Then by using whorl counts, the height growth of the last 10 years is determined on 

 the felled tree. From these data the following model is developed: 



In(HTGF) = oii * c^i ln(I?J+0.05) ^ c^i IniBBE) + c^i In(HT) 



where: 



HTGF = Periodic height increment in feet 



= Regression coefficients for the tth species 

 HT = Tree height in feet 

 DBH = Diameter at 4.5 feet, in inches 

 DC = Periodic diameter increment in inches . 



Model for Crown Ratio Development 



The model used to predict changes in crown dimensions is based on the rate at 

 which the base of the live crown recedes which is expressed as a function of the height 

 increment and the current level of stand density. For stands in which the crown 

 competition factor is less than 125, the rate at which the crown recedes is specified 

 to be equal to one-fifth of the increase in height for the tree. For stands having a 

 crown competition factor greater than 125, the crown is specified to recede at a rate 

 of 0.61 times the height increment rate. 



A different model is used for trees for which no crown measurement was obtained. 

 Under this alternative the height to the base of the live crown is predicted as a 

 function of tree height, tree diameter, the relative position in the diameter distri- 

 bution at the start of the prognosis, crown competition factor; and habitat type. 

 This function is: 



HCB = -29.26 * 0.61 HT * 9.178 In(CCF) - 0.222 EL - 5.80 DBH/RMSQD + HAB 



where the variables are as defined previously with: 



RMSQD = Diameter of the tree of mean basal area in inches 



HAB = ( 



0.0 for Abies/Xerophyl lum habitat 



-4.24 for Abies/Vaccinium habitat 



-5.86 for Abies/Pachistima habitat 



-5.47 for Pseudotsuga/Calamagrostis habitat 



Models for Mortality 



Tvs'o alternative models for mortality rates were developed for lodgepole pine 

 stands. One of these is based on the mortality study of Lee (1971). The other model 

 is based on the dynar.ic relation between a population cf mountain pine beetle 

 (^Dendroctonus "onder-osae Hopk . ) and the developing stand of lodgepole pine. The model 

 for beetle-induced mortality was developed in cooperation with, and using data from 

 studies by Walter E. Cole and Gene D, .Amman, on file at Intermountain Station, Ogden . 



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