FIRE
RESISTANCE
IN THE
FOREST
BxrT..J. STARKER
Pro/essoro/ Forest,
ry, OregonState College
A rating scaleof the resistanceto fire would be helpful knowledgein the management
of a forest in any region. The author has combinedhis wide knowledgeof conditions
with the best available information in the various regions of the United States. A comparison is made in regard to the developmentof scales of tolerance and of fire resistance. The need for more detailed and accurateknowledgeis pointed out.
be well for foresters to rate the trees
F FORESTERS
weregivenan oppor-not
of their region as regards resistanceto
tunity
to
rate
their
regions
treefire?
species
with
reference
to lowand
fire risk
But this has apparentlynot been
and fire resistance,
how many wouldpick done except in isolated cases,as little
the California fog belt with redwoodas literature appearson the subject,and cordoes not bring out a great
the species?The fact that a tree can grow respondence
to an ageof 1,000to 4,000yearsis fairly deal of authentic data.
good testimonythat that tree can resist NORTHERN ROCKY MOUNTAIN REGION
fire, insects,and fungi, or that it has not
been exposedto these dangers. Even
From general observationand tree
though many foresters,on this basis, countson fire trespasssurveys,Howard
would pick the redwoodsas the supreme Flint (2) compiledthe data shown in
fire resistanttree, let us examine briefly, Table 1.
what Fritz (!) has to say on the subject:
Table 1 was publishedin 1925. It •s
"Normally, it is difficultto start a fire one of the first systematicattemptsto ar•n the virgin redwoodforestsexceptwith range the speciesin a given region in
some preparation.
"Trees of great age---over1,000 years•
order of their fire resistance.
On two typical white pine areasburned
in August,1926, on the KaniksuNational
duly a few fire scars. Doubtless
such Forest, Mr. I. T. Haig (3) compiled
specimens
owe their long life and free- Table 2.
dom from more frequentinjury to a comFrom Table 2 a fire resistance table
bination of chance and a particularly could be arrangedas follows:
thick, denseand resistantlayer of bark.
Per cent of total
"The virgin redwoodforest has been Arranged in order of
still alive five
irreparably damagedby past fires; curfire resistance
yearsafter fire
resistant first)
rent fires aggravatethe damageand on Western larch (Most
..............................
87
cut-over land they materially reduce its Douglas fir ..................................
51
Western red cedar .......................
21
ability to producenew tree growth."
18
Withoutquestion,fire has causeda de- Lowland white fir .......................
white pine .................. :.._
16
creasein the densityof the stand,and in Western
Englemann spruce ........................
12
increment.The formationof "goosepens,"Western hemlock .........................
10
9
spiketops,and 90 to 100 per centof the Lodgepolepine ............................
0
decayat the baseof the treesis also due Alpine fir .................................
are often sound to the heart and show
It will
to fire.
be noted from
the above that
theorderofspecies
from
Thus,if fire ha• playedhavocwith such thislistchanges
a resistantspeciesas redwood,would it that given by Mr. Flint. This table, how462
FIRE RESISTANCE IN THE FOREST
463
464
JOURNAL OF FORESTRY
NORTHEASTERN UNITED STATES
ever, is.based on two plots only. Mr.
Flint's table is the result of observations
made in a broader field. Mr. Haig says,
"The values look reasonable to us for all
In an attemptto determinerelative fire
resistance
in
the
Northeastern
United
of the species
for whicha goodtree basis States,a questionnairewas mailed to 48
is available,with the possibleexception of the leadingforestersof this region,and
of western red cedar. It is believed that 41 replies were received.Thesedata are
this speciesis somewhatout of line, as almostentirely of an empiricalcharacter,
andthereforeopento muchcriticism.The
region is one of many species,various
was protectedby site conditionsto a sites, and with the fire hazard ranging
greaterextentthan the othertree species from low to high. Table 4 lists the resislisted."
tanceas tabulatedfrom thesereplies. In
It is to be noted that Mr. Flint and Mr.
tabulatingthesereplies,a strikingcorreHaig agreeon the mostresistat&t
and least lation wasevident,particularlyin the exresistantspecies,which is a sign o• prog- tremes of the table. Few items were disress. The fact that there is some variance carded, the highest being four for one
in the centralportionof the list merely speciesand there beingnone for twelve
points out the difficultiesof forming an species. The limit for discardingwas
twice the standard deviation.
exact rating scMe.
almost all western red cedar on the areas
covered,occurredin wet bottomswhere it
In two cases,the collection of accurate
PACIFIC NORTHWEST
data helpsto bear out the accuracyof the
In the Pacific Noahwest, the Cascade
table which is based on observations.
Data collectedby O. M. Wood of the
Mountainsseparate
twovastlydifferentreAllegheny
ForestExperimentStation(Tagions, climatically. Douglas fir is the
ble
5)
on
a number of trees give some
outstandingspeciesof the westernpart,
accurate
information
for that region.
while ponderosapine is the principal
In
a
study
of
bark
thicknessby A. C.
commercialspecieseast of the divide.
Both of these trees, however, appear on Mcintyre of •he PennsylvaniaState Coleach side, togetherwith mostof their as- lege on 1,163 oak trees from 2-inch to
sociates. A tentative list (Table 3) was 20-inch in diameter, he found that chest-
arrangedin collaboration
with W. B. Os- nut oak had the thickest bark, followed
borne,Jr., Inspector,U.S. ForestService by black oak, red oak, scarletoak and
white oak.
for this region.
TABLE 2
TRF..,ES
KILLEDOR DYINg FROM FIREIN,]'URYWITHIN 5 YEARSOF DATEOF BURN
Species
Original
1926 and
--Percentageof trees dying by years--
5-yr.
stand
1927
1928
1929
1930
1931
Total
59.5
13.9
8.9
0.65
1.3
842
W. wh. pine............... 881
W. larch........................ 70
White fir ..................
166
Douglasfir.................
W. hemlock .............
W. red cedar .........
100
574
185
Englemannspruce•- _ 49
Alpine fir ................... 175
Lodgepole pine_'_
.......
18
1.7
44.0
43.0
1.4
11.2
66.5
73.0
5.9
3.3
49.0
53.7
31.4
30.9
5.6
60.0
6.9
22.4
3.0
2.7
4.8
4.6
....
3.8
0.84
1.5
49.0
3.9
15.4
....
........
3.9
882
100.0
17.2
....
8.5
91 3
9.3
1.6
1.5
12 7
82.4
90.1
78.7
FIRE RESISTANCE IN THE FOREST
SOUTHWESTERN DISTRICT
465
CALIFORNIA PINE REGION
In correspondence
(6) with ,theSouthwesternDistrict it developedthat only a
little work had beendoneon the subject
of fire resistanceof trees. The following
would probably be the correct order:
Pinus apacheca(Arizona long-leafpine);
Pinus ponderosa(Ponderosap i n e );
Pseudotsugataxifolia '(Douglas fir);
Showand Kotok (7) say: "Like burning down,heatkilling affectssomespeciesmorethanothers.Yellowpineis the
mostresistant,followedby sugar pine,
whitefir and incense
cedar,substantially
in thesameorderasfor burningdown.
"Heatkilling is naturallymostcommon
and destructive
in standson the poorer
quality forest lands, for it is on such
Abies concolor (White fir) and Picea en- soils that the timber is shortest and the
gelmannii (Engelmannspruce).
crownsmore exposedto the intenseheat.
TARLE 3
RELATIVE FIRE RESISTANCE OF THE MOST IMPORTANT TREES OF OREGON ,&ND WASHINGTON
IN
ORDER
Thickness
Species
GREATEST
RESISTANCE
Foliage Most common
of bark
Branch
Canopy
Lichen
½ldtrees Root
habit
cover
growth inabilitykilling
Open
light
Western
latch
OF
High and
Very thick Deep
veryopen
inflam-
method of
Black-
Low
Most resistant
High
Crownfires
Low
Crownfires
0 to
High
Douglasfir
Very thick Deep
Yellow pine Thick
White
Deep
dense
Mod. high
and open
heavy
Dense,
Open
grey
Light-
black
firs
concolor lV•oderately
and grandisthick
Shallow
Low and
dense
Dense
Western red
cedar (sen-
tenacious)
Thin
Shallow
dense
grey
Dense
grey
Medium
Medium
low
dense
Medium
High and
dense
iV•oderately
Noble fir
thick
Low and
Rootcharring
and crown fires
l•oot charring,
roeder.
0
Mountain
hemlock
Med.
0 to
Low and
sit•ve but
O-heavy
crown fires and
High
burningdown
to
roeder.
High
Root charring
Dense
grey
and crown fires
Scorching of
Dense
Med.to
heavy
grey
High
foliageor
crowningand
coreburning
Moder.
cambium or
Scorching
High and
W•hite pine
Medium
Medium
moderate
Dense
grey
Med.
crowning
Model
Lodgepole
pine
Very thin
Deep
Western
hemlock
Medium
Shallow
Moderate
low and
open
Moderate
low and
dense
Shallow
Low and
dense
Very
shallow
Moderate
high and
dense
Engelmann
spruce
Very thin
Open
heavy
grey and Med.
black
low
Dense
grey
O-heavy
scorching
Dense
grey and Very
black
high
cambium and
crowning
0-heavy
High
Scorching
cambium or
crowning
Root charring,
crown fires and
core burning
Root charting,
0 to
Sitka spruce Vea'ythin
Dense
heavy
grey and
yellow High
Root charring,
occasional
c•owning
466
JOURNAL OF FORESTRY
TABtin
4
RELATIVE FIRE RESISTANCE OF 40 TO 80 YEAR-OLD
TREES
OF
NORTHEASTERN
UNITED
STATES
(Arranged in order of resistance)
Pinus rigida
Quercus montana
1. Pitch pine
2. Chestnut
oak
3. Norway pine
Pinus
4. Black oak
5. White oak
6. Scarlet oak
Quercus velutina
Quercus alba
Quercus coccinea
resinosa
7. N. white pine
Pinus
8. Eastern hemlock
Tsuga canadensis
9. Sugar maple
10. Red maple
11. Tamarack
12. Yellow birch
13. Red, spruce
14. Black cherry
15. Norway spruce
16. Gray birch
17. Paper birch
18. Aspen
19. Waite spruce
the subjectof relative fire resistanceof
the indigenousspecies.
strobus
Acer saccharum
Acer rubrum
Larix laricina
Betula lutea
Picea rubra
Prunus serotina
Picea excelsa
20. E. red cedar
21. N. white cedar
Betula populifolia
Betula papyri/era
Populus tremuloides
Picea glauca
Juniperus virginiana
Thuja occidentalis
22. Balsam fir
Abies
APPALACHIAN REGION
In a studycarried on by the Appalachian Forest ExperimentStation on 350
trees varying from 4 to 28 inchesd.b.h.
an attempt was made to correlate discolorationof the exterior bark causedby
fire to the death of the cambium.
The five
speciesexaminedvaried considerablyin
their relative susceptibilityto. wounding.
Yellow poplar was the most resistant;
chestnut oak, white oak and black oak
were intermediate; and scarlet oak was
most susceptible.It was found that scarlet oak is so low in resistance that the inner bark is killed sometimes for 20 feet
above the highestpoint of di.scoloration
of the exterior
bark.
The bark
of this
speciesis comparativelysmoothand as
thick as some of the more resistantspeUnfortunately,it is on just such soils
cies but, apparently,is a better conducthat the struggleof the forestto maintain tor of heat.
balsamea
itself is most severe."
THE
SOUTHEAST REGION
There is no questionthat longleafpine
(Pinus palustris),is the mostfire resistant speciesin this region. In most regions,it is agreedthat fire is a detrimental agencyin the forest,but in the
Nelson (8)
says, "Measurementsof
bark thickness made at six inches above
the ground on the differentspeciesand
diameters indicate that chestnut oak and
yellow poplar have the thickestbark,
scarlet and black oak are intermediate and
white oak has the thinnest bark. Yellow
poplar has an extremelythick layer of
phloemwhichmakesfor goodinsulation
thoughthavearisenon the value of fire. White oak bark is soft and flaky; whereOnemaintains,throughmanyyearsof ex- as black and chestnut oak bark is hard and
perienceand sampleplot observations
to
CONCLUSION
back up its judgment,that fire is beneficial. This is based on the fact that fire
Unquestionably
the problemof rating
helps to free the young longleaffrom trees in the order of their resistance to
grasscompetition
andhelpsto controla
Southeast two
controversial schools of
TABLE
needle disease.
The other schoolof thoughtmaintains
that fire is harmful and has sampleplots
TREES 6
ELEVEN
JERSEY DAMAGE PLOTS OF 1930
to backup its assertion.Photosof these
areasseemto provetheir point. It has
beendeveloped
recentlythat longleafmay 1. Shortleaf pine.............
Pitch pine ................
persistas a bud, protected
by its long 2.
3. Chestnut oak .............
needles,for a period up to fifteenyears. 4. White oak ..............
The writer is informed that the experiment stationof the region is working on
5
INCHES AND OVER, KILL•ED IN
5. Scarlet oak ..................
6. Black oak ................
Killed
No.
8
29
7
52
43
7
Total
Per
cent
No. of
trees
18.2
27.1
53.8
56.5
44
107
13
92
62.2
68
100.0
7
FIRE RESISTANCE
IN THE FOREST
467
fire, is very complicated.Many regions 2. Flint, H. R. 1925. Fire resistance of
have a great variety of speciesgrowing
NorthernRockyMountainconifers.(a)
on vastlydifferentsites. Treesof different
Applied ForestryNotesNo. 61, Dist. 1.
ages,when of the samespecies,vary in
their resistance.Fire damageis affected (b) The Idaho Forester, Vol. VII.
by the seasonof burning (9). All these 3. Haig, I. T. Assoc. Silviculturist, Misfactorsmultiplythe difficultyof makinga
soula,Mont. Personalcorrespondence.
rating scale. Yet is not fire resistance
one
of the tools with which the forester must
4. Starker, T. J. 1932. Fire resistance of
trees of Northeast United States. Forest
work? A knowledgeof toleranceis important, yet a scale of tolerancevaries
Worker, May.
widely, dependingon whetherit is taken
on a goodsite or a poor one,or if built 5. Wood,O. M. AlleghenyFor. Exp. Sta.
Personalcorrespondence.
up in the southernor northernpart of a
tree's range. If a scale of toleranceis
useful to the forester, is not a scale of 6. Miller, E.G.' For. Supervisor,Cocofire resistancemore so? Can management nino Natl. Forest and Quincy Randies,
plans,plantingwork, fire damagestudies, Albuquerque,N. Mex. Personalcorresand timber fire insurance,when it comes,
pondence.
be properlycarriedoutif we do not know
the relative resistance to fire of the trees
we are to handle?
REFERENCES
1. Fritz, E. The r61e of fire in the red-
7. Show, S. B., and E. I. Kotok, Fire and
the forest. U.S.
D. A. Cir. 358.
8. Nelson,Ralph M. Silviculturist,Asheville, N. C. Personal correspondence.
wood region.Cir. 323, Univ. of Cali- 9. Technical note No. 57 and No. 58, Lake
fornia.
StatesForest Exp. Sta.