FOREST PATHOLOGY IN FOREST REGULATION. 19 



Holier 1 touches upon the same point in a general way, without 

 trying to give the problem a more solid basis by exact material. 

 The following sentence is worth quoting : 



Whilst the mean annual increment of the stand is slowly decreasing, the mean 

 annual increment of decay is steadily on the increase. 



Here is the clue to the proper silvicultural valuation of cutting 

 cycles or rotation on a pathological basis. The time at which a tree 

 or a stand is to be cut may range from a comparatively low age to 

 the age of maximum production of lumber, according to the special 

 needs the forester has in view; but the upper limit of this range 

 should not lie beyond the period at which the gain from increment is 

 offset by loss from decay, irrespective of the ideal amount of timber 

 a sound tree or stand might produce under favorable conditions. 

 Not to cut a tree or a stand in which increment is offset or exceeded 

 by loss from decay, where cutting is possible, constitutes an unsilvi- 

 cultural act. Oilman 2 informs us that silver fir in the Black Forest, 

 Baden, Germany, "is unable to stand a long rotation, for after 100 

 years the per cent of rotten timber increases greatly." Here, ,the 

 influence of loss from decay on rotation is clearly shown; but it is to 

 be noted that the loss factor is derived in a purely empirical way and 

 is not based on exact studies. Hemmann 3 has published some 

 interesting and exact studies on the damage done by Trametes pini 

 in Scotch pine in a small area under regular management; that is, 

 where the disease was partly eliminated by improvement cuttings. 



All this somewhat scanty European material, valuable though it 

 undoubtedly is for transatlantic forestry, is of very little help to us. 

 What holds good for the managed forest raised in a century of careful 

 nursing can not serve for more than a clue in genuinely or practically 

 virgin forests, whether they be located in the United States, in 

 Canada, in Chile, in India, or in Siberia. Again we are confronted 

 with the necessity of working out our own problems in our national 

 forests. 



INFERIOR SPECIES. 



Most of the timbered parts of the national forests, especially in the 

 West, are practically virgin, seriously injured by fire, composed of 

 even-aged or many-aged stands, and generally of more than one 

 species, which are more or less exposed to heart rot caused by one 

 or more specific fungi. 



1 Holler, A. Uber die Notwendigkeit und Moglichkeit wirksamer Bekampfung des Kiefernbaum- 

 schwammes Trametes pini (Thore) Fries. In Ztschr. Forst- u. Jagdw., Jahrg. 36, 1904, pp. 677-715. (See 

 p. 712.) 



2 Oilman, E. C. V. Forest types of Baden. In Forestry Quart., v. 10, no. 3, pp. 440-457, 1912. (See 

 p. 452.) 



3 Hemmann. Uber den Schaden des Kiefernbaumschwammes. tn Allg. Forst- u. Jagdztg., Jahrg. 81, 

 pp. 336-341, 1905. 



