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CLARENCE F. KORSTIAN 



increment of both forms of western yellow pine for Sites I and II. 

 The data are significant in that they indicate the relative pro- 

 ductivity of the two sites and the variability of the increment 

 depending on the kind and amount of growing stock. The 

 data given in table 1 represent the net increment since the 

 volumes of all trees which died during the quinquennium were 

 considered as negative increment and the volumes of all trees 



TABLE 1 



Increment data for 26. Jj. acres of tTjpical ivestern yellow pine in the San Mateo 

 Mountains of west central New Mexico, based on five years' growth 



* Includes the volumes in feet, board measure, of all western yellow pine trees 

 12 inches and over in diameter breast high. 



t Includes the volumes in cubic feet of all western yellow pine trees 3.6 inches and 

 over in diameter breast high. 



gromng into the 4-inch class as positive increment. The fact 

 that the plots were cut-over in 1910 under Forest Service regu- 

 lations accounts for the relatively small amount of merchantable 

 growing stock. The abundance of poles from 4 to 10 inches in 

 diameter breast high which were left on the area accounts for 

 the proportionately greater cubic volume of the growing stock. 

 Since a number of trees grew into the merchantable class during 



