is called the site index. Thus a site with an index of 70 feet 

 produces dominant trees averaging 70 feet in height at 50 years. 

 The average site for each species encountered by the field crews 

 in the course of the present study had the following site index: 

 Loblolly, 92 feet; long leaf, 71; short leaf, 70; and slash, 81. 



Yields. — The yields in any unit are based on the same limits 

 of utilization as shown in the volume tables for that unit. By 

 all trees 2 inches diameter breast high and over is meant all those 

 1.6 inches and over; by all trees 4 inches diameter breast high 

 and over, those 3.6 inches and over; and similarly for all diame- 

 ters named. 

 LOG RULES. 



Doyle rule. — The Doyle rule, which even in virgin timber gives 

 an overrun of 10 to 25 per cent, does not begin to give the actual 

 contents of most second-growth trees and stands. Volumes and 

 yields by the Doyle rule are Included in the present publication 

 purely because this rule is the only one familiar to many southern 

 lumbermen. 



bner rule. — The Scribner rule, while not widely used in the 

 South, is employed widely in other Bections of the country, and 

 at present is used by th< Service in its timber sales in 



modified form (decimal C). Although fairly satisfactory for 

 virgin timber, it fails to indicate the true contents of small 

 second-growth timber asiderable margin. An overrun of 



10 to 20 per cent ii. Is common, but this 



varies with size of log; the overrun for 8 and 10 inch logs may be 

 as high as 40 per c 



itional rule i- given in Table 

 173; its derivati scribed in ( raves' EPoresI Mensuration. 7 



The rule is beli( pproximal ial quantities of lum- 



ber, without overrun, which may I it with good equip- 



ment, prop and markel conditions prevailing at Least in 



those portions of the South where virgin timber 18 small or not 

 sufficient in quantity to compel I ially with sec >nd growth. 



TYPE OF STAND. 



Pure stand. — A pure stand is one in which 80 per cent or more 

 of the 



; stand.— in which the 



oldest and youngest trees do not differ in age by more than 10 

 years. 



mat or fully stocl:' ■/ stand. — A normal stand is one which is 

 producing wood at the fullest capacity, in terms ni cubic feet, for 

 that species, age, climal I. The number of trees per 



7 Graves, H. S. forest mensuration. 458 p., illus. New York and London. 

 1906. 



H3 



