An interaction variable. LnD*LnC, was introduced in the 

 regression analysis and proved to be beneficial to some of 

 the prediction equations. For the pinyon equations, D is 

 the DSH and for the juniper equations, D is the DBH. The 

 advantage of using the interaction variable is that it in- 

 creases the precision of the equations while still lending 

 itself to the construction of weight tables using two 

 independent variables. The equations listed in tables 5 and 

 6 have the deadwood component included in the various 

 size fractions. The deadwood component was weighed 

 separately in the field because of its lower moisture 

 content, and then its ovendry weight added to the 

 appropriate size fraction. Although 76 pinyons were 

 weighed, the four trees in the <10 cm diameter class were 

 eventually deleted from the regression analysis. The pre- 

 diction equations were much improved by deleting the four 

 small saplings. Equations are being developed for seed- 

 lings and saplings in the <10 cm diameter class, and will 

 be reported elsewhere. 



Of the various tree measurements, the average crown 

 diameter was the most significant variable for both 

 species. Although the stem diameter measurements were 

 also significant, the stump height diameter was more use- 

 ful in the pinyon equations and the breast height diameter 

 was more useful in the juniper equations. Height had no 

 predictive value in the juniper equations, but it was 

 significant in the pinyon equations for the total biomass 

 and the biomass greater than 7.6 cm. 



Thus, in order to use the equations presented in this 

 paper, three variables are required for pinyon: crown 



diameter, stump diameter, and tree height. Only two 

 variables are required for juniper: crown diameter and 

 d.b.h. However, for multiple stem junipers, it is advised to 

 correct the greater than 7.6 cm biomass for the number of 

 stems. For single stem junipers, no correction is needed. 



Weight Tables 



Equations from tables 5 and 6 were used to construct 

 weight tables. Predicted ovendry weights of the greater 

 than 7.6 cm (3 inch) and the less than 7.6 cm biomass are 

 presented in tables 7-10 by stem diameter and average 

 crown diameter or height classes. The predicted total 

 aboveground weight for pinyon can be obtained by adding 

 the weights in tables 7 and 8. For juniper, the total 

 weight is presented in table 11. 



Note that the prediction equation for the juniper weight 

 of the greater than 7.6 cm biomass contains a correction 

 factor for the number of stems at d.b.h. This correction 

 factor ranges from only 1-2 kg for most junipers with up to 

 20 multiple stems, and thus is important mainly for the 

 smaller trees. 



The tables and equations presented in this report were 

 developed from trees sampled within Nevada and thus 

 should be validated in new areas before using. Extra- 

 polation beyond the data range or to species other than 

 singleleaf pinyon and Utah juniper is not recommended 

 without rescaling the variables to fit the population. Trees 

 with similar bole and crown diameters may vary consider- 

 ably in weight because of differences in crown size, crown 

 form, and density of foliage. 



Table 5 — Prediction equations for estimating ovendry weight of the aboveground biomass of singleleaf pinyon trees greater than 

 10 cm at the root collar (basis: 72 trees) 



Tree Standard error Percent mean Percent 



component 





Equation 1 





R 2 



of estimate 



error 



bias 



Total LnW= 



-2.025 + 1.399 (LnDSH) 



+ 0.671 (LnH) 



+ 0.922 (LnC) 



0.987 



0.156 



15.9 



4.0 



>2.5cm 



-4.280 + 1.762 (LnDSH) 



+ 1.146 (LnH) 



+ 0.653 (LnC) 



.988 



.173 



17.0 



5.3 



>7.6 cm 



-6.024 + 2.159 (LnDSH) 



+ 1.663 (LnH) 





.988 



.184 



18.6 



2.4 



<7.6 cm 



-3.203 + 1.761 (LnDSH) 



+ 3.280 (LnC) 



-0.554 (LnDSH'LnC) 



.973 



.194 



19.5 



-1.0 



2.5 to 7.6 cm 



-6.843 + 2.460 (LnDSH) 



+ 4.013 (LnC) - 



0.742 (LnDSH'LnC) 



.959 



.293 



30.3 



-2.4 



0.64 to 2.5 cm 



-6.128 + 2.211 (LnDSH) 



+ 3.685 (LnC) - 



0.727 (LnDSH'LnC) 



.935 



.312 



34.5 



-3.5 



< 0.64 cm 



-4.078 + 1.556 (LnDSH) 



+ 3.293 (LnC)- 



0.571 (LnDSH.LnC) 



.918 



.304 



34.2 



-2.5 



Foliage 



-2.434 + 1.082 (LnDSH) 



+ 2.814 (LnC)- 



0.378 (LnDSH'LnC) 



.912 



.305 



33.2 



-2.4 



Where 



W= weight, kilograms 

 DSH= diameter at stump height (30 cm), centimeters 

 H= height, meters 



C= average crown diameter, meters 

 Ln- natural logarithm, base e. 



6 



