18 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE. 



area investigated was 50 years in pure stands and 85 years when 

 mixed with hardwoods. They speak of butt-rot only, without 

 specifying the cause; unfortunately, the numerical basis from which 

 their figures are derived and their methods are not given. 



The bearing on management of the age at which decay becomes a 

 seriously damaging factor is very rarely realized. 



Clapp, 1 in speaking of incense cedar and white fir, clearly recognizes 

 that where these "inferior" species are also defective, "an attempt 

 should be made, at least in selection stands, to reduce their rotation 

 to one which will produce sound timber." 



In a recent article, D. T. Mason 2 advocates a rotation of 100 years 

 for western white pine, on the ground that this species on the average 

 gives a maximum yield at this age and that from about the same age 

 fungi, and particularly insects, generally succeed in doing a large 

 amount of damage. 



It would serve no purpose to continue quoting the few and scat- 

 tered notes on the relation of age to decay, of a similar indefinite 

 nature found in American literature. By way of consolation, it may 

 be said that foreign literature does not abound very much more than 

 our own in definite information regarding this point. Although 

 the importance of the age at which forest trees are most liable to 

 attack from heartwood-destroying fungi is frequently hinted at in 

 German literature, Martin 3 is the only German forester who, to the 

 knowledge of the writer, has given more than a cursory discussion 

 of the relation of this age to rotation. In speaking of the immense 

 damage done in Prussian pine forests by Trametes pini, he attempts to 

 show from somewhat meager material how the increase in loss from 

 this cause should lower the rotation. 



All computations of the amount of decay in German forests must 

 necessarily be incomplete, since from an early age all undesirable 

 individuals, including, as a matter of course, all trees with visible 

 signs of decay, are eliminated in improvement cuttings. The result 

 is a stand of a comparatively high degree of soundness. Even in 

 such stands Martin finds (p. 688) that in a given district the per- 

 centage of decay in wood good for fuel only in the 100-year class was 

 11, in the 120-year class 22, in the 130-year class 31, in the 140-year 

 class 37, and in the 160-year class 42. He points out that in unsound 

 stands the felling age must be lowered in order to secure the maximum 

 income. Martin 4 again discussed similar ideas in 1910. 



1 Clapp, E. H. Silvicultural systems for western yellow pine. In Proc. Soc. Amer. Forest., v. 7, no. 2, 

 pp. 168-176, 1912. (Seep. 175.) 



2 Mason, D. T. Management of western white pine. In Proc. Soc. Amer. Forest., v. 9, no. 1, pp. 59-68, 

 1914. 



3 Martin. Der Einfluss des Baumschwammes auf die Umtriebszeit der Kiefer. (Kritische Vergleichung 

 der wichtigsten forsttechnischen und forstpolitischen Massnahmen deutscher und ausserdeutscher Forst- 

 verwaltungen.) In Ztschr. Forst- u. Jagdw., Jahrg. 35, 1903, Heft. 11, pp. 685-690. 



4 Martin. Die Umtriebszeit der Kiefer in den Staatsforsten von Preussen, Bayern, Elsass-Lothringen, 

 Hessen und Anhalt. In Forstw. Centrbl., Jahrg. 54, 1910, Heft 7, pp. 363-387. 



