FOREST RESOURCES OF THE PONDEROSA PINE REGION 



Definitions and Specifications 



-»? 



General 



THE forest inventory included determination 

 (1) of areas of the several types, by ownership 

 class; (2) of areas of the even-aged immature 

 conifer types, by age class and degrees of stocking, 

 and uneven-aged immature conifer types, by de- 

 grees of stocking of poles and reproduction com- 

 bined; (3) a classification of forest areas according 

 to site quality: and (4) computation of the volume 

 of the present timber stands, including residual 

 stands on cut-over lands, by species and owner- 

 ship class. 



For convenience and facility of analysis and 

 discussion, the region was arbitrarily divided into 6 

 units. So far as was practical the units were 

 delimited so as to be homogeneous in economic 

 influence and industrial condition. Maps and 

 timber-volume information were obtained by com- 

 piling and field-checking existing data available 

 from public or private cruises, maps, and reports, 

 and making a field examination of all forest land 

 not covered by office data (fig. 1). 



The extent and character of the annual drain on 

 the forest capital was obtained by compiling, and 

 checking in the field when necessary, existing 

 records of cutting, insect, and fire loss, and of wind 

 throw. These data were analyzed for past and 

 present rates of depletion and future trends. 



Information on present and future forest growth 

 was obtained through application of growth and 

 yield rates available from previous studies to in- 

 ventory figures of the immature forests. Data 

 for the mature forests were obtained from field 

 examination. 



Unless otherwise indicated, all board-foot vol- 

 umes are in terms of Scribner Decimal C log 

 scale, hereafter referred to as Scribner rule. 



A complete account of field and office survey 

 methods is contained in the Appendix. 



S&r 



Standards of Measurement 



Timber volume estimates made according to 

 fixed, recorded specifications can be correlated 

 with estimates for other regions, can be adjusted 

 to meet changed economic conditions if desired, 

 and are stable. Standards were adopted that 

 conformed, as far as was practical, with current 

 utilization practice. 



Estimates of timber volume were made in board 

 feet, log scale, according to the Scribner rule, and 

 in cubic feet. The board-foot estimates included 

 only the stems of living trees that would make at 

 least one log conforming to these specifications: 



Conifers 1 6 feet long, 8 inches in diameter inside bark at 



small end. 

 Hardwoods 8 feet long, 10 inches in diameter inside bark 

 at small end. 

 Practically, this means making the 12-inch diam- 

 eter class (11.1 to 13.0 inches d. b. h. 2 ) the mini- 

 mum specification for both conifers and hardwoods. 



Allowance was made in the volume estimates for 

 decay, defects, and such breakage as is inevitable in 

 logging. In other words, the estimates are for the 

 net volume usable in saw-timber operations under 

 good utilization practices. 



The standards of utilization employed in the 

 survey are undoubtedly slightly more intensive for 

 the more valuable species, and considerably so for 

 the less-valuable species, than the current average 

 utilization practice of saw-timber operators, owing 

 chiefly to the inclusion of trees as small as the 

 12-inch diameter class. The volume tables used in 

 the forest survey estimated mature trees to a usable 

 top, and consequently survey estimates of saw-tim- 

 ber volume would closely approximate for a given 

 area the total amount removable by an average 

 operation. 



2 "D. b. h." signifies diameter at breast height (4^ feet 

 above average ground level), outside bark unless otherwise 

 specified. 



