Biomes: The
Earth, Sun, and
Energy Transfer
Global Cycles: the flow of NRG
(Energy) and elements.
With stops at climate change
The ‘greenhouse effect’
C sequestration
Ra
And Global Biomes
Biological Limits
NRG cycling
The Sun, our star, is the source of all NRG for life on earth
X-ray image
from Dec. 2002
The Carbon Cycle
NRG – Atmosphere Balance
Is there ever any potential
problem with linear
extrapolation?
Oxygen
Nitrogen Cycle
NRG Cycle (food chain)
Interdigitation… a ‘fuzzy’ boundary
Global ‘Biomes’
• “ a large, recognizable assemblage of plant and
animals in functional interaction with its
environment”… strongly related to climate
• Tropical rainforest
• Tropical deciduous forest
• Tropical Scrub
• Tropical Savanna
• Desert
Tropical Rainforest
Tropical Scrub
Desert
Mid and High Latitude Biomes
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Mediterranean woodland
Steppe
mid-latitude grassland
Savannah
Deciduous forest
Boreal Forest
Tundra
Mountain and Polar regions
“Mediterranean” woodland
Steppe regions are
transitional between
desert and
grassland/forest
biomes
Savannah: another transitional biome, between forest and grassland
Grasslands… some of
the most fertile soils on
the planet.
Mid-Latitude Forests
Boreal Forests
Arctic Tundra
Alpine tundra
Altitude Compensates for Latitude
Mt .Kilamanjaro, 200 miles S. of the equator displays
the full range of climatic conditions from equatorial
steppe and forests to tundra and permanent ice fields
Climbing Mt. Kilmanjaro
Photos courtesy of Will
Spivey
Adaptation and Succession
• A vast array of mechanisms have been
developed to spread organisms to
appropriate habitats.
• Organisms will take advantage of very
small differences (micro-climates)
• Nothing is stationary, everything changes
and organisms must adapt and shift with the
changing conditions.
The “Limiting Factor”
• Organisms spread to the outer limits of their
biological range…
• Usually a single factor prevents the further
spread (or continued growth) of an
organism.
• Nutrients (nitrogen, calcium etc.),
water (not enough… too much),
temperature (extremes of heat and cold).
Vegetative Succession
• Plant communities change on the landscape
through time.
• After a disturbance (fire, a pond silting in, a
landslide, an agricultural field) the first plant
community to colonize the site is the pioneer plant
community
• Following the first are an undefined number of
different communities… Seral stages
• Finally, barring additional disturbance the
vegetative community that can best utilize the site
becomes established… the Climax stage.
Succession in a pond. All lakes are very short lived
structures.
Vegetative Succession
• A theory that holds under a given set of
climatic/edaphic conditions vegetation will
follow a path of vegetative succession from
Colonizers to the “climax” vegetation…
that vegetation community best adapted to the
conditions.
An example for a hardwood forest
biome……
Fire Ecology
• Smokey Bear was not fully correct.
• Many ecosystems depend on regular fire to
create a unique ecosystem.
• The vegetation community can be called a
‘fire climax’
Fire is a natural part of the
ecosystem
• ‘ground fires’ tend to burn through the low
growing brush and small trees
• These flashy hot fires scorch the larger
vegetation, but leave it largely intact.
• In some environments, ‘natural’ fires are
supplemented by ‘controlled burns’
However,
• When natural fires have been suppressed, the fuel
load can build much higher than would occur under
a more frequent (“natural”?) fire regime.
• The resulting fires destroy virtually all vegetation,
resulting not in a ‘fire climax’ community, but bare
soil suitable for a ‘pioneer’ community. e.g.
Yellowstone
Sidebar:
Vegetative
dispersal
What is Natural?
• Is a beaver dam
“natural”?
• Is Wilson Dam
‘Natural’?