118 INTBODUCTION TO BOTANY 



most profitable to allow the sprouts to grow only twenty or 

 thirty years, forming a coppice woodland, which is then cut 

 and used for fuel and for making telegraph poles, fence posts, 

 and railroad ties. 



110. Tree belts and wood lots as windbreaks. Every one 

 who has observed the conditions in a country partly wooded 

 and partly cleared knows how much less severe is the effect 

 of winter winds in areas protected by neighboring woods. 

 Cattle that are allowed to range out of doors during cold 

 weather always resort to the lee side of wood lots for shelter. 

 Most orchards and many crops, such as winter wheat, are 

 greatly protected from the effects of destructive cold winds in 

 early spring by the presence of trees on the windward side. 



Damage from storms which would blow down corn or lodge 

 small grains may be almost entirely prevented by suitably 

 placed tree belts. It has been computed that a single storm 

 in 1862 damaged standing corn in Illinois to such an extent 

 that the loss was almost great enough to have paid for plant- 

 ing four miles of tree belts on every square mile of land 

 affected by the storm. 



Hot, drying winds which parch the crops, and those which 

 blow drifts of fine earth or sand from field to field, may be 

 made far less injurious by patches or belts of trees. 



For these and other reasons it has been found highly profit- 

 able in many of the comparatively treeless states to plant 

 wood lots and belts of trees in such a way as to afford a sup- 

 ply of timber and at the same time protect the cattle and 

 crops of the farm. The kinds of trees planted vary with local 

 conditions. In general, when protection from winter winds is 

 needed, in all the Northern states the belts should consist partly 

 of evergreen conifers. 1 



111. Regulation of the water supply by forests. It is not 

 fully known just how much influence forests exert on the tem- 

 perature and rainfall of temperate regions. On this account 



1 See Bates, " Windbreaks," Bulletin 86, Division of Forestry, U. S. Dept. 

 Agr., 1911. 



