A STUDY OF HEART-ROT IN WESTERN HEMLOCK. ie 
Table I represents all the trees of the 41 to 62 age class, inclusive, 
taken from plats classed in the river-bottom and southwestern-slope 
types. The 15 and 9 youngest trees of each site (river bottom and 
southwestern slope), respectively, were used to secure an average age 
representing the infection age. This age for each tree was secured 
by means of the formula, A,=A—(V-+V,), where A, equals age 
of first infection, A equals age of tree, V equals volume of rot of 
the tree, and V, equals the average annual increase in rot volume 
for the age class in which the tree is included. This last figure is 
obtained from Table II. It was attempted to use the first 15 trees 
of the southwestern-slope type. This gave an infection age of 70 
years but included trees as old as 99 years, while the oldest tree 
of the river-bottom type was only 62 years. in using 9 trees, the 
oldest tree of the slope site is 75 years, giving a more equal 
comparison. 
Taste I.—Data relating to the infection age of heart-rot in western hemlock on plats of 
the river-bottom and southwestern-slope types. 
Approxi- | Probable | Number of 
Age. atee ou of mate value; age of infected 
[icra ; for V+Vi. | infection.! |trees(basis). 
River-bottom type: 2 Cubic feet. Years. Years. 
ACRV CATS Rete a Serres fot ana tye arg = ere are ae | 82 0. 07 2 44 
A SRY COTS ae eae Fe erate SO eee ee 83 03 1 47 
PAV COTES et ete ee ae ee ch ayaei epee eS kn 84 06 2 52 
DAG CATS opie ee eres ete ere Ate rs gare et 85 68 19 35 
RVC S Bee ee ery Si acl s ea UG Rn OR 86 32 9 46 
ORV CALS Ae ase (ee el oP ein OMe Seneen aera 87 0 0 | 0 
DOP COLDS nea eye eee rene AS oe a SG ea 88 36 10 46 
DUP CATS Eston. Se ome nie ec ites Se ee 89 27 8 49 13 
SY NACI Ae SE eT ae ae er ee ee 90 19 5 52 
OERVICAES Beta So Sees oe IS I eee 91 44 13 45 
OWES a5 A See as Ae ee re ae 92 0 0 0 
GIB yeas Mes ne en crcl clea Ses a 93 59 17 44 
GARY. CATS eee recat apa aro one Sena 94 i, jul 32 30 
G2RV CANS Retain aera eps Sasi a Ns ees 5 95 a3 32 30 
GZaV-CaTSReee aes ae see ee oes Lee cee: 96 12 3 59 
PASVOTAG Olyre Heme epee aie oceans ke lone ceceesene=2-50-|)2c-ccme-s5- 4455 
Slope type: 3 | 
Pe See SC ESR ores CE = ee ea 1 0 0 0 
DGVICALS ere Pe ee ale ore Sinie Bee Lee cscs 2 - 07 4 53 
GO) WESUSS Shs sb acsncentnd Senor See coe ee aera 3 0 0 0 
OAV CLUS SSCS FS eS eee eee 4 0 0 0 
OY ACERS 3. ro 5 SES RS ee ee v3) 0 0 0 4 
ORV CONS ese meme abner screens eke 5 coke core base 6 oe 9 61 
TPA RISA AS Se IO, Rees se a ee ee 7 ol 26 46 
WOWVICALS etac Mer eria eee ie ae ek aes oS 8 o Ul 6 69 
OPV OCATS Reta s ere ne oe siete eins cise cise 9 0 0 0) 
PNGV.C Tiel © Opens ge merge Rc Bs op tate cello Sais a cvcicilisie SE eee ee eee Doh ae he hice oe 
| 
1 Formula: Aj=A—(V+Vj). Vi=0.035. 
_2Site description.—River-bottom flat, very moist; soil not well drained; stand very dense. Almost 
allindividuals of the tolerant species, such as western hemlock and grand fir, were overtopped or suppressed. 
3 Site description.—Southwestern slope, partly flat; old-age class of a white-pine type in which the 
hemlock has become a climax species; soil fairly moist and well drained; stand not overcrowded. 
Table I shows that the average infection age for the river-bottom 
type is 44.5 years and for the southwestern-slope type 57.3 years. 
It thus appears from a comparison of the results shown in this table 
63424°—18—Bull. 722——3 
