|
|
Alaska boasts the only arctic tundra within the United
States. Tundra exists in Alaska's northern and western coasts.
Alaskan tundra does not have any trees. It is also very windy
and has dramatic seasonal changes, including drastic changes in
daylight hours throughout the year. The Alaskan tundra boasts an
average annual temperature colder than five degrees Fahrenheit
The tundra biome receives as little precipitation as some
deserts. Average yearly precipitation, including snow melt, is
just 6 to 10 inches, compared to 30 to 60 inches in the
temperate deciduous forest biome. The summer is brief, with
temperatures above freezing lasting for only a few weeks.
Tundra comes from a Finnish word, tunturi, which means
"treeless heights". Despite the cold temperatures, many plants
thrive in the Alaskan tundra. There are about 1,700 types of
native plants living in this arctic biome. What most of them
have in common are growth characteristics; they tend to grow low
to the ground. The long day length that accompanies the short summer is a boon to
plants, which are able to photosynthesize 24 hours a day in some places.
This leads to rapid plant growth.
A surprising number of insects are able
to endure the harsh winters (many as frost-resistant eggs); these also undergo
rapid development in the summer. Among the common types of tundra plants
are willows, sedges and grasses, many in dwarf forms compared to
their growth forms in warmer climes.
Lichens and mosses are also important, particularly in the
harshest climates. Lichens are composite organisms made up of
both a fungus, which provides structure, and an algae, which
synthesizes chlorophyll for food. One lichen commonly found in
the Arctic tundra is caribou moss, also known as reindeer
lichen. This drought-resistant organism appears on rocks as a
spongy gray-green foam.
Labrador tea is a hardy bush native to the tundra's of Alaska,
Canada and Greenland. Its narrow 1- to 3-inch leaves grow on
woolly branches. In the summer, small clusters of white flowers
appear. The vitamin C rich leaves of this plant have been used
by indigenous peoples to brew a tea used to
treat stomach, skin and nerve conditions.
The U.S. Forest Service ranks only one tundra plant as federally
endangered, though three more have been assigned a global rating
of G1, which indicates a plant is “critically endangered
throughout its range” by The Nature Conservancy. The Alaska
Department of Fish and Game credits geographical isolation,
limited human impact, “and a little luck” with the state’s
comparably short list of threatened species.
The ecology of the tundra is controlled by the cold climate and the northern
latitude. A unique soil structure, permafrost,
forms and dominates the biology. Permafrost is a layer of soil that
remains frozen year-round. The soil above it may thaw during the summer,
but the soil below remains frozen and thus biologically inactive. Further,
the permafrost forms a barrier; in temperate climes many animals overwinter by
burrowing down into the soil to a point below where the soil freezes. This
is not possible in the tundra soils, and thus animals must contend with freezing
over the winter. It is no accident that there are no reptiles or
amphibians in the tundra.
Animals have adapted to the Alaskan tundra by developing warm
winter coats, compact bodies to preserve heat, and camouflage
for different seasons. Some animals found on the Alaskan tundra
include caribou, arctic fox, arctic hare, arctic ground
squirrel, and arctic grizzly bear.
Many bird species migrate
from southern areas to the tundra each year for the reduced competition
and plentiful insect harvest; this rich diet enables them to rear their young
in an otherwise bleak environment.
In the Alaskan arctic, fires may become more severe and frequent
as the climate warms. The Anaktuvuk River fire burned more than
621 square miles of tundra on Alaska's North Slope in 2007. One
possible reason for the increased intensity and frequency of the
fires is that warmer temperatures increase the growth of shrubby
plants, which then provide fuel for fires. When the weather is
dry as well as warm, the tundra burns. The arctic is warming
more rapidly than the rest of the planet. The year of the
Anaktuvuk fire had the lowest precipitation and highest
temperatures recorded, about 52 degrees Fahrenheit.
|