FUNCTION
  3. 3. Ecosystem function • Producers, consumers, and decomposers all have their part to play in cycling materials and energy in the ecosystem
  4. 4. Energy cycles
  5. 5. Material cycles • Refer to Topic 1 ppt Also • Photosynthesis • Photosynthesis and respiration • Carbon cycle
  6. 6. Nitrogen in the air animal protein dead plants & animals urine & faeces ammonia nitrites nitrates plant made protein dead rabbit decomposition by bacteria & fungi bacteria (nitrifying bacteria) nitrates absorbed denitrifying bacteriaroot nodules (containing nitrogen fixing bacteria) nitrogen fixing plant eg pea, clover bacteria Free powerpoints at http://www.worldofteaching.com Copy all!
  7. 7. Terminology Primary productivity – the gain by producers (autotrophs) in energy or biomass per unit area per unit time Secondary productivity – the biomass gained by heterotrophic organisms through feeding or absorption
  8. 8. Terminology Gross productivity (GP) – the total gain in energy or biomass per unit area per unit time Gross primary productivity (GPP) - GP of primary producers Gross secondary productivity (GSP) – GP absorbed in consumers
  9. 9. Terminology Net productivity (NP) – the gain in energy or biomass per unit area per unit time after allowing for respiratory losses (R). Net primary productivity (NPP) – NP for producers NPP = GPP – R. Net secondary productivity (NSP) – NP for consumers NSP = GSP – R.
  10. 10. • Would you consider open ocean or tropical rainforest to be the most productive? Why? • (consider area)
  11. 11. Is this primary or secondary productivity? Gross or net productivity? Biomass or energy?
  12. 12. 2.6 CHANGES
  13. 13. Limiting factors • Temperature
  14. 14. Limiting factors • Food source
  15. 15. Limiting factors Density dependent (negative feedback) • Competition for resources • Space • Disease • Parasitism • Predation • Population size Density independent • Extremes of weather • Long-term climate change • Volcanoes and tsunamis
  16. 16. S and J curves - animation
  17. 17. r strategists K strategists
  18. 18. r strategists K strategists Initial colonizers Dominant species Large numbers of a few species Diverse range of species Highly adaptable Generalists Rapid growth and development Slow development Early reproduction Delayed reproduction Short life Longer living Small size Larger size Very productive Less productive
  19. 19. 2.6.5 Succession
  20. 20. Succession 繼承法 Predictable changes in a community Knowing what animals and plants will dominate next
  21. 21. Primary succession A series of changes that occurs where no organisms exist
  22. 22. Pioneer species The first species in primary succession Pioneer species
  23. 23. Secondary succession A series of changes that occurs when there are organisms to begin with
  24. 24. Secondary succession A series of changes that occurs when there are organisms to begin with
  25. 25. Figure 53.18 Patchiness and recovery following a large-scale disturbance
  26. 26. Figure 53.18x1 Large-scale disturbance: Mount St. Helens
  27. 27. Figure 53.18x2 Forest fire
  28. 28. Figure 53.19 A glacial retreat in southeastern Alaska
  29. 29. Table 53.2 The Pattern of Succession on Moraines in Glacier Bay
  30. 30. Figure 53.20 Change in soil nitrogen concentration during succession after glacial retreat in Glacier Bay, Alaska
  31. 31. Figure 53.20 Alders and cottonwoods covering the hillsides
  32. 32. Figure 53.20 Spruce coming into the alder and cottonwood forest
  33. 33. Figure 53.20 Spruce and hemlock forest
  34. 34. Terminology Zonation – different to succession – difference due to environmental gradient (eg. altitude) Succession occurs over several seral stages where each sere is a set of communities. Plagiosere – humans prevent a climax community – growing crops
  35. 35. Hydrosere (water)
  36. 36. Lithosere (rock) – one type of xerosere (land)
  37. 37. Psammosere (sand) – one type of xerosere (land)
  38. 38. Climax community • Greater biomass • Higher levels of diversity • Better soil conditions • Better soil structure • Lower pH • Taller and longer living plants • More K less r strategists • More complexity and stability • More habitat diversity • Steady state equilibrium • Production:respiration ratio P/R reaches 1 (not ideal for agriculture)
  39. 39. 2.7 MEASURING CHANGES IN THE SYSTEM
  40. 40. Evaluating transects • Same time of day (abiotic and biotic variables) • Samples taken througout the year (seasonal variations) • Repeat transects for reliable data (minimum 3 times) • Random number generator for where to take transects to eliminate bias
  41. 41. Measuring changes – human activity • Satellite images eg. deforestation • Monitoring stations eg. Taiwan EPA • Erosion rates
  42. 42. Environmental Impact Assessments (EIAs) • To decide if the project will be too damaging or not, and to mitigate any damage. 1. Baseline study 2. Monitoring during and after development
  43. 43. Variables in EIA • Habitat type and abundance • Species list and diversity including endangered species • Land use – access and coverage • Water flow • Human population • Soil quality and fertility • Example EIA for a dam project

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