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Fragmentation and Edges

Fragmentation and Edges. Fragmentation. Total area decreases Size of patches decreases Number of patches increases Isolation increases, connectedness decreases Edge length increases But changes in habitat arrangement rarely occurs without habitat LOSS. What happens?.

roary-mcbride
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Fragmentation and Edges

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  1. Fragmentationand Edges

  2. Fragmentation • Total area decreases • Size of patches decreases • Number of patches increases • Isolation increases, connectedness decreases • Edge length increases • But changes in habitat arrangement rarely occurs without habitat LOSS

  3. What happens? • Island biogeography: sampling loss, extinction increases, immigration decreases • Genetics: sampling loss, effective population size decreases, drift increases, gene flow decreases • Populations: population size decreases, extinction risk increases • Metapopulations: immigration decreases, patch occupancy falls, extinction risk increases • Communities: species interactions change, integrity (area larger enough for key processes like top predators and fire) decreases

  4. What happens? • Deterministic change: habitat change • Random change: losses as f(area, isolation) [Extinction Debt] • Incidence functions, threshholds • Area-sensitivity • Isolation-sensitivity

  5. Megareserves for large predators >106 ha 100 km linear extent

  6. BobcatGeorge Hesshttp://www4.ncsu.edu/~grhess/research/regplan/

  7. Jordan Lake Macrosite

  8. Come In, 1942 As I came to the edge of the woods,

  9. Thrush music, Hark!

  10. Now, if it was dusk outside, Inside it was dark. Too dark in the woods for a bird By sleight of wing To better its perch for the night, Though it still could sing.

  11. The last of the light of the sun That had died in the west Still lived for one song more In a thrush’s breast Far in the pillared dark Thrush music went– Almost like a call to come in To the dark and lament.

  12. But no, I was out for the stars, I would not come in. I meant not, even if asked, And I hadn’t been.

  13. Come In! …Almost like a call to come in to the dark and lament. But no, I was out for the stars. I would not come in. I meant not even if asked And I hadn’t been.

  14. The Wood Thrush, Shade Grown CoffeeThe New Hope Audubon SocietyFred Houk, Jr. December 30, 2000, Chapel Hill Herald

  15. The 3 Step Process of Species Loss and Extinction Debt Instantaneous Fast Faster & Greater Loss as Area Slow Extinction debt Steeper z

  16. Changes around edges? • Greater number of invasives • Microclimate changes • Light • Soil moisture http://chesapeake.towson.edu/landscape/forestfrag/all_habitatfrag.asp

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