It

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Its a diverse planet
The Community Concept and Ecological Gradients
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Rainforests 6 of Earths surface- 50 of the
species In the Amazon- - 170,000 species of
plant (68 of the known total- 250,000) - In 5
acres- 300 species of tree. - 30 of all bird
species
http//www.exploratorium.edu/frogs/rainforest/inde
x.html
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Insect diversity is unimaginable, and
unknown One example 2.5 acres- 18,000 species
of beetle- most of them were new to science (had
no name).
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Humans, have no misconceptions about your own
importance! You and you mammalian brethren are
but a teeny grain on the sandy beach of
Biodiversity.
Figure from The Diversity of Life, EO Wilson,
University of Harvard Press
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These species interact, in complex ways, with one
another- and with the constantly changing
environment. And the complexity multiplies
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Community Ecology is sciences attempt to grapple
with this complex world...
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Ok, fine, but what IS an ecological community??
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Dr. Fredrick Clements The Community as
Superorganism
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Dr. Henry Gleason The individualistic
hypothesis of community organization
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Vegetation of the Smokey Mountains

• R. H. Whittaker (1920-1980)
• Vegetation of the Great Smokey Mountains
• (Ecological Monographs 26 1-69)

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a. Tilia heterophylla b. Halesia monticola c.
Tsuga canadensis d. Quercus alba
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Which archetypal view of the community does this
support?
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Edaphic gradient (salinity)
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Edaphic gradient (water-logged soil)
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Persistent-disturbance gradient
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Temporal gradients (long-term)
1) Climate changes constantly 2) This change
alters the tolerance vs. competition balance for
species. 3) In response, species ranges shift-
and thus- gradients move in space. 4) This
dynamics is unending, what we think of as static
(e.g., maple forests in New England) isnt.
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Margaret Davis...
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SCIENCE !
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Pollen (SEM)
Juniperus sp.

Acer rubrum
Ambrosia trifida
http//www.geo.arizona.edu/palynology
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Margaret Davis Rogers Lake Ecology
(50409-422), 1969
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http//www.ncdc.noaa.gov/paleo/pollen/viewer/webvi
ewer.html
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Shorter-term temporal gradients are successional
changes.
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Ecological Gradients