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UNITED STATES DEPARTMENT OF AGRICULTURE

Washington, D. C. A July 21, 1923

A STUDY OF DECAY IN DOUGLAS FIR IN THE PACIFIC NORTHWEST.

By J. 8. Boyce, Pathologist, Office of Investigations in Foresi Pathology, Bureau
of Plant Industry.

CONTENTS.
Page. Page.
_ Importance of decay in Douglas fir.........- foie Pnirance OF LE G@ecayss- 5 6 es 7
Method of coecting data.....-..........-.--. 2 | Indications of decay in living trees...._..... 10
Rete IAISINSVGCCAY. 8S. 2 so 2 22 2s oe- 3 | Extent ofincipient decay..................- 15
Position of the decays in the tree....--...... fee | ROUTER AY See a! ee ei an Be ie Gee ee 16
Relative importance of the decays......-..-- A ARM OOkas* = 5! hg eo Ss a = a 17
MMEEH tit aeETIEIGS = 25 eee es ls 5 | Literature cited 19

IMPORTANCE OF DECAY IN DOUGLAS FIR.

Douglas fir is the most important timber tree in the Pacific North-
west, covering, as it does, the greater part of the foothills and lower
slopes of the Cascade Mountains and the Coast Range in practically
pure stands of great density. The stand of this species in Oregon and
Washington is estimated at 505 billion feet (6, p. 23),1 or nearly one-

fourth of the remaining merchantable timber in the United States.

The loss through decay in Douglas fir in this region is very high.
While some overmature stands are relatively sound a loss of 20 per
cent in such stands is not uncommon. In certain cases the cull figure
may reach 50 per cent or more, so high that in timber on difficult
ground it becomes impossible to log at a profit. It is only in young
stands of second growth that Douglas fir is uniformly sound. Plate

_I shows defective trees left uncut after logging in an overmature

stand. In this instance about 25,000 feet board measure per acre
was left standing. Where clear cutting is practiced numerous logs
and entire trees remain on the ground after logging, absolutely worth-
less on account of decay. This is illustrated in Plate Il. Practically
all the large pieces were leit because of rot.

Recognizing the importance of this question, foresters and lumber-
men in the Douglas fir region have repeatedly felt the need for exact
information on decay in Douglas fir. This bulletin presents obser-
vations by the writer and the results of a preliminary study.’

1 The serial numbers (italic) in parent)e:e3 refer to ‘‘ Literature cited "’ at the end of this bulletin.
2 This study was made in the summer of 1917 under the direction of Dr. E. P. Meinecke. To him the
writer is indebted for supervision and assist.nce throughout the course of the field work.

Yt, y > >
rhe project
>

years.
42198— 23-1 1

2 BULLETIN 1163, U. S. DEPARTMENT OF AGRICULTURE.

METHOD OF COLLECTING DATA.

The trees selected for study were part of a defective, overmature
stand of pure Douglas fir on the west slope of the Cascade Mountains
at McCredie Hot Springs, above Oakridge, Lane County, Oreg.
The area was at an elevation of about 2,000 feet above sea level, and
the local topography was characterized by moderate slopes and almost
level benches. The stand was quite typical of the bulk of the Douglas
fir type on the west slope of the Cascade Mountains.

Hach tree was felled with a stump height of 14 feet measured at a
point halfway on the slope. The bole was then cut into 16-foot logs
to an 8-inch top-diameter limit inside the bark. Complete measure-
ments were then taken. Next, the logs were split open and any
further data available recorded. In this way it was possible to study
each tree very completely, particularly with reference to the character
and distribution of decay. Volumes of the trees were worked up in
both board and cubic feet. The board-foot volume included the
merchantable portion of each tree from the stump height of 14 feet
to a diameter limit of 8 inches inside bark. The 16-foot logs were
scaled with the Scribner Decimal C scale and the volume of decay
determined in accordance with the standard scaling practice of the
Forest Service (4).

The cubic-foot volume included the contents of the entire stem
from the ground level to the tip. in computing volumes the stump
was considered as a cylinder, each 16-foot log as the frustum of a
paraboloid, applying the Smalian formula (2, p. 161), the top (that
is, the section from the 8-inch diameter inside bark to the tip) as a
cone, and a broken section of the top which did not include the tip
as the frustrum of acone. The actual cubic-foot volume of decay
was computed by the same formulas.

A general idea of the size and age of the trees analyzed is given
in Table 1.

TABLE 1 —Size and age of Douglas fir trees studied.

atiited Petreniags of
Average | diameter ae Vee Number
Age class. age breast SSS oe
(years). ig ‘ asis.
Gnches).| quble | Hoard
|

Atsho 60 ears: 2 F5i jess ae | See eee. ee A he 59 9.5 | 0.04 0 1

BUILOISOIVORTS = 04.5 oe Fo eee ee Se 68 12 41e| 91 0. 62 ? 8

Sip 10) pobre i050) NOURI Sry 95 14.0 | -53 »42 @3
TOUGOWi20 WATS. 2. ES co oe bene re SSR 103 16.3 | = pe .62 3
MARAE SU VEAL. cone sen | ht See See si eae me eee 129 16.0 | 15 -ll 1
d40 60.160 yyears..< 1 2 pees 3 GR Faset IGRI EAD Ses £2)... PRON. OO. =2 OSS Eee (@)
NGAGE OU VIBATS 0 0b o-oo 2 ee She Oe ere oc er eee fo ae ello eee ee 0
ESISEO 200 YOaTS.2 22.5) ctc del. Se hae See ee ee 195 1g7 1.36 jing b 5
PASO VAAD EM CATS 25 5. 13 8 ce ate BS Soe cee cei aniee <r 214 25437 15.49 14.89 29
PABLO LAAO SY OATS nes Slee cere tan PS ne teeter ee 230 212d 32.69 33.91 47
CAL LO ZOO KM earsssste 1923). i- Fe RCA SB 246 27.9 | 10.81 11.26 15
Det OewS0 “VOATS. 2 cic 2. ora 3a coe et EE Ke a 271 28.1 | 15.81 15.74 25
Pal GOIOUO Wearses...52 . Ll Als ered Bee, 284 29.2 | 152 1.63 2
MO 20 OARS. ch 3 Sticks, cacy eee ate ee eee 309 29.7 | 6.07 5.97 9
Somos) VOATSGe aon .2 tors he cot ots cee Doe GE eee 333 29.8 | 10.38 10.22 16
Bae S00 CS CALS: 2. rts ve detec cede ee eee 348 28.9 2. 48 2.46 4
361 to 380 years........... Ae Maer nes ae 362 39.6 1.00 1.10 1

ves setts

G1) OTe: Maia See ae ES Pane BH Pot Se | 238 26 .Iotebowe v2 apt Ka tete Bal 169

i One tree, too small to consider.

DECAY IN DOUGLAS FIR. a

The trees studied were not clear cut from a given area, but average
trees both sound and decayed were selected to obtain preliminary
information on which an extensive study of decay in Douglas fir
could be based. ‘This will be brought out as the discussion proceeds.

In all 170 trees were felled, bucked up, split open, and studied.
One of these was only 2 inches in diameter breast high, so it was
dropped from consideration, leaving 169 trees with a total volume of
203,920 feet board measure and 33,703.12 cubic feet.

FUNGI CAUSING DECAY.

Four species of fungi are responsible for all but an infinitesimal
portion of the decay in Douglas fir. They are the ring-scale fungus
(Trametes pint (Thore) Fr.), the velvet-top fungus (Polyporus schwei-
mitzu Fr.), the quinine fungus ( Fomes laricis (Jacq.) Murr.), and the
} rose-colored Fomes (Fomes roseus (Alb. and Schw.) Cke.). The
| decays caused by these four wood-destroying fungi in living trees are
confined to the heartwood.

The ring-scale fungus causes decay commonly known as conk-rot
in this region (ring-scale or red-rot in the pine regions), in which the
wood is riddled with small white pits or cavities, apparently separated
by sound wood. This is shown in Plate III, Figure 1. In its incip-
ient stages, before the appearance of the white pits, the decay appears
as a pronounced reddish purple or olive-purple discoloration, often
bounded by a narrow zone of pronounced red color. The sporo-
-phores, or conks, are very common in overmature Douglas fir stands.
These fruiting bodies issue from the tree through knots and are
perennial. They vary in size and in shape from bracketlike to hoof
shaped. The upper side is a dull grayish or brownish black, rough,
and with concentric furrows parallel to the hght-brown margin. The
under side is a grayish brown or rich brown color with large irregular
pores. The substance or context of the sporophores is corky or
punky. Plate IV shows the appearance of the sporophores on a

living tree.

_ The velvet-top fungus causes a red-brown friable rot in the final
stage. The incipient decay is very difficult to detect. It first becomes
oticeable as a faint yellowing or browning of the normal heartwood,
which still seems to be firm and hard but in reality is seriously weak-
ened. The sporophores, or conks, of this wood destroyer appear
either on the infected tree or on the ground near by and are annual.
They are rather large, with a light-brown upper surface, an olive or
dirty green under surface, and have a cheesy consistency when young,
but when old and dry are a dark rusty brown and corky. Sporo-
phores on the ground have a short thick stalk. Plate V, Figures 1
and 2, illustrate both sporophores and decay of this fungus.

The quinine fungus has a large, conspicuous, whitish perennial
sporophore, not at all common on living trees. The substance of the
sporophore is white, soft, and cheesy when young and rather crumbly
Zand chalky when old and dry, with an exceedingly bitter taste.
Hence the name. On the older sporophores the upper surface is
rough and chalky white and brownishin color. The pores are small
and regular. Plate VI, Figure 1, shows a sporophore. The typical
decay is a crumbly brown rot easily recognizable by its mycelium
felts or sheets (i. e., closely woven masses of fungus hyphe). This
characteristic is brought out in Plate VI, Figure 2. The incipient decay
which appears as a faint brownish discoloration is not easy to recognize,

4 BULLETIN 1163, U. S. DEPARTMENT OF AGRICULTURE.

The sporophores of the rose-colored Fomes are easily recognized by
the delicate rose color of the under surface. The pores are small.
The upper surface is rough, hard, and black. This is illustrated in
Plate HI, Figure 2. The decay caused by this organism is a yellow-
brown crumbly rot, with mycelium felts much less conspicuous than
those of the quinine fungus. The incipient decay is indicated by a
faint brownish color, the outer limit of which is sometimes marked
by a zone of brownish green discoloration.

POSITION OF THE DECAYS IN THE TREE.

The decay caused by the ring-scale fungus and that caused by the
quinine fungus are not confined to any one portion of the bole but
commonly extend throughout the tree.

On the other hand, the decay caused by the velvet-top fungus is a
typical butt-rot. Of the 70 infections of this decay in 68 trees, each
separate focus of the rot in a tree being considered an infection, 94.3
per cent, or all but 4, were in the stump or butt log. The decay
usually does not extend higher than the first 16-foot log. In 10 trees
only did the decay go beyond the butt log, and the greatest upward
extent in any one case was 37.4 feet above ground level. The average
for all the butt infections was 10.41 feet above the ground. The
measurements given include the incipient decay.

The decay caused by the rose-colored Fomes is usually confined to
the upper portion of the tree in connection with dead tops, and often
the rot does not extend into the merchantable portion of the infected
tree. In all, there were 46 infections of this rot, and all but 9 of
these were in the upper bole. Of those in the upper bole, 18, or
almost 50 per cent, were in the top beyond the 8-inch diameter limit
and caused no loss in merchantable volume.

For the sake of brevity in the remainder of this paper, the decays
caused by these four fungi will be designated as follows:

Velvet-top fumes: $222 eh Ee red-brown butt-rot.
Bing-seale, fundub. ie: seen -bevk -p. ora asy = conk-rot.

Oring PUR eUe a. eo ee ee brown trunk-rot.
ose-colored Howieses. (nos. cle Sa aoe one end yellow-brown top-rot.

When used in tables the designations will be simply butt-rot, conk-
rot, trunk-rot, and top-rot.

RELATIVE IMPORTANCE OF THE DECAYS.

Conk-rot is responsible for by far the greatest amount of cull in
Douglas fir. In fact, if the species was free from this defect it would
take its place with the pines as a sound tree. This is brought out in
Table 2.

In considering Table 2 it must be remembered that it is not based
on trees clear cut from a given area. Consequently the figures on
the percentage of infected trees and volume of decay are not indica-
tive of the actual loss through decay in stands of Douglas fir, but
they do indicate the relation of the various decays. Under ‘‘ unknown
rots’’ are placed a number of small infections of decays whose cause
could not be determined and one infection caused by Ganoderma
oregonense Murr., which resulted in a slight loss. _

Conk-rot stands out as the all-important cause of decay. The
volume destroyed by this decay in comparison with the others is far

DECAY IN DOUGLAS FIR. 5
greater than the ratio of infected trees would indicate. For example,
only about one-third more trees are infected with conk-rot than with
red-brown butt-rot, yet the board-foot volume of decay is slightly
} more than 18 times as great. Conk-rot is usually quite extensive in
an infected tree, particularly in the mechantable portion of the bole.

TABLE 2.—Relative importance of the different kinds of decay in Douglas fir.

] 1

| :
| Volume of decay, Infections.
percentage of gross iB
volume. pee | |
’ A veracg 7
Kinds of decay. percent- | Average volume.
| age of | Number | ar |
i total. 5asi :
Sate oes basis. | total. Board | Cubic
' ¥ feet. feet.
| | Tr] |
S20) a | 38.4 2220 61.0 118 | Al6;1 663 64.2
UTEVETL 2 0) aie 0 en eae } 2.7 | Ss 5.9 15 Dees 369 | 28.7
Rema Seer 2 5 oe. oly 1:2 40. 2 70 24.6 | 62 5.9
“LTV USit 2a eee eee 1.6 | 1.6 22.5 | 46 16.2 | 7 7.6
Unknown:rets:-s- co Soca te S| | 18.9 | 35 TPS val | 4 | 1.0
Combined 200 cc. | 44.9 26.1 87.6 | 722). of Vga | 323 | 30.9
|

While only a few trees showed brown trunk-rot in comparison to
those with red-brown butt-rot and yellow-brown top-rot, yet the
volume of brown trunk-rot is greater than either of the others,
_ particularly in board feet. This is due to the fact that brown trunk-
rot when it does occur is quite likely to cause the loss of all or most
of the merchantable portion of the affected tree. Yellow-brown top-
rot and red-brown butt-rot, being localized, result in much less loss
per tree, but make up for this in the many more trees with these
decays. The greater loss through brown trunk-rot in board feet as
compared to cubic feet in relation to red-brown butt-rot and yellow-
brown top-rot is understood when it is remembered that the former
is usually in the merchantable portion of the tree, while the latter
two are often in the stump and top, which are not included in the
board-foot volume but are figured in computing the cubic-foot volume.

Furthermore, red-brown butt-rot is of more importance than the
figures would indicate, since seriously affected trees are quite subject

Rto windfall, breaking off near the ground. Then, too, this decay
destroys the valuable heartwood of the butt logs.

Of the total of 169 trees, 21 were free from decay, while in the
remaining 148 there were 284 infections, or an average of 1.9 infections
per infected tree. ‘Some trees had as many as 6 individual infections.
Again, in considering the infections conk-rot stands out both in the
number of infections and particularly in the average volume of
decay per infection. Trunk-rot has a high average volume of

_ decay per infection. which shows again that this rot is of minor
importance only because of the limited number of infections, but
when a tree is once attacked destructive and extensive decay usually

) results.

MECHANICAL INJURIES.

Mechanical injuries on trees are of importance in that besides some-
times reducing the annual increment or causing an actual loss in
merchantable volume from the mere presence of the injury they
afford access to the heartwood of the tree for the spores of wood-
destroying fung1.

6 BULLETIN 1163, U. S. DEPARTMENT OF AGRICULTURE.

Wounds in Douglas fir, though quite common, are mostly super- |
ficial and heal rather rapidly. Rapid healing is particularly the
case in younger trees. Wounds as a rule callus very irregularly, and
as a result it is usually difficult or impossible to determine the exact
dates when scars were made and callused over by counting the annual
rings. In this respect Douglas fir differs strikingly from the clear-
cut, regular calluses characteristic of incense cedar and white fir.
Furthermore, injuries in Douglas fir frequently result in the formation
of prominent burls.

Of the trees studied, only 11 were entirely free from scars. The
remaining 158 trees had 508 scars, open and healed over, an average
of 3.2 wounds per tree. Table 3 shows the relative frequency of the
various types of scars

TABLE 3.—Scars in Douglas fir.

! , | >
‘Number ofscars, basis.| per- || Number of sears, basis.) per-
| cent- || cent-
Type of Scar. eee age a Type of scar. a age of
eale tota Heale total
Open, over. Total. scars. || Open. over. Total. sears.
Fire Sears ..22...... 43 | 237 280 5dsLi|| Spikevtops esiless.): Ve zh re ae 10 2.0
Falling-tree sears. - . 25 | 61 66) 6390) (Broken tops 9-- <o-|o5-5.5-|eeeoeoee 58 11.4
Lightning scars..... bees 103] 38 49 9.6 || Unknown scars.... Ore en a 7 1.4
Sapsucker sears ..... 1 | 9 10 | 2.0 ——— $
BilazeiSears. oosese i 0 v4 2 || LOLA LS ele Soe: Ieee tagraier 508) |ea8 nee
Frosticrackst 2/22. 0 | 7 7 1.4 || |
| iI |

In Table 3 the healed-over, closed, or occluded scars are greatly in
the majority. This indicates that the wounds were mostly superficial
and that this tree species heals rapidly after wounding.

The predominance of fire scars is striking. While it was not pos-
sible to determine the years in which the fires occurred, for the reason
stated previously, it was noticeable that most of the injuries of this
nature had happened when the trees were relatively young—that is,
below 20 inches diameter breast high, more or less. This coincides
with our knowledge of fires in the Douglas fir region. In young
stands fires which run over the surface of the ground injuring but
not killing the trees are common, while in mature or overmature
timber fires have a tendency to run through the crowns, killing all but
scattered individuals outright.

Burls may form as the result of fire scars, but more common are
swollen, or churn, butts as the result of severe scars. These churn
butts extend usually from the ground level up the trunk slightly
higher than the limit of the fire scar. Even though a fire scar has
been healed over for a long time and there is no churn butt or burl
to indicate its presence, it can often be detected by the variation
in the appearance of the bark over the healed wound. This appear-
ance is hard to describe, but not difficult to judge after a little
experience.

Next in numerical importance to fire scars were wounds caused by
falling trees. These, of course, are more common in mature and
overmature stands than in second growth. Trees may die and ulti-
mately the snags will fall, or again large trees with butt-rot are
quite subject to windfall. Such trees on their way down strike
others, breaking off the tops or limbs or bruising the trunks and
knocking off pieces of bark. Falling-tree scars rarely extend deeply
into the tree.

: DECAY IN DOUGLAS FIR. 5

Lightning wounds occasionally occurred, although the Douglas fir

region is not subject to severe lightning storms. Injury by sap-

suckers was rare, and the few scars found were very superficial.
These birds do not seem to select a single tree and attack it year
after year, as they often do in other tree species. Frost cracks were
not common. This was to be expected, since the Douglas fir region
as a whole is not subject to sudden extreme variations of temper-
ature from relatively warm to very cold.

There were 10 spike-topped trees. Half of these dead tops had

- been caused by lightning, while two of them resulted from falling trees.

On the other hand, trees with broken tops were not unusual. The
most common cause of such injury was falling trees. This source
accounted for 31 of the broken tops. Snow was responsible for 4 and
lightning for 3, while the remaining 20 could not be determined.

- A load of ice or heavy wet snow is of more importance in causing

broken tops than appears from these figures, but most of the damage
occurs in young stands. According to observations of the writer and
others, heavy snow or ice injury occurred about 1888% in the imme-
diate section where this study was made. The damage was very
apparent from the number of broken tops, all having been made at

- the same time, 1 second-growth timber.

Broken tops require a long time to heal. Even after the volunteer
top is well started the stub of the old top protrudes, and when this
is finally grown over a slight crook still remains in the bole, which
does not entirely disappear for years.

In considering the data presented, it may appear from the total of
508 scars on 158 trees that the trees were subject to excessive injury.
It must be remembered that most of the wounds were superficial.
Then, too, several small scars on a single tree might be made by the
same agent. For example, one fire or one lightning stroke can

. readily cause several scars on a tree. Owing to the impossibility of

determining with any accuracy the dates of injury in Douglas fir, it
was necessary to consider each scar, with a few exceptions, as separate
and distinct.

ENTRANCE OF THE DECAYS.

® The wind-blown spores from sporophores of wood-destroying fungi

attacking the heartwood of living trees must light on exposed dead

‘wood in order to cause infection. But the type of infection court
varies with different species of decay, and it is of importance to

determine the common means of entrance in each case, since in so
far as the infections occur through controllable mechanical injuries

_ there is a possibility of reducing the amount of loss.

Pee .

eee Stee ere

Table 4 shows the. points of entrance for conk-rot. From this
table it can be seen that knots or branch stubs are responsible for
the major portion of the infections, and, what is far more important,
all but an infinitesimal portion of the total volume of conk-rot
resulted from these infections. :

The infections of brown trunk-rot both numerically and in the

resulting volume of decay were rather more evenly distributed, as

can be seen from Table 5; but here again knots predominate.

’ This date is from an unpublished record furnished by the Forest Service.

Be

TaBLe 4,—Infection court of conk-rot in Douglas fir.

Infection court.

mous 2235 3h2 1 FS Shc CRA hd SRR
INE \SCATS 4 2 se Yad § Ge ope eee ad Sea
Falling-tree wounds
Lightning scars
Wead! COPS. snk 4 eae See eee
Unknowascars sis [0 eee Sea

TABLE 5.—Infection court of trunk-rot in Douglas fir.

| Number,

basis.

98
10
3
4
1
2

Number.

CO
Nee

BULLETIN 1163, U. S. DEPARTMENT OF AGRICULTURE.

Average volume.

Infections.
Percentage of total.
Volume.
Board Cubic
feet. feet.
99. 62 99.48
. 04 -03
0 05
34 43
0 0
0 0

—"
eed

TOP OOO

Infection court.

Knots

Falling-tree scars
Dightning sears: jae ye? SS eels ss see

News

Number.

eh
SR WR
WraIwnt

Infections.
Percentage of total.
Average volume.
Volume.
Board Cubic Board Cubic
feet. feet. feet. feet.
44.6 46.1 353 28.4
0 0 0) )
30.0 26.9 415 29.0
25.4 26.9 | 705 58.0

Table 6 brings out the relation between fire and red-brown butt-rot.
The major portion of the infections entered through fire scars, and
the resulting volume of decay was proportionately much higher. This
butt-rot also attacks the roots and can probably be spread by the con-
tact of a diseased root with a sound one.
volume of rot is apparently traceable to this method of infection.
Besides these two the other infection courts are of no importance.

Taste 6.—Infeclion court of butt-rot in Douglas fir.

About 11 per cent of the

Infection court.

Infections.

Percentage of total.

Average volume.

Number, | Volume.
| basis. |
| | Number.
| Board Cubic Board Cubic
| feet. feet. feet. feet.
| 3
HOMOTS si oe ek well ee Fel pale a Ae Pie late 1 1.4 1.4 0.5 60 230
MIKO SCATS cette es oe ik eRe aka Septet mises | 41 58.6 73.2 79.1 83 3.0
Malling-tree searsifs! 224.2 yee eee 4 5.7 ok 5) 0 40 5.2
Wbight Ming Sars). Jou. 2 sora Genet erates t a: 7 2.5 1.8 28 1.8
SEVOOUS Bact uk esa ee ied ois So cae Ree oe eee 16 22.9 10.8 ies: 29 oFG
Unknown scarses.4 22.) - i 2ee8 Be te i 5.7 3.4 2.1 38 2.2

DECAY IN DOUGLAS FIR. 9

Yellow-brown top-rot, true to iis name, in Table 7 shows the
greatest number of infections entering through dead tops, which
include broken and spike tops. Knots, though with fewer infections,
were responsible for a greater volume of decay, since such infections
usually occurred lower down on the bole where there was more
heartwood for the fungus to work on than was the case when the
wood destroyer entered through a dead top. The large volume of
decay the cause of which is recorded as “unknown” resulted from
an extensive infection which could not be traced to its source.

Tape 7.—Infection court of yellow-brown top-rot in Douglas fir.

Infections.

Percentage of total. |

Average volume.

Infection court. |
Number, Volume.
basis
Number. |
Board Cubic Board Cubic

| feet. feet. feet. feet.
SHS eee eee te 12 26.1 Be 30:7 98 9.6
igen Cen 2f ge er ee 2 4.3 8.2 6.6 135 10.6
Batine-iree sears.) sol <ccseetees Seles es: 7 15.2 7.0 1.9 33 .9
ih sue So ie la I i hace ae 5 | 10.9 15.4 15.0 102 9.7
i oe i Sa ee ee ee 18 | 39.1 17.0 23.8 31 4.3
Miakaineumiiee re er 8 oo ee 1 4.3 | 16.7 17.0 275 27.5

|

Table 8 shows the infection courts of the unknown decays. Some
of these were undoubtedly infections of the four common rots, but
were abnormal or so small that they could not be accurately identified.

TABLE 8.—Infection court of unknown rots in Douglas fir.

| Infections.

Percentage of total. |

j Averé 7 :
Infection court. verage volume

basis.
Number
Board Cubic Board Cubic
feet. feet. feet. feet.
Lawes £C Xe! | t
NGS eee cee PRINT Eh add | 5 14.3 0 | 0 0 0
MET OISCATS er ert a. et sR LES: sas 12 | 34.3 80.0 | 62.5 10 1.8
PACMPMITIP SEATS (ens ca oes. eee ae 4 11.4 20.0 | 8.8 8 .8
PIGS meee me kh ENG Pe nl 11 31.4 pe | 20.8 0 | 6
ane Ete ee 3 8.6 0 | 7.8 0 | 9
|

In Table 9 the data in Tables 4 to 8, inclusive, have been combined.
Knots were responsible for the greatest number of infections and a
proportionately greater loss through decay.

Of all the infection courts fire scars, which were only responsible
for 4.2 per cent of the total rot volume, are the only factors that can
be directly controlled. With the increase of efficiency in fire-protec-
tion methods, injury from fires is being steadily reduced. But the
other 95.8 per cent of the decay is traceable to sources that can not
be controlled. Knots, falling trees, lightning, and snow or ice will

42198239

\ ™ . 5 a

10 BULLETIN 1163, U. S. DEPARTMENT OF AGRICULTURE.

be present in Douglas fir stands in the future, no matter how well
regulated. Consequently, the reduction in the quantity of rot in
Douglas fir by a.reduction in the scars caused by controllable
mechanical injuries can amount to little.

TABLE 9.—Infeciion court of combined decays in Douglas fir.

Infections.

Percentage of total.

Infection court. Average volume.
Number, Volume.
basis.

Number. | l
| Board Cubic Board Cubic
| feet. feet. feet. feet.

ieee SMe Ch 1 RGN 123 3.31! |. 8

9.2 89.2 664 63.9
LIT ( Ss aU aan a col ay WAIN | B7 23.6 | 4.2 4.2 57 5.5
Malling-tree-scars=<shecd. codices 18 6.3 2:9 heh 114 3.2
iphtninescarse: ceel ee eee ee oy 19 6.7 | 2.5 2.4 123 11.5
ID ERGO Sere a et a hoes ae eta eae 39 10.6 .6 1.0 19 2.8
PUOUOUS ys eee oe eer once soho een eee ee 19 6.7 BS 26 25 2.6
Winknowmniscars.2 3.222 esos fee eee 8 2.8 8 7 8.0

While it is true that infection courts resulting from all mechanical
injuries are of little importance in fhe total volume of decay produced
as compared to knots or branch stubs, it is of academic interest to
determine the kind of scar most susceptible to infection in the trees
studied. This is brought out in Table 10.

TABLE 10.—Susceptibility to infection of various scars in Douglas fir.

Scars infected. Scars infected.
Type of sear Number Type of scar Number
yP 7 of scars. yP : of scars.
Number. | Per cent. Number.} Per cent.
MIT@ISCAES - 22. cece 280 67 23.9 || Spike tops ..-%.¢.5:. \ 68 20 44.1
Falling-tree scars. . 86 18 20.9 || Broken tops .......} : 5
Lightning scars ... 49 19 38.8 || Unknown scars .... te 7 100
Sapsucker scars .-. 10 0 0 . SS |
Blaze seats 222s: 1 0 0 Tetali-= eas: 508 141 28.0
Frost eracks....... | 7 0 0

Dead tops, which include spike-tops and broken tops, followed
by lightning scars, were most susceptible to infection, according to
Table 10.

INDICATIONS OF DECAY IN LIVING TREES,

Recognition of the indications of decay in standing Douglas fir or
in logs is of the greatest importance from a practical standpoint.
A comparison of the cruise and actual cut on many operations in
overmature decadent timber brings this out forcibly. At present
there is a great deal of confusion and. misinformation among foresters
and lumbermen in regard to the detection of decay in living trees,
and the specter of “hidden defect”? assumes unnecessary proportions.
In fact, decay in Douglas fir is more easily detected than in most
species subject to a large amount of rot.

— - - -
SEES EE Sn — er Ra AE renee ee ee

an i x Coed
- nn ei dee! a % aes

ee ahaa i Seg

PLATE

wil eee

by atte ab gr, alata

Loe ae ee

a
AaB ace

. of Agriculture.

(Shy Va ae —

zs Bf aetna es, ast es

i63;. USS. Dept

ver

or,

of
Ry
&\

Ss Se ee

yh ET

‘ i
ee aca 1

Bul.

-scale fungus.

og

ed by the ring

S

The principal defect is decay cau

“wv

IN ¢

DEFECTIVE DOUGLAS FIRS LEFT STANDING AFTER LOGGING.

98—

421

Bul. 1163, U. S. Dept. of Agriculture. PLATE II.

A PRACTICALLY PURE STAND OF OVERMATURE DOUGLAS FIR AFTER
LOGGING.

Nearly all the large pieces were left because of rot, principally decay caused by the
ring-scale fungus. (Photographed by D.C. Ingram.)

PLATE

“SusUN] Sy AQ posuvo IOI UMOTG-MOTLOA OU] PUL
SOUTO] POLOJOO-9S0.1 OY} JO OLOYCdOOdsS BJO OOVJANS LOddH oy) SMOYS STUY,

‘dOlL Yly SVISNOG V AO NOILOSS SSOUO—’S ‘DIS

UOTPRLO[OOSTp OTdand ystppor vB AG poyworput

quordtout sqt uy “AtBoOop oY Jo osuyS [woIdAy oy

TOI oy

“SNONN4 JAIVOS-ONIN Ad GSSNVD LOY-yNOD

Tike
SsoyRqysnyyl

: |

STULL

‘OI4

PLATE IV.

1163, U. S. Dept. of Agriculture.

Bul.

IN THE

INDICATING CONK-ROT

HEARTWOOD OF THE TREE.

SCALE FUNGUS

SPOROPHORES OF THE RING-

Hedgcock.)

Ge

1
I.

(Photographed by G

Bul. 1163, U. S. Dept. of Agriculture. PLATE V.

FiG. |.—SPOROPHORES OF THE VELVET-TOP FUNGUS ON THE BUTT OF A
LIVING DOUGLAS FIR.

These sporophores indicate red-brown butt-rot in the tree. (Photographed by G. G. Hedgcock.

Fic. 2.—RED-BROWN BuUTT-ROT CAUSED BY THE VELVET-TOP FUNGUS.

Only a thin shell of sapwood remains. Trees so badly decayed are subject to

particularly if the rot extends into the roots. (Photographed by G. G. Hedgecock

ee ae

ee etetntnineeint

Se ee

ee F See eee ee

we

Bul. 1163, U. S. Dept. of Agriculture. PLATE VI.

FiG. |.—SPOROPHORE OF THE QUININE FUNGUS.

These conspicuous whitish fruiting bodies are not common on living trees, but are found more
often on dead down timber. The sporophore has a very bitter taste.

Fic. 2.—BROWN TRUNK-ROT CAUSED BY THE QUININE FUNGUS.

The decay is usually extensive in an infected tree

Bul. 1163, U. S. Dept. of Agricu!ture. PLATE VII.

wy

die

x
.

¥

=)

@

BURL ON A DOUGLAS FIR LEFT STANDING ON A CUT-OVER AREA.

Because of the burl the tree was thought to be badly decayed. Burls do not indicate decay
Compare with Plate VIII.

PLATE VIII.

1163, U. S. Dept. of Agriculture.

Bu..

ne ee mall

eet eh rong et

OES A. ty aead

SWOLLEN KNOTS OR BLIND CONKS ON DOUGLAS FIR.

Compare with Plate VII.

These indicate conk-rot in the tree.

DECAY IN DOUGLAS FIR. 11

DEAD LIMBS.

' large trees with many dead limbs in the lower crown are no more
_ likely to be decayed than a normal tree. Such ‘‘wolf trees,” as they
| are known to the forester, merely grew faster than their neighbors,
and their branches did not die so soon through lack of light; conse-
' quently it requires a longer time for these large limbs to drop off
_ and for the branch stub to heal over.

BRANCH FANS.

| Groups of branches, radiating like a fan from one point, are not

uncommon on Douglas fir. These branch fans have been considered
_ by some persons as indications of decay. A little thought will show
| that this is not within the realm of probability. That decay in the
' dead heartwood could directly affect the vital growing portion of
the trunk of a tree in such a way as to cause abnormal branching is

' directly contrary to all our knowledge of growth and development
' of trees. In all, these branch fans were found on 32 trees, varying

’ from 1 to 15 on a single tree, with an average of 4.4. Of these 32
_ trees, 2 were free from decay, while in 19 the infections were very
light, rarely causing a loss of more than 10 board feet, and the branch
_ fans were not on the same portion of the trunk as the decay. There
' was a considerable volume of decay in each of the 11 remaining
trees, but in 7 of these the decay was in the lower or middle portion
of the trunk, while the branch fans were above it in the crown. In
_ only 4 trees were part or all of the branch fans found on the decayed
- section of the trunk. These figures indicate the complete lack of
even an empirical relation between branch fans and decay.

BURLS,

Douglas fir when bruised is subject to burls at the point of injury,
but it is questionable whether or not all burls are caused by wound-
ing. Such burls are a disorganized mass of wood tissue with a
enarled or twisted grain. This formation is a direct response to the
irritation caused by the injury. Burls are often considered to
indicate decay. Plate VII shows a tree left uncut on a logging oper-
ation because it was presumed from the presence of the burl that the
tree was badly decayed. Data showing the relation of decay to burls
in the trees studied are presented in Table 11. The number of burls
to the tree varied from 1 to 20, with an average of 3.6.

TaBLE 11.—Relation of burls to decay in Douglas fir.

Character of data. Number. | Per cent,
AUBERT OPTS 2 ae “lg BE A gle 55 ed ly ed Reg ele OR MF IRN i ade a SE ARR SR pa
DT Sshy yuo ey is LG 06 OF avo) (cle pigs ead Seka ee = oy ee ae ee oe 6 | 14.0
Trees with burls and decay on different sections of the trunk..........-.........-- 19 44,2
Trees with burls and decay on the same section of the trunk..............-----++-- | is 41.9

Analysis of the data in Table 11 demonstrates that the presence of
burls does not mean decay in the tree. Of the trees with burls 14
oe cent were free from decay, while in 44.2 per cent the rot and

urls did not occupy the same section of the bole. Burls on the
butt of the tree, however, are sometimes an indication of decay, since
burls in this position often result from wounding by fire, and fire
scars are quite commonly infected with red-brown butt-rot.

12 BULLETIN 1163, U. S. DEPARTMENT OF AGRICULTURE.
CONK-ROT.

The decay causing by far the greatest loss in Douglas fir is relatively
easy to detect. Sporophores of this decay occur abundantly. This
is indicated by the local name of conk-rot used in the Pacific North-
west. Lumbermen observed the unusually common occurrence of
sporophores, or ‘‘conks,” on infected trees, as compared to those
with other decays, and the name followed. The prolific development
of sporophores is shown by the fact that of 83 trees with sporophores
there was an average of 14.4 per tree, or a total of 1,196. Considering
all infections both with and without sporophores there was an average
of 10.1 sporophores per infection, or 1 for every 6.34 cubic feet of
conk-rot in the trees and 1 for every 65 board feet.

It is of interest to consider the orientation of these sporophores.
Moller (4), working with the same fungus, found 89.4 per cent of the
sporophores on the westerly side of the trees. He explained this by
the facts that the prevailing winds were from the west and the trees
were most strongly struck by rain on the west side, and consequently
the branch stubs (a very common point of infection) were more moist
onthatside. Weir and Hubert (7, p. 30), in their work with the Indian-

aint fungus (Hchinodontium tinctoriwm E. and E.) on western hem-
ock (Tsuga_ heterophylla (Raf.) Sarg.), found that most of the
sporophores had a northwest to north-northeast orientation. The
same workers (8, p.18), studying conk-rot in western white pine
(Pinus monticola Doug.), found the largest percentage of the sporo-
phores develope on the west side of the tree, with the smallest per-
centage on the southeast side. Table 12 shows the orientation of —
the sporophores on the trees studied.

TABLE 12.—Orientation of sporophores of conk-rot in Douglas fir.

Orientation of sporophores.

; Character of data.

NW. N. NE. EB. SE. Ss. SW. Ww.
Number of sporophores...........-... 212 291 202 | 91 144 77 96 79
Percentage/of total 2222 2 tos 2es eee. 17.8 | 24.4 17.0 | 7.6 12-1 6.5 8.1 6.6

The largest percentage of sporophores occurred on the north side
of the trees and the smallest percentage on the south side. Adding
the sporophores on the north, northwest, and northeast it is seen
that 59.2 per cent were in the northerly grouping. Following this
system gives 36.7 per cent easterly, 26.7 per cent southerly, and 32.5
per cent westerly. The northerly direction clearly predominates.
This is logically explained by the fact that there is less light on the
northerly side and consequently more moisture, particularly during
the growing season, which in this region is a long dry period inter-
rupted by occasional thundershowers of brief duration. Conditions
on the northerly side of the trees are therefore more favorable for
infection and the subsequent development of sporophores.

As a rule very little rot develops in a tree before a sporophore
appears, or if not a sporophore at least a swollen knot, or “ blind
conk,”’ as it is colloquially termed. The sporophores can not pene-
trate the unbroken bark and issue only through knots or branch

fl

}
DECAY IN DOUGLAS FIR. 13

stubs not yet occluded. A swollen knot is the initial stage of a
sporophore in which the substance forming the conk is growing out
through a knot and forcing out the bark. The pressure may also
cause an increase in the width of the sapwood immediately around
the knot, which accentuates the swelling. Swollen knots are illus-
trated in Plate VIII. A swollen knot is just as good an indication
of the presence of decay as asporophore. Often the sporophore never
develops beyond this stage, remaining abortive. Chopping into one
of these knots reveals a brown, soft, corky or punky context, the same
as in a fully developed sporophore. Plate III, Figure 1, shows a sec-
tion through part of a decayed knot.

The effect of fire on sporophores or swollen knots is striking.
When mature timber is swept by fire, the flames running along the
trunk of the tree can not burn off the thick bark. However, the
corky context of the sporophores and decayed knots burns readily,
and this results in rounded, blackened hollows extending for several
inches into the tree where the fire has burned out the decayed knots.
This makes it possible to judge in a measure the extent of conk-rot
in recently fire-killed Douglas fir.

That the development of swollen knots and sporophores follows
rather closely the progress of conk-rot in the heartwood is brought
out in Table 13.

TABLE 13.—Relation of sporophores and swollen knots to conk-rot in Douglas fir.

|

Infections. | Volume of decay.

Percentage of total.
Average per

Decay. Px tt Pee l | infection.
Wee cent- Gross. Of conk-rot.
age of

| basis. total.

| Board Cubic | Board | Cubic | Board | Cukie

|
feet. | feet. | feet. | feet. | feet. | feet.

With sporophores_.: 22.2325... 96 81.4 | 36.83 | 21.71 | 95.94) 96.51 | 782 | 76.2
Without sporophores..............:- 22 18. 61; | 1. 56%] .78 4.06 3.49 144} 12.0
With swollen knots.................. 108} 91.5) 38.39] 22.49| 99.95 | 99.97| 725 | 70.2
Without swollen knots.............. 10 8.5 04 03 | 3 | 2

| k -s@n 4}? “LoL

Table 13 shows that while there was a noticeable percentage of the
infections which did not develop sporophores, these infections were
very small, as is indicated by the volume percentages and the average
volume per infection. The relation is even more striking with swollen
knots, where the volume percentages and the average volume per in-
fection of those infections without swollen knots is so small as to be
negligible.

This means, then, that it is possible to pick out rather accurately
the trees in a stand affected with conk-rot. When high up in a tree
among the branches swollen knots, or even sporophores, are not easily
seen, but if overlooked there it does not make so much difference in
the accuracy of an estimate, since the volume of the top logs is rel-
atively insignificant in the total.

EXTENT OF CONK-ROT.

It is not only possible to pick.out the decayed trees, but it is also
feasible to judge with some exactness the normal extent of conk-rot.

~

14 BULLETIN 1163, U. S. DEPARTMENT OF AGRICULTURE.

In the trees studied it was found that the average extent of decay,
including typical and incipient decay, above the highest sporophore
was 20.1 feet. This was based on 83 infections. In two infections
the decay ended at the height of the top sporophore, and in one tree
the rot extended for 61 feet above the highest sporophore. When
the downward extent of conk-rot below the lowest sporephore was
considered, it was necessary to discard those infections in which the
decay extended into the stump. Based on only 33 infections, the
average downward extent was 13.9 feet. The average of both
upward and downward combined was 18.3 feet.

The same figures for the highest and lowest swollen knots were as
follows: Upward extent, 9.5 feet, based on 93 infections; downward ex-
tent, 9.2 feet based on 41 infections; combined average, 9.4 feet. In
one tree the rot extended for 45.2 feet below the lowest swollen knot.
This difference in the extent of decay beyond sporophores as
compared to swollen knots is due to the fact that the swollen knot
in many instances is the initial stage in the development of a normal
sporophore, and consequently by the time a sporophore appears the
decay has been in the tree longer and has progressed farther than at
the formation of a swollen knot.

These data mean, then, that it is possible to approximate the
volume of conk-rot in defective trees when cruising. The figures, of
course, should not be applied to an individual tree as such, but should
be used in estimating the individual components of a stand in order
to secure an accurate figure on the total loss through conk-rot. In
actual practice the writer would use 20 feet as the upward or down-
ward extent of decay beyond the highest or lowest sporophore and
10 feet as the figure for swollen knots. In other words, in the case
of a decayed tree with sporophores the trunk would be considered
unmerchantable from a point 20 feet below the lowest sporophore to
a point 20 feet above the highest sporophore, while for swollen knots
the distance would be reduced to 10 feet below and above. These
figures are easy to remember and have checked well with the writer’s
observations since this study was made; but for greater accuracy in
any given locality it is well to study felled trees and watch long logs
through the mill, so that these limits can be corrected to fit local
conditions.

RED-BROWN BUT?-ROT.

Sporophores are, of course, the best indication of decay. The
sporophores of red-brown butt-rot being annual are not common
except in favorable seasons for their development, but can always
be found now and then in a locality where the trees are affected.
However, the best clue is fire scars. Noticeably fire-scarred trees
are commonly infected with this decay. Of the 125 trees with fire
scars that were studied, 41, or 33 per cent, were infected with red-
brown butt-rot. Healed fire scars can often be detected by a
variation in the appearance of the bark over the wound or by
swollen or churn butts. There are no swollen knots with this decay.

BROWN TRUNK-ROT.

Brown trunk-rot is rather hard to detect. Swollen knots are not
formed. Sporophores are rare on living trees, but when they do
occur they are very conspicuous and not readily overlooked.

DEGAY IN DOUGLAS FIR. E5

Furthermore, observation shows that they indicate extensive decay in
the tree. Only one tree studied had sporophores of this rot, and the
decay volume in cubic feet was 31 per cent and in board feet 74 per
cent of the gross volume of the tree. But the total loss caused by
this decay was trifling. (See Table 2.)

YELLOW-BROWN TOP-ROT.

Yellow-brown top-rot also israther hard to judge. Swollen knots
do not accompany the decay. Sporophores are not uncommon,
particularly with the more extensive infections. In the trees studied,
seven infections, which resulted in 42 per cent of the cubic-foot
volume and 41 per cent of the board-foot volume of yellow-brown
top-rot, had developed sporophores. However, the sporophores are
commonly so high up in the trees that they are easily overlooked
and, in fact, are often completely hidden by the branches. Broken
or spike tops commonly indicate infection (see Table 7). The
aggregate loss caused by this decay is small.

INDICATIONS OF DECAY IN FELLED TIMBER.

The estimate of the extent of defect in logs or felled timber is
much easier than in standing trees. The red-brown butt-rot is
revealed in the butt cut, and its upward extent can be more closely
approximated. Knots can be tested carefully for signs of rot, and if
the timber has been bucked the ends of the logs can be examined for
typical decay or the discolorations caused by incipient decay. How-
ever, if the logs have been exposed to the weather for several months
these discolorations fade and can not be seen.

It is not at all difficult to judge quite accurately the extent of
conk-rot in felled Douglas fir by chopping into the knots to reveal
the brown corky context of the abortive sporophore.

EXTENT OF INCIPIENT DECAY.

A knowledge of the vertical extent of incipient decay, which is the
term used to designate the early stages of rot, beyond the typical
decay or well-advanced rot is of practical value. In some infections
the incipient decay may end with the typical decay and in other
cases extend many feet beyond it. The horizontal or radial extent
normally amounts to only afew inches. Incipient decay, which is
usually indicated by a discoloration of infected wood, in some cases
pronounced and in others so faint as to be practically invisible, is
not always easy to detect. Affected wood in a casual examination
seems to be firm and strong. Consequently, it is the rule rather
than the exception in the lumber trade to include incipient decay
with sound lumber.

Wood is weakened by incipient decay, the degree depending on
the stage of the rot and also on the species of fungus at work. ‘Tests
(3) on Douglas fir with incipient decay of conk-rot showed that the
wood was apparently not weakened, but pieces with incipient decay
of red-brown butt-rot and brown trunk-rot, to which general type of
decay yellow-brown top-rot also belongs, were much reduced in
strength. Furthermore, if infected material is merely air dried, the
hyphze may remain dormant, ready to continue to decay the wood
again if suitable conditions arise. Hence, wood with incipient decay

16 BULLETIN 1163, U. S. DEPARTMENT OF AGRICULTURE.

should be excluded from all lumber to be used for purposes requiring
strength and durability.

The incipient stage of conk-rot is often quite extensive. In one
tree this stage of decay extended for 29.6 feet vertically in the heart-
wood beyond the typical decay, while in several infections this figure
ranged from 10 to 20 feet. The average extent upward of incipient
decay beyond the typical decay was 3.3 feet and the average extent
downward was 4 feet. The significance of this difference will be
touched upon later. The average extent both up and down was 3.5
feet, based on 145 measurements.

Red-brown butt-rot is less variable in respect to the extent of
incipient decay. The greatest extent found was 8.4 feet, while the
average based on 44 measurements was 1.95 feet. This average is
based on measurements of upward extent only, since most of the
infections began in the stump or extended into 1t and no downward
measurements were possible.

Only meager data were available on brown trunk-rot. Based on
13 measurements the upward extent of the incipient decay was found
to be 3.5 feet, while the downward extent was 3.6 feet. The com-
bined average was 3.6 feet. The extreme extent was 8.5 feet above
typical decay.

The incipient decay of yellow-brown top-rot had an average extent
upward of 2.2 feet and downward of 3.8 feet, while the combined
average was 3.1 feet, based on 58 measurements. In one tree incip-
ient decay extended up beyond typical decay for a distance of 25.4
feet.

rom the foregoing it can be seen that in all three of the rots in
which it was possible to make a comparison between the upward
and downward extent of incipient decay the downward extent
exceeded the upward on the average, and the difference is most strik-
ing in yellow-brown top-rot, where most of the infections occur in
the upper part of the bole. This difference is probably explained by
the well-known fact that older trees are much more subject to decay
than younger ones, and therefore it follows that older heartwood is
more susceptible than younger. As the fungus progresses downward
in the heartwood of a tree it encounters wood gradually increasing
in age and easier to decay, while as it moves upward younger wood
which offers more resistance is continually invaded, decreasing the
extent of both typical and incipient decay. This tendency for decay
to work more rapidly downward than upward is in keeping with
other observations (7, p. 21).

The figures presented on the extent of incipient decay show that
this 1s quite variable and indicate the need for careful inspection to
eliminate this type of defect from timbers where durability and
strength are a prerequisite.

SUMMARY.

The four principal decays in Douglas fir are conk-rot caused by
the ring-scale fungus (Trametes pini), red-brown butt-rot caused by
the velvet-top fungus (Polyporus schweinitzii), brown trunk-rot
caused by the quinine fungus ( Fomes laricis), and yellow-brown top-
rot caused by the rose-colored Fomes (Fomes roseus). Conk-rot and
brown trunk-rot usually occur in the body of the trunk, red-brown
butt-rot is commonly confined to the stump and first log, while yellow-

DECAY IN DOUGLAS FIR. 17

brown top-rot usually occurs in the upper bole or top. Conk-rot
causes by far the greatest volume of decay. The other three rots
are of relatively minor importance, except that red-brown butt-rot
predisposes an infected tree to windfall.

Douglas fir is subject to wounding throughout its life and partic-
ularly to injury by fire during its earlier years. On the whole, wounds
in Douglas fir are mostly superficial, and this tree species heals
rapidly after wounding. Scars callus very irregularly, and it is
usually difficult or impossible to determine the exact dates when
scars were made.

Mechanical injuries are of little importance in relation to the
entrance of decay. Knots were responsible for nearly 90 per cent of
the volume of all decay in the trees studied. Fire scars were the
entrance point for 4 per cent, and the remaining 6 per cent came in
through other scars. ire is the only factor which is controllable, so
there can be but little reduction in the extent of decay in future
stands by a reduction in the scars caused by controllable mechanical
injuries.

Recognition of the indications of decay in standing or felled timber
is of the greatest importance from a practical standpoint, yet this is
little understood. Branch fans, dead limbs, or burls do not indicate
decay. Sporophores and swollen knots which develop prolifically
indicate the presence of conk-rot. After a stand has been fire swept,
burned-out hollows show where there were sporophores and swollen
knots. It is also possible to approximate with some accuracy the
volume of the decay. Conk-rot, on the average, extended approxi-
mately 20 feet in the trunk beyond the highest or lowest sporophore
and 10 feet beyond the highest or lowest swollen knot. Sporophores
of red-brown butt-rot are not common. However, the relative fre-
quency of fire scars indicates somewhat the relative amount of this
decay. Churn butts often denote old fire scars. Brown trunk-rot
is rather difficult to detect in standing trees, but the loss caused by
this decay is insignificant. This also applies to yellow-brown top-rot.

Figures on the different rots, giving the extent of incipient decay
beyond typical decay, show that this is rather variable, thus requir-
ing careful inspection to obviate the inclusion of wood with this type
of defect in timbers selected for durability and strength.

OUTLOOK.

The work on which the preceding discussion is based is merely pre-
liminary. More extensive studies are needed to bring out new facts
and develop still further those already brought out. This should
aid materially in placing the estimating of Douglas-fir timber on a
more exact basis.

The biggest problems remain unsolved. Our half-formulated ideas
of control of decay in Douglas fir are based on observation without
a sound backing of exact data. Furthermore, while it is a well-
established fact that young stands or second growth are relatively
immune from decay, it is not yet determined at what age in the life
of the stand this 1mmunity ceases and the trees become subject to
extensive decay. Establishing this age will enable us in the future

——

18 BULLETIN 1163, U. S. DEPARTMENT OF AGRICULTURE.

to cut stands before there is any real loss and at the same time per-
mit the trees to attain the maximum size.

Equally important is the periodic rate of increase in the loss through
decay after the above age has been passed. Such information is of
the highest value to organizations holding extensive stands of mature
or overmature timber, enabling them to estimate the loss in their
holdings and adapt plans accordingly. But these questions can only
be answered by the study of all the trees felled and left standing on
a wide range of plats in stands of different ages and conditions
selected on logging operations throughout the Douglas-fir region of
the Pacific Northwest.

LITERATURE CITED.

(1) Boyce, J.S.
1920. The dry-rot of incense cedar. U.S. Dept. Agr. Bul. 871, 58 p., 3 fig.,
3 pls., 11 tables. Literature cited, p. 57-58.
(2) CHapMaN, HERMAN Haupt.
1921. Forest mensuration. xxii, 553 p., 88 fig., 89 tables. New York.
(3) Cottey, R. H.
1921. The effect of incipient decay on the mechanical properties of airplane
timber. (Abstract.) In Phytopathology, v. 11, p. 45.
(4) Monier, A.
1904. Uber die Notwendigkeit und Méglichkeit wirksamer Bekimpfung des
Kiefernbaumschwammes Trametes Pini (Thore) Fries. In Ztschr.
Forst. u. Jagdw., Jahrg. 36., p. 677-715, pl. 4-5.
(5) U.S. Derr. Acr., Forest SERVICE.
1916. Instructions for the scaling and measurement of national forest timber.
94 p., 10 tables. Washington, D. C.
(6) 1920. Timber depletion, lumber prices, lumber exports, and concentration of
timber ownership. 71 p.,.22 fig., 26 tables. Washington, D. C.
(7) Wetr, James R., and Huspert, Ernest E.
1918. A study of heart-rot in western hemlock. U.S. Dept. Agr. Bul. 722,
39 p., 13 fig. Bibliographical footnotes.
(8) 1919. A study of the rots of western white pine. U.S. Dept. Agr. Bul. 799,
24 p. Bibliographical footnotes.

19

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ORGANIZATION OF THE
UNITED STATES DEPARTMENT OF AGRICULTURE.

Secretary of Agriculture el oo. IVb PLS HENRY C. WALLACE.

Asostant sSecretary 22 2 ao aes Le tne | C. W. PuGsLey.

Direcionnof Seventi fa Work. —. 2.2 2. SAS E E. D. Bat.

Director of Regulatory Work. 02226... see aee

Weather Bitrenaie 2. fo. eS Ae ee hh ae Dee CHARLES F. Marvin, Chief.
Bureau of Agricultural Economics.........--- Henry C. Taytor, Chief.
Burcawiof Animal: brdusiry 2 2 of eee Joun R. Mouter, Chief.

BUTE OLE JAN LADOUSTY 2.025 kote ose oe WiuuramM A. Taytor, Chief.

DEAS AAS ISGP ER ERS aR eG DAE MIR RE W. B. GREELEY, Chief.

POET PALER) CO EDOUSET We. oe nee atte Ss See gees WALTER G. CAMPBELL, Acting Chief.
PMID OF SOUS = acer ee, aan ae eee Mitton WHITNEY, Chief.
Bureao7 Hutomology.'.. 2225s. 2. be Bese L. O. Howarp, Chief.

Birea of Botogical survey ere ee E. W. Netson, Chief.

Bureau of Public Roads 2. Ons eee Tuomas H. MacDonatp, Chief.
Fixed Nitrogen Research Laboratory........--- F. G. Corrrety, Director.
Division of Accounts and Disbursements. .....- A. ZAPPONE, Chief.

Daatsion of Publications... £ =... -..- Spa Epwin ©. Powe t, Acting Chief.
Keibragye = sak -saal?. POY sl staliced: Aaosese CLARIBEL R. Barnett, Librarian.
States Relahons Service: ...s adtigtanck lextke ae A. C. True, Director.

Federat Horiictliural Board « «0.222214 -i.2 sen wie C. L. Maruarr, Chairman.
Insecticide and Fungicide Board......-.-.---- J. K. Haywoop, Chairman.
Packers and Stockyards Administration........ CHESTER Morrit, Assistant to the
Grain Future Trading Act Administration. - . i Secretary.

ie: PY ane SOUCIOR, 225-2 oseha ete ae oe R. W. Witurams, Solicitor.

This bulletin is a contribution from

arco, Plant: Tndusiry st .2 oss. 22a Sc ee ho WiiirAM A. Taytor, Chief.
Office of Investigations in Forest Pathology. HaveN Mercatr, Pathologist in4
Charge.
20

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