Only a few
species live in this difficult environment. The food chains are
short, and vulnerable to stresses. Permafrost under the temporarily
thawed ground makes water drainage impossible, so there are many
small lakes and puddles, and much of the ground is soggy. When
all the water freezes it becomes unavailable to life forms, and
so creates a sort of cold drought in which animals and plants
may die of thirst. The detritus eaters, bacteria, fungi, and
tiny soil organisms, work very slowly because the cold temperatures
slow down chemical reactions. Available nutrients in the soil
are therefore scarce, even though undigested material lies on
the surface of the ground.
Plants in this
biome are small, perhaps four inches high. They form little cushions
or mats that lie closely on the ground. The albedo
of the plants is less than that of the surrounding soil, which
lets them absorb a little more of the solar heat. The ground
is a little warmer than the air, so the plants stay as close
to the ground as possible. Some of them have little hairs on
their stems to hold warmer air as the cold winds blow. The vegetation
consists of grasses, wild flowers, sedges, mosses, dwarf willows,
and lichens. Many of the plants are perennials so that they can
store food from season to season. Most can reproduce vegetatively
from underground shoots, as sudden freezing storms can occur
at any time, and make seed production a gamble.
The musk oxen eat
the plants, but their predators do not live in this biome. The
musk oxen reproduce slowly, and the availability of vegetation
limits the size of their herds. They are driven toward the predators
when food becomes scarce.
and the foxes are linked: more lemmings lead to more foxes,
and more foxes lead to fewer lemmings. Their numbers fluctuate,
but stay within the carrying
capacity of the vegetation. When there are too few lemmings,
the foxes starve.
The snowy owl also
hunts the lemmings. Snowy owls will leave the area when lemmings
become scarce, and many do not return, but are killed by predators
outside the tundra.
parts of the tundra have additional animals: seasonally migrating
birds, arctic mice, snowshoe hares, voles, and ptarmigans. Some
areas even have migrating reindeer or caribou. The population
dynamics remain carefully balanced, however. The plant communities
are fragile, and the availability of light, warmth, and nutrients
places absolute limits on the growth possible.
Elizabeth Anne Viau, 1999. This material may be used freely for
instructional purposes but not sold for a price beyond the cost
of reproduction. Please inform the author if you use it at firstname.lastname@example.org