8 MISC. PUBLICATION 16 2, U.S. DEPT. OF AGRICULTURE 



Like their elders, the younger generations of trees have to fight 

 for their existence. Openings in the forest are usually thickly filled 

 with young growth shooting up from the ground or sprouting from 

 the stumps of old trees which have died or have been cut out. Some 

 of the seedlings have outstripped their companions in growth and 

 have full benefit of the sunlight which filters down to them. These 

 the forester calls dominant, while those coming on, still in the thick 

 of the fight, he calls intermediate. Other seedlings, not being able 

 to keep pace with the vigorous ones, lag behind in the race. These 

 the forester calls suppressed trees and, unless a fortunate chance 

 gives them light and growing space, they will develop into unhealthy 

 and crooked trees, or perhaps die out altogether. Thus from begin- 

 ning to end the life of a tree is a struggle for a place in the sun. 



FOREST SOIL 



Next to sunlight, the forest soil is perhaps the most important in- 

 fluence in the life of young trees. If they are to develop into a 

 thrifty and upstanding older generation, the soil must furnish them 

 plenty of water and the various food elements that tree growth de- 

 mands from it; the soil must be porous, and not hard packed so that 

 it may be easily penetrated by water. 



Although trees make demands upon the soil, they also increase its 

 fertility. The top layers of the soil are full of decayed vegetable 

 matter, or humus. The humus is formed mostly by the decomposi- 

 tion of the leaves and twigs which each year fall to the ground. 

 With the decay of the leaves, large amounts of valuable elements 

 such as nitrogen and phosphorus are returned to the soil from 

 which they were originally taken by the tree. The humus gradually 

 works down into the mineral soil underneath, enriching it, and in- 

 creasing its power to absorb and store water. 



ANIMALS OF THE FOREST COMMUNITY 



Not only does the forest contain myriad varieties of plant life, but 

 it is also the home of countless members of the animal kingdom. 

 The timid deer cropping vegetation in the woodland, the stealthy 

 cougar, the bear in a tree stealing honey from the bees, the sly fox, 

 the busy squirrel, the inquisitive bobcat, the grouse upon his mossy 

 log, the musical thrush, the tiny wood folk beneath the leaf litter, 

 the gamey fish in the streams, are as much a part of the forest as the 

 trees themselves (fig. 5). Wild game and fur-bearing animals, which 

 the forests harbor, are valuable resources. 



FOREST REGIONS OF THE UNITED STATES 



Originally forests covered the entire eastern half of the United 

 States stretching in a practically unbroken area from the Atlantic 

 seaboard to the Great Plains. West of the Great Plains they were in 

 more isolated groups, lying mostly in the Rocky Mountains and the 

 mountainous parts of the territory now occupied by the Pacific 

 Coast States. The area of the original forests is estimated to have 

 been more than 820,000,000 acres, or about 42 percent of the land 

 area of the United States. 



