CALIPERING STANDS 211 



Rule-of-Thumb Methods. — There are various rule-of -thumb methods^ 

 all based on the metric system. They are chiefly of value in stimu- 

 lating local forest officers to study the laws of diameter, height, and 

 volume. 



(1) Bouvard formula: F = | D^H which is somewhat conservative, though used for 

 coppice-under-standards . 



(2) d'Auverne formula: V = 7/10 volume of cyUnder of size of middle girth, for 

 oak cut to top limit of 11.8 inches. 



(3) Villers-Cotterets formula: V in steres = circumference in centimeters minus one 

 meter (i.e., 1.70 — 1.0 or 0.7 steres) used for beech locally. 



(4) Algan formula: V = 0.33 D'H. Used for spruce 5.9 in diameter at small end; 

 or V = 0.42 Dm. 



(5) Plank formula: P = f A'-D^- 



In the Vosges it is customary to estimate in "board feet" or planks 4 M long X 0.25 

 wide X 0.025 thick or 1/40 plus or minus of a cubic meter. 



Ocular Estimating. — In regular fully stocked stands of coppice or 

 young high forest ocular * estimating is exceedingly accurate, and coppice 

 is rarely estimated by any other method since the number of steres per 

 hectare can be gauged if the age and soil quality are known. Then too 

 it must be remembered that each compartment has been cut over for 

 generations and where the rotation or treatment has not been modified 

 there are usually the records of past cuts to base estimates upon. Such 

 ocular estimates for coppice can be made within 90 per cent of the actual 

 cut or even closer so that they answer for sale purposes and the price is 

 usually a lump sum per hectare. High forest timber, except when in 

 the sapling stage, is never estimated ocularly. 



Calipering Stands. — The French measure the diameter or circum- 

 ference of standing timber at 1.50 meters (4.92 feet) or 1.30 (4.26 feet) 

 above the ground and on hillsides they measure the breast-height point 

 from the uphill side of the tree. They often take into account the fact 

 that the largest diameters are parallel with the wind or the crown or 

 root development; this would apply especially to an intolerant species 

 like the maritime pine in the Landes where there are strong winds from 

 the ocean. But generally these points are waived since the errors in 

 calculating volumes are even greater. In accurate estimating the mer- 

 chantable sawlog length is almost invariably measured or approximated 

 in the field; this is especially important with standards. In growth 

 studies in coppice-under-standards the length of the merchantable bole 



1 V = Volume in cu. m.; D = d. b. h.; L = length of merchantable bole; H = total 

 height, d = middle diameter of standing tree; P = plank; N = number of trees. 



8 A rule-of-thiunb method given by Huffel (p. 120, Vol. II) for estimating mature 

 (a) fir or (6) oak stands is to multiply the average merchantable length by from (a) 25 

 to (b) 30 the answer being cubic meters per hectare. This illustrates the bearing of 

 height on volume in fully stocked stands. 



