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I.
How did we get frozen poles?
A.Many of thousands of years ago, when the
continents were centered differently. ocean currents used to circulate
to poles, warming them
B. Towards the N. Pole, land masses encircled
the pole, enclosing the Arctic Ocean and cutting off its circulation (
see map below). The waters could no longer be warmed by more southern
ocean currents, and thus they froze. As the sun's rays are too weak at
the poles, major seasonal melting in the region can not occur.
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C. At S. Pole, Antarctic ice masses drifted
toward the pole and eventually settled directly over it. Because of this
large consolidated land mass, ocean currents could no longer circulate
within and the land froze.
Now it's all frozen year round.
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II. What defines the
tundra?
A. The tundra begins where the taiga, the
cold northern forest, ends. There are almost no trees in the tundra.
B. Physically it includes a thin band in Europe
and wider portions of Siberia and North America.
C. The transition between tundra and taiga
is more of an ecotone than a borderline. Flying north over the transition
zone, you would see the trees become smaller and more spread apart until
there was only a sparse spotting of dwarf spruces.
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III. Tell me about the
climate.
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A. The tundra eceives very little precipitation
- less than 25 cm or 9.8 inches/yr, half as rain and half as snow
B. Most of snow falls in Oct.
and Nov., when the air is warm enough to hold some
moisture.
C. If you only considered precipitation it
could be considered a desert, but permafrost keeps moisture imprisoned
there.
D. The tundra has a very short growing season
- about 2 months, because the snow reflects the sun's weak rays until
they become strong enough to melt it. The ecosystem compensates by its
high growth and turnover rate during this period. Average temperature
of the warmest month lies between 50F (10C) and 32F (0C).
E. Springtime brings a rude awakening- together
with the late snow and sleet, ice breaks off surface of rivers and crashes
into banks, tearing apart everything in its path. This is quickly replaced
with a moderating transition to summer and its green revival.
F. Daylight lasts almost 24
hrs a day during summer.
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IV. What is the tundra like?
A. With almost no trees, land formations stand
out i bleak contrast to the exposed landscape.
B. Lakes, ponds, and marshes are surprsingly
common.
C. Although very cold most of year, on the
warmest days of summer, it's possible to swim in the lakes. The average
temp is only 10 degrees C in summer, but some days get quite warm and
even hot.
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Vegetation on the
tundra consists of grasses, sedges, lichens, dwarf
heath,willow shrubs together with associated mosses and
lichens.. As one moves south, the vegetation changes into
birch-lichen woodland, and then into needleleaf
forest.
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Plants are adapted to gusting winds, heavy
snows, and widely ranging temperatures. They carry on photosynthesis under
brilliant light during short periods of daylight
Height wise they must stay within a few inches of ground because of the
strong cold wind and because it is warmest near the ground.....Collect
energy efficiently by holding lots of chlorophyll
Large root systems, often
several times the size of above-ground biomass. Plants send
stored energy, in the form of carbohydrates, into large root
systems so energy can be stored for spring when the growing
season is short and plants must grow quickly.
Growth is spread out over
several growing seasons because each season is so short -
some plants take several growing seasons for their seeds to
develop fully - bud lies beneath snow all winter and
continue developing in the following summer
Instead of seeds, many plants
reproduce by sending out runners, much like the ramet trees
which appear as individuals but are genetically
identical...
Berry bearing bushes and the
artic willow spread horizontally instead of vertically to
avoid transpirational loss of water by the dry wind and to
form a dense mat which stays warmer than above
Most vegetation has compact
shoot/leaf structures with leathery coatings to conserve
moisture
Go to
this page for more on the vegetation of the
Tundra....
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Animals
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 Artic
wildlife is circumpolar (surrounding or near either pole of
the earth), the same or closely related species are found
around the world.
Smaller herbivores:
Arctic hare, or snowshoe rabbit, and lemming, pika,
marmot feed on grasses, sedge and other vegetation. The
ptarmigan, a grouselike bird which we mentioned earlier can
change it feather color to match the
seasons.Go
to this page for more info on this group
Larger herbivores: Musk-ox,
caribou, and reindeer are the dominant large grazers,
feeding on grass, sedge, lichen, and willow.However also
common are the mountain goats, and big-horned sheep.
Go
to this page for more info on this group
Carnivores: include the wolf,
artic fox, and snowy owl. Polar bears, and sometimes brown
bears are seen.Go
to this page for more info on this group
Insects such as black flies
and mosquitoes are abundant as well as butterflies, beetles,
and grasshoppers.
Many birds nest in the tundra
shrubbery in summer, migrating to milder climates before the
winter season sets in.
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Continue on for more information on:
soils/nutrient flow and the
incredible geomorphic
features ( polygons, pingos)
E. Iglich and ecology students from previous courses,
with much indebtednesss to the many excellent web sites which are cited...