Dana Jenkins, age 13, of Utica, N.Y., for his question:
JUST WHAT IS TUNDRA?
Tundra is one of the vast, nearly level, treeless plains of the arctic regions of Europe, Asia and North America. Tundra encompasses most of the earth's terrain north of the coniferous forest belts.
Tundra is dominated by sedge or rush like plants, heath, willow, moss and lichen. Similar plains, called alpine tundra, occur above the timberline in the high mountains of the world. The antarctic region has a few areas of tundra as well.
Tundra climate is characterized by harsh winters, low average temperatures, little snow or rainfall and a short summer season. The arctic tundra, in particular, is influenced by permafrost, a layer of permanently frozen subsoil in the ground.
The surface soil of tundra, which tends to be rocky, thaws in summer to varying depths. The combination of frozen ground and fiat terrain on the tundra impedes the drainage of water. Held at the surface or saturating the upper layer of soil, the water forms ponds and bogs that provide moisture for plants, thereby counteracting the low precipitation.
In relatively well drained locations, the periodic freezing and thawing of the soil forms cracks in the ground in regularly patterned polygons. Poorly drained areas produce irregular landforms such as hummocks, or knolls, frost boils and earth strips. Thawing of slopes in the summer may move soil downalope to produce solifluction or "floating soil" terraces.
All of these patterns, pronounced on the arctic tundra, also appear on a smaller scale on the alpine tundra. Also common to the alpine tundra is bare rock covered ground, called fell fields, supporting a growths of lichens.
The number of plant species on the tundra is few and their growth is low.
The variety of animal life is also limited in the challenging environment of the tundra. Musk ox, caribou and reindeer are the dominant large grazers, feeding on sedge, lichen and willow.
Arctic hare, or snowshoe rabbit, and lemming feed on grass and sedge.
Tundra predators include the wolf, arctic fox and snowy owl. Polar bears and sometimes brown bears are also seen.
Many birds nest in the tundra shrubbery in summer, migrating to milder climates before the winter season sets in.
Invertebrate life is scarce, but insects such as black flies and mosquitoes are abundant.
Alpine animal life includes the mountain goat, big horned sheep, pika, marmot and the ptarmigan, a grouse like bird. Flies are scarce but butterflies, beetles and grasshoppers are found in large numbers.
The tundra ecosystem is extremely sensitive to disturbances with little ability to restore itself. Disruption of vegetative cover causes permafrost to melt deeply, with consequent collapse of ground and loss of soil. Vehicular tracks cause deep gullies that persist for years. The tundra wildlife is vulnerable to habitat destruction, to overhunting and to extinction through loss of any of the animal or plant species that make up the fragile, highly interdependent tundra community of life.