Se BULLETIN — U. S. DEPARTMENT OF ee 
— 
TaBie II].—Averazes computed from field daia relating to heari-rot in western hem- 
lock based uno trees of the several age classes on plats of the river-bottom and south- 
western-slone tyes. 
| | 
Vclume_ | 
| | | (cubic feet). (oat fet) | fe GEESE DE 
Num- | Diam- | Gere free Mies pe eet ee 
Type and age berof| eter |pichi (height Crown| ~~“; For stand. 
classes. trees oes Fee aae o | rating.| oor 
basis).| high. +32 = 
Coasis? 7 width). Total. | Of rot. rae tne 
Total. | fected 
| trees. 
River-bottom | Square | 
type: Inches.| Feet. feet. | Degree. 
41 to 100 years. 115 5.9} 47.0 400. 0 Sei eet! 1.1} --19 27.1 | 26.6 96.7 
101 to 160 years v4 8.4 65. 7 609.5 2.6} 3.4) 15.3] 3.6 23. 6 | ; | 
Slope type: : 
41 t) 100 years- 15 8.4 62.6 574. 2 2.6] 2.8] 19.8 . 62 3.1) 
101 to160 years 18 3.6 88.9 $33.3 2.8) 3.1 2.6 | 13.20] 25.1 
161t0 200 years} ~ 23 17.5 | 106.0 761.6 3.5] 3.3 | 107.6 | 33.50] 31.1 |} 30.8 90.1 
201 years and | 
Gere aes eres 2.4] 3.5| 175.5 | 59.40| 33.8 | 
r | 
117.0| 1,458.6 
From the viewpoint of the natural increase in heartwood due to 
larger size, etc., coincident with age, 1t is presumed that the amount 
of decay would increase proportionately. The figures obtained in 
the case of the southwestern-slope type show this to be not only true 
in this respect, but the proportion of the volume of decay to the 
total volume of the tree is also much higher. In the river-bottom 
site (Table ITT) the average volume of rot increases from 1.9 cubic 
feet in the 41 te 100 year age class to 3.6 cubic feet in the 101 to 160 
year age class. In the southwestern-slope type (Table ID) a better 
comparison between age classes can be made. Here a definite 
increase in rot volume from the 41 to 100 year age class to the 201 
year and older age class is evident. Table Ii also shows an irregular 
increase in the average annual increase in rot volume between age 
classes, though the general trend of the figures in Table I shows a 
gradual increase from the younger to the older trees up to the age 
class 81 to 90 years, after which a gradual decline is noted. This 
fact might possibly reflect the rate of growth of the tree and therefore 
of the heartwood and indicate a dropping off in rot activity simul- 
taneously with a slowing up of the annual growth. 
REL ATION OF DECAY TO VIGOR, CROWN RATING, SIZE, AND VOLUME. 
Deese: in western hemlodies is the main factor of depreciation outside 
of fire. No other destructive agency operates upon this tree to cause 
so much waste and none is so difficult to control. The preceding 
data have shown how the tree, especially when growing in river- 
bottom sites, is subject to attack by this fungus at an early age, and 
for the youngest age classes the river-bottom type shows a greater 
average volume of rot than the southwestern-slope type. In the 
data secured from lumbermen of the Northwest it is found that a 
~—is &' th 
