Primitive people living within forests have certain characteristics that 

 result from their surroundings — they may live in houses in treetops or make 

 abundant use of poles in building shelters; they eat largely fruit, nuts, fish, 

 and game; they travel usually by boat or on foot. The forest has kept 

 them from wandering, from contact with other people, and hence has 

 retarded their progress. The fact that the forest provides them with 

 protection, food, and shelter with little effort on their part mav also partlv 

 explain their lack of progress. 



When man progressed to a point where the forest no longer dominated 

 him, increasing use of forest resources became necessary for his further 

 progress. Access to forests has been an important influence in the develop- 

 ment of leading civilizations. 



People have adjusted their modes of life to different climates. So have 

 trees. Trees may be divided into two great classes — the conifers, which 

 include such species as the pines, spruces, cedars, and firs; and the broad 

 leaves, which include such species as the oak, maple, ash, hickory, elm, and 

 walnut. The conifers, or those we commonly call evergreens, live mainly 

 in the colder, drier parts of the world. The broadleaf species prefer the 

 warmer, more humid climates. Some oi those in tropical regions are 

 evergreen. The two classes of trees are also known as softwoods and 

 hardwoods ^fig. 1). 



There are no hard and fast distinctions between the two classes of trees 

 (table 1, p. 41). Exceptions to most points may be noted. Hollv and live 

 oak are evergreen broadleaf trees; larch and cypress are deciduous conifers. 

 Either class sometimes may be found growing under conditions best adapted 

 to the other. There is an abundance of pine in the South and conifers and 

 broadleaf species often grow in the same stand. Longleaf pine, a conifer, 

 or softwood, is more dense or harder than yellow poplar, a broadleaf or 

 hardwood. 



Kind of soil. — Trees are sensitive to differences in soil. Even slight varia- 

 tions in texture and fertility cause differences in forest growth. 



Soil furnishes anchorage, water, and mineral food. It therefore affects 

 a tree's rate of growth, length of life, form, quality oi wood, capacity to 

 endure shade, the quantity of seed produced, and its yield of wood and 

 other products. 



Some kinds of trees are most commonly found on clay soils; others on 

 sandv soils. Some need deep fertile soils; others will grow on almost 

 bare rock. White oak, maple, yellow poplar, and other important hard- 

 woods do best on a moist soil rich in organic matter. Blackjack oak, jack 

 pine, persimmon, and sassafras, do well on infertile soils. An experienced 

 woodsman can tell much about the soil by the trees growing on it. 



Water in soil and air. — Where the annual rainfall is below 20 inches per 

 year, under natural conditions few trees will grow in the region. They 

 will be found along water courses or in low places where the amount of 

 available moisture is greater. Trees need water to dissolve the plant food 

 in the soil, and to use in making starch. They also need water to circulate 

 their food and to cool them in the summer. 



A certain amount of moisture in the atmosphere is also necessary to tree 

 growth. Some kinds of trees need more than others. The atmospheric 

 moisture affects not only the amount of local rainfall, but also determines 

 the amount of water transpired or given off by the leaves, which is one of 

 the reasons relatively few kinds oi trees will grow in areas of high 

 and drv winds. 



