4 MISC. PUBLICATION 18, U. S. DEPT. OF AGRICULTURE 



management, called a working circle, must contain these groups 

 whether in one stand of many ages or in a number of separate even- 

 aged areas. 



As the individual tree grows from year to year, the total stand 

 increases in volume. Measurements in Colorado forests show this 

 increase to be from 50 to 150 board feet per acre per year. The 

 equivalent of this amount added on the whole unit at this rate may, 

 therefore, be removed annually from the mature age classes in any 

 particular part of the unit without in any way lessening the total 

 volume or disturbing forest conditions essential to watershed protec- 

 tion or forest reproduction. As the work of removing the mature 

 trees progresses from one part of the unit to another, growing space 

 is left which enables the thrifty young trees to graduate into the 



Fig. 2. — Felling a saw-log tree, Arapaho National Forest 



older classes and eventually be ready for cutting when the cycle 

 again returns, usually after 30 or 40 years. 



Timber on the national forests is sold " on the stump." That is, 

 the standing trees must be cut by the purchaser and converted by him 

 into lumber or any other finished product desired. In making timber 

 sales a large amount of supervision on the part of forest officers is 

 necessary in order to assure the proper location of cutting operations 

 and the observance of forestry principles in the course of the logging. 

 The selection of trees to be cut and the consequent regulation of 

 volume and growing conditions are also the responsibility of the 

 forest officer. He marks every live tree to be cut with "blazes" 

 stamped " U. S." He also supervises through frequent inspection 

 the disposal of slash, regulating the method of disposal primarily 

 from a standpoint of fire protection ; and he " scales " or measures the 

 logs, ties, or other special products. In this form the " cut " is charged 

 against the deposits of the purchaser. In Colorado the annua] cut 





