Pinyon 



H & H 



u *i 1 1 1 1 1 1 1 1 1 r 



0123456789 10 



DSQH (DRC squared times HT in 1000's) 



Figure 4 — Comparison of this study's pinyon 

 equation (Arizona) with other pinyon equations. 



only correspond to diameter at stump height for trees 

 larger than 10 inches. Equation 7 was used to obtain a 

 corrected equation ("B & F" in fig. 4), which appeared com- 

 parable to the rest. 



Comparison of the oak equations (fig. 5) showed single- 

 stem equations from this study (Arizona) as similar to Fort 

 Apache/San Carlos (Apache) single-stem equations. Ap- 

 parent low predictions from the Barger and Ffolliott 

 (B & F) equation probably resulted from their volume defi- 

 nition including wood only (the rest included wood and 

 bark) and possibly from excluding branches. 



Olson's mesquite equation predicted higher than the 

 others (fig. 6). Perhaps a change in mesquite tree form 

 over the past 45 years accounts for this difference between 

 Olson's 1940 work and the recent single-stem equations. 

 Andrew's equation was almost identical to the Arizona 

 single-stem equation for small and average size trees but 

 differed considerably for larger trees. Because Andrew's 

 work included no large trees with a DSQH larger than 4, 

 extrapolation error is a probable cause for this difference. 



Comparison of the available Arizona woodland volume 

 equations clearly showed differences. Those taken from 

 Barger and Ffolliott always appeared to give the lowest 

 volume predictions. In most cases, definition differences 

 explained these discrepancies. Differences between this 

 study's equations and the various Indian reservation equa- 

 tions showed no consistent pattern among the species 

 groups. 



Oak 



Single Stem 

 Multiple Stem 



i I 1 1 1 1 1 1 1 1 r 



0123456789 10 



DSQH (DRC squared times HT in 1000's) 



Figure 5 — Comparison of this study's oak equation 

 (Arizona) with other oak equations. 



35 



30 



C 

 U 



B 25 



I 



C 



20 



V 15 

 

 L 

 U 



"10 



Mesquite 



Single Stem 

 Multiple Stem 



Olson 



Andrews 



Arizona 



Arizona 



-I 1 1 1 1 r 



1 2 3 4 5 6 



DSQH (DRC squared times HT in 1000's) 



Figure 6 — Comparison of this study's mesquite 

 equations (Arizona) with other mesquite equations. 



6 



