212 GOVERNMENT REGULATION AND WORKING PLANS 



is often periodically measured by hand, through the use of ladders or by 

 climbing the tree. 



When stands must be calipered, the following principles govern the 

 valuation survey: 



(1) Diameter classes are 5 centimeters (or 1.97 inches). 9 



(2) It is not customary to note the height classes of all trees calipered 

 except in very large valuable timber; instead, the merchantable height 

 of a few normal trees of varying size is secured from felled trees or by 

 measurement. The results are averaged graphically and a local volume 

 table made for the compartment, cutting area, or working group. The 

 height classes are usually 2 to 4 meters (6.5 to 13.1 feet). 



(3) In merchantable stands 100 per cent estimates are almost uniform; 

 with cheap labor this is fully warranted. 



(4) In timber sales estimating is always done when trees are marked 

 for cutting. The usual and necessary errors in estimating are considered 

 6 per cent of the true volume even \mder favorable conditions; in virgin 

 or mature stands they count for possible errors up to 10 per cent to 13 

 per cent. But the French defend the volume table method of obtaining 

 volume, even in experimental work, against the German and Swiss 

 sample tree methods. In other words, they prefer volumes based on a 

 local table of 40 to 50 trees rather than on 5 to 10 sample trees chosen by 

 mathematical averages 10 but selected on the basis of judgment. 



The 1-inch diameter classes used by the U. S. Forest Service for its early working 

 plans was an absurdity. The writer used 3-inch diameter classes for estimates in western 

 yellow pine in Arizona and New Mexico. Captain Kittredge reported that 20 cm. cir- 

 cumference classes (2 inch d. b. h. classes) were used in the Cote d'Or. In practice 

 the French usually measure regular trees once; and irregular trees twice in order to 

 secure the average diameter. 



10 The valuation surveys in private forests bought by the A. E. F. were made as 

 follows, according to a report by Dunning: 



Estimators are equipped with calipers and scribes or marking hammers. They 

 proceed through the timber in parallel strips, mark each tree to be cut, taking the cir- 

 cumference at Im30 from the ground, or in the fir of the Jura at Im50. The tally- 

 man repeats each circumference announced to avoid mistakes. Trees from 20 to 30 

 cm. in circumference are recorded as poles. In hardwoods trees below 50 cm. are not 

 usually marked. 



The estimators rate the height of each hardwood tree in meters usually to a top 

 circumference of 60 cm.; if serious crooks, forks, or large limbs occur the height is taken 

 as far as a reasonably straight log can be obtained. 



In uniform stands of pine the chief of detachment or tally-man estimates the average 

 height for each circumference class, the trees being tallied by 10 or 20 cm. classes, and 

 the estimators announce only the circumferences. In open stands of old pine the 

 height of each tree is taken. 



In the fir of the Vosges the circumference only is taken, heights being given by 

 circumference classes in volume tables, to a top diameter of 20 cm. 



When the average height method is used allowance is made for exceptionally short 



