APPENDIX B: PROCEDURE FOR CALCULATING PAST BIOMASS 



Diameter and height can be used to estimate past biomass because they can be deter- 

 mined for any time in the past by stem analysis. 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: 



Piny on 



Y = 2.695Xj + 0.670X 2 - 0. 0806X^2 - 5.258 

 R 2 = 0.978 SDR = 0.205 



Juniper 



Y = 4.1S5XJ + 2.435X 2 - 0.5473X^2 - 11.504 

 R 2 = 0.926 SDR = 0.308 



The natural log of total aboveground biomass (kg), ovendry basis is Y. Natural 

 logs of stump diameter and total height (determined by stem analysis as described in 

 the Methods section) are Xj and X2 . 



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

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

 for 1978 equaled the estimated biomass as calculated by the more accurate equations in 

 appendix A. For the pinyon equation, the proper intercept term (I) was calculated by: 



I = Yi - 2.695X X - 0.670X 2 + 0.0806X2X2 



in which Y± is the natural log of total aboveground biomass in the particular tree as 

 calculated by the first equation in appendix A and X± and X2 are logs of stump diameter 

 and height measured in 1978. Intercept values for juniper trees were calculated sim- 

 ilarly. 



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