6 BULLETIN 199, U. S. DEPARTMENT OF AGRICULTURE. 



the white-pine study as were secured for the hemlock study/ and all 

 available factors were taken into consideration in the final results. 

 Forest descriptions were written for each sale area, and notes were 

 made of the moisture and shade conditions existing on each. 



The data obtained from a total of 1,417 trees, of which 135 were 

 grand fir (Ahies grandis), were first arranged according to site and 

 age class. While in the field it was found that the number of trees 

 needed in the two youngest age classes could be considerably reduced 

 from the 100-tree standard. It was found that the trees on the 41 

 to 60 age class in both types of sites, slope and bottom, were uni- 

 formly free from visible decay. Owing to this condition and to the 

 fact that young white pines of this age class are too small to be 

 merchantable and should not be cut needlessly, it was decided to 

 reduce the number of trees required. In the 61 to 80 age class it 

 was found that the rots were in the beginning stages, and 60 trees 

 per age class for each type of site were considered sufficient. In all 

 the other age classes the number of trees was either above or but 

 slightly below the 100 mark, except in the 121 to 160 age class on 

 the slope sites, where the number was doubled in order to make a 

 comparison between a similar age class and site for two widely 

 separated sale areas, and in the 201-j- age class, where it was impos- 

 sible to find more than the recorded number of trees. There was, 

 fortunately, one sale area which furnished a fairly large number 

 of trees of the very old age class (201 -f). 



Tables were prepared from the data collected, and these will be 

 presented in the order of their consideration in the text. The 

 volumes were figured by means of the Smalian formula. In these 

 tables the word " Infected " as used at the head of certain columns 

 is intended to cover all trees visibly infected. Early stages of 

 infection not determinable by field observations and not measur- 

 able as recognized cull are not included. 



RELATION BETWEEN ROT AND VARIOUS FACTORS. 



AGE. 



In Table I are found the data which show the relation between the 

 rot volume and the age class of the stand. These data are separated 

 under heads of " Bottom sites " (upper part of table) and " Sloj)e 

 sites" (lower part of table), and the data under each head are 

 grouped according of the sev«n principal age classes. 



Trunk-rot, indicated in the table by the initials T. E., re]presents 

 mainly Trametes pini. Butt-rot, indicated by the initials B. R., 

 represents Trametes pini when acting as a typical butt-rot, but in- 



^Weir, J. R., and Hubert, E. E. A study of heart-rot in western hemlock. U. S. 

 Dept. Agr. Bui. 722, 39 p., illus. 1918. 



