Current Literature. 451 



wesen* and has converted the yield tables into metric measure. 

 He comments on the great height growth and comparatively 

 poor volume production which these tables' show. He calculates 



(volume in cubic feet \ 

 — i — r—. — : — z ; I for all 

 height m feet x basal area / 



trees at 140 years of age and finds the factor to be .32, .35 and 



.37 for the three site qualities respectively, which is very low. 



This, Dr. Schwappach attributes to the volume tables ; Mr. Hanz- 



lik himself says' that his volume figures are very conservative. 



Furthermore, as Dr. Schwappach points out, the tables are for 



final yield only and do not take into account the intermediate 



yield from thinnings which, in Norway spruce, aggregate about 



50% of the total production. Even allowing 20% increase over 



Hanzlik's final yield figures to allow for trees dying out, the yield of 



the Douglas fir is only 20% greater than that of Dr. Schwap- 



pach's own figures for Norway spruce, Site Quality I, age, 120 



years. 



Comparing Hanzlik's figures with the latest Saxon yield table 



for spruce, printed in F. Q., Vol. XH, No. i, p. 114, one finds 



at age 100 years for Site Quality I : — 



Douglas fir, 17,600 cubic feet per acre. 



Norway spruce, ...14,915 " " 

 — an increase of only 17% over the Norway spruce. 



Assuming the stand- form-factor to be the same at 120 years 

 as that of Norway spruce — i. e. .44 — and using the values for 

 height and basal area as given in the table, the yield becomes for 

 120 years, 27,880 cubic feet as against 20,700 cubic feet per acre. 

 "One sees, therefore," says Dr. Schwappach, "what an influence 

 the method of volume determination has and how carefully the 

 data must be analyzed before the American figures can be used 

 as a comparison with the production of German species — in this 

 case with the production of spruce and fir." 



Dr. Schwappach concludes from Mr. Hanzlik's figures that 

 the plantations of Douglas fir in Germany are yielding, at least 

 in youth, just as much as similar stands do on their native sites. 



A. B. R. 



"Ertragstafeln fiir Pseudotsuga Douglasii," pp. 652-657. 



