The North hemisphere contains two typical biomes, that extends,
one after the other, between the polar regions and biomes
located more to the south. They are the tundra, devoid of
arboreal vegetation, and taiga, forest mainly of coniferous.
The tundra
The tundra name is applied, mainly, to the Arctic regions
of Asia that are between the perpetual ice to the north and
the forests of taiga to the south. The ground of the tundra
remains frozen most par of the year, and it melts partially
in summer. The water is accumulated then in quagmires and
marshes.
In the tundra, the aggravating factor is the temperature.
The average of annual precipitations is low, around 250 mm,
and the average temperature is 25ª F, although in winter
temperature can reach -50°F. The subsoil displays a permanent
frozen layer, whose thickness varies according to the station.
This ground layer receives the name of permafrost.
In the tundra, the dominant forms of life are mosses and
lichens. In spite of the shortage of rains, both forms grow
well, because the evaporation is almost nonexistent and there
are great humidity concentration.
The ground, poor in organic substances, presents shortage
of nutrients. All the tundra is zone of peat bogs, deposits
of a fossil fuel, the peat, formed by vegetal remainders that
were accumulated during thousands of years in marshes. By
the intense cold, the decomposition process is very slow and
the fertile ground formation is little.
The fauna of the tundra also presents little diversity. The
two main species are the reindeer, in Europe and Asia, and
the caribou in America. They are very similar animals that,
more likely, descend from a common ancestor.
The ground of the tundra defrosts
only 2 or 3 times to the year, originating small
water mirrors. The subsoil, call permafrost, is
permanently frozen.
GEOGRAPHIC
DISTRIBUTION OF THE TUNDRA
They are ruminats mammalian of the family of the cervids,
and live in flocks.
Approximately, they have a meter and a half of height (the
height of a quadruped, measurement from the ground to the
highest part of the back). Its coat, very dense, changes of
the brown grey to white, in winter.
They have spears, with which excavate in the snow in search
of lichens, its food. They migrate periodically, in agreement
with the cycles of reproduction of the life forms of which
they are nourished.
The reindeer domesticate, and serve like shot and load animals
. Other mammals that feed on plants and lichens are lemmings,
species of rat of field.
There are also arctic hares, polar wolves, foxes, lynges
and bears, and until a type of wild bovine adapted to the
intense cold, the almizclero ox. Many of these animals hibernate,
that is to say, enter in a winter lethargy state , after having
accumulated reserves in their organism during the brief warm
season. The variety of birds is greater: there are nivales
owls, palmípedos like the goose and the colimb, and
the greater hawk than knows , gerifalte. Other birds come
from the south, and find in the tundra the conditions necessary
to nest and reproduce.
During the little summery days there are
also jejenes and mosquitos. It is surprising that in zones
as cold as this ones, these insects get to reproduce until
forming gigantic clusters. In the short summer season, part
of the accumulated snow melts, the subsoil of the tundra,
frozen throughout the year, it prevents the drainage and pools
and marshes form.
The suspended water reaches then sufficient
temperatures after the reproduction of the larvae of the mosquitos.
Traditionally, the tundra been has inhabited
by eskimos - hunters and fishermen- and also shepherds of
reindeer, moving from the forests, in search of food for their
flocks and reach the tundra at the less cold time of the year.
it is interesting to observe that the life of these towns
evokes in certain way the one of the man called of Cro-Magnon,
a predecessor of the present man who inhabited the region
of Dordoña, in the south of France, about 30,000 years
ago.
The ground of taiga, put under
smaller cold than the one of the tundra, allows
the development of arboreal species, like the coniferous
GEOGRAPHIC
DISTRIBUTION OF THE TAIGA
That zone, temperate at the present time, was tundra in those
times. The archaeological discoveries and the paintings of
the caves in which they lived, show similarities with eskimos
groups of the present tundra.
Taiga
In Asia, to the south of the tundra and to the north of
the steppe is a wooded cold climate formation, with coniferous
predominance..
This biome of the north of Siberia, that has been called
taiga, also appears in the region of the sea of the Hudson,
in the north of Canada.
In taiga, the aggravating factors are the temperature and
the water. The average temperature is of 19º C in summer,
and -30ºC in winter; the annual average of precipitations
is 10 - 30 inches.
In all this zone the boreal forest grows, favoured by climates
less rigorous than those of the tundra and by a ground that
suffers less the effect of snow .
The Scandinavian countries, Siberia and Canada present forests
of firs, pines and larches, and of birches. The fauna is composed
by animals that resist the cold, many of which hibernate:
elk, bisons, wolves, bears, martas, lynges, squirrels, marmotas,
beavers, lemmings and deer.
