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Martin, Robert E., et al. 1969. Fire as a physical factor in wildland management. Pages 271-
288 in: Proceedings - Tall Timbers Fire Ecology Conference – Annual no. 9, held April 10-11,
1969. Tall Timbers Research Station, Tallahassee, Florida.
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Index (1988), compiled by the Alaska Power Authority.
Fire As A Physical Factor
in Wildland Management
ROBERT E. MARTIN, CHARLES T. CUSHWA AND
ROBERT L. MILLER1
WE USE FIRE to accomplish many goals. Most
of our use is based on long years of experience-experience that
enables us to predict the results we should obtain from the "feel" of
the situation. Research is being conducted, to assist less experienced
land managers to understand fire more completely and to provide
means for them to predict its effects in given situations. We must
better learn to understand and predict all the effects of fire if we
are to use fire effectively, or, for that matter, to use fire at all. Recent
pressures by various organizations and individuals are . directed at air
pollution caused by fire. Unless we can effectively demonstrate the
reasons we need to use fire as well as its effects on the atmosphere
we will find more laws enacted against use of fire.
The purpose of this paper is to present a mental model of some
physical aspects of fire. Perhaps these can be of use in planning some
prescribed fires as well as understanding some effects observed in
others. Each fire and therefore its effects are the products of many
factors. The basic fuel material, quantity, fuel bed geometry, and
moisture content are of elementary importance. Compounding the
1 Authors are respectively, Associate Professor, Department of Forestry and Wild-
life, Virginia Polytechnic Institute; Wildlife Biologist, North Central Forest
Experiment Station, U.S. Forest Service, and Graduate Student, Virginia Poly-
technic Institute.
271
R. E. MARTIN, C. T. CUSHWA AND R. L. MILLER
effects of the above factors are atmospheric conditions and move-
ment, and slope. Gradations in all the above factors generally occur
both horizontally and vertically, often in an erratic fashion, within
the bounds of a prescribed burn, greatly compounding the problem
of measuring and understanding fire and its effects.
As a fire progresses, it consumes fuel, releases heat and gases, leaves
charred material and ashes, and affects all the biota directly or in-
directly to a greater or lesser degree. Combustion of woody fuel has
been represented by Byram (1959) as:
4CuHs04 + 2502 + [0.322M H20 + 94N2] ~ 24C02 + 18 H20 + [0.322H20 + 94 N 2] + 4,990,000 Btu. (1)
Equation 1 represents four basic physical factors in the effects of
fire on the environment. First, C6H 9 0 4 represents the fuel material
which is consumed in a fire. Second, a tremendous amount of heat
is produced, the amount given here representing the heat from four
pound moles of woody fuel. Third and founh factors to be con-
sidered are the formation of carbon dioxide and water. The water
of combustion in addition to the water evaporated in the fuel may
have more significance in affecting the biota than has previously been
recognized.
Looking at a fire in detail, we might consider an idealized figure
or model of fire in relation to the fuel it is consuming (Fig. 1) . The
head fire under the same fuel conditions as a backfire will have a
higher rate of spread and, consequently, a higher rate of energy
release. Its flames will be higher and will have higher gas velocities
than the backfire. Radiation to fuel in front of the fire will be con-
siderable from the headfire due to its slope and height. The backfire
will have relatively little radiative effect from above the fuel in ad-
vance of the flame front, but will irradiate the remaining fuel or
soil behind it, perhaps contributing to a more. complete burn where
the lower fuel layers are moist, or to greater soil heating.
Combustion of fuel occurs in four stages. First, heat is transferred
to fuel before the fire by radiation, conduction, or convection, the
preheating phase of the fire begins. In our normal fuels, conduction
is probably of minimal imponance and the other two mechanisms
are the significant ones, both within the fuel bed and from the
272
FIRE AS A PHYSICAL FACTOR
I CHARCOAL I DISTILLATION I PREHEAT! NG
lcoMBUSTJ(:::lN COMBUSTION I
I I /J/0
I I (J w ~)
I 1/ ~t.!f I __ 11 ,p r
I /1 ~0 J
,'-'-'h""'"' /.. I f
r./ I BAC~\f I ;
1 \ I FIRE ; '\ r
1 \ I r \ I r
I \ ~ JJ '\1
1
/
I \ ll ::...._v .-------.---1
I )I --------AVAitABLE f
COOLING
I V · FUEL TOTAL
1----------'--~-- -_j -FUrL RESIDUAL FUEL
SOIL
Fm. 1. Stages in fuel combustion. As the fire moves from left to rig!Jt, the fuel
is first preheated and dried. Endothermic and exothermic decomposition occur, re-
leasing gases for the distillation combustion. The flames at any point diminish
and charcoal combustion occurs, followed by a gradual cooling of the area. ·
flames and wind above. In early stages of heating, the energy absorbed
by the fuel changes its temperature and moisture content.
As heating of the fuel continues, the second state, that of endo-
thermic decomposition occurs, releasing flammable and non-flam-
mable gases. The third stage of combustion occurs as decomposition
becomes exothermic, that is, the energy released exceeds energy
absorbed. Flammable gases emitted become concentrated enough to
exceed their lower critical flammability level and the flame or distil-
lation combustion stage of the fire occurs.
Finally, the flames pass the region, and charred fuel continues to
release energy in glowing or charcoal combustion. Depending on the
condition of the fuel, some fuel may remain in the charred condition,
273
R. E. MARTIN, C. T. CUSHWA AND R. L. MILLER
whereas in dry "hot" fires only ash remains. Where subfuels are
extremely moist and/or compact, these lower fuels may not even be
dried by the fire. The portion of the total fuel consumed by the fire
is the available fuel; that remaining after the fire is the residual fuel.
FUEL REMOVAL
Returning to equation 1, we might consider the removal of fuel
from the forest floor by fire. The fuel, represented here empirically
as C6H 9 0 4 , may vary somewhat in the ratios of C, H and 0. As
represented here C6H 9 0 4 is not a chemical compound but the ratios
of C, ~ and 0 in many compounds constituting woody fuels. Car-
bon, hydrogen, and oxygen constitute most of the fuel; however,
they are combined in different ways and in connection with other
elements. The other elements are low in percentage but often are
quite important as plant nutrients. Generally, a fire may be expected
to make available to plants great amounts of the nutrients, either
directly or indirectly. Removal of the fuel also has a significant
effect on soil temperatures and seedbed conditions, and generally
alters the environment of the biota.
Fires may increase pH of soil following fire, but the change may
be limited and be of little significance in the pine forests of south-
eastern United States.; The pH of litter as compared to ash is vastly
different, however (Fig. 2). In this limited study, litter from a 28-
year-old loblolly pine (Pinus taeda L.) stand in Montgomery County,
Virginia, was separated into fresh litter (dropped the previous fall and
winter, collected in March), old litter, and humus or duff. The pH
of fuels that were unburned, partially burned, and completely burned
were measured, using 4 grams of ground material in 25 grams of
distilled water at room temperature (Moore and Johnson, 1967).
Each experiment was replicated three times and the averages cal-
culated.
As can be seen in Figure 2, all three fuel portions are fairly acid
in the unburned condition. The pH increases somewhat as the ma-
terial is partially burned, where some parts were ashed, some charred,
and some unburned. A large increase occurs in pH as the material is
completely ashed, and the possible short time effects of the very
274
14
12
10
8
I
0. 6
r---
4
1/)
2
3: 0 :::::>
...J 2 w 0 :::::> z I
0
UNBURNED
FIRE AS A PHYSICAL FACTOR
-
r---
3: w z
!--
0 1/)
...J :::::>
0 2
:::::>
I
PARTLY
BURNED
-
3: 0 1/) w ...J :::::> z 0 2
:::::>
I
BURNEO
FIG. 2. Values of pH recorded from unburned, partly burned, and completely
burned litter from a 28-year-old loblolly pine stand in Montgomery County, Virginia.
The pH for all components of the fuel rose from less than 5 to greater than 11
when completely burned.
basic ash on soil flora and fauna as well as chemistry may be con-
siderable. First, the availability of some nutrients may be drastically
altered. Secondly, a less acid environment may reduce fungal activity
and increase bacterial activity. One offshoot of this may be a greatly
accelerated activity of nitrogen-fixing bacteria in the .first Y4 to Yz
inch of the soil where most nitrification is thought to occur. We
would like to emphasize that these results are not in contradiction
to our previous statement that pH change of soil may be limited
and of little significance. The differences lie in the materials analyzed,
and timing of the analysis. We have measured pH of the litter or
fire residue not that of the soil. We justify this procedure by con-
sidering very short term effects in the surface layers of the soil, not.
on long term effects on several inches of soil.
275
R. E. MARTIN, C. T. CUSHWA AND R. L. MILLER
TEMPERATURES
The high temperatures of a fire are one of the most imponant
physical factors to be considered. We might begin by considering
the rather generalized view of a fire (Fig. 3). Here, isotherms, or
lines of equal temperature, would form closed areas similar to contour
elevation lines on topographic maps. Around the bottom and sides
of the flame, the temperature gradients would be extremely steep,
and the lines tend to merge into one. Above the flame in the convec-
tion column, a gradual reduction in temperature occurs. Cooling
occurs due to radiactive loss and turbulent mixing along the edges of
the column. In actuality, .one would expect the temperature at any
point in the column, but particularly along the edges, to fluctuate
drastically since the entrainment of cool air into the column occurs
in a rolling, eddy-type motion. Over a period of time, however, the
time average of temperature across the column might be expected
to produce a fairly smooth curve with the highest temperatures in
the interior of the column. The flatness of the curve would be
affected by the degree of turbulence occurring in the column.
Surface temperature of a solid object exterior to the flame con-
vection may be considerably higher than the air temperature due
to the absorption of radiation. F ons et al. ( 1960) have shown radia-
tion from a fire to represent a considerable portion of the released
energy. Radiation occurs from all objects above absolute zero. Due
to the fourth power radiation law and the high temperature in the
flame or convection column, the net exchange is toward the cooler
object. Heating due to radiation can be of significance in fire effects
as well as behavior.
Switching from the situation considering the fire at a fixed position,
let us consider the exposure of points fixed in space as· the moving
fire passes. Any point on an object above the fuel bed will be ex-
posed, first to radiant heat, then to convective heating by the gases
of the column, and finally to a combination of radiation and limited
convection as gases rise from the burned-over area. The curves of
Figure 4 represent the average temperatures recorded by thermo-
couples at 1 and 4 feet above ground for palmetto-gallberry [Serenoa
repens (Bartr.) Small-llex glabra (L.) Gray] fuels in south Georgia.
276
FIRE AS A PHYSICAL FACTOR
FIG. 3. Idealized isotherms in the convection column above a fire. Temperature
decreases as distance above the flame increases. At any instant of time the isotherms,
in actuality, would be quite irregular due to turbulence in the colu01n, but time-
averaged isotherms would be quite smooth as depicted here.
The curves for 5 chains per hour spread were recorded on backfires.
The peaks at the 1-foot elevation were drawn so the peaks coincided.
At the 4-foot elevation, the peaks are displaced from the 1-foot peaks
by a time factor depending on flame slope and rate of spread. It
should be noted that the greater the rate of spread, the higher the
recorded peak temperature. The highest peaks recorded on individual
fires in this study were around 1000°C or 1800°F, for the most
rapidly moving fires, but are lower here due to averaging of many
fires.
Time-temperature curves such as those in Figure 4 have often
been considered to be fire or flame temperatures. The recorded
temperatures are not flame temperature, however, but merely reflect
the heat balance attained by the sensor. To understand this more
completely, let us consider the following heat balance equation for
a sensor in the flames:
277
R. E. MARTIN, C. T. CUSHWA AND R. L. MILLER
8 14
7 12 4FT. ABOVE GROUND
6
RATE OF SPREAD 10
5 CHAINS f HOUR
.. 5 8 4 5~10
(\j >10 ---'o ~ 6 ..--
X
u 2 ,4
0
~, 2b w ~==---------=-=--.........__.. ,.....
0::: X :::>
1FT. ABOVE GROUND 14 '*" ~
ffi 7 12 a.. 6 2 ~ 10
5
4 8
6
FIG. 4. Smoothed time-temperature records obtained by thermocouple from pre~
scribed fires in palmetto-gallberry fuel in south Georgia. Note that fires with
higher rates of spread indicate a higher temperature, probably due to higher gas
velocities by the t;hermocouples.
(2)
where q represents a heat flux or amount of heat transferred per unit
time, and the subscripts represent the following:
C = convective transfer from the flame to the sensor
GR = radiation from the hot gases of the flame to the sensor
R = radiation from the sensor to the surroundings (trees, forest
floor, atmosphere)
278
FIRE AS A PHYSICAL FACTOR
K = conduction along the leads of the thermocouple sensor away
from the sensing junction.
The left side of equation 2 thus represents processes transferring heat
to the sensing element; those on the right away from the junction. In
the small flames in which the temperatures of Figure 4 were recorded,
qan would be relatively small, and qK was reduced by exposing a
portion of the thermocouple wire to the same temperature. Thus,
the important transfer processes are q0 and qa.
To approach a "true" flame temperature, we should maximize q0
and minimize qa. In general terms, these factors are dependent on the
following relationships:
where
qc a: vx, x < 1
q11. a: (Tk -T:)
V = flame gas velocity and x is a fractional exponent
T To = absolute temperature of the thermocouple
T s = absolute temperature of the surroundings.
(3)
(4)
The obvious answer to obtain a better indication of flame gas tem-
perature is to increase gas velocity and the temperature of the sur-
roundings. This is often accomplished by placing a series of con-
centric shields around the thermocouple and drawing gases through
the shields and past the thermocouple by a vacuum system. The
resulting apparatus is called a shielded-aspirated thermocouple. Such
an apparatus was constructed and cribs of white fir [Abies concolor
(Gord. and Glend.) Hoopes], similar to those of Fons et al. (1960)
in Project Fire Model, were burned at 8-12 percent moisture content
(Fig. 5). The cribs were placed on sheet asbestos which in tum
rested on a rack of dead rolls. The rolls allowed the flame to
be centered alternately under the shielded-aspirated thermocouple
and an exposed thermocouple. A funnel-shaped outer shield aided
in concentrating the flame and in reducing the amount of cold air
drawn in from the surroundings. Temperatures were recorded on a
p-otentiometric recorder. •
The effects of shielding and aspirating a thermocouple were qutte
dramatic (Fig. 6). To the left of the figure the fire was started, and
temperatures were recorded alternately from the shielded-aspirated
279
R. E. MARTIN, C. T. CUSHWA AND R. L. MILLER
FIG. 5. Laboratory apparatus for recording shielded-aspirated thermocouple tem-
peratures and exposed thermocouple temperatures in flames from a crib of white
fir wood.
chromel-alumel thermocouple (SA) and an identical non-shielded,
non-aspirated thermocouple (NA). The SA thermocouple recorded
peaks greater than 1100°C (2100°F), whereas the peaks for the NA
thermocouple were around 870°C or 1600°F.
The peak temperatures recorded on the SA thermocouple still lie
somewhat below those calculated from thermocouple errors (Martin,
1963a), and a considerable amount of temperature fluctuation occurs.
It is possible that the thermocouple did not reach the temperature of
the hottest gases due to its finite size. It is also possible, however,
that the aspiration causes an increased temperature over normal flame
temperatures due to increased mixing. The fluctuation in temperature
could be due to varying temperatures within the flame or to drawing
of excess cooler air from the surroundings. It is further interesting
to note that the 1600°F recorded on the NA thermocouple corre-
sponds with temperatures often given for woody fuel flame tempera-
280
b x
u .
FIRE AS A PHYSICAL FACTOR
NA NA
10 15 20 25 30 35
TIME-MINUTES
FIG. 6. Temperatures recorded alternately on a shielded-aspirated thermocouple
(SA) and a non-shielded, non-aspirated thermocouple (NA) in flames of white fir
wood.
tures. The curves of Figure 4 recorded in the field can still be useful
in evaluating fires and fire effects as they reflect the ability of the fire
to transfer heat. For practical situations it might be easier to evaluate
heating of objects directly from the curves than to work from the
actual gas temperatures.
MOISTURE
Moisture is present in gases from a fire due to drying of moist fuels
and to water produced by combustion. Some prescribed burners
have occasionally noticed more scorch of live needles after burning
moist fuels than after burning dry fuels. Second, moist heat has been
shown to be important in the germination of hard legume seeds
(Martin and Cushwa, 1966; Cushwa et al., 1968).
In Figure 7, saturated vapor pressure of water is plotted against
281
R. E. MARTIN, C. T. CUSHWA AND R. L. MILLER
4~--~--~---r--~--~----r---~~
\I) a..
~3
0::
::J
\I)
\I) w g:2
0::
f2
~1
20
(;'40%
~-30%
......, 20% g; 10%
t.i..O%
40 60 80 100 120 140
TEMPERATURE-°F
160
FIG. 7. Dew points calculated for complete stoichiometric combustion of woody
fuel using Byram's equation (1). Oven-dry fuel yields a dew point of about
120•F, with dew point increasing as fuel moisture content increases.
temperature. This line represents the dew point, or the temperature
at which water vapor will condense, simultaneously releasing its
high heat of vaporization. Using Byram's equation (Eq. 1), the vapor
pressure for combustion of oven dry woody fuel was calculated and
is shown as a horizontal line for 0 percent M.C. The vapor pressures
were than calculated for fuel moisture contents at 10 percent M.C.
intervals and are shown as a series of horizontal lines. This figure
would indicate, then, that the dew point of the gases from combus-
tion of oven dry fuel would be around l20°F and that from fuel
at 30 percent M.C. near 140°F. It is interesting to note that as tem-
perature is increased in this range the time many plant tissues can
withstand high temperature changes from several minutes to about
1 minute.
Consider the effect of dew point on a pine needle exposed to the
convection column. Let's assume that the gas velocity is the same and
the temperature about 150°F in both cases. In the first case let the
dew point be l20°F as obtained from a dry fuel. Up to 120°F,
282
FIRE AS A PHYSICAL FACTOR
moisture will be condensed on the needle surface, releasing the high
heat of vaporization and contributing to a rapid heating of the needle.
As the needle is heated above 120°F, however, the needle would be
able to evaporate or transpire moisture, thus maintaining its tempera-
ture somewhat surrounding gas temperatures, due again to the high
heat of vaporization. Considering the second case with a dew point
of 140°F, as might be obtained from more moist fuel, the needle
would be brought quickly to 140°F before it was able to lose mois-
ture and reduce its rates of heating.
The dew points and effects covered above have not been studied
experimentally and represent conjecture on our part. In actuality,
the dew point could be lower for any fuel moisture content if:
1) the ratio of C to H in the fuel were higher
2) air is entrained into the convection column
3) if all the moisture from pyrolysis or drying were not all con-
tained in the gases.
On the other hand, the dew points may be higher if:
1) the ratio of C to H in the fuel were lower
2) one considers that the early stages of combustion involve pro-
portionately more water as a product than the later stages of
charcoal combustion, together with the fact that much of the
gas from the charcoal combustion may not be in the column.
At the present time, the above calculations might help to explain
scorch from moist fuels, but experimentation would be needed to
verify the calculations.
Moisture has also been shown to be important in breaking the
seedcoat dormancy of several legume seeds. Seed from these plants
would ordinarily be at or near the soil surface. The seeds also are
quite sensitive to temperatures above 100°C (212°F) (Fig. 8). The
moisture, from both pyrolysis and drying, might play a role ~two
ways with respect to the seeds. First of all, the vapor could diffuse
downward and condense on the seeds. At temperatures above about
60°C (140°F), the mucilaginous material on the seedcoat becomes
quite soluble in water, and the seedcoat dormancy is broken as a result.
283
R. E. MARTIN, C. T. CUSHW A AND R. L, MILLER
TEMPERATURE·-°F
130 140 150 160 170 180 5·~--~~--~~--~--~~--~~--_,~
20
;:310
~ z
~ I 5
w
:2:
F
2
~ '?"-v.
'0 '1~ ~ "'~..s:. ~~
<).)
~L0----5~5----~6~0----6~5-----7~0----~75-----8~0--~85
TEMPERATURE •c
FIG. 8. Lethal time-temperature factors for plant tissues as determined by several
investigators. Time is plotted logarithmically and the relationships for any investi-
gation approach a straight line.
Further, moist fuel or soil layers immediately adjacent to the seeds
may act as a temperature buffer, not going above 100°C until dried.
LETHAL TEMPERATURES
The time a living tissue can withstand high temperatures is in-
versely proportional to some function of the temperature to which
exposed (Fig. 8). Many people have used a semi-logarithmic form to
express the relationship, as:
where t = temperature
T=rime
t=a~lnT W
a & b = constants for the individual tissue considered.
As can be seen in the :figure, different tissues would have different
284
FIRE AS A PHYSICAL FACTOR
time-temperature relationships. In addition, the same or similar tissues
may have different sensitivities to high temperature, depending on
the condition of the tissue at the time of testing.
One important factor to consider, especially in relation to dew
point in the convection column is the change in time to cause injury
between 120 and 140°F. The data of Lorenz (1939) for red pine,
Nelson (1952) for southern pine needles, and Sileo (1960) for
Douglas-fir seedlings lie in this range. Some differences occur be-
tween tissues, and may be due to actual differences in tissue sensitivity
or to differences in techniques or criteria for evaluation.
The time-temperature relationships for injury to tissues are gen-
erally determined by rapidly raising the tissue to a constant high
temperature, maintaining this temperature for a given length of time,
and then rapidly lowering the temperature. From this, one is able
to obtain the type of curves given in Figure 8. We have already
indicated in Figure 4, however, that temperatures from a fire are
changing rapidly. Any tissue-heated by this shape of heat pulse,
whether exposed or isolated by bark, litter, or soil, would also have
a continuously varying temperature. If one makes the assumption
that the contributions to injury of tissue of temperatures above some
critical temperature are additive, then equation 5 may be converted
into a rate equation, giving (Martin, 1963):
1 (!.t-.!) - = e b b T (6)
Thus, knowing the time-temperature curve to which tissue is exposed,
and having determined the constants a and b for the tissue, one can
expand the exposure curve by equation 6. The area under the ex-
panded curve would indicate whether or not injury should occur.
In limited laboratory studies on Cassia nictitans seed, we have not been
able to demonstrate whether or not this approach is valid.
Finally, we might consider the effects of isolation on the tem-
peratures to which an object is exposed (Fig. 9, Greenstone, 1958).
In this computer-calculated figure for a semi-infinite solid-an ideal
solid with a :flat surface but extending indefinitely behind that surface
-all parameters are plotted in dimensionless form, making the curves
useful for any number of situations. The dimensionless temperature
285
R. E. MARTIN, C. T. CUSHWA AND R. L. MILLER
x' = x 1-v.:i(ir
2 3 4 5 6 7 8 9 10 18 19 20
t/r
Fm. 9. Dimensionless diagram of the effect of position on the time-temperature
curve a material would experience when the surface is exposed to a descending-ramp
heat pulse. Curves were calculated by computer for a semi-infinite solid (from
Greenstone, 1958).
T /T max on the ordinate indicates the ratio of the temperature at
any time or point to the maximum attained at the surface. Time
t/T on the abscissa is dimensionless where T is the length of time the
radiant heat pulse existed. The dimensionless position, X', within the
solid is given as the ratio of an actual position divided by the square
root of 4 aT, where a is the thermal diffusivity of the material. The
heat pulse used to calculate the curves is a descending-ramp type
curve, depicted in the upper right hand corner, beginning at t = o
and ending at t = T. Each curve represents the dimensionless time-
temperature curve at any dimensionless point within the solid. The
very rapid decline in maximum temperatures at points within the
solid illustrate the importance of a protective layer over temperature-
sensitive tissues. Thus limited depths of bark, litter, soil or other
material offer a tremendous amount of protection to living material.
286
FIRE AS A PHYSICAL FACTOR
Using an approximate value for the thermal diffusivity of soil
(,.,.9 X I0-4 cm2 /sec) and a.,. of 2 minutes, ~ inch of soil would
have a dimensionless position value X' of approximately 1, and * inch
of soil a value of approximately 2. The peak temperatures at these
depths would be only about one-quarter and one-eighth as high,
respectively, as at the soil surface.
The curves and calculations used in estimating the effect of isola-
tion on temperature are only approximate calculations. Variability
in surface temperatures and soil, as well as other factors, were not
taken into account. The -importance of the protecting duff or soil
layers in protecting living tissues is demonstrated, we feel, by these
calculations.
SUMMARY
In this paper we have attempted to illustrate some physical factors
of importance in the use of fire. Although we have ignored the fac-
tors affecting fire variability and behavior, the principles discussed.
should contribute to a better understanding of fire effects and, hope-
fully, to better use of fire.
ACKNOWLEDGMENT
The work reported here was in part supported by a grant-in-aid
from the Southeastern Forest Experiment Station, Forest Service,
U.S.D.A.
LITERATURE CITED
Byram, G. M. 1959. Combustion of forest fuels. Ch. 3 in Forest Fire: Control and
Use, by K. P. Davis. McGraw-Hill, New York. p 63.
Cushwa, C. T., R. E. Martin, and R. L. Miller. 1968. The effects of fire on seed
germination. J. Range Mgmt. 21(4) :250-254.
Fons, W. L., H. D. Bruce, W. Y. Pong, and S. S. Richards. 1960. Project fire
model. Summary progress report I. Forest Service, U.S.D.A.
Greenstone, R. 1958. Temperature rise in a semi-infinite slab subject to pulsed heat
input. Technical Operations, Inc., Rept. No. TOI 58-9, Burlington, Vermont.
Lorenz, R. W. 1939. High temperature tolerance of forest trees. Univ. Minn. Agr.
Expt. Sta. Bull, 141.
Martin, R. E. 1963. A basic approach to fire injury of tree stems. Proc. Second Ann.
Tall Timbers Fire Ecology Conf., Tallahassee, Fla. pp 151-162.
287
R. E. MARTIN, C. T. CUSHWA AND R. L. MILLER
Manin, R. E. 1963a. Thermal and other propenies of bark and their relationship to
fire injury of tree stems. Doctoral Dissertation, Univ. of Michigan.
Martin, R. E., and C. T. Cushwa. 1966. Effects of heat and moisture on leguminous
seed. Proc. Fifth Ann. Tall Timbers Fire Ecology Conf., Tallahassee, Fla.
pp 159-175.
Moore, W. E., and D. B. Johnson. 1967. Procedures for the chemical analysis of
wood and wood products. Forest Products Laboratory, Forest Service,
U.S.D.A.
Nelson, R. M. 1952. Observations on heat tolerance of southern pine needles. Forest
Serv., U.S.D.A., Southeast. For. Expt. Sta. Paper 14.
Silen, R. R. 1960. Lethal surface temperatures and their interpretation for Douglas-
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Susitna Joint Venture
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"1tL 10-11. 1969 T ALLAHASSEE. FLORIDA
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' FIRE ECOLOGY
ANNUAL ---CONFERENCE
NUMBER 9
APRIL 10-11, 1969 TALL.L\.HASSEE, FLORIDA
....
Fire and Mammals _________________ :,_________________________________________________________ 151
Charles 0. Handley, Jr.
Fire and Animal Behavior ----------------------------------------------------------------161
E. V. Komarek, Sr.
Co-CHAIRMAN--SEcOND SEsSION
Perry E. SkaTra
Chief, Forestry Program
Bureau of lndiam Affairs
Some Observations on Indian Forests and Prescribed Burning ____ 209
Perry E. Skarra
Wildlife Habitat Research and Fire in the Northern Rockies ____ 213
L. Jack Lyon
Research on Logging Slash Disposal by Fife --------------------------------229
Dale D. Wade
Postulates of the Prescribed Burning Program of the Bureau of
Indian Affairs --------------------------------------------------------------------------------2 3 5
Paul S. Truesdell
Controlled Burning on the Fort Apache Indian Reservation,
Arizona ------------------------------------------------------------------------------------------241
Harry Kallander
Prescribed Burning on. Recreation Areas in New Jersey: His-
tory, Objectives, Influence, and Technique ------------------------------251
James A. Cumming
Fire as a Physical Factor in Wildland Management--------------------271
Robert E. Martin, Charles T. Cushwa
and Robert L. Miller
Attendance ---------------·-----·-----------------------------------------------------·-----------· 289