|
When early voyagers approached the land that is now the United States, they noticed a sweet and surprising ,,land smell,\" a clue that they were near the shore. This ,,land smell\" came from the great, thick forest that covered all the eastern part of the country and stretched about 1,600 kilometers westward until it met the tall grass of the prairies.
No one knows just why the woods ended where they did, or why the tall grass of the prairies - the wide rolling and almost treeless plains - began at that point. The reason still remains shrouded in mystery, for the eastern part of the prairies' tall grasslands have soil that will support tree life. One explanation has it that the Indians burned off the forest in order to force game animals out to the hunters. Another reason given is that perhaps some early special conditions of soil and rainfall were responsible. This has been accepted as a more plausible explanation, but nobody really knows. Nevertheless, the early settlers wrote that the prairie grass was very beautiful, interlaced with flowers in the spring, and so tall that a man on foot could not see over it.
It is clear why the tall grass became short grass farther west - lack of rainfall.
Still farther west, the Vegetation Map looks quite mixed. Forests cover the slopes where mountains catch enough rain. A few favored grassy meadows lie in the high mountain valleys. On the dry lowland -and on high tablelands - dry, harsh bushes grow; so do kinds of grass common to and regions, with places here and there too dry or too full of salt for even this poor desert growth.
The greatest wonder of all are the forests of sequoia and fir trees on the northwest coast, where the mountains catch the heavy Pacific rains. These great trees, some of which are 3,000 years old, are among the largest and oldest living things known. Some were seedlings when Troy fell, and already giants when Rome was founded. The silent forests are filled with columns of great trunks lighted dimly by sun filtered through leaves far above. Most of these forests are protected by law and preserved as a national treasure.
|
