APPENDIX II — Regression Equations for Past Biomass 



Diameter, height, and age can be used to estimate past biomass because they can 

 be determined accurately for any time in the past. Crown parameters cannot be used as 

 they were for present biomass, because their past values cannot be estimated accurately. 

 The following equations were developed to estimate past biomass: 



(InF) = 2.229 (InD) + 1.027 (InH) - .201 (InH) • (InT) - 4.406 



(eq. 6) 



(InW) = 3.394 (InD) + 2.433 (InH) - .278 (InD) • (InH) - 13.521 



(eq. 7) 



(InM) = 2.695 (InD) + .670 (InH) - .0806 (InD) • (InH) - 5.258 



(eq. 8) 



The symbols are as defined in appendix I except for the introduction of T, the age 

 (years) of the tree at stump height, in equation 6. The coefficients of determination 

 (R 2 ), are 0.891 for foliage (eq. 6), 0.990 for wood (eq. 7), and 0.978 for total (eq. 8) 

 The standard errors of estimate are 0.342, 0.173, and 0.205, respectively, and are sub- 

 stantially greater than their counterparts in appendix I. 



The last term (the intercept) in the equations was not used in the calculation of 

 past biomass. A new intercept was calculated for each equation and each tree such 

 that biomass calculated for 1977 equals the measured biomass of weighed trees or the 

 estimated biomass of unweighed trees as calculated by the equations in appendix I. For 

 the foliage equation, for example, the proper intercept term (I) was calculated by: 



I = (InF) - 2.229 (InD) - 1.027 (InH) + .201 (InH) • (InT) 



(eq. 9) 



in which D, H, and T are 1977 values for diameter, height, and age of a particular tree; 

 and F is foliage biomass, either weighed or calculated by eq. 3. 



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