WHY FORESTRY IS NEEDED SUMMARY OF OBJECTIVES 13 



and the industries is included, generally about three times as many 

 men are required as in strictly forest work. 



8. Influence on Climatic Factors. Forests are generally recognized 

 to have a very definite effect on climate. Forests tend to ameliorate 

 the extremes of temperature. Hot summers are generally made cooler 

 by the presence of large numbers of trees. Forested regions are gen- 

 erally less affected by cold weather than treeless plains. Trees when 



FIG. 9. A Caterpillar Diesel 75 h.p. tractor bringing in several logs with Hyster- 

 Willamette arch. Choker lines of steel cable are placed around the ends of each 

 log and brought up and underneath the load to facilitate skidding and reduce 

 tractive resistance. These tractors are replacing railroad spur line tracks and 

 power skidding under some conditions. Tractor skidding is much less destructive 

 to reproduction and young growth than power skidding. Tractors are used with 

 selective logging which is a silvicultural as well as utilization phase of forestry. 

 Logging is when our forests may be best treated to insure future growth. The 

 axe is the best silvicultural tool. 



grouped together in rows as shelterbelts have a marked influence in 

 decreasing the extreme chilling effects of winter winds. The tran- 

 spiration of large quantities of water through the leaves of trees defi- 

 nitely cause forests to be cooler than treeless areas in the same region. 

 Forests also serve as snow breaks and they are extensively used for 

 shade for both man and beast. 



