3316 Chapter 27 



If the sample line is measured in chains, the equation becomes 



V = S(0-00^454d^) x 1.037 (27-46) 



where: 



N = length of sample line, chains 



Martin (1976b) verified that the line intersect method gives unbiased esti- 

 mates of hardwood logging residues in the Appalachians and its reliability is 

 little affected by species, type of cut, slope, road influence, or length of residue 

 pieces. He also provided a computer program to expedite the required computa- 

 tions (Martin 1975 a); the user's guide is available on request from the US DA 

 Forest Products Marketing Laboratory, Princeton, West Virginia 24720. 



Another approach is a series of photos showing various residue levels generat- 

 ed by different cutting practices in a given forest type and forest size class; 

 information on residue quantities, sizes, and fuel ratings is given below each 

 photo (Maxwell and Ward 1976). The user simply looks for the photo that most 

 resembles his situation. As yet, however, such series are available only for 

 softwood forests in the Pacific Northwest. 



If logging residues are piled in windrows rather than scattered uniformly over 

 the area, then the inventory technique developed by McNab (1980) can be 

 applied. First, compute the wood ratio (proportion of the windrow profile area 

 that is occupied by solid wood) using the following equation: 



Wood ratio = (0.635 + 0.251/H - 1.625/0)^ (27-47) 



where: 



H = maximum windrow height, feet ^ ' 



D =mean diameter of residues larger than 3 inches, inches 



This equation has an R^ of 0.88 and a standard error of estimate for wood ratio of 

 0.036. 



Second, calculate the average cross-sectional area of the windrow, as follows: 



Area, sq ft = 3.39 + 1.19(H x L) (27-48) 



where: 



H = maximum windrow height, feet 

 L = horizontal distance from the near edge to point of maximum height, feet 



The relationship between actual and predicted area was close, with an R^ of 

 0.96. 



Third, then the residue volume = wood ratio x average cross-sectional area x 

 total length of windrows on the tract. 



McNab's formulae are based on a total sample of 54 transects in 28 windrows 

 in the lower Piedmont of Georgia. At these study sites, merchantable pines were 

 harvested by tree-length logging to a 4-inch top and residual hardwoods were 

 sheared at groundline and pushed into windrows with other debris by a crawler 

 tractor equipped with a brush rake attachment. 



Estimated amounts of logging residue. — For a discussion of logging resi- 

 due per acre, see the subsection by this title in section 16-2. 



