from the ratio of inside-bark to outside-bark diameters at breast height by the 

 relation : ^ 



DBT=D(I) * [BARKBH/DBH] * [QUAN/ (DENO-D(I) /DBH) ] 



in which 



DBT = double bark thickness 



D(I) = outside bark diameter at the level for which bark is being estimated. 

 DBH = diameter outside bark at breast height (B.H.) 

 BARKBH = double bark thickness at B.H. 



QUANjDENO = constants establishing the asymptote of the hyperbola, such that 

 DENO-1 .=QUAN. 



Additional variables available to BARKEQ that are useful for estimating bark thickness 

 are : 



ITYPE--the species code 

 IAGE--the tree age 



HT(ITDIA) --the height of the top of the tree 

 HT(I)--the height at the estimation point 



VARTCF 



This subprogram calculates the top diameter to be used with output code 2. The 

 version of VARTCF distributed with NETVSL calculates the variable top as a fraction of 

 DBH. The fraction is obtained from IVTPC/100. The latter variable is input data from 

 columns 13-16 of PROBLEM OPTION CARD (2). The argument list with which VARTCF is calle 

 is (DBH, IVTPC/100, IVTFC/IVTFLT, VT) . 



IVTPC and IVTFC are read from PROBLEM OPTION CARD (2) . IVTFLT is a scale factor 

 set to 10 in BLOCK DATA. VT is the calculated variable top. Although IVTFC is avail- 

 able, it should be used with caution because a nonzero value of IVTFC will cause cal- 

 culation of volumes in cubic feet to this fixed top diameter (output code 3 in table 2) 



VARTBF 



This subprogram is analogous to VARTCF except that it uses IVTPB and IVTFB in the 

 second and third calling arguments. A similar caution applies to using the third 

 argument . 



BRDCUL 



Defect deductions in board-foot units have not been programed because the rules 

 for these deductions are quite variable. However, the NETVSL program does provide for 

 reading the necessary data and transmitting these data to the BRDCUL subprogram, which 

 is called after log intervals, diameters, and gross volumes have been calculated. 



The data for computing cull in board feet are stored in locations identified by 

 the following names: 



IBOTM(J) Index of the data for the bottom section of the 



Jth fork 



ITOP(J) . Index of the data for the top section of the J"th 



fork 



Clement Mesavage (personal communication) has found that this formulation of the vertical trend of 

 bark thickness has wide generality with QUAN=1, DEN0=2. 



15 



