APPENDIX I 



Field Plot and Computation Procedures for Describing 

 Competitive Status of Growth-Sample Trees 



Many of the growth functions that have been useful for predicting the growth rate 

 of an individual tree include variables that describe the competitive status of the 

 subject tree relative to the surrounding trees that make up the forest stand. Some of 

 these methods require that the map-wise relations between trees be recorded in order 

 to compute the measure of competition (Bella 1971) . Others might be as simple as a 

 variable defined by the ratio of the subject tree d.b.h. to the root -me an- square d.b.h. 

 of all trees in the stand. In my studies of growth of grand fir, and studies with 

 D. M. Cole, of Intermountain Station, on the growth of lodgepole pine, it appears that 

 if the crown development of the subject tree and its relative position within the diam- 

 eter distribution of the stand are both included in the statistical model, then there 

 is little added explanatory value to be derived from variables calculated from the map- 

 wise distribution of stems. These studies admittedly were based on trees growing in 

 undisturbed stands where the crowns had evolved in relation to local variations in 

 stand density. However, even in stands where the equilibrium has been disturbed, there 

 is evidence for tree-soil moisture relations that would permit trees to benefit from 

 decreased competition for moisture in parts of the stand farther from the subject tree 

 than is usually considered in competition models based on stem distributions in space 

 (Bormann 1957). This view is supported by the analyses of subject tree growth showing 

 that as the zone of competitive influence is increased, the explanatory power of the 

 tree-centered measure of competition is increased (Opie 1968; Lemmon and Schumacher 1962) 



The variables available in this prognosis program to represent the competitive 

 status of the ith sample-tree record in relation to its surrounding stand are either: 



DBH(I)/HMSQD 



or 



PCT(I) 



where 



DBH(I) 



Diameter of the ith tree in inches 



EMSQD 



Diameter of the tree of mean basal area in inches 



FCT(I) 



Percentile in the basal area distribution. 



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