384 JOURNAL OF FORESTRY 



Height classes Numbers assigned 



(feet) to the classes 



A. — CLASSES WITH 10-FOOT INTERVALS 



to 10 ; 10-20, etc., up to 190-200 1, 2, etc.. up to 20 



B.— CLASSES WITH 20-I'OOT INTERVALS COMMENCING AT THE GROUND 

 to 20; 20-40, etc., up to 180-200 I, II, etc.. up to X 



C. — CLASSES WITH 20-EOOT INTERVALS COMMENCING 10 FEET ABOVE THE GROUND 



10 to 30; 30-50, etc., up to 190-210 la, Ila. etc., up to Xa 



Although three sets of standard height classes are indicated. A, B, 

 and C — the last two (B and C) are merely combinations of the first 

 "A," on the basis of 20-foot instead of decade intervals, the "B"' series 

 being for classes separated at even decades, while the "C series are 

 separated at odd decades. Where 20-foot intervals are desired in some 

 cases it would be more convenient to have curves for a given species 

 coihcide at 100 years with the "B" height classes and in others with 

 the "C." A 20-foot height interval will be sufficiently close for many 

 of our species at the present stage of forestry development in this 

 country. When the standard "A" site classes are applied to a given 

 species, the Arabic numerals at once indicate the heights attained, as, 

 for example, if a species were classified as reaching class 9 as a maxi- 

 mum this would at once indicate that 90 feet was the best it could do, 

 while one which reached site 10 would have a maximum of 100 feet, 

 and so on. This is one of the advantages of numbering the sites from 

 1 up, instead of vice versa. In the standard "C" classes, the average 

 height of a given class would be double that indicated by the height 

 class numeral, and in "B" it would be double minus 10 feet. 



The yield table to be discussed is largely the work of Mr. Frothing- 

 ham, using as a basis plots I had under compilation for a bulletin on 

 the eastern oaks. The computing was largely done by. Miss Elsie B. 

 Stabler of the Forest Service. 



The yields in cubic feet for dift'erent ages are graphically shown by 

 the curves (see figure). The curves are based on 370 plots, of 

 which some 345 were taken in western Maryland in 1910, 1911, and 

 1912, by crews working under State Forester Besley, in co-operation 

 with the U. S. Forest Service, and some 25 were taken in the Southern 

 Appalachians, in 1915 and 1917, by Frothingham. 



These curves indicate the growth and yields of well-stocked stands 

 (density 0.8 or more) of southern upland hardwoods on the different 



