142 THE THEORY AXD PRACTICE OF WORKING PLANS 



rv. Regulation of Tctrpentlnte Forests 



The imminent dearth of timber available for naval stores * 

 emphasizes the urgent necessity of abandoning wasteful, destruc- 

 tive methods of turpentining in favor of a more conservative 

 utilization and a regulated yield. 



The field data necessary for the regulation of the turpentine 

 yield are, besides a thorough acquaintance with the general and 

 local turpentine business: 



(i) The distribution of the diameter classes on each manage- 

 ment or survey unit.f This need not be by inch classes, but 

 according to the cupping limits, explained below.- Strip sur- 

 veys, two chains wide, are excellent for this purpose. 



(2) The local turpentining quality of each stand, gauged by 

 the number of cups per acre. 



(3) The amount and character of young growth below the 

 minimum turpentining diameter for each management or survey 

 unit, supplemented by detailed figures from sample areas more 

 carefully measured, i.e., calipered instead of estimated ocularly. 



(4) The board measure contents of stands. The cord-wood 

 contents of undergrowth, etc. 



(5) The silvical characteristics — maturity, height, thrift- 

 iness, etc. 



(6) Diameter increment tables showing time required to 

 grow from one diameter class to the next. 



For conservative turpentining, the use of a system of cup- 

 ping is basic. Scarcely less so is the cupping to a diameter 

 limit — e.g., no cups on trees below 11 inches in diameter, and 

 never more than three cups on any tree. Furthermore, in order 

 to prolong the productivity of the tree and minimize the injury, 

 the chipping must be shallow and light. 



A definite rotation must be adopted for the working of the 



* See " The Naval Stores Industry," Bulletin 229, new series, U. S. Dept. of 

 Agriculture. 



t E.g., blocks, compartments, subcompartments, or tovmships, sections, 

 quarter-sections, etc. 



