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UNITED STATES DEPARTMENT OF AGRICULTURE
BULLETIN No. 275

Contribution from the Bureau of Plant Industry
WM. A. TAYLOR, Chief

Washington, D. C. PROFESSIONAL PAPER April 7, 1916

FOREST PATHOLOGY IN FOREST
REGULATION

By :

EK. P. MEINECKE, Forest Pathologist, Office of apiece in
Forest Pathology

CONTENTS

Methods of Investigation
Conclusions and Outlook

WASHINGTON
GOVERNMENT PRINTING OFFICE
1915

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UNITED STATES DEPARTMENT OF AGRICULTURE

Contribution from the Bureau of Plant Industry
WM. A. TAYLOR, Chief

Washington, D. C. PROFESSIONAL PAPER. April 7, 1916

FOREST PATHOLOGY IN FOREST REGULATION.

By E. P. MEINECKE,
Forest Pathologist, Office of Investigations in Forest Pathology.

CONTENTS.
Page. Page

Imntroduction\s- 2 s-22--- I a ee _ 1 | Methods of investigation—Continued.

HEP lation) Onyield pessoa yee el efi) 2 Local pathology of white fir... .. Sec aot yea 35
AN Omaha RMI AG Ses seU es ole aeeuse 2 Tabulation of data. 322 eee ae oe 36
TROY REY RALOD O95) A ale a a 12 ct a 6 Condensation of data.......:..-- aes 41
Cuthing CyCleseeeeyy ee tay eee ts = 3 0 oe 8 Imterpretation: ay. cose e sages SHO Sas 46
Crammer tive ise ee ee esas yaa cee aoe 9 | Conclusions and outlook.........--.-.-.---- 53
IREROGOitTAMSIGIOT sere = yee eerie 15 Decay in relation to wounds......------- 54
Condition of timber stock...........---- 16 Horestiregnlatiomes =. seen eee eae 54
MOTD PLOSSeaw eee Ss SZ Beats crash ara a Wan 16 Care of virgin forests.........-..-..-- 54
Mniferior; Species Ses eeeieeise ce eee esses es 19 Forest regulation through timber

Methods of investigation........-----------. 22 SaTOS) fF) ee Oe a SG es 55
Choice of species and site......-......-.. 22 Marking.) 2 ae Dea. oui sy Sa a 57
ING GhiNg NOY ooo oso odd Soke eeanoEas 23 Pathological rotation and cutting
Pathologysofwihite tinea yes. 582 e Ls 2 27 GYCIOS si SURI 2 Bask er sae Eas Tae 59
Description ofareas eso -- cc ss4--2- 226-42. 33 OUtlOO Kee SG Ee ie I Aes IOVS 62

INTRODUCTION.

At the time of the creation of the national forests in the United
States the Government very suddenly found itself confronted with
the problem of organizing an enormous acreage of practically virgin
timber. It was natural that American forestry turned to the expe-
rience of the Old World for guidance in this huge task; it was quite
as natural that the present state of European forestry should have
served as the ideal to be reached in the shortest time possible. In
organizing the administrative machinery, European precedent could
be followed more or less closely, but not so in almost all other phases
of forestry. Except for certain economic factors and the develop-
ment of modern machinery, conditions influencing the lumber
industry in the United States are very dissimilar to those in the
typical forest countries of central Europe. Our virgin forests them-

NotE.—This bulletin discusses the bearing of modern forest pathology on forest regulation,
98035°—Bull. 275—16——1

9 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE.

selves, and consequently the timber for sale, are more or less in the
condition of European forests of several hundred years ago. The
administration found itself then in the position of a man forced to
take over not only an obsolete factory producing at random arti-
cles of daily necessity in enormous quantities without having any
control whatever over the quality turned out, but also a huge stock
of products of all kinds and all values. Modern sales methods
alone can not make the product any better, and the sudden adoption
of modern methods of efficiency in the manufacturing end of the
business would soon disorganize the entire factory.

It is clear that in the most important branch of forestry, silvi-
culture, the blind adoption of European methods must encounter
serious difficulties. Perhaps we are too prone to look upon Euro-
pean forestry as a science worked out in all its details, the results
of which are universally accepted as definitely settled. Critical
perusal of modern European forestry literature shows an entirely
different state of affairs. Even in Germany many of the funda-
mental problems of forest organization are steadily discussed and are
far from being considered as settled. Furthermore, what Gaskill *
sald 11 years ago is true to-day, namely, that ‘‘EKuropean foresters
have not developed a true system or science of silviculture capable
of being applied to virgin conditions or to all conditions.”

The lessons taught us by earlier forest history in Europe, the
adaptation rather than adoption of European principles to American
conditions, and the development of new principles to suit our own
special needs are therefore the means by which forestry in the United
States will finally solve the silvicultural problems before it at the
present day. :

_ REGULATION OF YIELD.
WORKING PLANS.

One fundamental problem has occupied the administration of the
national forests ever since their creation, that of working plans as the
expression of forest organization leading to sustained yield.

Any speculation with regard to the adoption of a system of regula~
tion must necessarily refer to the normal stand, whether this is clearly
understood and stated or not. Now, there is no such thing as the 100
per cent normal stand. Consciously or subconsciously the normal
stand is taken as the ideal, and from this allowances are made accord-
ing to the degree in which the stand deviates from the normal. It is
a remarkable fact that even in European forestry no working system
has developed of expressing with accuracy the value of allowances
to be made. ‘This is partly due to the fact that the managed Euro-
pean forests are relatively closer to the normal. Frequent thinnings
and improvement fellings eliminate most of the undesirable indi-

1 Gaskill, Alfred. Silviculture applied to virgin forest conditions. In Proc. Soc, Amer. Forest., v. 1,
No, 2, pp. 62-69, 1905, (See p. 67.)

FOREST PATHOLOGY IN FOREST REGULATION. 3

viduals from the stand, which is kept as fully stocked as possible.
The problem is further simplified by the prevalence of pure stands or
of stands composed of two, rarely more, well-matched species. The
management of even-aged stands or stands of all ages also permits a
relatively close approximation to the normal.

All these factors are comparatively rare in our practically virgin for-
ests, which are about as far from the normal as possible. As forests
they are with few exceptions rather 100 per cent abnormal, and this
applies equally weli to all unmanaged practically and genuinely virgin
forests of the world. The farther the forests are removed from the
normal the less can European results from relatively normal stands
be applied, and particularly if the abnormality is complicated by the
presence of a greater number of commercial species on the same-
stand, as is so often the case in our forests. Itis not to be expected
that at the very beginning of its career the Forest Service should have
possessed all the facts upon which to base a rational system of sus-
tained yield. Intensive work of decades is necessary to secure even
the very foundations.

It is clear that this lack of fundamental facts must be reflected in
any attempt to establish some system of sustained yield and, there-
fore, in any policy of regulation of cut. While Kirkland + emphat-
ically demands a policy of cutting national-forest timber on the
Pacific coast on the basis of a sustained annual yield, Greeley,” on the
other hand, points to the difficulties confronting the establishment
of a sustained annual yield in the forests of the United States. In his
opinion even, “modern conditions governing the distribution and
sale of lumber make the sustained yield from the standpoint of a
permanent supply for consumers of wood very much of a fiction.”
We have at the present time no more authoritative statement con-
cerning the policy of the administration of the national forests.

With regard to the regulation of sustained yield, Chapman ® arrives
at a similar result in discussing the regulation of cut on national forests.

Until recently the annual cut permitted upon national forests has been determined
by Von Mantel’s method, based solely on the present nature of the merchantable
stand and a somewhat arbitrary rotation. A few attempts have been made lately
to base the cut upon the increment of the forest by use of the Austrian formula. Atthe
same time there has come a general awakening to the fact that our knowledge of the
actual increment of virgin forests is conspicuously lacking. Without this knowledge
systematic regulation of yield must remain on crude and wholly unsatisfactory founda-

tions. The question can not be dodged by quoting the generality that in virgin
forests growth equals decay.

1 Kirkland, B..P. The need of a vigorous policy of encouraging cutting on the national forests of the
Pacific coast. Jn Forestry Quart., v. 9, no. 3, pp. 375-390, 1911.

2 Greeley, W. B. National forest sales on the Pacific coast. Jn Proc. Soc. Amer. Forest., v. 7, no. 1,
pp. 42-50, 1912.

3 Chapman, H.H. Coordination of growth studies, reconnaissance and regulation of yield on national
forests. In Proc. Soc. Amer. Forest., v. 8, no. 3, pp. 317-326, 1913.

4 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE.

This ‘generality,’ m which almost every word is open to criticism,
seems to have become one of the stand-bys of American forestry. It
finds its chief support in the assumption that our forests to-day,
having been untouched by man and exposed to the same factors of
their surroundings since times immemorial, must represent more or
less exactly the same character they had 100 or 1,000 years ago. But
we have practically no genuinely virgin forests; in the great majority
of commercial accessible stands—and here we are interested only in
these—man has for centuries practiced some kind of primitive for-
estry by setting fires. This “ Piute forestry” has changed the aspect
of many stands so completely that the term “‘ virgin forests” is far
from being correctly applied. At best, can one speak of scattered
virgin stands here and there. Even in the latter the assumption that
the present stand has more or less the same character as 100 to 1,000
years ago reposes upon another assumption, namely, that here the

ecological formation has reached the final stage of development and ©

has come to stay. Of the remaining part of the cited rule of thumb
all factors are more or less unknown.

Our knowledge of increment is, according to Chapman, “con-
spicuously lacking.” We know just as little about actual extent
and progress of decay in virgin forests, so that the “generality” is
reduced to an equation in which all factors are unknown. Besides,
the term ‘‘decay” leaves out all losses from the decrease in number
of trees steadily going on in the forest, as in every community of
living beings. Prompted, perhaps, by a subconscious realization of
this fact, the term ‘‘ decay” in the equation is sometimes supplanted
by “deterioration.” This makes matters even worse. Deteriora-
tion in this connection often means the visible loss irrespective of
cause. It is primarily a numerical consideration. A number of

trees containing certain amounts of timber annually drop out through

various causes, and this loss is then said to offset the annual incre-
ment. Secondarily, it might include loss from decay. In forest
regulation it is not the number of trees and the volume of timber they
produce per acre that count, but the volume of sound, merchantable
timber that we can expect to raise; and the only factor in the equa-
tion of any value would be, therefore, not decay only and deteriora-
tion or numerical loss of individual trees but “total loss.” The
components of this total-loss factor are known. They include the
dropping out of individual trees by death from suppression or “old
age,” fire, snowbreak, lightning, windfall, insects, diseases of vital
parts of the tree, and finally loss through decay. What we do not
know are the respective values to substitute for these components
in the actual figuring of total loss.

1 More recently Barrington Moore has published a valuable study—Yield in uneven-aged stands—in
Proc. Soc. Amer. Forest., v. 9, no. 2, pp. 216-228, 1914.

FOREST PATHOLOGY IN FOREST REGULATION. D).

The same laxity noted in the use of the terms ‘decay’ and “ de-
terioration’’ is commonly found in the use of the term ‘ decadence,”’
as applied to a stand or a given species, which is often understood to
include individual decadence from old age; that is, arrested or min-
imized growth, liability to attack from fungi and insects, and finally
decay. The fact that a given species is unusually liable to heart rot
does not make it decadent. Many of our most thrifty and aggres-
sive species are particularly subject to heart rot. It is also doubtful
whether this hypothetical knowledge, if ever attained, of the total
rate of total loss in “virgin”’ forests, as compared with the equally
hypothetical rate of increment of the forests as a whole, would help
us to any extent. The vastness of our forests in area creates a.
tendency either to think in broadest terms and to overlook the fact
that a forest is an artificial unit made up of natural units, the stands
- with all their immense variety of character, or, on the other side, to
take a familiar unit and to transfer its characteristics to the whole.
The latter mistake is more easily remedied than the first. As a
science, forestry must be founded upon inductive methods. Inten-
sive study of detail alone can form a solid basis for the formulation
of principles.

What is needed is exact studies of all components of the total-loss
factor per species before we attempt to fix the total-loss factor for
_ the stand. :

Such detailed studies will be easiest in all-aged pure stands of a
thrifty species little liable to decay. Unfortunately the vast majority
of stands on national forests in the West are composed of two to
five or more species of very different characters. It may be that the
total annual loss equals the annual increment in some of the medium
long-lived species of the pine group least hable to decay. It can
not be true for the extraordinarily long-lived redwood and big tree,
with their unusual resistance to decay, insects, and storms. It is
equally untrue for all shorter lived species much exposed to decay
and other influences that make for loss. Libocedrus decurrens, for
example, although most aggressive and thrifty, is from an early age
on liable in an uncommon degree to the attacks of Polyporus amarus,
which renders as much as 70 or 80 per cent and even higher per-
centages of the stand completely unmerchantable. Merchantable
incense cedar is of high value; so much the greater, then, is the
total-loss factor. The same is, mutatis mutandis, true for white fir
and a number of other species. For all these the increment is not
only offset but far exceeded by the decay of the valuable heartwood;
the total annual loss is far greater than the annual increment,
although numerically the loss may not be apparent.

The gain through increment, we must remember, consists of sap-
wood of little value; the loss by decay, on the other side, affects the

6 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE,

valuable heartwood. Neither is there any constant accumulation of
gain; after some years the sapwood is turned into heartwood and
as such becomes lable to decay. In other words, in trees of this group
infected with heartwood-destroying fungi, the value of newly formed
wood is small; when it becomes valuable by transformation into
heartwood it becomes subject to decay—that is, loss. _ This loss from
decay is by its very nature as a heart rot confined to those individ-
uals in which heart-rot formation has taken place. All trees below
the age of heartwood formation do not enter into consideration. In
speaking of a given stand the representation by ages must be of
prime importance. In all considerations of regulation it is neces-
sary, therefore, to make a clear distinction between forests and
stands, between many-aged and even-aged stands, between mixed
and pure stands, with particular emphasis on the composition of the
stand-as to species. All generalization is not only useless but mis-
leading. |

But in full realization of the almost complete lack of fundamental
knowledge, American forestry is confronted with the urgent neces-
sity of adopting, even temporarily, some kind of a system of regula-
tion of yield. Whatever this system may be, its tentative, tempo-
rary, and local character can not be overemphasized. :

Various attempts at adopting local temporary systems have found
an expression in the shape of working plans. Inseparable from the
problem of working plans is the choice of a rational rotation and
cutting cycle.

ROTATION.

The gleanings in American literature treating on the choice of
rotation from a general point of view are rather meager, outside of a
few well-known handbooks, such as those by Recknagel,! by Fernow,?
and by Roth,’ particularly in so far as the practical application to
our virgin forests is concerned. Recknagel * excludes financial rota-
tion from North American forests with the following words:

Since this method of calculating the rotation [financial rotation or that of highest
soil rent] is suitable only to very intensive conditions, it would serve no useful pur-
pose to elaborate it at this point.

On the other hand, the strong influence of European forestry is
clearly felt in the ever-recurring advice to adopt some kind of a
financial rotation in the national forests of the United States. Kirk-
land * is of the opinion that—

1 Recknagel, A. B. The Theory and Practice of Working Plans (Forest Organization), 235 pp. New
York, 1913.

2Fernow, B. E. Economics of Forestry, 520 pp. New York, 1902.

3 Roth, Filibert. Forest Regulation, or the Preparation and Development of Forest Working Plans,
218 pp., illus. (maps). Ann Arbor, Mich., 1914. (His Michigan Manual of Forestry, v. 1.)

4Recknagel, A. B. Op. cit., p. 39.

5 Kirkland, B. P. Working plans for national forests of the Pacific Northwest. Jn Proc. Soc. Amer.
Forest., v. 6, no. 1, pp. 16-37, 1911. (See p. 21.)

x

FOREST PATHOLOGY IN FOREST REGULATION. 7

A rotation based on the financial rotation, possibly modified somewhat towards the
rotation of the highest income, is no less adapted to Government forestry than to pri-
vate forestry.

Greenamyre ‘ advocates a financial rotation in the composite type
of the Apache National Forest, the “rotation of greatest volume pro-
duction being out of question.” In his specific recommendations
for western yellow pine, Douglas fir, and blue spruce, however, rota-
tion of greatest volume plays a far greater réle than financial rota-
tion. Such important factors in financial rotation as soil capital,
quality increment, and rent are neglected or only hinted at. Value
increment and depreciation enter into his calculations in a general
way only, evidently from a lack of exact figures.

Barrington Moore? expresses himself strongly against the adoption —
of a financial rotation.

It would be out of place in this paper to enter into a discussion of
the possibility at the present time of fixing a rotation of greatest
income or a financial rotation more deeply than to point to the
immense difficulties encountered as soon as we try to substitute actual
values for the factors entering into their computation derived from
experience in our own country. We lack at the present time the very
fundamentals on which to base the determination of highest forest
rent or highest soil rent.

The Forest Service has, in full realization of the uncertainty of
almost all factors which would or should enter into a financial rota-
tion formula, adopted, for the present at least, a tentative silvicul-
tural rotation of maximum-volume production.

The factors entering into the determination of silvicultural rotation
or of greatest volume being more easily accessible, it is quite natural
that American forestry should show a tendency toward its applica-
tion, as shown in a number of published and unpublished working
aleve

Attempts at fixing some rod of a rotation age are found in several
publications. Woolsey * tentatively proposes a rotation of 200 years
for yellow pine without giving a basis for the choice of any particular
system of rotation.

Barrington Moore‘ says that on the Plumas National Forest ‘‘the
rotation should theoretically be that of maximum-volume produc-
tion. The use of a financial rotation by the Government, in a region

1 Greenamyre, H. H. The composite type on the Apache National Forest. U.S. Dept. Agr., Forest
Serv. Bul. 125, 32 pp., 4 figs., 1918. (Seep. 30.)

2Moore, Barrington. The essentials in working plans for national forests. Jn Proc. Soc. Amer. Forest.,
v. 6, no. 2, pp. 117-128, 1911. (See p. 126.) .

3Woolsey, T.S. Western yellow pine in Arizona and New Mexico. U.S. Dept. Agr., Forest Serv. Bul.
101, 64 pp., 11 figs., 4 pls., 1911. (See p. 51.)

4Moore, Barrington. Chapman’s method of studying yield, p. 93, 1913. To accompany forest plan,
Plumas National Forest, district 5. Appendix (continued), Silviculture. (Unpublished. Furnished by
courtesy of the U.S. Forest Service.)

8 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE,

capable of producing large saw timber, can not be justified. * * *
It would probably be better to fix the rotation at the period during
which the rate of volume production is greatest or shortly after it,
provided this is long enough to give the most valuable product.”

Munger ' comes somewhat closer to a consideration of the financial
factors for a rotation of Douglas fir in pure even- ee. stands in the
Pacific Northwest.

From the quotations given, one fact stands out clearly: We are still
groping more or less in the dark where choice of rotation is con-
cerned, and we are even lacking the fundamentals upon which to
base the principles to govern us in making a proper choice. It also
appears that in many cases the term ‘‘actuai fellmg age’’ should be
substituted for rotation. Rotation in itself signifies return or succes-
sion in a series. Fernow ? has warned, as early as 1905, against mix-
ing up “‘actual felling age, the time when a stand is actually cut or to
be cut, and normal felling age (rotation), the time when in a scheme
of continued management it is proposed to have it cut again and
again—a mere standard time. Few stands are cut in the age of the
rotation determined for the forest as a whole.’’ Where a ‘‘rotation”’
of yellow pine, for instance, of 200 years is advocated, it is evident
that this can not be meant to constitute the fixed period at which
yellow pine should be cut again and again in the future. It is really
the actual felling age, the time when a given stand of yellow pine is
actually to be cut in the future, not a succession of 200-year periods.
The rotation itself will be much shorter, as European experience has
shown us. Moreover, it is more than doubtful whether our successors
in 200 to 400 years will pay much attention to the rules we may try to
lay down for so remote a future.

CUTTING CYCLE.

The impossibility of predicting with even a modest degree of proba-
bility what will happen in the future and of anticipating changes in
conditions of an economic nature is responsible for the vagueness with
which the question of fixing definite cutting cycles is treated. Tenta-
tively, cutting cycles of about 50 years have repeatedly been advo-
cated for uneven-aged stands (mixed and pure) under the selection
method, as a policy to be followed on virgin national forests. If
present economic conditions should prevail in the next 50 years—that
is, if the demand for timber should continue to fall far short of the
actual annual increment—it would hardly pay a lumbering concern
of the future to extend its operations to cut-over areas before 50 to
60 years had elapsed. Even then it seems doubtful whether the

1Munger,T.T. The growth and management of Douglas fir in the Pacific northwest. U.S. Dept. Agr.,
Forest Serv. Cire. 175, 27 pp., 4 figs., 1911.
2Fernow, B. E. Forest terminology. Jn Forestry Quart., v. 3, no. 3, pp. 255-268, 1905. (See p. 264.)

FOREST PATHOLOGY IN FOREST REGULATION. 9

amount of timber contained in the few overholders left as seed trees
and in individuals at or just below the diameter limit established in a
first cutting would prove attractive to purchasers of the future, pro-
vided always no change in the lumber market should take place.
The diameter limit now fixed on many national forests may be said
to be about 12 inches, varying somewhat with the species and local
conditions. Few trees below this diameter will reach such dimen-
sions in 50 years as to form a merchantable stand, judged by our
standards of to-day.

If it is unwise blindly to take over principles and policies developed
and more or less accepted in countries with old-established and far-
advanced forestry and apply them to the first stages in the organiza-
tion of our virgin forests, the study of the history of the forestry
movement and development in other countries can not but be of the
greatest practical value. We are justified also in assuming that the
history of forestry will repeat itself and that forestry in all countries
with large virgin or practically virgin forests in touch with the gen-
eral market will run through the same phases of development as it
did during the last centuries in central Europe, but at a very much
faster pace, owing to the enormously enhanced facilities of transpor-
tation and marketing and the rapidly increasing demand for timber.

If this be true, a cutting cycle of about 50 years may prove too
long. To judge from the development of timber values in Europe,
our once cut-over stands should prove attractive in a shorter period.

In determining the duration of cutting cycles, it is reasoned that
the accessible virgin timber in the national forests should be cut once
before operations return to the first areas logged over. How much
time this first culling may consume we have no means of telling. It
should be remembered, however, that the system naturally present-
ing itself is that of selection cutting, and although there is a decided
tendency toward heavier marking approaching clean cutting, this
latter should be taken cum grano salis. Actually, the reproduction
left includes all individuals up to and sometimes beyond 12 inches
diameter breast high; that is, trees that have reached a considerable
age and that in 50 years will have grown to what would be classed in
European forestry as veterans.

CUMULATIVE RISK.

In fixing long-term cutting cycles, a most important point has not
been sufficiently emphasized, namely, the ‘cumulative risk” from fire,
windfall, frost, and so-called deterioration to which a given stand is
exposed during so long a period. The longer the cycle the greater
the ratio of risk. The unparalleled development of fire protection
in the national forests of the United States, itis true, promises fairly to
exclude actual destruction from fire on any large scale; but, as long as

10 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE.

there will be fires from unpreventable sources (lightning), the risk in
extended cutting cycles increases from year to year with the growth
in value of the stand. The shorter the period in which a merchant-
able stand can be produced and turned into cash the smaller will be
the risk of loss.

Loss from windfall is inevitable in many localities as a direct con-
sequence of selection cutting. It is clear that the cumulative risk
of a longer cycle is far in excess of a shorter one. Evidently, devas-
tating windstorms are more likely to occur during a period of 50
years than during a shorter one. Moreover, the loss in cash value,
even in single trees, from windfall is bound to be heavier in the older
stands. The larger, bulkier, and therefore the more valuable the
tree, if sound, the more it is exposed to windfall. Falling trees in
brushing against their standing neighbors not infrequently cause
more or less serious wounds by bruising or tearing off the bark.

The greatest risk, however, involved in the long cutting period is
from ‘‘deterioration,”’ so called.

In nature a steady process of elimination goes on. Of thousands
of seedlings springing up together in dense growths, comparatively
few reach sapling size, very few grow into poles, and fewer, even, to
standards. This natural thinning through competition in the fight
for soil, food, and light is furthered by various dangers to which the
young plants are exposed, such as from certain insects, foliage and
twig diseases, injury from mammals, snowbreak, frost, and drought.
Later, the surviving members of the stand are confronted with dangers
from the same and other sources, such as suppression, lightning, in-
sects, frost, and decay. The elimination of the weaker members
effects a selection of older, well-established individuals, some of which
may still suffer from the competition of their thriftier neighbors, but
are not forced out of the community, or, to use Fernow’s? well-
chosen terminology, trees which are “oppressed,” not suppressed. As
long as improvement cutting on a larger scale on the national forests
is impossible, the percentage of oppressed trees will depend upon the
length of the cutting cycle. Both these oppressed trees and their
more favored companions are exposed to dangers from which their
earlier life was free.

Frost does a good deal of damage; here we are. less interested in
the damage done to the foliage or to the bark than in those more or
less long cracks in the wood which are caused by very low tempera-
tures. In cold weather the wood cylinder shrinks more in a tan-
gential than in a radial direction. Particularly at sudden low
temperatures, when the volume of the outer layers decreases rather
suddenly while the inner layers are still free from frost and have

1 Fernow, B. E. Forest terminology. Jn Forestry Quart.,v.3,no. 3, pp. 209-268, 1905. (See p. 266.) |

FOREST PATHOLOGY IN FOREST REGULATION. 11

shrunk but little, differences in internal tension will cause the outer
layers to split vertically. With rising temperature the frost crack
closes. Not always is the bark able to stretch sufficiently over a
frost crack. Often the bark tears open, and if low temperature
occurs again and again, the cracks will not be able to heal over and
will remain open for many years, giving the air access to the heartwood
and incidentally allowing spores of wood-destroying fungi to ger-
minate and infect it. Even if no infection takes place, these frost
cracks very seriously impair the value of the timber. The older and
bulkier the tree the greater is the danger of frost-crack formation.
The risk naturally increases with the length of the cutting cycle.
Infection, of course, can take place only through open frost cracks; _
internal frost cracks, besides impairing the value of the timber, can
not be without influence on the chemistry and physics of the wood.

Although lhghtning occasionally strikes the smaller trees, even
poles and saplings, it is to be expected in the nature of things that
taller trees will be more exposed to injury from this cause. Very
little is known, so far, as to the actual damage done by hghtning in
our forests. Destruction of individual trees has been frequently
reported, and Plummer’ gives a series of illustrations of injury to forest
trees from lightning. He treats, however, only of those very gross
cases in which even the least educated eye will recognize the cause
of the injury.

We know through Robert Hartig’s? classical investigations, which
were continued by Von Tubeuf, that destructive lightning is rare
in comparison to the overwhelmingly greater number of cases of
lighter injury from lightning, varying from more or less large wounds
visible on the outside of the tree to the small and insignificant local
killing of parts of the cambium and of the living bark which can
only be detected by careful dissecting.

The symptoms of lightning injury in our forest trees are easily
recognized from Hartig’s excellent descriptions. They are particu-
larly common and conspicuous in white fir. ;

For practical purposes, we have to consider here only those forms
of hghtning injury which in some way endanger the life, the health, or
the commercial value of the tree; this will include not only actually
destructive cases, but also very large numbers of lesser injuries.
The accumulation of risk during a long-time cutting cycle becomes
self-evident, particularly in view of the fact that the danger from
lightning increases quite out of proportion to the increase in height
of the tree and the development of the root system.

1Plummer, F.G. Lightning in relation to forest fires. U.S. Dept. Agr., Forest Serv. Bul. 111, 39 pp.,
16 figs., 1912.

2Hartig, Robert. Untersuchungen tiber Blitzschlage in Waldbiumen. Jn Forstl. Naturw. Ztschr.,
Jahrg. 6, 1897, Heft 3, pp. 97-120; Heft 4, pp. 145-165; Heft 5, pp. 193-206. 83 figs.

Hartig, Robert. Neue Beobachtungen tiber Blitzbeschaidigung der Baume. Jn Centrbl. Gesam.
Forstw., Jahrg. 25, 1899, Heft 8-9, pp. 360-381, figs. 47-71; Heft 12, pp. 523-544, figs. 81-110.

12 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE.

Although young trees are also exposed to the attack of insects, it
is clear that a colony of bark beetles will prove far more injurious
in killing a merchantable tree than in killing a small pole. Moreover,
certain insects seem to have a predilection for larger sizes. The
probabilities of attack increase with the length of the cutting cycle.
Besides, the older the tree and the more it has been exposed to
wounding the more liable does it become to attack by wood-boring
insects which materially reduce the value of the timber.

The timber contained in trees killed by lightning, as long as they
are not destroyed, and in those killed by bark beetles may be utilized,
and, with increasing timber values, will be utilized before they
deteriorate.

The few veterans which have withstood the many dangers of earlier
life do not go on living forever; they finally succumb like the rest.

It is still an open question whether forest trees are theoretically im-
mortal and die only through the devastating influence of severe
storms, lightning, insects, certain diseases caused by fungi, such as
Armillaria mellea and Fomes annosus, or because the root system of
the veteran finally has exhausted all available resources of the soil
within its reach. As we are interested here only in the future of cut-
over areas in relation to the length of the cutting cycle, it is unneces-
sary to enter into a discussion of this question. The cutting cycle for
any one species will in all probability never be long enough to raise
individual decadence from old age to the rank of an influencing factor.
We should bear in mind, however, that individual decadence is not
in itself deterioration unless decay sets in.

The importance of the reduction in the timber value of the tree
through the agency of fungi, on the other side, can not be overempha-
sized. This reduction in timber affects either the prospective timber
values—that is, the increment—or the present stock, or both. In the
first case, the fungi in question (mostly Pyrenomycetes and rust fungi)
inhabit living tissues of the foliage or of the young bark. The con-
tinuous drain on the assimilates of the foliage either in the leaves
proper or on their way down through the bark is evidenced by a
decrease in increment of the tree, which in long cutting cycles will
represent a very considerable loss in timber values. In other words,
trees affected with foliage or bark diseases will be far from yielding the
timber we might expect from sound trees. It must be mentioned
that losses in prospective values are not alone due to fungi; mistle-
toes and leaf-inhabiting insects are responsible for enormous deficits
in yield. The economic réle of the fungi, mistletoes, and leaf-inhab-
iting insects in our virgin forests is highly important and will remain
so for a long time, on account of the difficulties connected with their
control and even more on account of our very limited knowledge con-
cerning their life histories and specific action. More intensive studies

Ne TESTA ay a a ah al i la aly Agia eae nt ee ney on te

i fcsmgaesee er thane

FOREST PATHOLOGY IN FOREST REGULATION. 13

on the members of this group must be left to the future. At the
present time we are more interested in the preservation of our actual
timber, including such values as will be formed in the near future.

Actual timber values are seriously endangered by wood-destroying

fungi, all of which belong to the Hymenomyeetes. With the exception
of a very few (Armillaria mellea, Komes annosus), which in attacking
living roots first cut down the increment of their host and then invade
the wood of the bole, they all inhabit the heartwood and generally
leave the sapwood intact. As the principal timber values are stored
in the heartwood, the enormous damage they are able to cause is all
the more in evidence. All of these fungi are adapted to given hosts
or groups of hosts; these groups are seldom very large. Polyporus
amarus, for example, the cause of the extremely destructive heart -
rot of Libocedrus decurrens, can not grow, as far as is known, inany
other host species. Trametes pum, on the other hand, attacks a
number of pines, Douglas fir, and other conifers. The composition of
the stand, as weil as the representation of species, is therefore an im-
portant factor in the ecology of these fungi. Only those fungous
spores which land on trees of the species to which they are adapted
have a chance after germination to enter into the tree.
. Being strictly heartwood inhabiting, these fungi, with the excep-
tions mentioned above, can, of course, only attack trees which already
have formed heartwood. But as they are unable to penetrate the
bark, they are harmless unless their spores are carried on to some
wound or opening (branch stubs) in the protective skin represented
by the bark. The longer the host is exposed to wounding, the greater
will be the chances for infection.

As might be expected, therefore, the losses from decay in standing
living trees are enormous in virgin forests. Even in the best managed
forests of Germany losses from decay are heavy. Méller,' in figuring
the damage done by Trametes pun in. the pine forests of the Prussian
Government, arrives at the astounding figure of more than 1 million
marks (about $250,000) annual loss from this source alone. In the
period from 1905 to 1908 the Prussian Government spent $87,480 in
the control of Trametes pinz in its pine forests. In 1914 this sum had
increased to about $120,000.*

In American literature no reliable figures are available relating to
the annual loss from decay in standing timber in virgin forests.
Such figures can be obtained only by exact studies on representative
areas, the methods of which the writer has been trying to work out

1Mdller, A. Uber die Notwendigkeit und Méglichkeit wirksamer Bekimpfung des Kiefernbaum-
schwammes Trametes pini (Thore) Fries. In Ztschr. Forst- u. Jagdw., Jahrg. 36, 1904, Heft 11, pp. 677-
715, pls. 4-5. 5

2Moller, A. Der Kampf gegen den Kiefernbaumschwamm. In Ztschr. Forst-u. Jagdw., Jahrg. 42,
1910, Heft 3, p. 133.

3Moller,A. Der Kampf gegen den Kiefern- und Fichtenbaumschwamm. Jn Ztschr. Forst- u. Jagdw.,
Jahrg. 46, 1914, Heft 4, pp. 193-208.

14 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE.

. during the last few years. In reason, all figures relating to loss in
timber from decay, insects, lightning, etc., should apply only to such
forested areas as are accessible at present or which will be in all
probability accessible in the not too remote future. Inaccessible
stands, whatever their protective value, do not represent timber
values, and it is obviously wrong to include them in any estimate
of the damage done to our timber stock on hand. |

The rate of progress of decay in the individual -tree is altogether
unknown beyond vague guesses.

Hartig * has tried to figure the rate of growth of the mycelium, for
instance, of Fomes igniarius. Moéller ? has made an attempt to figure
the rate of growth of Trametes pina and resulting decay in Pinus
silvestris from actual measurements in artificially infected trees. It
is clear that unless such experiments are carried over a great many
years, only the rate of growth of juvenile fungus plants starting from
the infection can be measured, which can not be taken directly as a
guide for figuring the growth of the older or mature fungus plants.

Besides, the experiment is based upon the assumption that the —

fungus, after once having gained access to the interior of the tree, is
independent of possible individual differences of its substratum, or,
in other words, that the rate of growth is a fixed factor, irrespective
of individual properties of the heartwood. This assumption has no
solid basis. The rate of growth of the fungus plant, and therewith
of decay, is undoubtedly one of the most inaccessible chapters of
forest pathology, on account of the difficulty in finding a stable point
of issue. There is at present no reliable method known of deter-
mining the actual extent of decay in the standing living tree. In-
direct methods are the only means presenting themselves to-day;
they leave much to be desired with regard to accuracy and can not
be expected to yield results unless carried on over a long period.

What we do know is that decay in standing living timber from
heartwood-destroying fungi causes very heavy losses and that decay
is progressive. Sporophores develop on decaying trees, and the dis-
ease spreads through spores from one tree to other individuals of the
same and sometimes of other species. Moreover, the decay starting
from an incipient infection progresses in the heartwood of the in-
dividual tree until its most valuable lumber is destroyed. Decay
being progressive, the cumulative risk from this source in long
cutting cycles is therefore far greater than in the case of lightning or
other injurious agents.

Unlike insects, heartwood-destroying fungi have few or no natural
enemies; there is no such thing as ‘‘biological control”’ of decay. ,

1 Hartig, Robert. Die Zersetzungserscheinungen des Holzes der Nadelholzbiume and der Eiche... p. 116.
Berlin, 1878.

2Moller, A. Der Kampf gegen den Kiefernbaumschwamm. Jn Ztschr. Forst- u. Jagdw., Jahrg. 42,
1910, Heft 3, pp. 129-146. (See p. 145.) ;

ane:

FOREST PATHOLOGY IN FOREST REGULATION. 15

PERIOD OF TRANSITION.

American forestry stands now at the very beginning of a period of
transition from the handling of virgin forests to actual forest regula-
tion. The most urgent problem, therefore, consists in how to take
care of our forests as we have them, with all their defects, with in-
dividual decadence and decay, and to leave them to future genera-
tions in as favorable a state as possible, judged by our very limited
insight of to-day. At the present time the only means at the disposal
of the Government to carry out any plans in forest regulation based
upon what appears to us as sound silviculture is through timber sales.
The Government does not and can not cut its own timber. It is
therefore entirely dependent upon a highly variable outside factor
with regard to the most important part of its silvicultural work, a -
factor over which it has but little control. All attempts at the regu-
lation of yield must then be concentrated on timber-sales areas. A
comparison between the area actually cut over annually and the
total national-forest area that may eventually become accessible to
logging operations will show the severe hardship under which the
Government is forced to work. Moreover, timber sales do not
always occur where they are most needed from a silvicultural point
of view, nor do they always cover the entire natural units upon
which it is desirable to prepare for a system of regulation. A com-
prehensive system of regulation on a larger scale following natural
units is out of the question as long as the Government is not in a
position to do silvicultural work on its own land where it is most
needed.

The aim of the Forest Service at the present time consists less in
how to do the greatest amount of good to future generations than in
how to do the least harm and at the same time to do justice to our
present-day conditions. Instead of exhausting our energies in sterile
speculation of what might happen in 100 to 200 years from now, there
is a strong tendency toward applying them first to the analysis of the
most urgent needs of to-day and then to the exact and painstaking
study of all the innumerable factors which enter into a comprehensive
plan for the future structure of American forestry. It is well to
remember that so far, not even the methods leading to the majority
of such studies are worked out. The necessity of taking care of our
present-day timber supply and of providing for the future in an exten-
sive rather than intensive way has found strong expression in Chap-
man’s “‘American Method,”’ where regulation is based not only on
present volume and annual growth, but also on the “‘actual condition
and amount of timber in the different age classes, with approximate
knowledge of the behavior and condition of the age classes for an

1Chapman, H. H. Coordination of growth studies, reconnaissance and regulation of yield on national
forests. Jn Proc. Soc. Amer. Forest., v. 8, no, 3, 1913. pp. 317-326. (See p. 323.)

16 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE,

extensive future period.”’ If “‘condition”’ is defined as state of health,
not only as far as thriftiness of growth is concerned, but also with

special regard to degree of merchantability as influenced by decay, |

the condition factor becomes a subject of pathological study.
Condition of the timber we hope to raise for the future, in the
definition as given above, has a strong bearing on the possible
regulation of yield. There can be no sense in figuring cutting
cycles or rotation for future generations to follow unless we assume
that our successors will find the area we have cut over covered
with a stand not only apparently but really merchantable; in other
words, with timber that is not rendered valueless by decay. The
most ingenious speculation as to future yield is without any value
whatever unless we have some way of figuring how long the steadily

increasing but admittedly perishable timber stock can be left in the

forest before it is Hable to destruction by fungi.

The most important problem before us, therefore, is the determi-
nation in definite values of the condition of timber stock, present and
future. |

CONDITION OF TIMBER STOCK.

The condition of the timber as a factor in regulation may be
expressed as the relation of the volume of timber destroyed or rendered
unmerchantable by injurious agencies to the ideal volume of merchant-

able timber; or, in so far as forest regulation is interested not merely

in the present but in the future, as the relation of the mean annual
total loss to the mean annual increment.

It has already been pointed out that the concept of the relation of
the mean annual total loss to the mean annual increment is without
any value whatsoever as long as both factors are unknown. We are
beginning to know in a small way something about the mean annual

increment of certain species in certain types of some of the national

forests. We are still completely ignorant as to the influence that the
only silvicultural act of any importance open to the Forest Service,
that is, cutting on timber-sales areas, will have on the increment of
the remaining trees. This knowledge will come in due time. The
value of the total-loss factor is altogether unknown. In order to
attack this problem it is necessary to analyze it, to reduce it to its
several components, and to study each in its turn. By synthesis the
total loss can then be computed and the true relation to increment
determined.
TOTAL LOSS.

The analysis of total loss already given shows that its components
are known, but not their values. Of all these components the most
important, the one that has the strongest bearing on the value of the
stock of timber at hand, is loss from decay or heart rot caused by a
group of heartwood-destroying fungi. Very young trees are not

E

tr Sagi

FOREST PATHOLOGY IN FOREST REGULATION. 17

susceptible to heart rot. No heart rot is possible before heartwood
is formed. Unfortunately, we do not know anything about the
formation of heartwood in our American species with relation to the
age of the tree. The younger trees, while at present immune, will,
in growing up and after formation of heartwood, become just as subject
to heart rot as are their older companions. It is, then, of prime
importance to know at what age living trees of a given species become
particularly hable to attack from the one or more heartwood-destroy-
ing fungi that use their heartwood as a source of food. It is, further,
of the utmost importance to know whether there are any conditions
in the tree or outside of it that exert an influence over the develop-
ment of the fungi once they have gained access to the heartwood

of a tree to which they are adapted. ;

Beyond general statements to the effect that overmature trees do
deteriorate from heart rots, very little information is to be gathered
from American literature concerning the average age at which certain
tree species become liable to attack from heartwood-destroying fungi.
Greenamyre! mentions that in the Apache National Forest the
decay in Douglas fir ‘‘no doubt largely offsets the growth”’ after the
age of 210 years is reached.

- Munger? gives a little more specific information:

The amount of decay found in living Douglas firs up to the time they are 150 years
old or so is very small, but in mature and overripe timber there is a great deal of
defect due to decay. . . . Douglas fir trees resist infection from fungi well until
they become mature, when, because of the opening up of a stand, breakage, and scars

due to the action of the elements and of fire and insects, and also because with advanc-
ing age their resistant power becomes less, they offer entrance to fungi.

It is not clear from the context whether Munger’s figures are an
estimate or are based on actual methodic investigation and measure-
ments.

Findley Burns,’ in speaking of conditions on the Crater National
Forest, gives the following information:

Many of the older Douglas firs are affected by a dry rot. . . . White fir is especially
susceptible to decay, and many trees above 40 inches in diameter on the forest are so
rotten as to be valueless, even for cordwood.

In the latter case, age is supplanted by diameter, which answers
perfectly well if diameter invariably corresponds to age.

Barrington Moore and R. L. Rogers* incidentally give some
interesting notes on the age of infection of balsam fir, which on the

1 Greenamyre, H. H. The composite type on the Apache National Forest. U.S. Dept. Agr., Forest
Serv. Bul. 125, 32 pp., 4 figs., 1913. (See p. 31.)

2Munger, T.T. The growth and management of Douglas fir in the Pacific Northwest. U.S. Dept. Agr.,
Forest Serv. Circ. 175, 27 pp., 4 figs., 1911. (See p. 10.) i

3 Burns, Findley. The Crater National Forest. U.S. Dept. Agr., Forest Serv. Bul. 100, 20 pp., 4 pls.,
1911. (See p. 12.)

4 Moore, Barrington, and Rogers, R. L. Notes onbalsam fir. Jn Forestry Quart., v. 5, no. 1, pp. 41-50,
1907.

98035°—Bull. 275—16 2

18 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE.

area investigated was 50 years in pure stands and 85 years when
mixed with hardwoods. They speak of butt-rot only, without
specifying the cause; unfortunately, the numerical basis from which
their figures are derived and their methods are not given.

The bearing on management of the age at which decay becomes a
seriously damaging factor is very rarely realized.

Clapp,' in speaking of incense cedar and white fir, clearly recognizes
that where these ‘‘inferior”’ species are also defective, ‘‘an attempt
should be made, at least in selection stands, to reduce their rotation
to one which will produce sound timber.”

In a recent article, D. T. Mason ? advocates a rotation of 100 years
for western white pine, on the ground that this species on the average
gives a maximum yield at this age and that from about the same age
fungi, and particularly imsects, generally succeed in doing a large
amount of damage.

It would serve no purpose to continue quoting the few and scat-
tered notes on the relation of age to decay, of a similar indefinite
nature found in American literature. By way of consolation, it may
be said that foreign literature does not abound very much more than
our own in definite information regarding this pomt. Although
the importance of the age at which forest trees are most liable to
attack from heartwood-destroying fungi is frequently hinted at in
German literature, Martin * is the only German forester who, to the
knowledge of the writer, has given more than a cursory discussion
of the relation of this age to rotation. In speaking of the immense
damage done in Prussian pine forests by Trametes pini, he attempts to
show from somewhat meager material how the increase in loss from
this cause should lower the rotation.

All computations of the amount of decay in German forests must
necessarily be incomplete, since from an early age all undesirable
individuals, including, as a matter of course, all trees with visible
signs of decay, are eliminated in improvement cuttings. The result
is a stand of a comparatively high degree of soundness. Even in
such stands Martin finds (p. 688) that in a given district the per-
centage of decay in wood good for fuel only in the 100-year class was
11, in the 120-year class 22, in the 130-year class 31, in the 140-year
class 37, and in the 160-year class 42. He points out that in unsound
stands the felling age must be lowered in order to secure the maximum
income. Martin ‘ again discussed similar ideas in 1910.

1Clapp, E. H. Silvicultural systems for western yellow pine. Jn Proc. Soc. Amer. Forest., v. 7, no. 2,
pp. 168-176, 1912. (See p. 175.) ,

2 Mason, D. T. Management of western white pine. Jn Proc. Soc. Amer. Forest., v. 9, no. 1, pp. 59-68,
"i aa Der Einfluss des Baumschwammes auf die Umtriebszeit der Kiefer. (Kritische Vergleichung
der wichtigsten forsttechnischen und forstpolitischen Massnahmen deutscher und ausserdeutscher Forst-
verwaltungen.) Jn Ztschr. Forst- u. Jagdw., Jahrg. 35, 1903, Heft. 11, pp. 685-690.

4Martin. Die Umtriebszeit der Kiefer in den Staatsforsten von Sear SSan, Bayern, Elsass- Lothringen,
Hessen und Anhalt. Jn Forstw. Centrbl., Jahrg. 54, 1910, Heft 7, pp. 363-387.

FOREST PATHOLOGY IN FOREST REGULATION. 19

Moller! touches upon the same point in a general way, without
trying to give the problem a more solid basis by exact material.
The following sentence is worth quoting:

Whilst the mean annual increment of the stand is slowly decreasing, the mean
annual increment of decay is steadily on the increase.

Here is the clue to the proper silvicultural valuation of cutting
cycles or rotation on a pathological basis. The time at which a tree
or a stand is to be cut may range from a comparatively low age to
the age of maximum production of lumber, according to the special
needs the forester has in view; but the upper limit of this range
should not lie beyond the period at which the gain from increment is
offset by loss from decay, irrespective of the ideal amount of timber -
a sound tree or stand might produce under favorable conditions.
Not to cut a tree or a stand in which increment is offset or exceeded
by loss from decay, where cutting is possible, constitutes an unsilvi-
cultural act. Gilman? informs us that silver fir in the Black Forest,
Baden, Germany, ‘‘is unable to stand a long rotation, for after 100
years the per cent of rotten timber increases greatly.’’ Here, the
influence of loss from decay on rotation is clearly shown; but it is to
be noted that the loss factor is derived in a purely empirical way and
is not based on exact studies. Hemmann? has published some
interesting and exact studies on the damage done by Trametes pint
in Scotch pine in a small area under regular management; that is,
where the disease was partly eliminated by improvement cuttings.

All this somewhat scanty European material, valuable though it
undoubtedly is for transatlantic forestry, is of very little help to us.
What holds good for the managed forest raised in a century of careful
nursing can not serve for more than a clue in genuinely or practically
virgin forests, whether they be located in the United States, in
Canada, in Chile, in India, or in Siberia. Again we are confronted
with the necessity of working out our own problems in our national
forests.

INFERIOR SPECIES.

Most of the timbered parts of the national forests, especially in the
West, are practically virgin, seriously injured by fire, composed of
even-aged or many-aged stands, and generally of more than one
species, which are more or less exposed to heart rot caused by one
or more specific fungi.

1Mdller, A. Uber die Notwendigkeit und Moglichkeit wirksamer Bekiimpfung des Kiefernbaum-
schwammes Trametes pini (Thore) Fries. Jn Ztschr. Forst- u. Jagdw., Jahrg.36, 1904, pp. 677-715. (See
Nice’ E.C. V. Forest types of Baden. In Forestry Quart., v.10, no. 3, pp. 440-457, 1912. (See
p. 452.)

3Hemmann. Uber den Schaden des Kiefernbaumschwammes. fn Allg. Forst- u. Jagdztg., Jahrg. 81,
pp. 336-341, 1905.

20 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE.

A systematic study of the relative position occupied by the heart-
rot factor in the economy of the forest presupposes a knowledge of the
morphology and biology of the specific fungi attacking the species of
which the forest ismadeup. Morphologically, most fungi of economic
importance are well known; biologically, there is much left to be
learned. The susceptibility of each host species to specific attack,
the age at which a given species becomes liable to attack by the
fungi adapted to live on it, the age at which a given species is liable
to suffer appreciable loss from this source, the relation of accessory
factors in the tree and outside of it to fungus growth, the relative
loss caused by each fungus in its specific host—all these are funda-
mental problems which must be solved for every important fungus
on every commercial species of our forest trees. So far, no definite
and clear, comprehensive answer can be given to any one of these
questions.

In determining upon a suitable starting pomt in the overwhelm-

ingly large amount of work before us, the question is that of deciding —

where such work is most needed at the present time.

Leaving out of consideration such species as bigtree (Sequoia
gigantea), which is never cut in national forests, and redwood (Sequoia
sempervirens), which is hardly represented in national forests, the
commercial timber of the national forests in the western part of the
United States is composed of coniferous trees, such as pine, larch,
spruce, fir, Douglas fir, hemlock, incense cedar, and western white
cedar. They constitute the goods the Government has to offer for
sale. Of these the pines cause least trouble. Pine lumber is eagerly
sought and pays good prices; moreover, the loss from decay is com-
paratively small. In Government timber sales there is never any

difficulty about pine timber; the more the Government has to sell

on a given tract the better. Not so with the so-called “inferior
species.”’

The term “inferior or undesirable species,”’ as it is generally applied,
is originally not a technical one. It is meant to designate those more
or less heavily represented commercial species which suffer from a
distinct prejudice on the part of the purchaser. If we could grow
sound incense cedar, for instance, there would be a ready market and
a good price for every foot, board measure, of it that the Government
could offer on timber sales. Distinction should be made between
species which actually yield technically poor lumber, even if sound,
and species, on the other hand, which when clear and sound yield
valuable material, but which are in general underrated by the pur-
chasing public on account of the extraordinary prevalence of decay.
An example of the first class is eastern hemlock. An example of the
second class is incense cedar, which, although of excellent quality
when sound, suffers from a very bad reputation among lumbermen,

SS) oy Mer hear

FOREST PATHOLOGY IN FOREST REGULATION. 91

because it is so very commonly rendered useless by dry-rot or pin-
rot. The numerically and economically most important species of
the accessible merchantable national forests in southern Oregon and
California are sugar pine, Jeffrey and yellow pine, Douglas fir, white
fir, and incense cedar. To these may be added, for certain localities,
lodgepole pine, red and Shasta firs, western larch, Sitka spruce,
western hemlock, and western red cedar. Of the six main species,
all three pines command good prices. They are comparatively free
from heart rot. White fir and incense cedar are in general so badly
defective that, as Clapp! states, they are “under present conditions
almost a drug on the market.’”’ Douglas fir stands in a class by
itself. The value of its timber is well known; in fact, it competes
with pine timber as far as quality for many purposes is concerned.
On the other hand, Douglas fir is in a far higher degree susceptible
to the attacks of several heartwood-destroying fungi, and, although
it is not classed among the inferior species, the very prevalence of
decay makes it less desirable than the pines, from a silvicultural
point of view. )

Incense cedar and white fir are frankly classed as inferior. Whether
this view is correct or not, we must reckon with it as a powerful factor
of influence in all timber sales where these species occur. They are
the lower grade by-products of the factory, the production of which
can not be stopped; it goes on in spite of what we may wish or what
we may do. The logical conclusion appears to be, then, to concen-
trate all efforts on detailed and comprehensive studies of the properties
of these by-products, desirable or undesirable, and to incorporate
the results in a rational system of management, rather than to attempt
to stop their production. The attitude of American foresters toward
these and similar species is undoubtedly changing. There was a
time when they were considered little better than weeds, to be gotten
rid of as soon as possible and to be kept out of the forest wherever
possible. This concept is giving room more and more to a considera-
tion of how best to regulate the unavoidable reproduction of both
species and how best to utilize the timber they produce.

The so-called inferior or undesirable species have their very definite
place in the ecology of the mixed forest, and many examples could
be cited from European experience of the disastrous results of an arti-
ficial change in representation of species and reduction of the mixed
stand to a pure stand composed of an apparently more desirable
species, without due consideration to the local soil and climatic condi-
tions. Greeley? seven years ago expressed the opinion that “‘it 1s

1Clapp, E.H. Silvicultural systems for western yellow pine. Jn Proc. Soc. Amer. Forest., v. 7, no. 2,
pp. 168-176, 1912. (See p. 175.)

2Greeley, W.B. A rough system of management for forest lands in the western Sierras. Jn Proc. Soc.
Amer. Forest., v. 2, no. 2, pp. 103-114, 1907. (Seep. 112.)

29 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE.

both impossible and undesirable to eliminate these species altogether.”
He specifically names white fir and incense cedar. Their ageressive-
ness makes it impossible to eliminate them, even if this were desirable.
But more than one species, not so many years ago considered inferior,
has now come into its own. ‘The history of the lumber markets of
Kurope and our own country shows conclusively that with closer
utilization necessitated by the growing scarcity of timber, the value
of lower grades, as well as of so-called inferior species, is advancing
more rapidly than that of upper grades or more valuable species. In
the case of incense cedar this evolution may be watched at the present
time. Up to avery short time ago incense cedar was ‘‘almost a drug
on the market;’’ now even very short logs when sound are utilized for
pencil wood spd priced accordingly.

Concentration of study on the inferior species, therefore, promises
the most immediately applicable results.

METHODS OF INVESTIGATION.
CHOICE OF SPECIES AND SITE.

Forestry is not interested primarily in the morphology and life
history of a given heartwood-destroying fungus. Such studies, though
indispensable and of the highest value, belong to an altogether differ-
ent realm of science. The forester thinks in terms of trees, not of
fungi; he concentrates on timber species to be protected or utilized,
not on parasitic organisms, however interesting they may be from a
mycological point of view. If forest pathology is ever to be of any
value to practical forestry, all work and all conclusions must be
focused on the tree, the species, as a producer of timber values and as
a member of the forest community.

The fact that the same species may be subject to serious loss from
several fungi and that the same fungus often works differently in
different host trees complicates the difficulties naturally connected
with all work for which a basis first had to be constructed. Partly
for this reason, the writer first worked on incense cedar, which, so far
as known, has only one heartwood parasite, Polyporus amarus. The
studies deel in the following pages were concentrated on white
fir, because its management presents, perhaps, the most embarrassing
problem of to-day on the Pacific coast and because, in by far the greater
number of cases, serious loss is caused by one fungus only, Echinodon-
tium tinctorvum.

After deciding upon the species to be investigated, the choice of
the sites for the study becomes the main question. One single type
will probably yield interesting clues, but the result can not with impu-
nity be applied to all sites and types within the range of the species.
It is clear that studies within what might be termed the merchantable
range of the species must be most important from a practical point of
view. But inside of the merchantable range the species is subject to

FOREST PATHOLOGY IN FOREST REGULATION. 23

so many varying conditions with regard to soil, climate, admixture of
the species, and representation that here again typical areas must be
chosen for independent studies. The more diversified the types
studied and the greater the number of trees per type and in the aggre-
gate, the more reliable will be the results.

The choice of the particular area to be studied is, of course, impor-
tant. The unit of study should be representative, typical for the
larger unit. In general it will not be difficult, with some care, to make
the proper choice.

The result of the writer’s studies, still unpublished, on the critical
age of incense cedar served to work out the methods which should be
applied in a modified form to the at present more important investi-
gations on white fir. Huropean precedent could not be used; Martin,.

Moller, and Hemmann worked on managed forests. New methods to
suit our conditions had to be evolved.

The only satisfactory result could be expected from careful dis-
section and analysis of as large a number as possible of trees of dif-
ferent ages. Unlike other investigative work, studies of this kind
can not well be carried out on timber-sales areas where the actual
felling and bucking of the trees is done by the purchaser. The
purchaser is none too willing to cut trees containing rot unless he is
compelled to do so; much less does he care to buck such trees, which,
after all, are the ones from which we must expect most valuable
instruction. He is not obliged to cut trees below a certain diameter
limit, which, of course, can not be left out. All this is particularly
true for the so-called inferior species, the handling of which often
comes so near being a loss to the purchaser that any additional cost
would work a distinct hardship. For the same reason it is impos-
sible to have the trees on timber-sales areas bucked in odd log lengths,
as dictated by the irregular and varying extent of the decay. As
will be seen, a few of the notes used for this study are incomplete,
because they had to be taken in connection with timber sales.

It becomes necessary, therefore, to carry on investigations of this
kind on representative areas chosen for the purpose and to have the
systematic cutting and dissecting of the trees done by crews, involv-
ing much work and a large expenditure. This way of handling the
problem has proved to be the only feasible one; and, as long as
immediate results may be expected, which if properly applied must
lead to very considerable savings as well as to progress in silvicul-
tural management and forest regulation, the expense and work seem
to be justified.

FIELD METHODS.

Before the actual felling begins, notes are taken first on the larger
forest unit of which the area to be studied forms a part, such as eleva-
tion, climate, water table, soil in general, history (lightning and

94 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE,

forest fires), composition, representation of species, ground cover,
possibilities of future logging operations as a first step toward regula-
tion, and local valuation of the species; more detailed notes of a
similar nature then describe the particular type and stand which is
the object of the study.

When a new species is to be studied, trees of all sizes and all con-
ditions must be cut. It is absolutely necessary constantly to guard
against picking out trees either because they appear sound or because
they are liable to contain decay. According to the attitude of mind
of the investigator there will always be a tendency, conscious or sub-
conscious, to think of the final result and accordingly to choose par-
ticular trees for felling. The personal factor must necessarily

influence the result of the equation and can not be warned against too ~

emphatically.

Correctness and accuracy in detail are the basis of any scientific
work worthy of the name. Where the one chief aim is to substitute
reliable figures for guesswork, to establish facts, from which con-
servative interpretation may derive certain working rules, observa-
tions and measurements can not go too far in detail and exactness.
On the basis of experiences in the incense-cedar studies, a printed
sheet was prepared, to be used in a loose-leaf binder of pocket size,
in which a set of standard notes was to be entered. Each sheet
contains the notes for one tree only.

The first notes to be taken on a tree chosen for analysis are general;
they are taken before the tree is felled. Slope, exposure, soil com-
position, and moisture are taken for the individual tree; the next
notes concern the outward appearance of the tree, crown class, as
far as can be determined, condition of the bole, whether forked or
leaning, presence and degree of fire scars, resin flow on butt or bole,
swellings, sporophores of fungi, condition of the crown, development
and state of health; in short, all notes that can and should be taken
from the standing tree. nae this time an assistant takes the
diameter breast high and sets the fellers to work. Thenotes on the
bole and crown are completed when the tree is down. They concern
the presence of mistletoes or needle diseases, witches’-brooms of any
kind, their number and relative importance, presence and extent of
lightning injury, condition of top, and similar data that might have a
bearing on the pathology of the species. It goes without saying that
the tree is felled at the regulation stump height of 18 inches, never
higher unless absolutely unavoidable. The assistant now measures
the height of the tree from the ground and counts the age at the
stump. ‘This, of course, does not give the true age; but instead of
adding, more.or less at random, a small number of years corresponding
to the height of the stump, it seems advisable to accept the count
at the stump as the age. The fewer the figures based on an estimate

FOREST PATHOLOGY IN FOREST REGULATION. 95

that are included in our computations, the narrower will be the
margin of error. Besides, in practical work, the age is generally
counted at a stump height of 18 inches, and, since for all purposes of
management we have to deal with the standing tree where diameter
is the only indicator of age, it is of little importance whether the age
counted is absolute, within narrow limits, as long as all figures are
directly comparable with each other. Moreover, in practice it is
impossible to have all trees cut at exactly 18 inches. With the
ereatest of care, the stump height will vary. It is an easy matter,
where desired, to add a number of years corresponding to stump
height as soon as reliable figures, which now are lacking, are obtainable.

The limbs and branches are now lopped off and the brush piled for
burning.

In the bucking of the bole some judgment should be used, guided
by the object of the study. We want to find all traces of decay in
the bole and take exact measurements of them. Obviously, then,
the aim of the dissection must be to open up the tree in such a way
that no decay can escape the observer. It would not do, therefore,
to buck all trees in even log lengths of the usual commercial measures.
A straight, clean bole without any blemish whatever is bucked in
16-foot logs, which then are individually split; this will, as a rule,
bring out any hidden decay. Both the cross sections at the opened
surfaces of the split wood must be searched very carefully for any
abnormal sign. This makes full knowledge of the properties and
aspect of the normal wood a prerequisite. In the beginning, there-
fore, it is advisable first to study very closely the sound, normal wood
of the species, until the operator is able to detect at a glance and
automatically any deviation from the normal. The success of the
study hinges upon the development of personal skill in judging wood.
In order to prevent the dulling of this sense during the course of the
work, check studies of perfectly sound wood will prove very bene-
ficial. Any slight real or apparent deviation from the normal in
physical properties or aspect, particularly in color, must be followed,
of course, to its source.

Trees without any blemish are rare; generally there is either some
irregularity in form, fork, unusually heavy branching, or there are
sporophores of fungi, badly healed-over branch stubs, swellings, de-
pressions, catfaces, fire scars, lightning scars, or frost cracks and frost
ridges. In choosing the proper places for bucking, it is generally
advisable to start at the most salient malformations or defects; they
will often lead to the focus of decay, if there is any. In case of fail-
ure, the less prominent defects are investigated, and so on down the
line until there is no doubt left that no decay is present in the bole.
Particular attention must be given to branch stubs, which, by extend-
ing through the sapwood to the outside of the tree, offer an easy

26 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE.

entrance into the heartwood. After infection has taken place in
this manner, the mycelium grows im the heartwood. Before sporo-
phores are formed it is often impossible to locate the presence of
the mycelium in the tree. This is particularly true for quite young
fungus plants, and the possibility that the begmnings of decay
may be hidden im a log, both ends of which are perfectly sound,
must ever be present in the mind of the operator. It is impos-
sible, except by mere chance, to detect the very first stages m the
field. As soon as the fungus plant, the mycelium, has reached a
certain stage of development, represented by visible alterations of
the wood, there is no excuse for overlooking it. As a rule, the oldest
part of the focus of infection shows the strongest evidence of
fungus growth expressed in what we call decay. - Decayed stubs
are a valuable index as to decay im the tree, although there are cases
where, for unknown reasons, the infection does not, or only very
slowly, result in more extended decay. Duesberg * has advocated the
location of infected trees by the presence of diseased branch stubs. —
Such decayed branch stubs may also correspond to that stage of —
development of the mycelium-just before the formation of sporo-
phores through the stub takes place. Im this case also decayed
branch stubs will be most valuable in detecting heart rot in the bole.

If decay is found, it is followed throughout its entire extent by
splitting the logs with wedges and with the ax. To avoid this often
very tedious and time-consuming work, splitting with black powder
has been tried, with rather unsatisfactory results. In partly decayed
logs the splitting is very irregular, and the wood surfaces are badly
stained and blackened, the stain generally interfering with the mspec-
tion of the wood. When the full extent of the decay is determmed,
notes are taken on the character of the discoloration or decay and on
the stage of development, and the extent is carefully measured. For
studies of this kind it will often be sufficient to note the extent in
length in linear feet, under the assumption that in low-priced species
any lumber that might be cut from an affected part of the bole will
not pay for its transportation to the mill. In higher grade species
the lateral extent must always be considered.

This complete and detailed dissection usually allows the tracing of
the decay to some poimt of entrance, whether fire scar, lightning ~
wounds, frost cracks, or branch stubs. The result is entered on the
sheet. Finally, any notes not specially foreseen on the sheet are
entered under “‘ Remarks.”

As a general principle, all observations that can be expressed
numerically must be given im figures. It is essential that all esti

tDuesberz. Das Auisuchen von § aU in Kieiernbesianden vor der Ausbildung von
Pruchtiragern. In Ztschr. Forst- u. Jagdw., Jabrg. +4, Heft 1, pp. 42-48, 1912. Reviewed m Foresizy
Quart., ¥. 11, p. 251, 1913.

FOREST PATHOLOGY IN FOREST REGULATION. Diy

mating should be reduced to a minimum. In order to render this
unavoidable minimum, which undoubtedly constitutes a source of
error, aS innocuous as possible, the operator must constantly be on
the guard against any variations of his standard by which he is guided,
consciously or subconsciously, and from time to time check up on
this standard. The notes to be taken by estimate concern degree
or grade. Soil moisture, seriousness of wounding by fire, degree of
resin flow (whether light or heavy), condition of crown (for example,
unhealthy color or thin foliage and the presence and degree of needle
diseases in their bearing on the thriftiness of the tree), degree of dis-
coloration of the wood—all these can be expressed in figures only
with difficulty. Even if a scale of 1 to 10 is adopted for these pur-
poses it is extremely difficult to decide whether the change of color
of the wood under the influence of the fungus is to be classed as 6 or 7.
The writer therefore has adopted a simpler system, which, while far
from being exact, at least avoids gross errors and at the same time is
graphically clear and sufficiently elastic to cover all cases of impor-
tance. It expresses the information asked for on the sheets with the
aid of crosses and dashes. A dash after ‘‘Fire scars,” for instance,
is negative; there is no fire scar. One cross, x, is simply affirmative;
there is fire injury, but it is not to be considered as serious. Two
crosses, xx, indicate that the fire injury is fairly bad, distinctly
beyond the mere presence of an injury. ‘Three crosses, xxx, em-
phasize the damage; the fire injury is unusually large and severe. By
putting the crosses in parentheses, (x), or x (x), or by hyphenating two
consecutive degrees, x-xx, intermediate grades may be given when
desirable; and finally the last grade, xxxx, can be used in very extraor-
dinary casesfor emphasis. In general, x, xx, and xxx will answer the
purpose. Thus, the estimate is really reduced to a simple system of
three grades, which allows for a more constant mental reference to
the standard. Whenever necessary or feasible, special notes or meas-
urements are entered after the crosses. This system is also used in
our tables. With the exception given above, all these notes are
taken by the chief of the party. Meantime, the assistant counts the
age and diameter at every cross section, takes growth measurements,
measures the width of sapwood and the length of the sections, and
records such other data as may present themselves in the course of
the work.

In complicated cases, drawings or notes are added on blank sheets
bearing the numbers of the trees.

PATHOLOGY OF WHITE FIR.

The studies on white fir presented in the following pages are not
meant to give definite results valid for the entire range of the species.
They were primarily intended to develop the more practical methods

28 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE.

to be employed and secondarily to gain reliable material to be used
in a chain of similar studies on different types, from which conserva-
tive interpretation may derive final conclusions. They are given
here as examples only, as illustrations of the general considerations
presented in this bulletin. Since making these studies, others on a
larger scale and on different types in different parts of the range of
white fir were carried out with improved methods durmg the summer
of 1913.

A short review of our present knowledge of the pathology of white
fir will be of help in the discussion and interpretation of the data
presented in this paper.

White fir (Abies concolor (Gord.) Parry) can not be called a decadent
species; on the contrary, it is very aggressive and possesses remarkable
elasticity and resistance to injurious influences. Its tolerance to
shade is well known. Not only does it survive dense shading to a
high age but it responds readily to light and then reaches considerable
diameter and height in perfect health, provided it has not been seri-
ously wounded and infected. The oldest tree examined in this
study was 258 years old; it was badly suppressed and but 67 feet
high with a diameter breast high of 17.4 inches. In the trees tallied
between the ages of 130 and 140 years, the diameter breast hich
varied from 8.8 to 30.7 inches and the height from 47.5 feet to 125
feet.

In speaking of tolerance which allows suppressed trees to reach a
high age under the most unfavorable conditions and with a minimum
of annual growth, the behavior of the species with relation to light
is generally meant; but this toning down of the life functions of the
tree, visibly expressed in growth, very often has nothing to do with
lack of light. A tree may become suppressed to the lower limits of
its tolerance by any agent severely attacking any of its vital organs.
Of these, the organs of the crown are both most easily accessible and ©
most sensitive; hence, the heavy damage resulting from a serious
attack by insects devouring and killing the foliage or by leaf-inhabit-
ing fungi. White fir is subject to a disease of the foliage caused by
Lophodermium nervisequium, which often kills all needles except
those of the current year’s growth. The !oss in foliage surface, and
therefore in photosynthetic capacity, may suppress a white fir just
as lack of light would. Witches’-brooms caused by Peridermium
elatinum on white fir are not common. They are very rarely of such
development on the tree that they should be classed as an injurious
factor to be reckoned with. Incidentally, it should be mentioned that
the swellings and cankers so commonly connected with Peridermium
elatinum on Abies pectinata in Europe are unknown in Abies concolor.
On the other hand, very similar swellings and cankers caused on white
fir by Razoumofskya abietina Englm. are extremely common. The

FOREST PATHOLOGY IN FOREST REGULATION. 29

actual connection is readily established by either the living mistletoe
erowing out from. the swellings or by the small cuplike remains of
the stem bases. The swellings render the affected part of the bole
unmerchantable. When they break open into what are termed
cankers, infection by fungi very readily takes place and a focus of
heart rot forms, very much as in the case of Peridermium elatinum
on Abies pectinata where Polyporus hartigu and Agaricus adiposus *
commonly start from cankers caused by the rust fungus.

The mistletoe cankers very often are the cause of white-fir stems
breaking off in a storm, just as Peridermium cankers affect Abies
pectnata. This mistletoe is more generally found in the middle or
lower parts of the crown; infection takes place only on the very
youngest twigs.

Another mistletoe (Phoradendron bolleanum (Seeman) Coville)
nests high up in the top. It often kills the leader; volunteers spring
up, which are frequently killed in their turn. Considered in its rela-
tion to the totality of leaf functions, the loss from a killing of the
leaders can not be very serious, although it may count in combina-
tion with other injurious agencies. The same is true for the host of
minor parasites and injuries to which the peripheral growing parts—
‘in contrast to the column of wood—are exposed.

We have seen that the wood of the living tree itself is generally
immune to attack from heartwood-destroying fungi as long as it is
protected by bark and sapwood. ‘The few exceptions, it seems, are
of no great importance in the case of Abies concolor. Pholota flam-
mans 18s not uncommonly found in white fir and seems to take the
place of Armillaria mellea. The exact damage done is still to be
studied. Homes annosus is not yet reported on white fir to the
writer’s knowledge. Polyporus schweimitzu is not common on the
species. All other fungi causing decay can not enter the living
tree except through some opening, as far as is known at present.

In white fir, as in other coniferous trees, small superficial wounds
are readily covered over with resin from the bark; this natural dressing
does not allow fungus spores to germinate or the hyphe to develop
after germination. Now, white fir is distinctly poor in resin. Large
superficial wounds may therefore prove to be more serious. If the
bark is destroyed, the cambium is killed and the sapwood dries out
and cracks. Through these cracks air gains access to the interior of
the tree and must in some way alter the chemistry and physics of
the heartwood. The spores of heartwood-destroying fungi lodge in
the cracks and upon germination may find a well-prepared substratum
in the heartwood. Fungi, like all plants, make certain specific
demands as to the chemical composition, water content, oxygen,
etc., of the substratum they live on. Given the proper temperature

1 Hartig, Robert. Lehrbuch der Pflanzenkrankheiten, Ed.3,p.153. Berlin, 1900

30 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE.

and the species of wood on which, for instance, a fungus like Echino-
dontium tinctorium (Indian-paint fungus), the most common de-
stroyer of white-fir heartwood, can exist, its growth will still be
dependent on the presence of heartwood of a certain character and
on the water content of the heartwood. This is evidenced by the
fact that decay is so commonly found in concentric development at a
certain distance from the sapwood. The heartwood contains water
in varying degrees, although it does not lift water like sapwood.
But there is nothing surprising or irrational about the assumption
that the water content of the heartwood will depend more or less
on the water movement in the sapwood. The water in the heart-
wood of conifers is found in the membranes of the tracheids, not in
the lumina. In a normal sound tree, heartwood of a given age and
diameter surrounded by sapwood of normal width, corresponding to
a certain crown development, will contain approximately a standard
amount of water. Decrease in crown activity through some cause
or another (suppression, injury to the crown, etc.) will soon be
expressed in a rapid progress of heartwood formation, leaving only a
narrow strip of sapwood, through which very much less water will
move upward to the crown than in the normal tree. We may safely
assume that the water content of the heartwood will change to a
certain degree with the amount of water moved upward in the sap-
wood. The water content of the sapwood changes, furthermore,
with age, and also with the season. Both changes must also appear,
although in a far less degree, in the heartwood. Minch! has em-
phasized, in a series of very interesting papers, the relation of wood-
inhabiting fungi to the water and air content of the host tissues.
Water-logged tissues are inaccessible to these fungi; a certain mini-
mum of air, as Miinch expresses it, must be present in the tissue in
order to allow the development of the hyphe.

Variations in the water contained by imbibition in the cell mem-
branes must influence the degree of humidity of the air in the lumen
of the cell itself; it is quite probable that this factor also plays a réle
in the distribution of hyphe in the wood.

What percentage of water in the cell membranes and of air in the
lumina of the heartwood presents the optimum for the development
of Echinodontium tinctorium and other similar fungi we do not know;
but evidently there must be an optimum, a maximum, and a mini-
mum. Any factor influencing the quota of water and air in the heart-
wood must, therefore, be of great importance. Cracks in the sapwood

1 Miinch, Ernst. Die Blaufiiule des Nadelholzes. In Naturw. Ztschr. Land- u. Forstw., Jahrg. 5, 1907,
Heft 11, pp. 531-573; Jahrg..6, 1908, Heft. 1, pp. 32-47, 33 figs.; Heft. 6, pp. 297-323.

Miinch, Ernst. Untersuchungen tiber Immunitaéat und Krankheitsempfanglichkeit der Holzpflanzen.
In Naturw. Ztschr. Forst- Land u. w., Jahrg. 7, 1909, Heft 1, pp. 54-75, 5 figs.; Heft 2, pp. 87-114; Heft 3, pp.
129-160.

Miinch, Ernst. Uber krankhafte Kernbildung. In Naturw. Ztschr. Forst- u. Landw., Jahrg. 8, 1910,
Heft 11, pp. 533-547; Heft 12, pp. 553-569, 2 figs.

FOREST PATHOLOGY IN FOREST REGULATION, 31

reaching to the heartwood admit air, and by evaporation change the
water content of the heartwood; by oxidation, changes in its chemistry
probably also take place.

The change must necessarily be intensified, the more serious the
injury. Wounds exposing the heartwood heal over very slowly, and
the heartwood which receives all its water from the sapwood must be
modified very markedly in its chemistry and physics, particularly in
its water and oxygen content, by the long exposure to the air. More-
over, from the time the injury happened until the time the wound is
completely healed the heartwood is directly exposed to inoculation
from spores of wood-destroying fungi adapted to white fir. Although
the production of spores by a sporophore is enormous, by far the
ereater number are carried by air currents to places where they can.
not germinate for lack of moisture; many are intercepted by the
natural screen (‘‘forest screen’’) formed by the foliage and trunks of
uninjured trees or by trees to which they are not adapted, and only a
very small number finally land in the cracks of exposed sapwood or
on exposed heartwood of white fir of the proper age. Of these, again,
a very small percentage find temperature and moisture favorable for
germination. This explains the fact that so many trees, although
‘badly wounded, are not infected. But it stands to reason that every
year during which the heartwood remains exposed adds to the danger
of the tree becoming infected.

By far the deepest wounds are caused by fire. Although in white
fir the danger in repeated fires feeding on the pitch flow following a
first injury is comparatively slight, and although the lack of resin in
the wood does not favor the hollowing out of the interior of the tree
as it does in yellow pine, fire frequently causes very long wounds, which
reach into the heartwood.

Spores can gain entrance to the heartwood through open frost
cracks. Low temperatures and sudden drops of temperature are
common throughout the range of white fir. Inside of the range they
are more or less confined to certain localities and zones.

Lightning in white fir generally causes more or less superficial
wounds. The peculiar injuries to be traced to ightning in white fir -
present many interesting features. Here we are only interested in
injury which might lead to the infection of the heartwood. As in
yellow pine, lightning sometimes tears long strips of bark off the tree
and leaves the cambium and sapwood unprotected. In such cases
both die and dry out, with the result that cracks in the sapwood lead
into the interior of the tree. Smaller superficial hghtning wounds
locally kill the sapwood, which is very commonly attacked by second-
ary fungi, which do not do very serious damage. However, logs with
lightning injury of this kind are liable to be thrown out as culls,
although they generally contain some sound heartwood.

32 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE,

Other causes of serious wounds are comparatively rare. Occasion-
ally a falling tree will brush off part of the bark of its neighbor. If
the wound is large, the exposed sapwood dries out, cracks, and the
heartwood becomes exposed. Very rarely a living tree shows signs
of early girdling by rodents. Girdled trees as a rule are killed within
a short time. |

With very few exceptions the entrance of the fungus into the tree
can be traced to one or more of the wounds just discussed. Occa-
sionally, however, a tree showing no wounding at all is found to be
decayed. In such cases the only means of entrance for the wood-
destroying organism is through knots.

White fir prunes itself very poorly; the wood of the twigs is tough,
hard, and resistant, and the branches do not break off very readily.
Later, dead twigs may break off; in the cracks of the wood of the
stubs spores of fungi may find proper conditions for germination and,
once established, use the pin knot as a bridge from the exterior of the
tree through the bark and sapwood into the heartwood. This is par-
ticularly true for twigs in which heartwood formation has begun. In
this sense the opening afforded to fungi by a pin knot that is not
healed over may be likened to a wound. The opening formed by the
pin knot, however, is too small to materially influence the chemistry
and physics of the heartwood of the tree. ©

White fir is not exposed to a great number of heart-rot fungi.
Polyporus schwevmte is not common. Polyporus sulphureus and
Trametes pint are rather rare. The parasitism of Yomes pinicola is
not fully established, at least not in white fir. The writer has found
it on thrifty sugar pine in central California, where it was undoubt-
edly parasitic in the sense of attacking the sound heartwood of living
trees through an open fire scar and extending toward the sapwood.
- There would be no incongruity in assuming that it may also occur
parasitically on white fir; m fact, a number of observations rather
speak for the correctness of this assumption. :

By far the most serious danger to white fir throughout its range
comes from Echinodontium tinctorium Ellis and Ev. This fungus
seems to be particularly adapted to Abies concolor and does not
appear on many other species. In California it is, though not very
often, found on Abies magnifica shastensis and also rarely on Douglas
fir. This fungus must therefore be considered as the chief fungus
enemy of white fir. The sporophores are easily recognized. They
are rather large, from 2 to 10, 12, and more inches in width (measured
horizontally from side to side where they are attached to the tree),
distinctly hoof shaped, with a black, dull, cracked, rough upper sur-
face, and a lighter, grayish, level under surface, which is thickly set
with hard, coarse spines. In young specimens the under surface is
whitish and rather dedaloid prior to breaking up into spines. The

FOREST PATHOLOGY IN FOREST REGULATION. ao

interior of the sporophore is vividly rusty red. This rusty color is
most characteristic of the fungus and repeats itself very often in the
decayed tissues of the host. The sporophores are never formed on
the bark of the tree; invariably they appear from the under side of
stubs of dead twigs or branches, and commonly the rusty color can
be followed through these stubs or knots. As the sporophore is
nothing but the fruiting body of the mature fungus plant living in
the heartwood of the tree, which alone it is able to attack, every
sporophore is a certain sign of far-reaching decay in the tree. The
typical rot may be characterized as a stringy brown rot. Wood in
this stage of decomposition is brown, with rusty reddish streaks, and
becomes distinctly fibrous and stringy. Following the rot away from
its maximum of development, we find wood still brown, with rusty
streaks, but quite firm. Farther away, the brown color becomes less
noticeable, the rusty color disappears, and finally we come to a point
where the wood seems to be sound enough to be sent to the mill. A
little care exercised in examination, however, will show in this seem-
ingly sound wood the presence of small light-brownish spots and dis-
colorations, particularly in the summer wood, intermingled with hor-
izontal burrows, which at first glance could almost be taken for very
shallow insect burrows. The burrows are not easily detected on a
cross section. The small brown spots, which give the wood a faintly
brown, mottled appearance, cause the entire cross section to beslightly
darker than normal and discolored; but they show up very much
more clearly in a longitudinal section. A small piece pried out of the
end of the log with a hatchet or strong knife gives sufficient informa-
tion about the real state of health of the log. This timber at present
invariably goes to the mill and without doubt furnishes the lumber
that, after being sawed, dries out and by becoming brittle causes the
well-known prejudice against this species. It is often characterized
by a peculiar sour smell and by a spongy consistency of the wood.

Cull from decay in white fir, therefore, includes not only typical
rot but also this discolored material, which, although not distinctly
rotten, is already under the influence of the advance guard of the
fungus mycelium and will become completely decayed later on. For
this stage of incipient, or, better, latent decay, the writer proposes
the term ‘‘advance rot,’ which is used throughout this bulletin.

DESCRIPTION OF AREAS.

The three areas chosen for investigation are located on the Crater
National Forest, in southwestern Oregon, all of them in the neighbor-
hood of the Upper Klamath Lake, a large shallow basin with vast
swamps, into which unusually large springs of clear cold water empty
themselves. Very few streams of running water come from the

98035°—Bull. 275—16——3

34 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE.

surrounding mountains. Dense timber frames the swamps and ex-
tends up the slopes to the mountain tops. The elevation of all three
tracts varies from 4,150 to about 4,400 feet. Low winter tempera-
tures and severe lightning storms are frequent in the entire region.
Two of the tracts, the Pelican Bay Lumber Co. sales area and the
Odessa ranger-station tract, are situated on the west shore of the lake.
They are about 2 miles apart and present conditions so o much thesame
that they can be considered as one.

The Pelican Bay tract on the west side of Pelican Bay lies, as far as
the area covered by this study is concerned, along the slopes; the
aspect is east to northeast. That is, it is exposed to cold wintry
winds, sweeping unbroken across Upper Klamath Lake. We may |
expect frost 1 injury. The volcanic soil is fairly deep and loose; the
humus layer is rather shallow. There are no rock outcrops. The
underbrush is composed of Ceanothus, manzanita, and some chin-
quapin.

The Odessa ranger-station tract is far less steep than the Pelican
Bay tract. A considerable part of it is a gentle slope, almost level.
The general aspect is north; presumably the tract is less exposed to
sweeping winds of very low temperature. The soil is decomposed
lava, but richer in humus than the Pelican Bay tract. Outcrops of
rock are frequent. There are a number of large springs in the neigh-
borhood. The underbrush is rather dense and is composed of
Amelanchier alnifolia, Ceanothus velutinus, with some Saliz sp.; the
ground cover consists of Ceanothus prostratus, Berberis aquifolium,
and Symphericarpus racemosa.

The third tract, the Otter & Burns sales area, lies about 15 miles
north of the north end of Upper Klamath Lake. The tract is level,
the soil very loose, sandy, decomposed pumice, with no indication of
rock. Under the influence of the Fort Klamath Valley with its
swamps, the atmospheric humidity is rather high, as is evidenced by
the rich lichen flora, Alectoria fremontit beng common. Thus the
immediate surface of the soil is kept damp, and litter disintegrates
very rapidly. The humus is about 1 to 2 inches deep; the soil imme-
diately underlying it is remarkably well drained. The rapid humifi-
cation in the top layers favors the development of mycorrhiza on the
roots of white fir in surface strata. White fir seedlings show a thick
matting of mycorrhiza, confined to the same strata of a certain humi-
fication, and a very long taproot seeking water. Yellow-pine seed-
lings also develop a taproot, but the mycorrhiza rootlets are found
at a greater depth than those of white fir. They are not as closely
bunched as in white fir and are distributed over a larger area in a
vertical direction. The underbrush is formed by Ceanothus velutinus
of medium density, from 4 to 6 feet high, in a uniform cover.

FOREST PATHOLOGY IN FOREST REGULATION. 35

On the two tracts near the lake white fir is mixed with yellow pine
and Douglas fir, a little mcense cedar, and a very little sugar pine.
On the Otter & Burns tract the stand is composed of yellow pine
and white fir, with occasional lodgepole pine.

On each tract conditions were more or less uniform, differences in
elevation were negligible, and neither deep gulches nor steep slopes
had to be figured with as disturbing factors. Allin all, 160 trees were
dissected and notes taken on all factors which possibly would have
some bearing on the subject of this bulletin. In operating, the tracts
were not clean cut; that is, not every white-fir tree in the area was
felled and examined, since it was not the object of the study to estab-
lish a cull per cent for that particular region.

The data obtained are from selected trees. On the Pelican Bay
Lumber Company’s sales areas the trees, of course, had all been
marked by the Forest Service officers in charge; on the Otter &
Burns sales area some trees were marked, and others were felled inde-
pendently of marking. On the Odessa ranger-station tract all trees
examined were felled for our special purpose. The representation of
trees of different ages, diameter, and height classes on the three tracts,
therefore, is not expressed correctly by the number of trees examined

on each tract.
LOCAL PATHOLOGY OF WHITE FIR.

The pathology of white fir in the Upper Klamath Lake region is
comparatively simple. Of injurious factors of an manimate nature,
fire, lightning, and frost are common.

Very few species of fungi inhabiting living white fir are found on
the three tracts. As we are mainly interested in the pathology of the
the wood, the occasional occurrence of Peridermium elatinum and of
Lophodermium nervisequium becomes an entirely negligible factor.

Of heartwood-destroying fungi in living white fir, Hchinodontium
tinctorium is by far the most common, and sporophores are numerous.
About 75 per cent of all cases of decay were due to this fungus.
Occasionally decay may with some certainty be traced to Fomes
pinicola. In one case a sporophore of an Irpex was found in the
decayed hollow of the trunk. Trametes pint is missing altogether,
though found occasionally on neighboring sugar pine. Decay caused
by Polyporus schwevnitzeit was found in several cases, never with
sporophores.

In other cases the decay was too indefinite to allow an identification
of the fungus causing it. This is particularly true for the many cases
of localized advance rot connected with scars from diffused lightning.

The preponderance of E'chinodontiwm tinctorvum, especially in con-
nection with really damaging decay, is so marked that in this study
all important cases of decay are considered to be caused by this
fungus.

36 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE.

A study of the fungi destroying down timber lies beyond the scope
of this bulletm. The only practical aspect of their activity lies in the
fact that down timber, limbs, branches, twigs, and needles are decom-
posed very rapidly.

It is evident that all the pomts discussed in the preceding pages
must be kept in mind in taking field notes. But this is not sufficient.
Work of this kind has very much the character of an exploration;
surprises and discoveries are possible at any point of the road, and it
is therefore indispensable constantly to be on guard in order not to
overlook any phenomenon worthy of observation.

TABULATION OF DATA.

The next step is proper tabulation of the data obtained. The three
tracts were so close together and conditions so similar that they were
considered as one, and all notes were combined. Separate interpreta-
tion of the notes of each tract showed differences only in detail. The
procedure was as follows:

A first table was compiled from the field notes giving all important
data as well as all such data which might have a bearing on the
subject of this bulletin. As we are particularly interested in the
problem of the relation of age to infection and subsequent decay, a
second table gave the same notes arranged progressively by the ages
of the trees examined. This table formed the basis for further
operations.

The youngest tree dissected was 60 years old, and it is the first to
show decay (Table I). The possible age limit of infection is therefore
at least 60 years; it is probably lower. But in practical forestry we
do not seek an answer to the question of the earliest age at which a
tree might become infected, interesting as this is from a mycological |
point of view, but, rather, from what age may we with reasonable
certainty assume that serious decay becomes so prevalent as to
distinctly impair the merchantability of the timber.

The tree in question has a diameter breast high of 10.1 inches; it is
44 feet high. A healed-over broad scar still visible externally at 2 to
8 feet above ground corresponds to an internal scar, reaching from 2
to 10 feet, and was probably caused by lightning. The injury happened
22 years ago and was distinctly superficial; the deterioration, in the
form of a slight discoloration of the sapwood, follows this scar only,
without extending any farther into the wood. This superficial dam-
age does not render the affected logs unmerchantable. For practical
purposes, therefore, such cases may be disregarded; they are negli-
gible. In the interpretation of our material, the character and the
degree of the damage must be considered with special relation to their
bearing on the merchantability of the lumber. Not only the extent
in longitudinal direction but also the distribution of the decay over

FOREST PATHOLOGY IN FOREST REGULATION. 87

the cross section enter into the valuation of thisfactor. In the present
study, the lateral extent of decay, the distribution over the cross
section, was estimated, as it is in practical scaling. Actual measure-
ments are difficult to take, on account of the immense variability of
the decay. In Table I, decay which neither in lateral extent nor in
degree was considered sufficient to seriously injure the merchanta-
bility of the part affected was marked as negligible. The longitudinal
decay was taken in linear feet, and the entire length was considered as
affected, in order not to complicate the computation too much. We
must distinguish between superficial decay of the sapwood and the
more serious decay of the heartwood. Figures of superficial decay
of sapwood are given in brackets (Table I, column 5).

The next trees are sound. A negligible decay occurs in a tree 73
years old. Its diameter breast high is 11.2 inches; its height 58 feet.
The light decay started from an internal scar, caused by fire 23 years
ago and healed over in 5 years, but it remained in close proximity
to the scar without spreading. Again, a number of sound trees fol-
low. Then the first more serious decay appears.

The tree in question is 84 years old, its diameter breast high only
8 inches, height only 45 feet. Both fire and lightning have played
havoc with this individual. An open scar extends from the ground
21 feet up the bole. The tree is quite evidently not in good health,
the sapwood is very narrow, and the crown is lopsided and very short.
Even in this case the decay follows more or less the open scar, but it
is sufficiently serious to cull the affected parts in so small a tree; in a
larger and thriftier one the damage would be called more or less local
and a nominal deduction made in the scale. From a lumbering point
of view this tree may be disregarded.

So far, all trees considered had been either thrifty or not very
seriously wounded. Here we have an obviously suppressed, un-
healthy, and badly wounded tree; it presents at the same time the
first case of decay that is not to be called negligible. The following
trees are sound; then follows a negligible trace of decay in an 86-year-
old tree, badly suppressed (diameter breast high 4 inches, height 13
feet), grown in dense shade, with a remarkably small crown and with
a healed-over frost crack, but no other wounds. After several sound,
fairly thrifty trees follows a tree 87 years old, badly suppressed
(diameter breast high 7.8 inches, height 39 feet), with a very short
crown, wounded badly by fire and lightning (open scar from ground
to 18 feet), and with decay following more or less closely the open scar.

From these and the following trees, it appeared possible that with
increasing age the crown class, or rather the degree of suppression and
dominance, played a réle with regard to the extent and seriousness of
the decay. Preliminary studies on incense cedar had given the same
indications. It seemed desirable, therefore, to express this degree of

38 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE,

suppression and dominance by a figure which would allow direct com-
parison between trees of the same age. Height alone would be mis-
leading. Volume table figures can not be used, since they are based
on sound normal trees. The relation of height to diameter breast
high, expressed in total volume, was thought to be a safer index.
The object being to obtain directly comparable figures by ages and
not the exact volume, the tree was considered as a perfect cone over
the stump, at which we had taken the ages. Fromsomewhat scanty,
but individually reliable notes, the diameters at the stump (diameter
outside bark 18 mches) were obtained, and from these and the height
the volume of the cone in cubic feet was computed.

TaBLe I.—Fundamental data on the pathology of the white fir.

| Volume (cubic feet).
: - Of rot, in- :
No. of iree. Age. Average | cluding ad- Character of wounds.
For each | for trees | vance rot
tree. ofsame | (perceni-
age. age of total
volume).
1 2 3 4 BY 6
5 eae. rm seer nari Ope | 60 11.3 15(?)| 134.2] | Lightning.
Ul ee ee ee ee eS 69 25.1 Lit) = —- Leader healed in.
CY Ua a ee, ie ep ee 71 11.8 20 — No wounds.
es ee aos oe een 72 18.8 20 — Very slight lightning.
ty ae a a A eee 72 dod. 20 _— No wounds
BAe Se a See S Te 18.5 20.3 12.7 | Fire; healed.
ch Pe = SO oN eae ayaa alee 7 23.0 21 — Lightning.
Bde ew re et ee 78 12.4 2S —_ Very little lightning.
aes Soe oe Fee ee See 80 31.4 2 _ Do.
150 i. feet est eee 81 45.5 24 — Several scars.
i het gee ap aa AES a 82 29.9 24.1 — Lighining (?).
Se FACE ta ets $3555 ee 84 44.4 24.6 — No wounds.
Os Fn eee Se ee 84 8.9 24.6 §2.8 | Fire, open; lightning.
ASO sh Vo SS SS ES 84 25.6 24.6 _- Little lightning.
Be See ae ee 85 5 25 — No wounds.
< Ey (Ree eee ee an ae 86 33.7 26 — Little lightning.
cE eee aye een. ee 86 6.3 | 26 | Negligible. | Frost ridge.
G8Ge Sc Pts eR ree ee 86 22.8 26 — No wounds.
WAR A Ee eer ea Bens ou 87 (53: 26.5 —_ Ligihning.
EU) SoRS eeee rains Bere ee ge 87 27.1 26.5 — Very little lightning.
nA es eee ee 87 6.38 26.5 $2 Lightning with fire.
AOS eerie aks ERE 2 Wt. 6 87 9.6 26:5 — Fire; healed.
REM eee ee ne 2 90 30.1 29 19.9 | Fire, healed; lightning.
QOE oe ee a Ee 92 | 128.1 30 — No wounds.
PBR At ee eee eS 92 10.2 30 — Very little lightning.
GOS 52 esate bye ee Q4 44.8 31 _— Fire, open; lightning.
i bees see eee 96 38.1 32.5 [4.53]| Fire, open.
dee Se et PE EEE Se 96 32.9 32.5 — No wounds.
AG ee ee 96 25.1 | 32.5 55.3 | Fire, open.
1GH¥y 2 ee be a hae SE 96 25.1 32.5 13.5 Lightning.
= peace maa Gaia | 101 46.5| 37 a Do.
ib. aes SS ee oe es 2 SO ES 8 102 22.3 38 16.8 | Fire, open.
Lh aE a ate ee eee 103 34.2 39 61 Fire; lightning.
ABSA: wa eae 103 35.2] 39 — _| No wounds.
7 eg OAR Ae wet" sap 104 25.5 | 40 [2.39]| Lightning.
12D. eee Se ee 104 25.5 40 71.8 Do.
CLS Se et oes Sey Se Hes 104 | 68.2 40 47.6 | Old girdling: lightning.
ADH AS oh Meee brs oF ENS Toe 105 20.7 41 43.5 | Fire, open
A se oe ee any) Pee 105 90.3 41 — No wounds
5, ee eee SO Bae eg ee eee 105 32.2 41 _ Do.
Be ee oy eee eee 105 58 41 _ Do.
Bree ike eevee ta Te 105 52 41 _ Do.
AQ Sek a See eee 106 29 42 46.9 | Fire, open.
Cb been aarp te gS meee ee ee 106 48.3 | 42 Traces. | Lightning.
fe eS, ees Pe ee 107 17.0 | 43 45.5 Falling tree.

1 The use of brackets ([]) in column 5 indicates superficial decay of sapwood.
2 The letters a and b indicate two distinct foci of decay in the same itee.

FOREST PATHOLOGY IN FOREST REGULATION.

TaBLE I.—Fundamental data on the pathology of the white fir—Continued.

No. of tree. Age.

Volume (cubic feet).

tree.

Of rot, in-

Average cluding ad-
For each | for trees

of same
age.

vance rot

(percent-
age of total

volume).

Character of wounds.

1 2
SOM res ee MELEE ENG PS 107
OA: cy ni ares nn: Perera 107
TO as 8 ade We 107
ZU ES ey aie ha ea 107
Doe ERAT bys tehe. F 4) 108
GoM Se nani a 109
LOOPS Sti ITEMS 110
SOME UTNE ha OPN LAL 110
ate ed SUELO AN as 110
TNT CONVERSE ea 110
TOS es Me ey ch el 110
OMe aia ea 110
LOM MRR TA SORT NS 111
TSI ee alata tad 111
Gun er. AES 112
ey AL TU 112
Cy) Ey, A) GRAB OS 3 LEO SEEN 112
GGse ree 1 a ee Ta 113
LODE eee NOU SAL 114
G75. eS fel chad gael 116
LOOM ocean oe ay: 116
Ye ARI Si le Nn aie 118
ATA ead a at 1 ne 118
Ase a ane a Sg 119
HE es INS i Al I a 119
WS Soe eT Tne 2 121
Oe ee RUC an 122
GMT Mie neni kasi alge 123
(30) tt se ea 123
ithe arte ek ee ee one np 123
Bulge Mn nestle 124
Le De Un nae ana eae 124
TMeree ee eeehs ee 124
Sie Pat ese bs WN 125
Airey tee UN Tn Ny nte 125
COdsene lsh eon ipEn 126
TOU inc oe. LA sean din 129
Ge at ae nay a FW 130
ea Me imieal C5021 Th 130
dee ee aeons eae 131
Le oot ene ae 132
Rete he h aobte ta pane a 132
HO Aan Sah 132
AD pe 6x9 ec ae ERG |. 133
Tek eae a i | 133
BSED VRE) ei ei thai 134
DION es ee a 135
FAR sel Toy Se CWE I 135
DG nae Sm CARON oa Siok gn 136
(Gece eee yes ge ee eee 136
CSD Vga = Sars SR aoe 136
IP yas, Pave Alec e nine oe. 137
EU ARG, RR VO RN IN 137
DN Nin ti Vg iit 08 Bus la 138
SU he ai lta CS 138
Ga MAS TA tile 140
i A cg I ct dD, 140
TOR dey nse 8 cgunes «ood 'Y. 140
UIA ee eel eae 140
Re eee, ee ee 140
Tacos at alt (a a 140
Aelia Getilier, pate. eh Ae 24, 140
iG a Rs os a velg ana 141
Gilat says Us see ete yc), 143
Teese eet ment ne 144
Aid, ses to Ra alah 8 146
1063 s:ci) see anes 146
Bubs lei.» Dyas W Be 148
Fi Rea MRR SOE 5, 5 wii 148
OF vet en cee. de gun ia Hs 149
LOSe Te erates. 150

50.

0

60.0

Lightning.
Little lightning.
No wounds.
Frost crack.

No wounds.

Do.

Fire, open.

No wounds.
pire ODe nt:

Little lightning.

Very little lightning.

Fire, open.

Fire; little lightning.

Twin healed in; frost crack.
Fire, open; lightning.
Frost crack.

Fire, open.

Fire: lightning.

Fire, open.

N g wounds.

Fire.
Fire; lightning.
Li ghtning.
Little lightning.
Frost-crack.
Lightning.
Fire, open.
Fire.
Frost crack; lightning.
Fire, open; ‘lightning.
Lightning.
Fire, open.
Frost crack.
Fire, open; frost crack.
Lightning.
Fire, open.
Frost crack.
No wounds.
Do.
Frost crack.
Fire, open.
pene

No wounds.
Fire; frost cracks; lightning.
Frost crack.
No wounds.
Do.
Do.
Lightning.
Do.

Frost crack.

Fire.

No wounds.
Lightning.
Lightning, severe.
Lightning.

Fire, open; lightning.
Fire, open.

Do.
Falling tree; frost crack; lightning.

No wounds.
Fire.
Frost crack; lightning.
Frost crack.
No wounds.
Fire, open.
> No wounds.

39

40 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE.

TasLe 1.—Fundamental data on the pathology of the white fir—Continued.

Volume (cubic feet).

|
Of rot, in-

No. of tree. Age. Average | cluding ad- Character of wounds.
For each | for trees | vance rot
| tree. of Same | (percent-
age. |age of total
volume).
|
1 2 3 4 3 6
7 Se ee a 150 | 123.5 | 97 81.5 | Frost crack.
0 re oe See a 150 | 45.6 97 55.5 | Fire, open; lightning.
LY (Re ae ee ee, 150; 112.5 | 97 68 Do.
dee eer ek cece e eee sees 151 16.6 99 41.3 (?) |
a eee eRe | 152) 192.5 101 58.1 | Frost crack.
ee ee ee anni Lise EO | 12) 75 | 101 15.7 Do.
| 78 Repay ce ee | ABS4 e235 Spe) 107 63.2 | Fire, open.
ie ee ete Pate. eee 155 121 107 36.2 Do.
PERE Te. MAW ses 155 S77 107 | Negligible. | Lightning.
Se reer see g ee 156 380 109 36.5 | Fire; frost crack.
Oise ee ee 156 96.5 109 32.8 Do.
Phe oe nas oe ee 159 | 152.0 109 — No wounds.
(yaa ee SES Pee ae a 160 224.5 116 73.7 -| Fire, open.
Ss eee. er ee ee 160 26.8 116 98.5 | Fire, open; lightning.
APRs 2 1 io gah ee orl | 161 68.6 118 = Lightning. |
SOQ e =S s. e ee 161 | 68.2 118 89.4 | Frost crack.
1G Pa Ser ee a 162 38 Gild 196 = Lightning.
=i) s pao Se 2 a BS See 163 122.5 123 — Notes missing.
Siiwe es ten hey 163 | 106 123 82.9 | Fire, open.
“ot: hie Saar Bit eo Ue ee eee | 164; 417 125 25.5 | Frost crack (healed); lightning,
Spee Ae Sr oe eds ey 165 (?) 127 |Incomplete.| Fire, open.
pyb ee eS er oe oe te ele 165 128.5 | 127 53.4 | Fire; lightning.
2s aes wes ee es Eee oR 166 57.2 129 (2?) | Notes missing.
Bee ee es ee ee 166 afd 5) | 129 — ; No wounds.
Ppl) Reel ey ee ee = 2 2 168 179 134 = j Fire.
“37 Aig nasser ey Sete ae 169 291.7 136 6.8 | Fire; frost cracks.
See ees see ee 170 328.5 | 138 53 Fire.
Ty falak Sains Soe eh eee oe, i7 121 138 87.4 | Frost crack.
Green es ee eee 170 | 123.8 138 67.2 No wounds.
Pian ol ER ek ee ee 175 | 68.0 150 47.1 | Fire, open.
64a ere 175 | 68.0 150 16.4 | Lightning.
Sao eo a nes 178352212: 7 158 _ Frost crack.
Pe See ee Oe 4784-7427. 7 158 [5.1] | Lightning.
i Lea es eee TOE 180} 133 164 16.7 | Fire, open.
ffl SS ages et eu tet See ah ate 183 | - 100 [166] 39.5 | Lightning.
37, Eee ab SEN peat oe Oh | 185 148.3 [166] — No wounds.
Goa ee oe eee mee gee 185 | 100.5 [166] 53.6 | Fire, open.
AO 2 rs 186 | 42.85] [166] = Lightning.
Gites ese eee | 189 64.4 [168] oa Frost ridge; lightning.
or ie Seeiertate Ce Otis oo eee 191 546 [168] 52 Fire.
Rhee et eee nee Se | 192] 110.7 [170] 95.5 | Fire, open; frost cracks.
1h: Nite ne Bee A me aU | 200} 115.7 | [180] | Negligible.| Frost crack. :
Lf Fe ey pt pepe Meee eae | 200} 26.0 [180] 100 Fire, open; lightning.
7 pes Shek he ee oe Oa ane 221} 196 [190] 100 Frost crack; lightning.
rl nae len ae epee pen 932 | 235 [200] 71.3 | Lightning. ee Se
Pibs (laa Shee ae | 258] 46.7 | [220] (100) | Fire, open: frost cracks; lightning.

These volumes are, of course, not directly comparable with each
other; they have a meaning only when individually compared with
normal volumes for the same age. It was necessary, therefore, to
curve data collected on normal trees, such as were selected for vol-
ume tables in larger numbers on the same area. The most reliable
portion of this curve lies between 80 and 180 years. The relation of
the actual to the average volume of trees of the same age we may
use as an index of suppression or dominance of the individuals in
question. |

The volume of the decayed part of the bole was figured as the
affected part of the cone. But instead of giving the decay simply mm.

FOREST PATHOLOGY IN FOREST REGULATION. 41

cubic feet, making constant reference to the total volume of the
tree necessary, the volume of the rot was expressed in percentage of
the total volume. Advance rot—that part of the wood already under
the influence of the mycelium—is included. It must be kept in mind
that all figures given under this heading (column 5) are therefore
likely to be high. To be on the conservative side, all measures of
decay were taken very carefully, and in all cases where there was
any possible doubt the uncertain part was measured as decay. But
since the same procedure was followed consistently the results are
directly comparable.

Table I gives us our working material in figures. Column 1 shows
the individual number of each tree from the field notes and is given
only for convenience of reference, the trees being arranged in the
order of their ages (column 2). Column 3 shows the actual or total
volume in cubic feet of each tree, considered as a perfect cone.
Column 4 gives the volume in cubic feet for the average tree of the
same age. Column 5 shows the volume of rot (including advance
rot) in cubic feet expressed as a percentage of the total volume of
the tree. Column 6 shows the character of the wounds.

CONDENSATION OF DATA.

It proved difficult to interpret intelligently this mass of figures.
If there existed any relation between decay and possible influencing
factors, it certainly did not appear very clearly from this table.
It became necessary to simplify and condense the material.

Instead of expressing dominance or suppression by the relation
of the actual to the normal volume in figures, the system of crosses
described above for the field notes was used. Three classes were
adopted—dominant, intermediate, and suppressed. ‘Those volumes
which came closest to the average were considered intermediate
and entered in the table with one cross, which expresses the affirma-
tive; a dash signifies negation. In the intermediate class therefore
there can be not more than one cross. The deviation from this
average shows in the two other classes, and as here all degrees are
possible, the degree of suppression or of dominance is shown with one,
two, or three crosses. Thus, three crosses under ‘‘ Dominance”
mean that the tree is as far beyond the average as is possible in that
locality. On the other hand, one cross under ‘‘Suppression”’ means
that the tree is decidedly suppressed, two crosses that itis badly
suppressed, and three crosses indicate the highest degree of sup-
pression. This classification is admittedly arbitrary; it seemed to
answer the purpose, however, and has so many advantages, with its
possible grades and its graphical clearness, that it may be retained
until some better method is devised. (Table II, columns 3, 4, and 5.)

42 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE.

To reduce the figures in column 5 of Table I to simpler symbols
was more difficult. Here the entire affected part of the cone for
practical purposes was considered as cull, including the sapwood.
In reality, there are, of course, all gradations from a slight discolora-
tion of the sapwood following a long lightning scar or a number of
smaller scars to complete destruction of the heartwood by decay.
In order to simplify this column and to bring out more forcibly its
relation to influencing factors, the writer tried to reduce the percent-
age figures to ratings, applying the system of crosses used throughout
this study, taking into account not only the volume percentage of rot
in cubic feet, but also the character of the mjury with regard to the
degree of rottenness. Thus, one cross in parentheses, (x), signifies
slight and negligible local discoloration; one cross (not in parentheses)
shows distinct rot, but affecting not more than about one-third of
the tree; two crosses, about two-thirds of tree affected; three crosses,
more or less of the entire tree affected. In each case, the character
of the decay as indicated by the detailed field notes was given due
consideration. ‘This explains apparent discrepancies between decay
rating and decay volume in the percentages in Table I, where the
affected part of the bole was considered as cull for the entire length

of the decay. In decay rating, the actual loss in merchantability -

was expressed according to the character of the rot and its extent.
This valuation of the decay, it is true, is necessarily somewhat arbi-
trary. Itis really the condensation of carefully taken field notes and
measurements and must serve until a more satisfactory method can
be found. Where general relationships only are concerned, as in
this case, our symbols may be sufficiently correct, provided they are
based on exact figures and reliable field notes. (Table II, column 6.)

In order to insure a higher degree of reliability for the decay-rating
symbols, the operation was repeated some time later without con-
sulting the results of the first. With insignificant exceptions, both
ratings were identical.

In much the same way the character and degree of wounding was
reduced to a system of crosses. Plainly, this can be done only from
field notes, which were generally amplified by actual measurements
of the size and extent of the wound. The chances of inoculation
offered by a wound decide its rating. That deep wounds, particu-
larly such as have remained open for a longer time, are rated higher
than small superficial injuries, soon healed over, is self-evident. The
system of crosses is the same as heretofore explained. (Table IJ, col-
umn 7.)

The next column (Table II, column 8) indicates the means whereby
the fungus entered the tree, as evidenced by the analysis.

ie ma eee ee

FOREST PATHOLOGY IN FOREST REGULATION.

43

Taste I1.—Condensed data on the pathology of the white fir.

Degree of dominance or

of suppression.

Domi-
nance

3
OX —
_— xX:
xx —
XXX —
KX: —
XXX —
— x
Exe —
_ x
—_— x
b:0:0:¢ —
x —
D:€ —
— x
SOK: —_
XOX: —
XXX —
D:€ —
x —
—_ x
—_— x
BKOX: —
xx —
XX: _—
—_ x
XOX _
x —

Decay | Wound) Infection traced
to—

rating. | rating.

———— | | |

i ns ay

eee cecee

eeacccee

eeccecceoe

eeecceee

eececeee

—
oa

Fire; lightning.

Frost crack. Ae

Lightning; fire.

Fire, open......
Fire, open......
Lightning. ......

Fire, open......
Ti

Lightning S6eo0e
ae C6 (oe area a
Girdling........

Fire, open......

Fire, open......
Lightning.......
Falling tree.....
Lightning. ......

Frost crack.....

Fire, open......
Fire, open. .....

Fire, open......

Twin and frost
crack.
Lightning. ......
Frost crack. ....
Fire, open......

Appar-

ent

condi-
tion of
crown.

SOCIO OEIGNS

o
~~

a

Pa Pd PP a Pd Pd ds

wa

Wee

MP od

Remarks.

Negligible; advance
rot.

Negligible.

Advance rot.

Negligible.

Advance rot.
Do.

Advance rot.
Open 22 years.

Advance rot.

0.
Almost completely
girdled 82 years
ago; wound open

31 years; mostly
advance rot.

Negligible.

Advance rot.

Advance rot local-
ized in scars.

Negligible.
Mostly advance rot.

Rot following two
very long open
scars.

Advance rot.

Very slight advance
rot.

Slight advancerot.

0.
Little typical rot.

44 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE.

TaBLE Il.—Condensed data on the pathology of the white fir—Continued.

Degree of dominance or

of suppression. Appar-
No. - ent
of | Age eey woud ea anes condi- Remarks.
tree. Inter. 8: g- tion of
Domi- | meai- | SUPPFes- crown.
nance ion.
ate.
1 2 3 + 5 6 7 8 9 10

97| 116; — — xxx = 2-9 9) ADIs ee ee ee x Negligible.

109 | 116 _ — OX = xx Fire, open--.... SS Mosily advance rot.

98 | 118 — — SEX) ose _— — ae

140} 118 _ _ pO. Otek Caeser © (x) — (x)

40} 119 xx _ — Se ceee ae D2 _ x

741 119 = — Pos x Xxx | Fire (?), with | x(?) | Advance rot.
lightning.

115 | 121 _— — D-0. oan) Peace x — x

150} 122 _ —_ 5 ie | eee — — (x)
58 | 123 _ — xo 20-4 xXx Frosterack.2.2.| c= Much advance fot.
69 | 123 _ — 539.5 — x Lightning....... x Mae Tot; negli-

gible.

154 | 123 = — XxX > O.8 ee ire Oper 2.2 == x Very long scar.
S13y| IPL | Soa — — x D.2-% IFO. 3. oss = Je x8 Little advance rot.
56 | 124 _ — Xxx x xx Frost crack. -..- x Advanee rot.

113 | 124 _ — 28 — DO Fire; lightning..| =x

33 | 125 _— _— peel) Peers x _ ae

Al) 625) oxoex — — ee xkx! | Fire; open=s..-- Xe Much advance rot.

60 | 126 — _ xx Xxx xx Frosterack.—-...| x Sporophore.

79 | 129 > _ — XXX xxx | Fire, with frost x Two very bad burns
crack. held open by frost

crack for 85 years;
sporophore.

54] 130 — — 0:S.9.8 xx xxx | Lightning....... Xe Much advance rot;

young sporophore.

63 | 130 — _ xx Deke ox | ||, Pure operas. 35) - sox Very bad open fire

; scar.

65 | 131 — — XXX EX xx Frost crack.-..-| (2)

LYFE B- xO — =a pd posal Be — | - Be

30 | 132] xxx —_ ried Bo eee _ — x

49 | 132 xx _— — 39.0.1 xx Hrosberacke' 22) 2c Much advance rot;

2 sporophores.
-42 | 133 D9. — — =x or) | Hire opernse 233: f xx Mostly advance rot.
112 | 133 — — p. 6.9 Sey (en a eee Bex: — 29.

53 | 134]- — i XXX x x wir (2). 2-22 —- Petoae Advance rot.

23) 135 — — p22 x _ Knotso.c ass x Slight advance rot.

555) 235 a5 = — p-8.4 mek =|/ Hare: wit frost 55 Much advance rot.
crack.

26} 136 _ — XXX SEE xx |. Frostcrack.....| xxx | Sporophore.

16} 136 xx — wey Nib ee a _ ; — x

43 | 136 _ x _ XXX = Kos seas ea x Sporophore.

12) PLB Y? _ — See Pe ea _— — ¥
50 | 137 — —_ Xxx 5.9.4 ae zaehenns and > Much advance rot.
ots.
2} 138 _— x = At ee xx — = (2)
15} 138 — x Semel Renee ee 3.8 — at
6| 140 — — 3.0.9.2 52.6.2 ea EW aPGL? Sosa eae (2) Sporophore.
7| 140] xxx — weil ese = = 8 — — x
70} 140 — — 0.0.5 4 Sek p Lach times = oo s- a Slight advance rot.
119 | 140 _ — XXX 20.9.4 5.2. | (ey eee do. tess ee: DRD.s
153 | 140 _ — DO: Sha) exes x _— (x)
155 | 140 — — 3.0. See ex) | hire joper—o. - XXX
43 | - 140 xX _— — =x 300.48 retioe dove es ee Da Tree almost killed at
age of 81 years;
mostly advance
{ "3 Trot.
156} 141 — — XXX XXX axons pe dona aseesa" >.

61 |. 143 — — Xxx 3D. 2.2.4 Frost crack; x Much advance rot
wounds from near wounds.
falling tree.

11 | 144| xxx — ——eprihaeeiek ot _— _ x

4} 146 = x _— x xx ig igre 2 eee een = x Advance rot.
106 | 146 — = JER: B38 xxx | Lightning and om Much advance rot
frost. in sears.
5] 148| xx _— _ xx xx Frost crack.....| = Small sporophore.

35 | 148| xxx _— = onfaetee-t. _ — x :

92} 149 — =— Se xXx xxx | Pirejopen:=:- 2) x Rot following scars.

10 | 150 — _— Ses eee — — x

25 | .150 xx _— = 2.2.0-8 ax | Frost erack::. 222 x

114} 150 —_ — xxx xx =xx | Pire,open=- --- x
157 | 150 a _— —_ xx 22.0.5 a) Ge dO sete Ee xx
151 | 151 — — 2 O5:4 xx xx (2) xX Much advance rot;

small tree.

FOREST PATHOLOGY IN FOREST REGULATION. 45

TaBLE II.—Condensed data on the pathology of the white fir—Continued.

‘| Degree of dominance or

of suppression. Appar-
No. Decay | Wound] Infection tracea | °24
of | Age ti ys H ° a Taced’ | condi- Remarks.
tree Inter fang) Teaume ca tion of
Domi- aati Suppres-
nance sion eae
ate.
1 9 3 4 3 6 7 8 9 10
8 | 152 xeX — = XX x Frost crack.....- 2.6 Two sporophores.
9} 152 — — XOX: x 3.0.59) |booge One x Scar long healed
over.
13 | 155 — — SXEXOX: XOX XX | EyHITes OPeNssens = x
ST e155 x _— — x XXX ITE LOLA Ayes as x Slight advance rot.
117 | 155 _ — 2.O:0.6 = xx Lightning......- Xxx
83 | 156] xxx — = xx xxx | Frost-crack:...:- x Much advance rot
and shake,
91 | 156 — — x x xxx | Fire, open... xXx
Die) LOO | sxoKoK: —= Shh (al OC ae = — x
120 GOe |) xxx _ — XXX 0.0; . Gi Fd bee ee lik Bie aa x
93 | 160 = = 0.0.4 XXX XK WP HIne, OPEMNsss.2. x
118} 161 — — .©.0.00 | Ee ae gee x = XXX
160 | 161 — — XXX Xxx xxx | Frost crack...... xxx | Sporophore.
116} 162 —_— — aXSKeR Wh /| Mee x = x
47 | 163 — x EN GHB eS x ; = x
81} 163 — — x Xxx xxx | Fire, open.......| xxx
84] 164) xxx — — xx XxX SMO CS Eee eee De Small sporophore.

3] 165 (?) (?) (?) 2.0 p.9.0.05H| Bde a4 4 a eee x Notes — incomplete;
De Be Hi 26:5
inches.

51} 165 — x —_ xx 2:38) debs ays do:cc. x Much advance rot.
24 | 166 — — XXX x (?) (?) x Notes incomplete.
32 | 166 xX = MR De, Sere = = x

29} 168 XX — Se SED (x) — x

82] 169] xxx — — x 9.0, 6.¢/ NA Ginko} Rare ay Ae (x) | Very thrifty.

Sil pal OM ie Kexexs — — xx xX Bre) 0 FRO ea x(?)

S| IUDs a = x xxx xXx Frost crack....-.. xx Five sporophores.
67 | 170 — — x xKxXX _— KO GSA Sy ees x Small sporophores.
64-a | 175 — — 0.0.4 Xxx xxx | Fire, open.....:. x
64-b | 175 — — XXX BXSXs XKKG | ish toime.t 645: D6 mdwance rot; small
ree.
36 | 178 KX — = RUN eeeie fe x = x
52 | 178 — — x — X ightmine ses x Advance rot.
77 | 180 — _— xx XK Xxx iret eee ce se x Advance rot and
shake.
71 | 183 — — xXx x xxx || Lightning si) 22 xx Advance rot.
34 | 180 = = D.Sc SIECoE eee = = Xs
95 | 185 = — Xx 2:0. xxx | Fire, open....--- x
107 | 186 == = 2-0. 0.8 | rg ine XxX = x
66 | 189 = = 0.0.6) 5 gl Espa ea xx a x
39} 191 | xxx — — XOX DOK yy ITO sae sates x Fire 110 years ago.
86} 192 — —_ xx BKEXGK: xxx | Frost crack....- x Large sporophore.
14} 200 — — xx — Ke gales CKO SSeNieie aes | \b-0:0.<
142 | 200 — _ SXexeX: KOXOX: 2.0.0.0) 1 il I Lge eae a ea xxx | Much advance rot;
small tree.
73 | 221 _ x — XXX xx Frost crack with | xx Four sporophores.
lightning
59 | 232 X: — —_ XXX 5 Lightning.......] (?) Much advanee rot.
141 | 238 — = XXX Xxx xxx | Fire with frost | xxx | Mostly advance rot
crack. with shake.

Another column concerns the apparent condition of the tree (Table
II, column 9) and indicates the appearance of health of the crown,
taking the healthy, thrifty tree as normal (indicated by one cross)
and marking the degree of deviation from the normal in the usual
way. ‘Thus, one cross in parentheses, (x), means that the tree is an
exceptionally healthy one; two crosses (not in parentheses) indicate
that the crown is rather poor, either in development or that the color
is abnormal, etc.; and a tree having a very much underdeveloped
and sickly looking crown is marked with three crosses. The personal

46 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE.

factor may, of course, lead to misinterpretations unless the same
standard is applied throughout the entire study. For this very
reason it seemed doubtful from the beginning whether these data
would be of much value. They are given here merely for the sake
of completeness.

The condensed material was again tabulated. In the condensed
table (Table II) the relation of decay to age can easily be followed by
comparing columns 2 and 6. ‘Decay rating” is placed between
“Suppression”? and ‘‘ Wound rating” in order to bring out forcibly
any possible relation between these factors.

INTERPRETATION.

The column that interests us most is apparently the sixth, “Decay
rating.’”’ In glancing over this column and comparing it with the
neighboring ones we can read directly the connection of decay with
factors that may be of influence. Each separate case of decay, of
which one, two, or even more can occur on the same tree, may be
called, for simplicity’s sake, in this study, a ‘‘cull case.”” Each cull
case is the result of a separate infection. The actual loss of timber
by fire burning out the stump does not concern us here; cull from
this source is included in the ‘“‘ volume of rot’? whenever the decay
is directly traceable to the fire wound. Otherwise the cull from fire
is neglected. Cull from knots, limbs, or wind-shake is not considered.
Altogether there are 97 cull cases.

The first two cull cases are negligible for practical purposes. Some
loss occurs in tree No. 125, 84 years old. We see that this is a very
badly suppressed tree, very seriously wounded, in very bad health,
and that it is injured by both fire and lightning. Another case occurs
in tree No. 124, age 87 years. Again suppression, wounding, and
condition of health are marked with three crosses, indicating the
worst possible conditions, together with two causes of wounds—fire
and lightning. In both cases fire is the more serious, lightning often
occurring higher up on the tree in numerous small wounds. It
carries advance decay to the upper part of the bole and materially
increases the volume-rot figure and the decay rating. The next cull
case is a slight one (tree No. 88, age 90 years). The tree is inter-
mediate, wound rating medium, health good, the decay only advance
rot. Continuing down the ‘ Decay-rating”’ column and comparing
the symbols with those in the neighboring columns, we find that in
almost every case the rating of rot more or less expresses or is ex-
plained by the factors of suppression and wound rating. Apparent
discrepancies generally find their explanation under ‘‘Remarks’’
(column 10).

Suppression shows at an early age. A distinct preponderance of

suppression is noticeable from about the age of 84 years. The first.

PR Se tie ass

FOREST PATHOLOGY IN FOREST REGULATION. 47

very pronounced cases appear in the same year. They seem to be-
come particularly common from about 110 to 120 years.

Suppression stands out strongly as an important factor. Out of
the total of 97 cull cases, 66 are connected with suppression. Consider-
ing that our average volumes over ages were curved from figures
which were rather low and that the intermediate white firs in a virgin
uneven-aged mixed stand are rather to be considered as recovering
suppressed trees than as dominants decreasing in rate of height growth
the intermediate class may consistently be added to the suppressed,
giving 73 in all, or about 75 per cent. Suppression is commonly con-
nected with a more or less high decay rating, provided the tree is
wounded seriously. Again, low-volume trees with marked decay are
more liable to be a total loss on account of their form. <A rot volume —
percentage of 50, for instance, leaves still a good deal of merchantable
stuff in a tree with high volume, but it would make a small tree com-
pletely unmerchantable. In the comparatively few cases where
dominant trees show decay, the wounding is either of very momentous
character or the decay is more or less insignificant and localized near
the scars. ‘This is true at least for the younger trees.

In glancing over the decay column we see that the higher ratings,
xx and xxx, begin rather suddenly to become more frequent after the
trees have reached the age of about 123 to 126 years; after the age of
about 129 or 130 years they become very common. While decay
in the broadest sense of the word may show in trees 60 years old and
perhaps younger, the critical age of white fir with regard to more
serious decay appears to lie at about 130 years, at least for the region
investigated, taking into account that we have to deal here with a
practically virgin stand grown up under the cumulative risk from
suppression, frost, lightning, and the other factors of influence.
Decay of any consequence appears at this age in trees with a combina-
tion of wounding and suppression. In the few apparent exceptions
the decay is localized near unusually large wounds.

We find, further, that up to about 150 (148) years in badly wounded
but dominant thrifty trees the decay is either not very far advanced
in degree, if in extent, or that the wounding is of quite extraordinarily
severe character.

Tree No. 49, age 132, seems to form an exception, but we will see
later that frost cracks, though not offering a large opening by virtue
of their length, are instrumental in the longitudinal advance of the
decay. It seems that after about 150 years thriftiness as expressed
by dominance is less able to outbalance the influence of serious
wounding. |

If it is at all permissible to draw any inference from the compara-
tively small amount of material at hand, we may distinguish three
critical stages in the life history of wounded white-fir trees, and we

48 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE.

must remember that by far the greater number of our trees, especially
after they have reached the age of about 80 to 90 years, are wounded.

The first is the ‘‘age of infection,’’ which may be at 60 years or
below. Here the infection rarely leads to more than negligible decay
unless the tree is handicapped by quite unusually severe conditions,
such as very large old wounds.

The second, at about 130 years, which we may term the “critical
age,” marks the point after which a combination of pronounced sup-
pression and heavy wounding generally results in distinct decay.
This combination of deleterious factors is one commonly found in
virgin forests. Wounding alone is not sufficient to unfavorably
counteract thriftiness of growth.

Another change comes about at 150 years, when even dominant
(that is, thrifty) trees become subject to extensive and intensive
decay. We might term this the “age of decline,’ because the inability
of the individual to throw off or keep in check the growth of the wound
parasite in its heartwood indicates a distinct decrease in resistive
powers, whatever their specific action may be, induced by age. For
thrifty but wounded white fir, Such as we may expect to raise under
management, the age of decline is, therefore, the factor which will
influence the rotation and cutting cycles of the species, since for many
years to come the risk of imoculation will be more or less the same.
There will be fires as long as there are hightning storms. Wounding
through lightning and frost are inevitable. Besides, many trees are
already wounded.

It is of interest to note that of a total of 160 trees only about 25 per
cent did not show any wounds except very slight lightning scars. All
the rest were wounded from some cause or other. Often a combina-
tion of fire, lightning, and frost cracks results in scarring a tree to such
an extent that almost in every foot some blemish will be found. This
is particularly true of the older trees which have been exposed to the
cumulative risk of many years. Any of these wounds, if large enough,
may offer an entrance to fungi. After the trees have reached the age
of about 80 to 90 years, more than 70 per cent of them are already
more or less badly wounded and therefore exposed to moculation.
After they are about 106 years of age more than 80 per cent are
wounded.

In the remote future, when all these wounded trees are removed
and when the risk of wounding for the trees growing up meantime is
minimized, a new age of decline may be established. What this age
of decline might be for unwounded white fir in managed forests we
can not tell from our material, because of 97 cases of decay only 6
were not to be traced to some wounding. It is obviously out of the
question to take even a clue from data of so scanty a nature. It

may simply be mentioned that the first case of this kind appears at

FOREST PATHOLOGY IN FOREST REGULATION. 49

an age of 134 years in a suppressed tree. After all, it may be more
than a coincidence that the first case of such infection in a sup-
pressed tree occurs near the critical age for suppressed white firs in
this region. It is within reason to assume that thrifty, uninjured
white firs run only the evidently not very great risk of becoming
infected through branch stubs. But decay entering through knots
is always caused by fungi of a very aggressive character, such as
Echinodontium tinctorium, which is not always the case with wounds.
As a possible cause of infection we may also mention dead and broken-
off leaders or volunteers, the stubs of which are only slowly overgrown.

It would appear that, if infections of unwounded trees are really
so rare, white fir will take care of itself on the managed areas of the
future. This would probably be the case in an ideal, 100 per cent
normal forest. But this is utopian. There will always be a certain
risk of wounding. Even after the already wounded individuals are
eliminated, which will consume a number of decades, it is unreason-
able to expect that our forests should then be so much closer to the
normal than the best kept European forests are at the present day.
How severe the loss from Trametes pin is in the Prussian forests has
already been shown. Whatever may be the final verdict as to the
age of decline of unwounded thrifty trees in managed forests, it can
not be of more than purely theoretical interest to us and the next
following generations. We must cope with present-day conditions
as we find them, not as we would wish to have them.

The immense importance of fire in connection with decay appears
so plainly from Table II that it is hardly necessary to emphasize the
fact. The field notes show that in 59 trees wounded by fire, in only
11 was no decay traced to the fire wound. Fire, then, is one of the
most important factors in connection with decay; all the more so,
as fire generally attacks the butt part of the tree, and decay starting
from fire wounds therefore destroys a much greater part of valuable
timber than decay in the upper part of the bole.

Lightning generally results in comparatively light advance rot.
From Table II it appears that the only tree in which serious decay
could be traced to lightning, and in which it was neither connected
with suppression nor with a serious wound from another source, is
No. 59, 232 years old. To judge from our data, lightning is rarely
connected with typical decay, although it often renders large parts
of the tree partly unmerchantable.

The cumulative risk of wounding is shown in Table II (column 7)
by the fact that the cases rated with three crosses become far more
frequent after the trees have reached the age of about 90 to 100 years.
After they have reached about that age such cases are commonly
accompanied by decay. Serious decay follows serious wounding after

98035°—Bull. 275—-16——4

50 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE,

about the age of 130 years (critical age) when combined with pro-
nounced suppression, and without this it follows after the age of
about 150 yearsisreached. The risk of wounding increases naturally
with the age of the tree.

A number of wounded and badly suppressed trees escape infection,
although they are far beyond the critical age. Not every wound must
necessarily be imoculated. All such cases found are compiled in
Table III.

TABLE II1.—Data on suppressed and wounded but not infected white-fir trees.

[
Suppres-| Wound | Character of |

Age. sion 2 ELD: Wound | Character of

Age. sion

rating rating. wound. rating. rating. wound.
Sie he Xxx x | Fire. LL ESk esas oe x | Lightning
TAQ eee BKEKOX: SXEX: Do. HIG a cere rer ss BROKER:
de eee. ee EXOROX Do. PEt e ooaee 0.0.0.4 Xe Do
i AY Lae ee ee SREXOR: x | Lightning. 1 eo Re eee ts Ae ROKER SOX: Do
TSS eens ye PREREK: Do. 1 oS ies se esis ee XXX 5:O:¢ Do

In all cases but one in Table III the degree of suppression is very
high; in this case the wound rating is low. The dangerous fire
wounds in this table are confined to the youngest ages, 87 to 111
years; they were comparatively small in each case. The rest of the
wounds are all due to lightning, which, as will be remembered, does
not open up the interior of the tree unless very large parts of the
bark are killed. For inoculation and infection, the character of the
wound is all important. Suppression has nothing to do with inocu-
lation; only after infection has taken place does its influence make
itself felt.

The characteristics of each of the three ages, of course, hold good

through the following ages. The combination of Sones with

suppression, as shown in the critical age, for instance, must continue
to favor decay in the age of decline.

Relative thriftiness (apparent condition of the tree) seems to have
the least influence on the decay factor. It is really nothing but a
statement of the present temporary appearance of the individual
tree, which may be entirely different from what it was a few years
ago or what it will be in the near future.

That far-reaching decay must not necessarily be reflected in the
appearance and increment of the tree is shown, for instance, by trees
Nos. 25 (age 150), 157 (age 150), 85 (age 152), 83 (age 156), and
others in Table Il. In all the trees mentioned, Hchinodontium
tinctorium had established itself and was vigorously growing. ‘Tree
No. 85 (age 152) even had two sporophores, and more than half the
volume of the tree was decayed, indicating that the fungus must have
lived in the tree for many years. The tree was apparently very
thrifty; its volume, 192.5 cubic feet, as against 101, the average for its

FOREST PATHOLOGY IN FOREST REGULATION. 51

age (152 years). The increment was good. We can not, therefore,
make Echinodontitum tinctorium responsible for the decrease in
thriftiness of infected white fir.

In order to further fix the relation between the character of the
opening through which the fungus gains entrance into the wood and
the character and extent of the decay, all cull cases were tabulated
separately (Table IV).

Taste [V.—Cull cases of white fir, showing the extent of typical rot and its relation to
the wound through which the infection took place.

Wounds. Typical rot.
No.| Age.| Infection traced to— Tn- outings Extend- Remarks.
Oven ternal | Porh a q | ing much
Ua iota, | Does
> | wounds s
il 2 3 + 5 6 7 8
We op Pee a ae ieee = x x -- Negligible.
Sap EaNy SI Le NN MR UGS TC A — x x a
125 84 | Fire with lightning..... x — x =
144 SGn|prostierack2 e425 2 ee = x x — Negligible.
ae a eee with fire....-. x — xX — Advance rot.
BN SEALE Le a DOL NE Ye — x x ==
122 96:2 2258 OS eeu ae x — x =
76a, 96) pene COLO eral ali a dat x — — (x)
iop ie reas BIE aS ca! oye /=/s x — — -- Advance rot.
TRO ees MS a Aa | x — x ==
te i ci 05 Lae LY td pa Se — X: — (x) Remained open 22 years.
72a ighiiming eee ese se = x x —
2D OS) eo ne Oe ee en ae eter ota a0 — X Xi —
158 \4 104) |hGirdling sh) fo Wat ye _ x x a Almost completely firdled 82
ie ate ie years ago; Open 31 years.
Ths Petey Ne UNE Le Mae CE oA Ds — X —
102 106) |2eees GOs. eee eee x — x —
1212 106) )}) Laghinin gee eee ee x Xe Xs — Negligible.
68 | 107 | Wound from falling tree. x — x —
SOOM) eighitnin sees -- x x —
44) 107 | Frosterack..--..-..2... x — x —
100} 110 ATG aie pay igs SA UNL x — X =
78 UO) | eASH OKO Las WES Nees ten ak sxe — xX —
104s |) SERIES See GOES Or SULA Saar x — x —
94} 112 | Twin and frost crack...) — Xs x —
99)| tI 2 i auie ntmin gy ee ae — x x —
Simin 120 Brosheracksys) (2 _ aX (?) — Frost.
FGy ell Bey ir Ory syne year al x _ X —
Oil) BUOY esses Co a Mig Sih aia eeogi Sy X — exe —
LOOM eel G eee (6 (I SCLC Fae ey su x — 5. _—
CAS) Rial QUE Ire Ch )eremeciee oe csc — x2 Dx —
TeNoy \ WK Wbatalon ponerse Cee eS ae cn aX — x —
584 123 | Frostcrack.-22...2.2..- —_— x — x Frost.
CON A235 | ee hiGMin gyn ses eee — x 5 —
LAR eel Doe |e ITO es a Mae een x — x _
ate) [Le MIPH ES eae 2 TO aa Pe MN ee e x x —
5Gnl elo TOStCTack=]c as. eee eee x — — — Advance fot.
113 | 124 | Fire with lightning..... x — x —
AAT eh ASAI Dns eae ON Mace rer a aS — x —
GOP A26 trosterackss sen Sse 8: — X — aX: Frost.
79 | 129 | Fire with frost crack... 5X: — — x Do.
54) alsO i Mvightmin gy heen 22 ea — x Xs —
GSaIMASON METRE ks cote ee anne x — 5< —
Sonlelo LE LOSLCTACks ae. faa ae — X — x Frost.
49 TSA [eh COE ee a ae gi ayaieae — 55 — exe Do.
Z Moola BY M Wes) Bl ey MN potas ayer ey Xx — Dd --
Done OAn | elavval) (to) Perse ejaets ea a — (?) XK —
QS IMeLOOM KO USCET FE pliasiaieeuciraS oe — — — 2 Knots.
55 | 135 | Fire withfrost crack... — x -- x Frost.
26 eel SGl | Hrosteracks: (eee) ae ny eX — — % Do.
des) We ALS YB) ot | VERO E TIS) 2 Uh as RR a A — — — x Knots(?).
50 137 | Lightning and knots.... is x _— ps Aiur ad yanes rot.
140 THES SS a a Ma aa pH (?) (?) — BK porophore.
10) is 140) aightninge eee. ee. — x x —
x — x --

DO AO eaters Oe seat tejetdiciw alates

Sy BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE,

TaBLE IV.—Cull cases of white fir, showing the extent of typical rot and its relation to
the wound through which the infection took place—Continued.

Wounds. Typical rot.
No.| Age.| Infection traced to— Tn- penance’ Extend- Remarks.
Onan ternal aan ae d ing much
Pen. | (healed a beyond
over). | zeae wounds
1 2 3 + 5 6 7 8
555i] SA Os ARMRO nae Se x _— — x Condition very poor; sup-
pression xxx.
43]. 140}... 76 Ko MRR AC es eg x — X =
5G el Ae ee C6 Ko ee Tae be — x —
6la | 143] Frostcrack.......--.--- — xXé — x Frost.
61b | 143 | Falling tree.......-..--- — x x — Advance rot.
AAAS, 1 MATTEO eyes Sue Ona ge ae a (?) (?) (?) (?) Notes incomplete.
106 | 146; Lightning and frost...-. x — x — Advance rot.
Of 1487 eh rosterack.. secs seas — x — x Frost.
OQ AO SHAT eels yersranwalolae Ceca x — x —
D550) METOSECEAC Ke estan ons a Xs — — x Frost.
DAS SOLS Oi | HM ITO Siac ese ee ee ete ae x _— _— x Butt open from fire 73 years
ago; Suppression xxx.
Dall ero On he CO Ee ee Pee EN De — x —
TTS pane Ue ba hod eg) yc ence so eg we sie x x =
Soil LOZ EOS TChAC kan ae a. hea — XK — x Frost.
CO | LSPA fat sae GO See eee OL & -— aXe Xi —
13) GLO S | ITO es awe Sale em oa Ie x — —- X
Oe eob Gee GO ep aisaee ee aL x — > —
17h oo Lagi timing Se Ke es -- Ds x oss
SBalmlooumNrOSLCTACk sen eere aan — x — X Frost.
CO aia SY SMI Wl a ag ey ape ECG Fae ae x — Xs _
LQ eG On| hemes CG oy Sip Sy iy ee aa x — — x
OS GO ees ra Ko eee e eae a es x _ _— x Suppression xxx.
160) |p Gla) Hrosticrack: ee een. 2 X _ — x Frost.
SL OSs rel ows Sa ea ACh ak BX: — — aX Condition very poor; sup-
pression x.
SAR SGA | KG OTS ee See eee — — — a8 Knots.
Bilin Ma PMO neseiey see MA ee eo) x = — x
SLAG neers 3 GOR See aun — x -— x
Wal Sa GY Cet DN G72) RRR ire an 2a (?) (?) (?) (?) Notes incomplete.
82)| 2169) |) Knotes eee sane eee — _ -- x Knot.
Se eTOsl (Mire ete tenho (?) (?) = x
od | L70)| sBrostierack. 2 2252 sees — ! x — X Frost.
C/A eb 7Oa| RMOTA Les Sas eee — — — xs Knot.
GE Wa Ea iy olin Qu bse A alas hee x _ _ x Suppression XxX.
6A bilo) abish tin os seks — ax x —
EP Woo TWAS} | eee OP ee aa — Xe xX — Advance rot.
CAPUeN yn Wo ONal Ng ht as Ps ete es MPAs NEN a Up x — aX: —-
ZAy RBI ed on aba kee es aes eo ee a -- De x —
COP a bevay [iW sub RSA ea eteaeas ana Dahil i Xs — — x Suppression xx.
SO, LOUIS ee GOS Re BX — — x Dominance xxx; fire 110
years ago; deep burn.
$6) 192) roost cracke22-2e ese eee — x — ax Frost.
AY ZOOM eee OA SE AME hel oe a X xX: —_
NAD i ZOO sar eee De a es xX: _ — x Condition very poor; sup-
pression Xxx.
(aul 2215) | MNrosterackes 225. oe. 2 _ x — x Frost.
esos hh CAL bred okrau Ente Ara oe A x — x —
DOM 2d 2 eeeee GO Sea — x — De
141 | 258 | Fire with frost crack.... aX: — xX — Advance rot.

Table IV is designed to show whether and in which cases typical
rot extends much beyond the wounds forming the entrance for the
fungus. Column 7 is the one to be followed (‘‘Typical rot, extending
much beyond wounds’’). The affirmative is expressed by a cross, x,
the negative bya dash, —. Cases which are on the line between the
two are marked by a cross in parentheses; they are negligible for
our purposes. The first tree to be considered, No. 58, is 123 years
old and has a frost crack. From this age, or rather after 126 to 130

x

FOREST PATHOLOGY IN FOREST REGULATION. 538

years, these cases become more and more frequent. In most cases,
to judge from this table, frost cracks are a strong factor for extending
typical decay much beyond the poimt of entrance of the fungus. By
splitting the bole for a considerable length they allow air to enter the
wood, which evidently stimulates the growth of the fungus.

In noting the cases of decay ieaecd to the wounds or openings
through which the fungus found its entrance, it is seen that two and
even more cases of decay (cull cases) may be ound on the same tree,
but each case is counted separately. Where decay is traced to a com-
bination of two factors, each factor is shown separately. The means
of entrance of the fungus causing decay are thus shown to be as fol-
lows: Fire, 48; frost, 25; lightning, 23; other causes (including knots,
girdling, etc.), 13; total, 109.

These 109 wounds (including knots, etc.) led to 97 cull cases. Out
_ of 109, only 13 were other than wounds from fire, frost, and lightning,
and 11 of the 109 cases of decay were the effect of a combination of
two of the causes named. Fire has by far the greater share; frost and
lightning are second, but the preponderance of fire and frost over
lightning is greater than would appear, since they are far more serious
with respect to causmg decay. If ratings are given, more or less
arbitrarily, but yet in keeping with our field observations, to the var-
ious causes of wounds in the order of their importance with relation
to damaging decay in white fir, takmg mjury from lightning (the
least consequential) as the unit, we have: Fire, 3; frost, 4; lightning,
1; other causes (including knots, girdling, etc.), 3. Then, multiply-
ing the figures for means of entrance by these relative ratings we have:
Fire, 144; frost, 100; lightning, 23; other causes, 39. These figures
express the following facts: (1) Fire injury isnot only numerically the
strongest, but also commonly leads to considerable cull; (2) frost dam-
age is less frequent (above all, less ubiquitous) than fire damage,
because it appears only in typical frost belts or frost holes, but it car-
ries decay over a much greater length of the bole; (8) lightning injury
is fairly common, is also restricted to certain belts, and leads more
often to superficial rot; (4) other factors are of importance as causes
of damaging decay, but they are comparatively rare.

CONCLUSIONS AND OUTLOOK.

The interpretation of the results of this study of the white fir from
a practical point of view can not leave out of consideration the fact
that the basis for all computations and tables is a comparatively small
one and that the actual figures and many of the principles derived
therefrom have more the value of strong indications for local appli-
cation than the force of general laws. Still quite anumber of the con-
siderations will be directly applicable, at least im all similar types,
some throughout the range of white fir. The writer would emphasize
again that the aim of the present study is not to lay down laws, but

5A BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE.

to show by means of one example the problems before us and the
various steps leadimg up to a working method for the future estab-
lishment of laws which may—or may not—confirm the conclusions
from this study, and to strongly advocate similar studies on a larger
scale. With this point plainly in view, but assuming that our con-
clusions are a step in the right direction, we may discuss their bear-
ing on the silvicultural problems that are before us. _

DECAY IN RELATION TO WOUNDS.

In most cases, decay in white fir is caused by Echinodontium tinc-
torvum. ‘The mycelium never enters through the intact bark. Fire
wounds offer the most common way of entrance; hence, in the major-
ity of cases, decay starts in the butt; frost is less common than fire,
but favors the vertical spreading of typical decay. Localized and
superficial advance rot, frequently leaving enough merchantable
timber in the log to make it worth while handling except when
occurring in the upper part of the bole, is often connected with light-
ning. Other means of entrance, such as knots, wounds from falling
trees, and girdling by rodents are comparatively rare.

These factors group themselves naturally into such as are uncon-
trollable and such as may be controlled directly or indirectly. The en-
trance of decay through knots, wounds from trees and limbs thrown
in heavy storms, or from excessive snowfall hes beyond our control.
Injury from mammals as a starting point of decay is very rare and
will become even more so with the decrease of the forest fauna.

The other factors are more or less open to influence. Fire is dis-
tinctly a directly controllable factor. Lightning and frost are, of
course, not directly controllable. Itisafact, however, that both do
not occur to any damaging extent except in more or less well-defined
belts, and generally more heavily in foci inside of these belts. The
natural inference would be not to favor white fir in such belts when
possible. Asa first step in this direction the establishment and map-
ping of frost belts, frost holes, lightning zones, and lightning foci
would be of particular value, which should not be confined to white
fir alone. Other forest trees are also more or less subject to injury
from both factors. The value of such maps should also make itself
felt in forest-fire control, for the proper distribution of protective
forces and improvements.

FOREST REGULATION.
CARE OF VIRGIN FORESTS.

Tt has been heretofore pointed out that practically the only means

of silviculturally influencing the national forests on a larger scale at

the disposal of the administration at the present time lies in the han-
dling of timber-sales areas. On all the vast forests outside of these

FOREST PATHOLOGY IN FOREST REGULATION. 55

comparatively restricted areas the same beneficial and injurious con-
ditions must continue to prevail, which on one hand govern the annual
increment and on the other make for annual total loss. Only one
single component of the total-loss factor, though a most important
one, may be controlled to a certain degree directly. Forest fires are
in ever-increasing ratio eliminated from the national forests and,
therewith, also the danger of trees being fire scarred and opened to
the attacks of heartwood-destroying fungi. But the best of fire pro-
tection can not restore to their original state of intactness the over-
whelmingly large number of older trees which have been opened by
previous fires. The open fire wounds continue to offer an easy
entrance to fungi. It is true that fire protection prevents small
wounds from becoming larger and keeps healing wounds from being.
opened again by repeated fires. The sooner such fire-wounded trees,
as well as all other undesirable individuals, including all badly
injured, diseased, and misshapen ones, can be eliminated from the
forest, the better. There is little hope, however, for this to be done
outside of timber sales. Adequate fire protection, both of water-
sheds and of commercial timber, must of necessity be paramount to
silvicultural work of this kind.

Practically virgin forests may also be influenced by sowing and
planting. This is done on so small a scale, compared to the total of
existing forests, that we can hardly speak of any real silvicultural
change. Knowing, however, that white fir can not be expected to
yield full returns in belts subject to lightning and severe frosts, the
forester should avoid favoring white fir in such localities.

FOREST REGULATION THROUGH TIMBER SALES.

Cutting timber does not in itself constitute sound silviculture. It
may lead to regulation, or it may spell ruin to the forest.

The administration of the national forests is not able to have
timber cut by selling it where cutting is most needed. Accessibility,
local demand, and last, not least, the quality and condition of the
timber are stronger factors in finally locating a timber-sales area
than silvicultural needs. A strong admixture of inferior species in
itself is often sufficient to let an otherwise attractive sale fall through.
Here, the prejudice of the purchaser against such species as white fir
- and incense cedar is responsible for forcing the Forest Service to leave
an area badly in need of improvement in its virgin state, with all the
cumulative risk to which it is exposed. The prejudice against white
fir is widely established and not always confined to the lumberman.

From a silvical point of view the prejudice is directed against its
very aggressiveness, which tends to give the species an ascendency
over the more valuable but less tolerant pines. But the disfavor in
which it is held by the forester is really nothing but a reflection of

56 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE.

the strong objection made by the purchasing lumberman to accepting
white fir in Government timber sales, and this is based mainly upon
the unsoundness of the timber. At the same time, there is a fair local
demand for sound white fir for a number of uses. There is no valid
objection to clear and sound white fir. In fact, many a purchaser
would rather pay higher stumpage for white fir if he were allowed to
take only sound young stuff, which is in demand for dimension stuff
(2 by 4, 4 by 4, etc.), for frame stuff, timbers, and stickers, and for
butter boxes, etc. Purchasers complain that much of the material,
though seemingly sound, “‘has no life”’ after going through the mill;
it becomes brittle and falls to pieces when dry. Sound white fir
neither becomes brittle nor does it fall to pieces. It is the unsound
material (advance rot) only which is objectionable. The remedy is
easily seen; it consists in liberal and judicious scaling, which would
rather give the purchaser the benefit of the doubt. The scaler will
find valuable aid in the occurrence of decayed knots on the boles of
trees affected with stringy brown-rot. To the casual observer they
may appear normal; when they are knocked off with a hatchet or
similar instrument the decayed rusty interior is exposed. These ‘‘rusty
knots” afford, in the vast majority of cases, a valuable indication
_ of more or less far-gone Echinodontium rot in the heartwood of white
fir. Occasionally, the rusty color is missing, but the center of the
knot is unmistakably decayed. The verdict as to the rottenness of
the heartwood will be the same. The knots are often very small.
When sound, they are very brittle and glassy in appearance. To
give a practical example:

No. 82 on the Otter & Burns tract, a very fine tree with a long clear
bole, 29.4 inches diameter breast high, and 154 feet high, had been
given a full scale. The bole had been bucked into 16-foot logs. To
the scaler there were no indications of decay. After examining the
tree the writer threw out log 5. The only indication for spotting
Echinodontium decay in this log was the presence of the rusty knot.
The log was opened and found to be unmerchantable from 0.5 to
5.6 feet from the lower end, leaving as merchantable 0.5 foot on one
end (diameter 19.5 inches) and about 10 feet on the other end (upper
diameter 16.3 inches). Had the defect been known to the bucking
crew a more advantageous dividing up of the bole in log lengths to
the exclusion of the decay would have meant a saving to the operator.

Among others, Bryant! has pointed out the necessity of more judi-
cious bucking and of closer utilization.

1Bryant, R.C. Waste in cutting timber. Jn Amer. Forest., v.19, no. 11, pp. 790-799, 7 figs., 1913.

FOREST PATHOLOGY IN FOREST REGULATION. 57
MARKING.

The entire silvicultural results obtainable by way of timber sales
are directly dependent upon proper marking, the importance of
which can not be overemphasized. Marking is by far the most
portentous of all silvicultural activities and requires a very specific
training, of which a complete knowledge of all components of the
total-loss factor must be a prominent part.

Marking in the selection forest has a threefoid object—to select
trees to be cut and utilized at once, to leave others. as a basis for
future cuttmgs, and to establish desirable reproduction. Here the
interests of the Government as timber owner and timber producer
frequently conflict with those of the purchaser. The purchaser can
not be expected to take a strong interest in the future of the area he
is to cut over. He quite naturally wants as much sound, merchant-
able timber from a given stand as possible. The larger the amount
of timber he can cut from an area the smaller the overhead charges
will be per thousand feet, board measure. In offering white fir for
sale it is, therefore, important to be able to estimate more or less
correctly the amount of sound timber on a given tract. If our
figures prove correct, the loss factor in white-fir trees will be com-
paratively small up to an age of about 130 years; after trees with a
combination of wounding and suppression have reached the age of
130 years they are liable to contain decay; after they have reached
the age of 150 years wounding alone, even in dominant trees, is
liable to lead to damaging decay. That trees with sporophores are
decayed, at least partly, is self-evident. The actual cull per cent
from decay is at present only guessed at. It is the constant aim of
forest pathology to reduce this guesswork to actual and concrete
figures. It is intended to repeat similar studies throughout the
range of white fir and later also on other species in the order of
their importance and finally to establish broad zones of equal path-
ological conditions, in which the rot percentage may be given in
definite figures. —

Marking can only be done correctly if the outcome of the marking
with regard to the trees left standing is constantly kept in mind. In
our specific case, for instance, white fir on typical lightning and frost
belts should be marked very heavily. We know that here the loss
from decay, particularly following frost cracks, is heavy and will grow
through cumulative risk. White firs with serious wounds, especially
with partly open fire wounds, must be marked heavily to as low a
diameter as practicable.

On the other hand, thrifty unwounded trees, where desirable, may
be left without much risk up to the age of about 150 years, and prob-
ably much longer.

58 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE.

The effect of logging on the pathological condition of white firs that
are left on the area may be twofold. The opening of the crown cover
through cutting will prove beneficial to all suppressed and interme-
diate white firs. The ready response of the species to light is well
known. It is probable that such trees, if already infected, will not
allow the decay to proceed very much farther, i. e., the newly formed
upper logs may be sound. These trees move up into the dominant
class. The mycelium in the heartwood, however, if well established,
will not die out, and after a while sporophores appear which carry the
disease to hitherto sound trees. As there can not be any infection
except through spores coming from sporophores on diseased trees, it is
evident that it is poor silviculture to leave individuals infected with
any parasite of economic importance on cut-over areas. Such trees
on timber-sale areas should be marked and cut under all circum-
stances if we expect to save and utilize the sound timber they may
contain and to protect other trees from decay. Sanitation of the
forest must be the first and fundamental step in forest regulation. The
introduction of the so-called sanitation clause in the timber-sale con-
tracts of the Forest Service aims at this very point.

It is evident that blind enforcement of the sanitation clause,
following the letter and not the spirit of the principle expressed, is just
as pernicious as laxity in its application. Not all parasites are of
equal importance; our efforts should first be concentrated on the most
dangerous ones. The time will come when forest sanitation will
include all controllable elements making for loss in timber volume and
timber values.

On the other hand, if only thrifty trees are left standing after log-
ging operations, they are, by the very opening of the “forest screen,”
more exposed to flying spores from surrounding untreated tracts, but

unless wounded they are in no great danger of infection. Thesmaller —

the tract, the more will this influence make itself felt. The improved
conditions under which they grow will help them to either overcome
or limit the extent of decay in case they do become infected. As long
as we do not possess any exact figures on the recovery of white fir on
cut-over areas, however, it is advisable to consider wounded white-fir
trees left standing as unaffected by the opening up of the stand, at
least during the transition period, that is, in first fellings. All these
trees have grown up under unfavorable conditions, and the chances
that they are lastingly injured are considerable. By the time second
logging operations cover the area, it is to be assumed that a more pro-
found knowledge of the life history of white fir will be at hand.

The choice of white-fir trees to be left on the area, with the expecta-
tion that they will be sound and merchantable at the next felling,
depends altogether on their condition and the length of time probably

elapsing until that fellmg takes place. Assuming that our figures

FOREST PATHOLOGY IN FOREST REGULATION. 59

are correct and that the next cutting may occur, for example, in 30
years, we may with comparatively small risk leave thrifty unwounded
trees of any age on the area; wounded but thrifty trees of more than
120 years are to be cut, wherever practicable, because in 30 years
they will be over 150 -years old, at which age trees of this class are
more liable to deteriorate. Wounded trees which at the same time
are suppressed should be eliminated. It is bad silviculture to leave
individuals in the forest which not only do not produce the maximum
of timber but which in all probability will prove a total loss and which
occupy the place that should be fully stocked with trees promising
a full and sound crop. In case of an emergency, such as occurs
under very unfavorable market conditions or where the protection
of young stuff is the most important feature, wounded and sup-
pressed white firs left standing should not be older than 100 years,
since in 30 years they will have reached their critical age—that is,
130 years. After they have reached this age it appears that dam-
aging decay becomes prevalent in trees of this description. Very
severely injured trees have, of course, no place in the managed
forest. The same is true for unusually suppressed or unhealthy
trees, unless it may be expected with reasonable certainty that the
opening of the crown cover will benefit them materially. Trees with
open fire scars and with open frost cracks should be cut in preference
to those with lightning scars or those having wounds from falling
neighbors. In short, all wounds reaching iar into the wood are to
be given a higher rating with respect to decay than superficial wounds
unless the latter are unusually large.

PATHOLOGICAL ROTATION AND CUTTING CYCLES.

Since we may expect that cutting during the period of transition
will practically eliminate all those trees which by their combination
of suppression and wounding become subject to early decay (critical
age), the age of decline forms the basis for what might be termed the
‘“nathological rotation,” for want of a better expression. It does
not indicate that a given species should most advantageously be cut
in regular intervals expressed by the pathological-rotation age, but
that it should not be cut at a higher age. It is really a factor limiting
the rotation and therefore also the cutting cycle.

- Rotation based on maximum volume alone can not be more than
a makeshift during the transition period; logically it should be nar-
rowed down to maximum-volume production of sound timber. Such
species as Sequoia gigantea and Sequoia sempervirens are so resistant
to decay that their pathology will not influence their rotation at all.
In some of our valuable pines the pathological rotation will probably
be very high, either coinciding with or reaching beyond the age of
maximum-volume production. In white fir, incense cedar, and a

60 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE.

number of other so-called inferior species, the pathological-rotation
age is presumably lower than the age of maximum-volume pro-
duction. We must look to forest mensuration for final data to settle
this point.

Barrington Moore‘ advocates a rotation based on the “period dur-
ing which the rate of volume production is greatest or shortly after
it, provided it is long enough to give the most valuable product.’”
Here, again, the pathological rotation will be the limiting factor,
except for species in which the rate of greatest volume production
possibly occurs at a lower age than the pathological rotation. That
the value of lumber grades is bound to play a far more important
réle in the future than at present, with regard to rotation, is a fore-
gone conclusion.

So far, we have considered only the rotation per species. In pure
or almost pure stands the rotation of the unit is determined by the
rotation of the species clearly dominating, not only numerically, but
also in value.

As soon as two or more equally valuable commercial species appear
together in about the same proportion, the rotation of the stand
becomes ‘“‘synthetic;” that is, the rotation for the unit is governed
by the individual rotations per species. Im the great majority of
cases neither the representation of the species nor their individual
values are the same. Nearly always there will be certain species
more desirable than others, which latter then are classed as more or
less inferior. A weak representation of inferior species with low
pathological rotation will be without much effect upon the synthetic
rotation of the unit. The stronger the representation of inferior
species, the heavier will be their bearing on the synthetic rotation.

On many of the large private holdings of the West the inferior
species are disregarded altogether: they are simply left standing in
logging operations. Unless the logged-over area is burned, the
representation of inferior species is then an unduly heavy one. They
must necessarily dominate the stand in the future.

The national forests, on the other hand, will be the regulated for-
ests of the future. In many of the national forests, particularly in
the West, several species of unequal value are represented on the
same unit in such a manner as to make each one a strong factor to be
considered. Here, regulation of yield must be based upon synthetic
rotation and synthetic cutting cycles. Rotation and cutting cycles
for each species must be determined separately, each on the chosen
basis of either maximum-volume production, or rate of maximum-
volume production, or production of maximum value, limited in

i1Moore, Barrington. Chapman’s method of studying yield, p. 94,1913. To accompany forest plan,
Plumas National ia district 5. Appendix (continued), Silviculture. (Unpublished. Furnished by

courtesy of the U.S. Forest Service.)
2See also Zon, Ha, Balsam fir, U.S. Dept. Agr., Bul. 55, 68 pp., 2 pls., 8 figs., 1914. (See p. 67.)

FOREST PATHOLOGY IN FOREST REGULATION. 61

every case by the age of decline. The synthetic rotation is figured
on the basis of the specific rotations, under due consideration of rep-
resentation and relative value of each species from a commercial and
silvical point of view. The same is true for cutting cycles. It should
not prove impossible to express both representation and relative
value for each species in symbols, which, together with the specific
rotation, would permit the balancing of each species against the
others, and thus to arrive at the synthetic rotation of the entire unit.
In this way the inferior species will be given their proper place in for-
est regulation. This procedure is undoubtedly followed more or less
consciously wherever regulation is planned by way of timber sales.
It can not be reduced to a practical working system, however, until
all factors upon which it is based are iene ae known.

The pathological rotation limits the rotation of white fir, on the
basis of our present knowledge, to 150 years—at least during the
transition period. Perhaps the actual felling age for the species will
be shortened long before that time arrives. The chances of pro-
viding for the next decades are distinctly better. On areas cut over
to-day we may expect second operations in not too remote a future,
taking the place of asecond improvement felling. Provided our etnias
‘prove correct, the critical age and the age of decline will be a safe
guide in tentatively fixing cutting cycles for white fir, which, together
with the cutting cycles for the other species present, will permit the
establishment of the synthetic cutting cycle for the unit.

Our present knowledge of the pathology of white fir leads us to the
following practical conclusions for the period of transition:

Prejudice against white fir as an inferior species.

Conservative scaling (excluding advance rot) in favor of the purchaser on the one
hand and of better utilization of sound white fir (where market conditions
permit) on the other will in time overcome the prejudice.

Silvicultural treatment of white fir. |

Reproduction: Frost and lightning zones are to be avoided.

Marking on timber sales:

On frost and lightning zones marking should be heavy.

Badly wounded trees,’ particularly those with open fire scars or frost cracks,
should be marked heavily.

Badly suppressed trees should be marked heavily.

Trees with a combination of wounds and suppression can not be figured on
to remain fairly sound beyond the critical age of about 130 years. The age
of such trees, if left standing, added to the number of years to elapse before
the presumable next cutting takes place, must not exceed 130 years.

Trees wounded, though thrifty, can not be counted on to remain sound
beyond the age of decline of about 150 years. The age of such trees, if left
standing, added to the number of years to elapse before the a
next cutting takes place, must not exceed 150 years.

Rotation and cutting cycles.

The rotation for white fir, as far as we can judge now, can not exceed 150
years.

Cutting cycles for white fir must be limited by the age of deciine.

62 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE.
OUTLOOK.

The weak point in the example (white fir) discussed in this paper
lies in the fact that the numerical basis of trees examined is insuffi-
cient. Besides, what may be true for one set of conditions may
prove wrong in another. Extensive additional studies on white fir
in different regions of its range have been carried out during 1913.

What has been done for white fir must be done for the other species
as well. Investigations on incense cedar have yielded suggestive
results; others are to follow. But not before all important species,
from the lowest to the most valuable, have been studied carefully
with regard to their pathology can we expect to definitely figure the
total-loss factor for any unit. To-day we are standing at the very
beginning. Each species has its specific fungi, either one (as in the
case of incense cedar), or practically one (as in the case of white fir),
or several (as in the case of Douglas fir, sugar pine, and yellow pine).
The relative importance of each of these fungi, their relation to
influencing factors, their prevalence throughout the range of their
hosts, and, finally, the establishment of the critical age and age of
decline from a pathological point of view, are still to be worked out.
_ To this we must add the study of all the other components of the
total-loss factor.

The amount of work left to be done is enormous and will require
many years. Concentration on the inferior species will yield results
in a shorter time, enabling us to establish general rules to guide us in

the transition period without causmg too much damage to the

interests of future generations.

PUBLICATIONS OF THE U. S. DEPARTMENT OF AGRICULTURE RELATING —
TO DISEASES OF TREES.

AVAILABLE FOR FREE DISTRIBUTION.

Death of Chestnuts and Oaks Due to Armillaria Mellea. (Department Bulletin 89.)

Disease of Pines Caused by Cronartium Pyriforme. (Department Bulletin 247.)

Larch Mistletoe: Some Economic Considerations of Its Injurious Effects. (Depart-
ment Bulletin 317.)

Miscellaneous Forest Tree Diseases Common in California and Nevada. (Forestry
Miscellaneous. )

FOR SALE BY THE SUPERINTENDENT OF DOCUMENTS.

The Present Status of the Chestnut Bark Disease. (Bureau of Plant Industry
Bulletin 141, pt. 5.) Price, 5 cents.

Diseases of Deciduous Forest Trees. (Bureau of Plant Industry Bulletin 149.)
Price, 15 cents.

Mistletoe Pest in the Southwest. (Bureau of Plant Industry Bulletin 166.) Price,
10 cents.

Timber Rot Caused by Lenzites Sepiaria. (Bureau of Plant Industry Bulletin 214.)
Price, 10 cents.

Diseases of Ornamental Trees. (Separate 463, from Yearbook 1907.) Price, 5 cents.

Chestnut Bark Disease. (Separate 598, from Yearbook 1912.) Price, 5 cents,

Practical Tree Surgery. (Separate 622, from Yearbook 1913.) Price, 5 cents.

63

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