282 THE ESSENTIALS OF AGRICULTURE 



367. Forests modify climate. It is well known that forests 

 reduce the wind velocity along the surface of the ground within 

 their territory. The reduction of the wind velocity, in addition 

 to equalizing atmospheric temperature, reduces the evaporation 

 from the leaves and soil. The average humidity of the atmos- 

 phere within a forest is always much greater than in the open 

 country. Forests are great conservers of moisture, because the 

 roots open the soil and enable the rain or snow water to find a 

 ready passage into the substratum, and the blanket of leaves 

 and twigs over the surface operates as a sponge to absorb the 

 moisture and to prevent surface run-off, thus insuring a more 

 uniform flow of water in the streams throughout the year. This 

 is a matter of the greatest importance in irrigable sections of 

 the country, which must have a continuous supply of water 

 throughout the growing season to mature the cultivated crops. 



368. Forests prevent floods. The retardation of melting snows 

 and surface run-off water is also a great factor in preventing 

 floods during seasons of heavy precipitation. Otherwise, damage 

 to property, erosion of soil, and possibly the loss of lives in the 

 river valleys many miles from the source of rainfall or snowfall 

 might result. 



369. State and national ownership. About one fourth of the 

 timberland of the United States has been set aside as state and 

 national forests. The purpose of these forests is to insure a 

 future supply of timber and to protect the agricultural and other 

 interests within drainage basins of the streams that have their 

 source within the regions covered by these forests. It is the 

 work of the Forest Service, which has control of the national 

 forests, to put into execution the regulations prescribed by the 

 United States government for the cutting and handling of timber 

 in these forests. 



370. Government and private forest policies. Practical forestry 

 demands that all materials within the forest be put to their greatest 

 use for the greatest number of people concerned, and every 

 mature tree that is not needed to protect the watershed should 

 be cut and sawed into lumber to meet the needs of the home 



