SUBROUTINE E SS T T E ( A ,H , S 1) 

 DI MFNSinN X(ll) ,B(ll) 



0=A 

 P = H 



DATA 8/ 10. 71 7 23, Co 4633. ^ 7BE -2 , Co 744711 5 ♦ -2 6^1 3, 76 , -Co 42 81 9RE-1 , -Co 4 

 1 7<5 1 20 6F-2t 0,492 5434r-5» 0,21975 91 E-6 , 5 , 1 575° 5 , 1 4349 1 4E-7 , -9, 48 1 

 214/ 



si=c,c ' 



02=0*0 " ■ 



03=02*0 ■ ' 



04=02*02 

 05=02*03 



REC05=1.0/05 • •- :. ■ . ; '.^.j 



P2 = D*P ' ■ ' \ • 



P3=P2*P 

 P4=P2«P2 



X( 1)=AL0G( 0)-3» 912023 



X( 2) = l,0f=l O*RECQ5-32,0 



X( 3) =P*{ lo 0E4/02-4, 0^ 



X(4)=P*(SQRT(PEC0 5»-5o656854E-5) 



X(5)=P*X(1)*X(1 ) 



X(f))=P*X(3) 



X(7)=P2*X(2) 



X(8)=P*X(7) 



X( 9) = P3*(S0''T(QECn5*S0RT(l,0/Qn-2, 12 73iaE-5 ) 

 X( 10) =pi^*{ IOC. 0/0-2,0) 



X( 11)= P4*( (1.0/04) /S0PT(Q)-2.2 62 742E-ft) 

 DO 1 1=1 tU 

 1 SI=SI+B( I ) *X{ I ) 

 SI=SI+H 

 RETURN 

 END 



Figure 8. — A site index estimating subroutine for Engelmann spruae. 



If a shorter but less precise equation is desired, the following is recommended: 



5 ■ . 



S = H +7! k .Z ., 

 ^=l 



where 





0. 



,32158242 



k2 = 



-0. 



,98468901X10'+ 



k3 = 



-0. 



,12253415X10" 



K = 



1. 



,0662061 



ks = 



-0, 



.80894818X10" 



2 



8 



Zi = H [(10Va2) - 4] 



-? S -2 5 

 Z2 = H (A - 50 • ) 



Z3 = H2[(10^/A2) - 4] 



_ ,,Qr.-2.75 _„-2.75t 

 Zi^ = [A - 50 ] 



Z5 = H'*[(100/A - 2] . 



For this equation, S^^ = 1.22 feet. 



These equations are valid for trees between the ages of 20 and 200 years and for 

 site indices ranging from 10 to 95. A site index estimate should be computed for each 

 sample tree. The average of the individual tree estimates will be the average site 

 index for the stand. If trees older than 200 years must be used as site trees, estimate 

 the site index as if tree age were 200. Above that age, height increases very little. 



14 



