Stability through Biogeography

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Stability through Biogeography
2013-04-26 00:08:22
stability ecology biogeography landscape

Chapters 21-23
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  1. Succession
    Change in plant, animal, and microbial communities in an area following disturbance or the creation of new substrate
  2. What makes up a landscape?
    • 1) It's a heterogenous area consisting of distinct patches or landscape elements
    • 2) Structure includes size, shape, composition, and position of patches in a landscape
    •     - fractal geometry can be used to quantify the structure of complex natural shapes
  3. Stability facts
    • Stability is the ability of an ecosystem to bounce back from a disturbance
    • Occasionally the ecosystem tends to flip its stabilizing feedbacks
    • The stability of an ecosystem is the amount of work required to push it into a new regime
  4. What is hysteresis of a system?
    Hysteresis—the path out is not the same as the path back; the state of a system depends on its history
  5. Regime of an ecosystem
    The particular species and energy/matter flows present at any given time in an ecosystem
  6. Where do alluvian fans come from?
    • They typically form at the base of topographic features where there is a sudden flattening of slope between mountains.
    • Overlapping of alluvian fans is called bajadas
  7. Examples of ecosystem engineers
    Elephants, beavers, humans, moles - any organism that changes the landscape
  8. What factors determine whether a species has a successful, self-sustaining population in any given area?
    • Isolation factors - determine whether a species can get to a place and can overcome dispersal limitation
    • Extinction factors - determine whether a species persist and becomes established in the community
    • It has to get there
    • Once it is present, it must persist
  9. How are insular habitats important?
    • They help studies of how diversity is influenced by balance of isolation and extinction factors.
    • Some examples are lakes, wetlands, mountaintops, and nature preserves
  10. Species-Area relationship
    • Species richness tends to increase as area increases
    • Shown the most by insular habitats
  11. Beginning with this graph, compare rate of immigration of closer islands to immigration of farther away islands.
    • As species richness increases the rate of immigration decreases.
    • Isolation will decrease the immigration rate because more isolated habitats are harder to colonize
  12. If immigration continues, how does the rate of extinction affect the rate of immigration?
    • As immigration declines with the higher number of species present, extinction rate goes up.
    • When comparing far and near insular habitats from the colonial habitat, the rate of extinction is less in far insular habitats as less species inhabit.
  13. How is the extinction rate affected with small versus large insular habitats?
    Large habitat size will decrease the extinction rate because large habitats likely provide greater niche diversity to reduce competitive exclusion and over-exploitation
  14. Hypothesis for latitudinal diversity gradient?
    • Although there are exceptions, many groups of organisms exhibit the greatest diversity in the tropics
    • Diversity decreases moving away from the tropics toward the poles
    • Time since disturbance
    • Productivity
    • Environmental heterogeneity
    • Land area
  15. The Suess effect
    The decrease in 14C with fossil fuel burning of 12C, measured by tree bark rings
  16. What causes the climate to switch between La niña and El niño?
    • During La niña, there is low barometric pressure, high precipitation, and warm temperatures over Australia; high pressure, strong westerlies, and high primary productivity due to upwelling in South America.
    • During El niño, westerlies weaken or shut down, pressure evens out or maybe flips, and thermocline evens out causing upwelling to stop.
  17. How are humans contributing to the increase in mineral Nitrogen?
    • Fertilizer production
    • Legume/N-fixing crops
    • Fossil fuel burning