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Succession Slides 2012


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Slide deck from APES class on 11/13/12.

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Succession Slides 2012

  1. 1. Population Changes in Context - in Communities!
  2. 2. Succession Defined:• The gradual, sequential change in the relative abundances of the dominant species in a biological community following a disturbance…• Primary succession: beginning from an abiotic environment following a cataclysmic disturbance• Secondary succession: beginning from a major disturbance, but all forms of life are not destroyed
  3. 3. Primary or Secondary? Volcanic Island
  4. 4. Primary or Secondary? 1988 Fires in Yellowstone NP
  5. 5. Primary or Secondary? Old Parking Lot
  6. 6. Primary or Secondary? Glacial Retreat
  7. 7. Primary or Secondary? Old Farm
  8. 8. Primary Succession (forest)• Colonization: of bare rock, tiny seedless plants like mosses, and lichens, “pioneer species”• Early: plants typically small with short lifecycles (annuals), rapid seed dispersal, “environmental stabilizers”• Middle: plants typically longer lived, slower seed dispersal (herbs, shurbs, perennials)• Late: plant species are those associated with older, more mature ecosystem-largest vegetation (trees)• “Climax Community” mature forest in this case (but varies by biome) *Note: Consumers and decomposer populations will also vary as producer populations change…as well as nutrient cycling…
  9. 9. Research on Primary Succession
  10. 10. Research on Secondary Succession
  11. 11. Hutcheson Memorial Forest Center (NJ) Old Field Secondary Succession1962-1995
  12. 12. Hutcheson Memorial Forest Center (NJ) Old Field Secondary Succession1962-1995
  13. 13. Hutcheson Memorial Forest Center (NJ) First Year
  14. 14. Hutcheson Memorial Forest Center (NJ) Fifth Year
  15. 15. Hutcheson Memorial Forest Center (NJ) Tenth Year
  16. 16. Hutcheson Memorial Forest Center (NJ) Twentieth Year
  17. 17. Hutcheson Memorial Forest Center (NJ) Twenty-Eighth Year
  18. 18. Changes in Biodiversity
  19. 19. © 2003 John Wiley and Sons Publishers
  20. 20. © 2003 John Wiley and Sons Publishers
  21. 21. Succession in Aquatic Ecosystems © 2003 John Wiley and Sons Publishers
  22. 22. Succession in a Pond 1960s to 1990s
  23. 23. Is a Climax Community Always Inevitable?• New research suggests that we cannot always project the course of a given succession or view it as preordained• Communities are always subject to disturbances and we cannot always know the outcome• Disturbances can be beneficial for communities…
  24. 24. The Intermediate Disturbance Hypothesis• Hypothesis: Communities that experience fairly frequent but moderate disturbances have the greatest species diversity• Reasoning: Moderate disturbances are large enough to create openings for colonizing species in disturbed areas, but mild and infrequent enough to allow the survival of some mature species in undisturbed areas
  25. 25. ‘General Ecology’, D.T. Krohne
  26. 26. Ecotones• Disturbances often create ecotones, but they also exist as natural transitions between biomes or ecosystems• An ecotone is a transition area between two adjacent ecological communities – a sharp boundary or a gradual blending effect – particularly significant for mobile animals, as they can exploit more than one set of habitats within a short distance – this can produce an edge effect along the boundary line, with the area possibly displaying a greater than usual diversity of species
  27. 27. Edge Effects• Disturbances can fragment ecosystems and create edge effects• An edge effect describes the differing abiotic and biotic conditions that exist at a border between contrasting environments in an ecosystem – the increased light, greater wind and temperature extremes and lower humidity at the boundaries of fragments favor some plant species over others (native colonizing species or invasive species) – this can make the combination of species present near the boundary different from that inside the fragment (more diverse or less depending on the factors)
  28. 28. Remember This Edge Effect? Kudzu at DCEP
  29. 29. The Island Theory of Biogeography• Small islands have fewer habitat types and greater risk of extinction-smaller islands have less genetic diversity too• The more distant the island, the less chance of reaching it• Over time, an island tends to maintain a constant number of species, because the rate at which species are added is about the same as the rate at which other species become extinct
  30. 30. The Island Theory of Biogeography• Species often evolve to a smaller size on islands because islands often have a limited supply of food, fewer predators, and fewer species competing for the same resources• Examples include island foxes, pygmy mammoths, and a dwarf human species Homo floresiensis
  31. 31. The Island Theory of Biogeography• Island concepts can also be applied to “ecological islands”• Ecological islands are comparatively small habitats separated from a major habitat of the same kind – A small stand of trees within a prairie is a forest island
  32. 32. Habitat Fragmentation (and ecological islands)
  33. 33. Solution: Wildlife Corridors
  34. 34. Bibliography•• 20Intro.htm•