1 904 



FORESTRY AND IRRIGATION 



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4J 







At first glance the B thinning seems to 

 give the greatest volume, but the num- 

 ber of trees is not much less than that in 

 A, and therefore the quality and price is 

 not radically bettered. On the other 

 hand , C has 400 trees to the acre less than 

 A, with a greater actual volume of 400 

 cubic feet standing, exclusive of 1,400 

 cubic feet more yield in the thinnings. 

 It is also evident that the D thinning is 

 too severe. 



From a great mass of facts compiled in 

 this report and covering about 150 ex- 

 periments in all ages, certain important 

 facts may be summarized. 



The volume of merchantable wood 

 left after thinning has never fallen below 

 the volume left after the previous thin- 

 ning. 



The cleanness of bole decreases with 

 the degree of thinning. It is relatively 

 best in B and C. 



The greatest production of merchant- 

 able timber is obtained in the grades B 

 and C. The best condition probably lies 

 between B and C, with an inclination 

 toward C. (This probably corresponds 

 with the C thinning at Tharandt.) 

 When expressed in money value, the C 

 grade shows an even better result. 



The current yearly height growth is 

 better in C than any other grade of thin- 

 ning. The lightly thinned area A shows 

 the poorest height growth, and the in- 

 crease in B is not remarkable. This 

 point is clearly shown in every instance 

 and is very interesting. It has been 

 generally held that close- grown trees are 

 very much stimulated in height growth, 

 but these figures prove that a reasonable 

 amount of room not only increases the 

 diameter, but also the height. In this a 

 most important argument has been ad- 

 duced in favor of thinnings. When 

 grown too openly, however, the relative 

 height growth falls off, as shown in the 

 D thinning. 



The greater diameter growth in D 

 takes place only in the lower part of the 

 stem. The bole is more tapering and 

 has less volume than in B or C. The 

 best proportion between height and di- 

 ameter is shown in C, with B closely 

 following it. 



In young and middle-aged spruce 

 stands the thinning should lie between 

 B and C, inclining more toward C. 



