QUAKING ASPEN 



Site Index - 



A table published by Jones (5) gives site index of quaking aspen according to 

 stand age and dominant height. Age at breast height is used, and it is important that 

 average dominant height not be estimated from trees that are all of the same clone. 

 In Jones' table a site index base age of 80 years is used. Equations were fitted by 

 regression methods to the site index values in Jones' table, using stand age and height 

 as independent variables. The best of several equations fitted is: 



10 



S = H + 2^ b.X., 

 ^=l 



where 



S = site index at an 80-year base age 



A = stand age at breast height 



H = average height of the dominant stand 



bi = -8.7810841 







[(100/A) - 1.25] 



= -5.1824560 





\ = 



(In A - In 80) 



b3 = -40.260849 





X3 = 



H[((ln A)/A) - ((In 80)/80)] 



b, = 1.8589039 





\ = 



H[(100/A) - 1.25] 



bg = 0.34567436X10" 



1 1 





H[A5 - 3,276,800,000] 



bg = -0.16454828X10' 



6 



h = 



H[a3 - 512,000] 



b^ = -11,647,641.0 





h = 



H[exp (-A) - exp (-80)] 



bg = 0.19235397X10" 



3 



h = 



H2[ /a"- /80] 



bg = 0.30310790X10" 



14 





H2[A5 - 3,276,800,000] 



b^Q= -0.84256893X10" 



3 



^10^ 



H2[ (10,000/a2) - 1.5625] . 



The standard error of estimate for this equation is 0.55 foot. The equation is valid 

 for breast high ages between 20 and 160 years, and site indices (base age 80) between 

 20 and 90. Figure 13 shows how this equation might be programed in FORTRAN IV (360). 

 This equation will not be valid for ages beyond 160 years. Older trees should be 

 treated as if age were 160 years. 



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