cedar and table 11 for second-growth Cottonwood 

 was extended and used for all hardwoods. 



Timber-volume data were computed in three 

 units of measure: In board feet, log scale, Scribner 

 rule; in board feet, lumber tally; and cubic feet. 



In determining the board-foot volume in log 

 scale, Scribner rule, all live conifers 11.1 inches 

 d. b. h. and larger that would make at least one 

 16-foot log to an 8-inch top diameter and all live 

 hardwood trees 11.1 inches d. b. h. and larger that 

 would make at least one 8-foot log to a 10-inch top 

 were included. Utilization of all conifers to a top 

 diameter about 40 to 60 percent of the breast-high 

 diameter was assumed. Decay and other defects 

 were subtracted from the gross estimate. Ponder- 

 osa pine, western white pine, and sugar pine trees 

 were totally culled for defect only when over two- 

 thirds of their gross scale was unmerchantable. All 

 other species were totally culled only when over 

 one-half of their gross volume was unmerchantable. 

 Timber-volume data in board feet, log scale, were 

 computed by species and ownership class for each 

 section in surveyed townships and for each mer- 

 chantable-timber type area in unsurveyed town- 

 ships. Compilation of the volume on areas covered 

 by reliable preexisting cruises consisted of adjusting 

 the cruise by factors previously determined through 

 check cruising. Volume on areas not covered by 

 preexisting cruises was computed by the application 

 of stand-per-acre values, determined in the field, to 

 the acreages of merchantable-timber types. Vol- 

 umes resulting from these computations were then 

 posted by section, species, and ownership class on 

 township summary sheets and finally combined 

 into a county total. 



Volume of merchantable saw timber in board 

 feet, lumber tally, was determined by applying a 

 conversion factor of 1.10 to the log scale, board-foot 

 volumes. 



Cubic-foot volume of solid wood in all living and 

 standing dead trees 5.0 inches d. b. h. and larger 

 from stump to a 4-inch tip inside bark, excluding 

 bark and limbwood, was computed, by species 

 and ownership class, for each county. Cubic-foot 

 volume of trees of saw-timber size was determined 

 by applying a conversion factor to the merchantable 

 board-foot volume. This conversion factor varied 

 by species; for ponderosa pine and sugar pine the 

 board-foot-cubic-foot ratio was 5.5, and varied 



from 3.8 to 5.8 for other species. The cubic-foot 

 volume of trees less than saw-timber size was com- 

 puted by several methods. The volume in under- 

 story trees in saw-timber stands was determined 

 from data obtained in field samples taken in the 

 growth phase of the survey. The volume of even- 

 aged pole stands other than ponderosa pine was 

 determined from partial yield tables, and in pon- 

 derosa pine pole stands by multiplying the number 

 of poles per acre by the volume of the average 

 pole, as determined from growth-study samples. 

 The latter method was also used for lodgepole pine 

 pole stands. Some of the cubic-foot volume was 

 derived from cordwood estimates of such species 

 as Sierra juniper, mountain mahogany, and aspen. 

 A converting factor of 65 cubic feet of solid wood per 

 cord was used for Sierra juniper and mountain 

 mahogany and 72 cubic feet for aspen. 



Methods in Depletion Phase 



The immediate purpose of the depletion phase 

 was to determine the quantity and kind of timber 

 annually removed by cutting or killed by insects, 

 fire, wind throw, disease, and other causes, and 

 the area deforested by all causes; in short, the 

 extent and character of the drain on the forest 

 capital. The ultimate object was to determine 

 the trends of depletion and growth, present and 

 potential, and the net result of the two trends. 

 To estimate the quantities of wood material in 

 the future it was necessary to project the depletion 

 figures into the future. 



Cutting Depletion 



The estimate of the average volume of material 

 removed annually during the 12-year period, 

 1925-36, from the forests of the region as sawlogs 

 was determined from statistics on sawlog produc- 

 tion compiled annually by species and counties by 

 the Forest Service in cooperation with the Bureau 

 of the Census. Unavailable, however, was any 

 similar statistical record of the volume of material 

 removed annually as minor products, such as fuel 

 wood and fence posts. 



In estimating the production of fuel wood from 

 live timber, a per capita consumption for each 

 county was set up for both urban and rural districts. 

 This assumed consumption, based chiefly on a 



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