A STUDY OF HEABT-ROT IN WESTERN HEMLOCK. 33 



contains. The total percentage of infected trees as well as the total 

 rot percentage of this type in comparison to the slope site bear out 

 this statement (Table III). The relation of moist sites to the degree 

 of infection of a stand has been noted by Hartig/ who says: "The 

 climatic conditions peculiar to a given district may render it especially 

 liable to outbreaks of certain diseases. Thus, in alpine districts 

 proximity to lakes and narrow valleys specially predisposes to cer- 

 tain fungoid diseases, because the moist air of such places favors the 

 fructification of fungi in a high degree." The loss of vigor due to the 

 unfavorable environmental conditions and principally due to sup- 

 pression by shade is responsible to a certain extent along with other 

 factors in the rapid and universal spread of the decay on this site. 

 Meinecke ^ states: "The relative extent of decay by EcJiinodontium 

 tinctorium is far greater in slow-growing, suppressed white firs than in 

 thrifty ones." And in discussing the susceptibility of hemlock to 

 injury Hanzlik and Oakleaf ^ state: "Broken branches and injuries 

 to the bark account largely for the spread of conk (Trametes pini) 

 and the stringy brown-rot (EcJiinodontium tinctorium), these being 

 more abundant in overmature stands and in suppressed stands over- 

 topped by mature growth." 



That on the river-bottom type the trees are decayed at an earlier 

 age, is brought out by a comparison of the data given. The river- 

 bottom type in comparison with the slope type exhibits not only 

 extensive decay at an earlier age and a younger age of infection but a 

 larger number of branch stubs and sporophores for similar age classes 

 for the stand. The data secured from the lumbermen of the north- 

 western region also aid in determining the fact that hemlock is more 

 defective on lower elevations, on bottom or flat sites, and on poorly 

 drained soils. 



In making use of pathological data in the determination of patho- 

 logical cutting ages for a stand, the rot percentages as given here for 

 separate age classes of the stand are of some value. With the rot 

 percentages as a basis (indicating the ratio of the rot volume to the 

 total volume of the stand for each age class), the forester can deter- 

 mine a cutting age for that stand, using all the economic and silvicul- 

 tural factors to aid him in a correct determination. The average 

 annual increase in rot volume between age classes can also be used 

 to advantage, in determining the rapidity of increase in rot volume. 

 Forest pathology can thus serve to furnish pathological data for 

 particular stands, which data can be applied by the practical forester 



1 Hartig, R. Textbook of the Diseases of Trees. Translated by William Somerville, p. 10. London 

 and New York, 1894. 



2 Meinecke, E. P. Forest-tree diseases common in California and Nevada, p. 27. 1914. Published by 

 U. S. Department of Agriculture, Forest Service. 



8 Hanzlik, E. J., and Oakleaf, H. B. Op. cit. 



