open stands, where crown coverage of mature trees may range from 5 to 35 per- 

 cent, characteristic shadows aid the interpreter in recognizing the type. 

 Because of these silvicultural characteristics, and because tests indicate 

 volumes significantly lower than those obtained from the composite aerial 

 volume tables published in Research Paper 41, a separate aerial table has been 

 prepared for ponderosa pine. 



Procedure 



The following tables were compiled from 84 plots measured in Idaho, Utah, 

 Colorado, and the Black Hills of South Dakota. They relate gross board- foot 

 and cubic-foot volumes from field measurements of 1/5-acre plots with direct 

 photo measurements of the same plots. 



Photo measurements consist of: 



1. Average total height of the dominant stand. 



2. Average visible crown diameter of the dominant stand. 



3. Crown coverage of the dominant stand. 



Photo measurements of total height were checked against the ground meas- 

 urements of the three tallest trees on the 1/5-acre plot. 



Gross volumes were computed from field data using total height-d. b .h. 

 tables developed by Forest Survey and include: 



1. Gross cubic volume — trees 5.0 inches d.b.h. and larger to a 4-inch 

 top. 



2. Gross board foot International %-inch Rule--trees 11.0 inches and 

 larger to a variable top with a minimum of 5.5 inches. 



2/ 



3. Gross board foot (Scribner) --trees 9.0 inches— and larger to same 

 top diameters. 



Volumes include cull trees and sound and cull portions of sound trees 

 since the interpreter cannot recognize these conditions. 



These tables were constructed by the alignment chart method of solving 

 problems in multiple curvilinear correlations described by Bruce and 

 Reineke.^/ They are designed for use in direct photo estimates of ponderosa 

 pine stands throughout the central Rocky Mountain areas. Use of a limited 

 field sample should allow adjustment of these estimates to fit local areas. 



Ij The 10- inch diameter class is used in many regional timber sales and 

 accounts for the apparent inconsistency in the tables where a larger volume 

 is shown for Scribner than for International %-inch Rule, particularly in the 

 smaller stands. 



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