GROWTH 



For the area covered by complete survey only net growth was 

 determined „ For that purpose the forest area was arbitrarily 

 classified into (1) nongrowing stands in which experience in- 

 dicated that gross growth generally was .offset by mortality 

 and (2) growing stands in which gross growth generally exceeded 

 mortality., Category (2) consisted of all uncut stands of 

 ponderosa pine,, larch , and Douglas-fir less than about 200 

 years of age,, uncut stands of other species less than about 

 160 years ? and partially cut stands of all species regardless 

 of age. Average net growth per acre by type, stand-size, age, 

 stocking, and site classes was derived from modified normal 

 growth tables o Modification of normal tables was based on 

 actual net growth as determined from increment borings and 

 mortality tallies on 375 l/5-acre sample plots covering the 

 range of age, stocking, and site classes within types. 



Gross and net growths for the area sampled were derived from 

 increment borings of sample trees and mortality tallies on 

 each sample plot measured for inventory purposes. Three 

 sample-plot sizes were used to measure growths 1/500 acre for 

 trees 5<>0 inches to 10,9 inches d b,h„, 1/50 acre for trees 

 lloO inches to 24,9 inches d„b„h„, and 1/5 acre for trees 25,0 

 inches d„boh. and larger. Radial growth was determined for 

 the 10-year period preceding the date of field examination. 

 Radial growth was converted to volume growth by subtracting 

 the reconstructed volume of sample trees 10 years ago, taking 

 into account changes in height and bark thickness as well as 

 diameter, from current sample tree volume. For the total growth 

 determination sample trees were divided into two classes (l) 

 ingrowth trees — those that either developed from sapling 

 into pole size or that grew out of pole size into saw-timber 

 size, and (2) main-growth trees — those that remained either 

 of pole size or of saw-timber size during the growth-study 

 decade. Total ingrowth was derived by multiplying the mean 

 ingrowth per acre by the appropriate area by type, stand-size, 

 and stocking classes,' Main growth was calculated from simple 

 growth per cents ana total inventory volumes by type, stand- 

 size, stocking, species, and diameter classes. 



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