THE CULL FACTOR, OR DEDUCTIONS FOR DEFECTS 271 



217. The Cull Factor, or Deductions for Defects. Most timber 

 estimating for board-foot contents of stands is based on the amount 

 which the logs will scale (§116). Since a sound scale of logs requires 

 deductions for defects which will not make sound boards, the timber 

 estimator must make the same deductions in the standing trees. This 

 deduction from total sound scale is independent of any separation 

 of the timber into grades or quality, which calls for additional special 

 attention. Deductions from full sound scale of standing timber are 

 made either by the log unit or by the tree unit on the basis of the judg- 

 ment and experience of the cruiser. Where the estimate is made by 

 logs, only sound logs are tallied. Culled logs are dropped from the 

 tally altogether and trees which contain defective portions are scaled 

 by shortening the length or decreasing the size of the logs tallied so 

 as to represent only their net sound volume. Where it is impossible 

 or inaccurate to use this method of omission, a straight percentage 

 deduction for cull is either substituted for the method of dropping 

 or reducing logs or is subtracted after all of the clearly visible defect 

 has been deducted. 



Tree units are handled in the same manner. Trees so defective 

 that they are practically cull are not tallied at all, but in species where 

 few, if any, trees are cull and the defect constitutes a portion of a large 

 per cent of the logs and is not easily deducted, cruisers deduct a straight 

 per cent from the total sound scale of the trees tallied. Usually a com- 

 bination of these methods is necessary since the per cent deducted 

 represents more accurately the loss in the sound scale of logs actually 

 sawed and taken to the mill, while a considerable additional cull is 

 found in logs and trees not utilized at all. 



Foresters, in making a tally of diameters and heights, customarily 

 tally all trees, regardless of their condition, omitting only dead timber 

 which is unmerchantable, and then apply to the total volume a per- 

 centage deduction for total cull, which will cover both that portion 

 left in the woods and that lost in sawing. 



218. Total, or 100 Per Cent Estimates. To completely cover a 

 small area, it is only necessary to avoid duplicating the count or measure- 

 ment of the individual trees. This may be done by the use of a bark 

 blazer or scratcher, or by tagging the trees, a method employed in India 

 where labor is cheap. 



Trees may be given a light bark blaze. In working over a tract 

 in this manner, the blaze is placed upon the same side of all trees, facing 

 the direction towards which the measurement is proceeding. Where 

 topographic features are present on small areas, duplication may be 

 avoided by covering sections bounded by these natural features without 

 the necessity of spotting the trees. 



