for loblolly shows that only 70 per cent of these trees are 9.6 

 inches diameter breast high or larger; a 10-inch tree being the 

 smallest likely to contain at least a 16-foot log 8 inches inside 

 the bark at the small end. (No tree without a 16-foot log, 5 

 inches inside the bark at the small end, contributes to the 

 tabular yields in board feet by the international rule.) Whether 

 10 inches is the correct minimum diameter on the site in question 

 must be determined from a field study of felled trees on this site; 

 it is assumed as correct in the present example. Then the 

 volume of all 7, 8, and 9 inch trees included in the yields given 

 in the board-foot table to a 5-inch top must be subtracted from 

 the yield at 50 years on the 90-foot site. The stand table shows 

 that about 5 per cent of the trees in this stand are 7 inches, 8 

 per cent are 8 inches, and 10 per cent are 9 inches, 11, 18, and 

 22 being the absolute numbers. At least an approximation of 

 the number of logs to a 5-inch top in such trees will have been 

 obtained in the course of the held study just referred to or may 

 be estimated from the total-height tables. Their total volume 

 may be calculated from the volume tables. If the number of 

 logs were two in each case, the total volume for the 3-inch 

 classes would be l. v I feet. This, then, would be the 



deduction necessary for trees which, under the actual limit of 

 utilization, contain no merchantable logs. 



The lessened volume per tree of the remaining 109 trees may 

 be calculated roughly by assuming an average deduction, based 

 on the tree of median diann •' g them. From the stand 



table it will appear that about half of the 169 trees 10 inches and 

 over arc above 13 inches in diameter, and half are below that 

 size. Assuming that investigation has shown that a 13-inch 

 tree has, by the Internationa] rule, 10 board feet Less to an 

 8-inch top than to a G . the deduction for 169 tree- would 



then be 1,690 feet, which added to the 1,844 board feet in the 

 trees below in inch a total deduction of 3,534 board 



feet. The yield of 37 ard feet for a 50-year stand on a 



90-foot Bite then becomes 34,000 board feet (rounded 1 , when an 

 8-inch top Limit . place of a 5-inch. 



DETERMINATION OF NORMALITY AM) PREDICTION OF FUTURE 

 YIELDS. 



The yield tables should never be used as a substitute for an 

 actual cruise of an e and. That a stand is of a certain 



age and occupies a c by no means proves that its yield 



per acre will be the same i hown in the tables for that age 



and site. This is of course because the stands vary widely in 

 stocking from the 100 per cent stocking represented by the tables. 



By actual mea ' of a .-ample plot or strip it will be 



le to establish a percentage relation-hip between the 



actual values and the tabular values. The two most satis- 



12 



