Measures and yields of products and residues 3255 



27-7 lists the number required for trees of various sizes and two form classes. 

 Form class is an indication of stem taper and is calculated as follows: 



Form class = 100 Bib at top on6-foot butt log ^^^_^^ 



Small hardwood timber usually has a taper within the range of form class 75 to 

 80 (Worley 1958). 



Cords of topwood per tree after removal of saw logs. — Substantial vol- 

 umes can be cut from the tops residual after hardwood saw logs are removed. For 

 example, in a North Carolina study of mixed oaks (Barrett and Buell 1941) 

 topwood yield per tree ranged from 0.01 long cord (peeled) for a 9-inch, 2-saw- 

 log tree to 1 .3 long cords (peeled) for a 32-inch, 1 '/2-saw-log tree (table 27-8). 



Cords per acre. — When entire stands are converted to pulpwood, the yield is 

 proportional to basal area and total tree heights in species with undivided stems 

 such as sweetgum, black tupelo, hickory sp., and yellow-poplar, as follows 

 (Minor 1953): 



Volume per square foot 

 Average tree height of basal area 



Feet Cords 



30 0.14 



40 .18 



50 .24 



60 .30 



70 .34 



80 .37 



Yields per acre have been tabulated for upland oak stands based on site index 

 and stand age (table 27-9) and on site index, stand age, and basal area (tables 27- 

 10 and 27-11). 



A study of mixed hardwood stands throughout the South (Porterfield 1972) 

 showed that upland slopes and ridges in Piedmont and mountain regions general- 

 ly had lower cord volumes than branch bottoms, wet flats, bottomlands, and 

 swamps (table 27-12). 



THE BOARD FOOT-LUMBER SCALE 



Traditionally, lumber was sawn to correspond to nominal thickness in inches 

 and designated by thickness in quarter-inches, e.g., 4/4, 6/4, and 8/4 corre- 

 sponded to 1-, 1.5-, and 2-inch-thick boards. Boards were also sawn to even 

 widths of 4, 6, 8, 10, and 12 inches. A board foot (lumber scale) is the volume of 

 wood in a 1-foot length of a 12-inch, 4/4 board; alternatively, it could be defined 

 as a 1-foot length of a 6-inch, 8/4-board or any other combination that would 

 yield a similar volume. 



Although softwood lumber is frequently sawn thinner than nominal thickness 

 (e.g., a 4/4 board is sawn only 15/16-inch thick), hardwood lumber must be 

 dried to the thickness called for. Thus, 4/4 hardwood lumber must be a full inch 

 thick when it is dry or it is scaled at the lesser thickness (Smith 1967). Further- 

 more, a hardwood board from 1 to VA inches thick (4/4 to 7/4) must not vary 



