CR = ratio of live crown to total height in percent 



lER = an integer used to flag possible errors in calculation. 

 (Should be zero if no errors.) 



If required, site index can be approximated from Q by the FORTRAN equation: 



SI = 4.5 + SQRT(Q) * 172.32 * (1. - EXP (- . 6905*Q) ) **2 . 



Yield Capability 



The yield equation also already has been published (11). The maximum m.a.i. for 

 average stocking corresponding to this equation can be solved by the FORTRAN function 

 CUPGF illustrated in figure 11. The single argument to the function is Q obtained from 

 the previous subroutine RPGF in figure 10. Figure 12 shows the linear approximation 

 of the relationship between yield capability and site index. 



Figure 1 1 . — The function 

 subprogram for grand fir 

 yield capability. 



FlNCTIuN CUPGF(S> 



3 = 89. 761/S - ^Z. ICl 



A = B *(C.5 + b(-KT(C.25 + 1^./(S*B)>) 

 CUPGF - 22223.*EXP i-e/A ) / ( A + 12./:>) 



RETUHN 

 £NC 





















GRAND FIR 























































































































































































































































































10 20 30 40 so 60 70 80 



Site index (height in feet at 50 years) 



Figure 12. — Relationship between site index and yield capability. 



19 



