186 OUR NATIONAL FORESTS 



When the Operation May Begin. As soon as 

 the contract has been executed and the first pay- 

 ment has been made a portion of the timber is 

 marked for cutting and the purchaser may begin 

 operations at once. Sometimes cutting in advance 

 of the execution of the contract is allowed to pre- 

 vent serious hardship and unnecessary delay and 

 expense on the part of the purchaser. 



Marking the Timber for Cutting. In order to 

 insure a proper restocking of the ground, all live 

 trees must be marked or otherwise designated by a 

 Forest officer before cutting can commence. Usu- 

 ally from 1/10 to 1/3 of the stand is reserved, either 

 scattered over the entire tract or distributed in 

 groups. These trees are left for various reasons, 

 depending upon circumstances. The most impor- 

 tant consideration is, of course, to leave enough 

 seed trees to restock the cut-over area. On steep 

 slopes a certain number of trees must be left to 

 protect the watershed and to prevent the erosion of 

 the soil. Many species of trees are subject to 

 windthrow when the stand is thinned out. To 

 counteract this tendency a sufficient number of 

 trees must be left to prevent the wind from getting 

 an unobstructed sweep. In many semi-arid por- 



