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Blue Mountains, Oregon 1
Fire History -
Frederick
c.
Hall2
Interpretation of underburning effects in mixed conifer/pinegrass
plant communities (Blue Mountains, Oregon) suggest: underburns
occurred at 10-year intervals; ponderosa pine is being replaced by
white fir; pine stands did not develop according to "normal stand
development"; pine stands require stocking level control to prevent stagnation; range condition must be rated on successional
vegetation not climax; range grasses show "downward range trend"
due to increasing tree cover complicating trend interpretation;
herbaceous plants can sustain livestock use since they developed
genetically under periodic 100 percent use by fire; livestock
fill a major biotic niche not occupied by wildlife; some plants
are dependent upon fire for regeneration; some wildlife depend
upon stocking level control and successional trees (pine and
larch) formerly provided by underburning; soils developed under
fire and are brown forest rather than podzolic; fire hazard is
changing from light, flashy fuel under open tree cover to heavy
fuels under dense tree cover.
INTRODUCTION
Fire in Western forests has been common. Its
influence on vegetation and soil was studied in
conjunction with a comprehensive ecological evaluation of the five-million-acre (two-millionhectare) Blue lwuntain land mass in Eastern Oregon
and Southeastern Washington. Both conflagration
fire and natural underburning have left their mark.
Plant communities dominated by lodgepole pine or
western larch are the result of conflagration fire.
In contrast, underburning effect on vegetation is
often difficult to see. In this paper I will deal
only with underburning. Evidence will be presented
to document underburning frequency, the influence
fire had on tree dominance, interaction effect
between tree cover and ground vegetation, fire
influence on genetic development of ground vegetation, influence underburning had on soil development, and implications these have for land
management.
communities by the dominant tree, shrub, and herbaceous species. In this case, shrubs are absent;
therefore, we call it the ponderosa pine/pinegrass
community. It occupies nearly one-fifth of the total
acreage in the Blue Mountains.
EVIDENCE OF UNDERBURNING
Underburning has been common in the Blue Mountains
as shown by numerous fire-scarred trees. A fire scar
is a storybook, a history of fire. The easiest way to
open the storybook is shown in Figure 1. When cut in
cross-section, a number of ripples or wayes can be
seen. Each one of these waves indicates the occurrence of a fire.
The waves or ripples are formed as follows
(Fig. 1 ). \.Jhile the tree is young, lightning strikes
the ground and starts a fire in the easy-to-ignite
pinegrass. Fire burns over the ground to the base
of the tree igniting an accumulation of pine needles.
A hot fire will scorch part of the bark on the tree,
resulting in death of the cambium. Eventually, the
dead bark will fall away as the wound begins to heal.
When this happens, the tree will usually produce
pitch at the point where new bark begins to grow
around the wound. Some years later lightning strikes
again, burns through grass, into needles at the base
of the tree, and ignites the pitch. The pitch burns
up the side of the tree, killing bark at the edge of
the wound. This bark falls away as the tree again
grows around the wound. Later, lightning strikes
again, burns through the grass and ignites the pitch,
killing the bark.
I will illustrate interactions of fire with
vegetation in the ponderosa pine/pinegrass
ecosystem one of 18 kinds of forest communities
in the Blue MOuntains (Hall 1973). We name plant
1. Paper presented at the Fire History
Workshop, University of Arizona, Tucson, Arizona,
October 20-24, 1980.
2. Frederick C. Hall is Regional Ecologist,
Pacific Northwest Region, u.s. Forest Service,
Portland, Oregon.
75
dominant , suppr ess th ~i r neig hbors , and fi nal l y
e l i minate the s uppr essed tree s from the s t a nd . Wi th
f ire contr ol , hundr eds a nd sometimes thousa nds of
yo ung ponde r osa have become est ablis hed per ac re.
These yo ung t r ees have not grown accor ding to
normal stand development t heor y ; i ns t ead t hey hav e
almost univer sall y become s t agnat ed. l~e have fo und
l it tl e ev idenc e in the Blue Hountains to indicate
tha t po nder osa pine can, within a so- to 100-yea r
t imespan , br eak out of s t agna tion . Instead trees
persist and gr ow in diame t e r a t SO t o 70 r ings pe r
inch and in height at 4 to 6 inches pe r yea r to a t
l east age 80. Dougl as- fi r, wh ite fi r, lodgepo l e
pine and wes tern l a r ch behave s imilarl y.
Figure 1. Cross -section of a fi r e scar . Tick mark
at l ef t indicat es t he tree cen t er and the year
1763 . Numbers between tic k marks indicate years
be t ween marks . Eac h tick ma r k l ocates the annua l
r i ng of the yea r i n whic h fir e da maged t he t r ee .
In Fig ur e 1, the date was 1763 when this ponde rosa pine reached 18 inches t al l (stump height) . Fr om
then, the t r ee grew fo r 26 years before underburning damaged the bark and cambium , forming a
first fi r e scar. Each number on the tape between
the tick mar ks ind icates t he number of annual rings
be t ween fi r e sc ars . Af t er the f i r st scar , the tr ee
was damaged at yea rl y i nte r val s of : 9, 10 , 13, 8,
10, 10, S, 9 , 6 , 1S, 9, 38, and 36 years . The fi r e
scar occurr i ng between 6 and 38 was 1893 . Ten
years late r, t he United States Forest Service began
fire pr even tion in this a r ea. Therefore, the next
fi re di rl no t occur for 38 years . Since then , the
tree grew f o r 36 years un t i l it was cut in 1967.
This s tump shows a fire scar being prod uced
abo ut once ever y 10 yea r s prior to the start of
protecti on of fo rest lands fr om wildfi r e in 1904.
The 10- year average is a maximum time between
underburnings. Lightning coul d have ignited
pinegrass and burned up t o the tree without causing
a fire sc ar i f pitch or need l es were not present .
l~e have evi dence here t hat f ire bur ned at least
once every 10 years . I feel t hat underburning has
been a nor mal part of the envir onment in the Blue
Ho un tains (Ha nson 1942) . In 1973 , 220 fires were
started by lightning i n the Blue Houn tains ; an
average of one fire fo r each 23 , 000 acres eac h yea r
( Ano n 197 3 ) .
He i g ht and diame t e r growt h of tr ees wh i ch developed with r ec urrent und e r burning i s en t i r el y dif fe r e n. Incremen t cor es show diame t e r gr owth (BH) of
three to five rings pe r i nch at the center of a
tree . Rate of diameter gr owth gr adual ly slowed as
s t a nd densi t y i nc r eased. This s ugges t s that ini t ial
s t ocki ng dens ity of mos t na utral pine s t ands was
quite low. Lo w stocking de ns ity i s fur the r s uppor ted by pr esence of l a r ge de ad limbs close t o the
ground . Hany old-gr owt h ponde rosa pi ne still r etain
l imbs two t o fo ur i nches in diame te r in the lowe r
third of the bol e which could only develop under
open stocking .
The rel a t io nship be t ween unde r burn ing and t ree
stocki ng has impor ta nt l a nd · managemen t i mpl i ca tions .
First , s t ocking l ev el control is mandato ry . Ove rly
dense yo ung s t and s mus t be pr e- commer cially t hinned
so tees can gr ow to comme r cial size . Once of commercial size , pe r iodic thinning is desirable to pr event stand s t agna t io n and red uced growth. A second
concern deals with estimating al l owable cut volumes .
Some methods acce pt " f ully stocked stands" as
contributi ng a full share to ha rvest able volume .
Smal l - di ame t e r stagna t ed s t and s of pre- commer cial
s i ze will no t furni sh f uture scheduled harvestable
vol ume .
The typi cal s t a nd is fo rty ye ars ol d , e i gh t
feet tall , t wo inches DBH a nd growi ng at SO rings
per inch (0. 4 i nches diamete r gr owt h i n 10 yea r s).
A land manager dealing wit h po nderosa pine , Dougl asfir or whi t e fi r in the Blue Hountains is no t fa t
a nd happy wi th "well-stocked s tand s ." Instead , he
has an economic liabili ty on his hands r equiring
sta nd treatment prior to realizing an eco nomically
saleabl e produc t . The manage r s hould be mor e
satisfied wi t h "unde r stocked stands " which wi l l gr ow
r apidly to a s ui t ab l e diamete r.
FORESTRY
Underbur ning has affec t ed trees in ano the r way.
Fire has selectively killed wh ite fir and Douglasfi r while favo ring po nderosa pine due to highly diff e r ent bark conditio ns . Pi ne develops fi r e- resis t a nt
bark containi ng a one-eig hth- t o one- fo ur th- i nchthick dead oute r l aye r a t abou t two i nches diame t e r .
Fi r bark remains gr een and pho to syn the tically al i ve
up t o fo ur inches diameter. This ba r k is so sensi t ive
to heat that fi re bu rning qui ckly thr ough pineg r ass
i s able to kill t he bark a nd destroy the tr ee . I n
fact , white fi r bark is so sensitive t o hea t that
understory t r ees r eleased by overstory r emoval of t en
Recur ren t underburning in the ponderosa
pi ne coni fe r /pinegrass plant community maintained
a very ope n s toc king of t rees by periodic thinning .
Gro ups of young po nderosa pine under significant
Competi t io n could not grow fas t eno ugh i n diamete r
or height t o e scape the fi r es . This means t hat ponderosa pi ne s t a nd s did no t develop according t o t he
classical conce pt of "no r mal stand development"
(Heyer 1961) . No r mal stand devel opment suggests
that t housands of seedlings become established,
some seedling s grow faste r t ha n othe r s , become
76
suffer sunscald due to temperatures created by
direct sunlight. With the demonstrated success of
wildfire suppression, ponderosa pine is being
replaced by white and Douglas-fir. By eliminating
underburning, we have changed the environment to
such an extent that a new "primary'' succession is
taking place. The ponderosa pine/pinegrass community is changing to a fir/pinegrass-heartleaf arnica
plant community "mixed conifer/pinegrass" rather
than ponderosa pine/pinegrass. Our data indicates
that cubic volume productivity of wood is about 20
percent greater when the site is dominated by firs
than when it is dominated by ponderosa pine. (Hall
1973 ).
RANGE
Underburning has had both a direct and indirect
effect on ground vegetation; directly by burning and
indirectly by permitting tree cover to increase.
Fire-dependent ponderosa pine/pinegrass produces 500
to 600 pounds of forage per acre in pinegrass and
elk sedge under 50 percent tree crown cover. As pine
is replaced by fir, tree crown cover increases
significantly. This crown cover drastically reduces
ground vegetation under 100 percent tree cover,
grass production is only 50 to 100 pounds per acre
and heartleaf arnica becomes apparent. Clearly,
control of underburning has not only caused an
increase in fir and a change in tree dominance but
also has caused a dramatic shift in ground vegetation.
Realizing that underburning has tended to favor
ponderosa and discourage white fir is significant
information for the land manager. He has the opportunity of growing at least three different tree
species on this site instead of just ponderosa. He
~as an opportunity of increased fiber production by
converting pine to fir. But he should note that fir
only regenerates under a shelterwood often of ponderosa pine,· whereas ponderosa can regenerate in
full sunlight. This means silviculture for maintaining ponderosa pine is different from Douglasfir or white fir.
This shift in ground vegetation has significant
livestock management tmpacts. In 1940, 64,000 antmal
units grazed in the Blue Mountains for three months.
By, 1970, 10,000 animal units were lost because of
increasing fir cover, a 16 percent reduction. An
animal unit is one cow and her calf or five to seven
sheep. This reduction represents not only a significant financial impact on ranchers dependent upon
National Forest land but it also significantly reduces red meat for the consumer. In 1940, the Blue
Mountains supplied 64,000 people with their one-year
supply of beef (114 pounds per person per year). By
1970, only 54,000 people were supplied. Even though
population of the United States increased, the ability to produce red meat was eliminated for 10,000
people.
Lack of underburning has apparently retarded
growth of ponderosa pine trees. On several sites we
compared height and diameter growth between ponderosa pine and white or Douglas-fir in full sunlight
under low stocking conditions. On one site, ponderosa was 41 years old, 2 inches diameter, and 8
feet tall. Within 10 feet of this tree in equally
full sunlight was a white fir 20 years old, 3
inches diameter, and 18 feet tall. Pine grew 6
inches in height last year and the fir grew 20
inches in height; Pine averaged 40 rings per inch
diameter growth and fir averaged 13 rings per inch.
Old-growth ponderosa on this site, which developed
with periodic underburning, showed 3 to 5 rings per
inch diameter growth at the tree center and 5 to 7
rings per inch at 3 inches DBH. Something seems to
inhibit growth of ponderosa pine while not adversely affecting white fir or Douglas-fir.
Changing ground vegetation due to tree cover
poses a problem in evaluating condition of the
rangeland and trend in dominance of forage plants
(Dyksterhuis 1949, Ellison 1951 ). In "typical"
rangeland evaluation, good condition is equated with
climax vegetation dominance. If livestock are forced
to overgraze the range, they kill the most palatable
forage plants, causing a downward trend in their
dominance. The range is then considered to be in
fair or poor condition. This very same situation is
occurring without livestock influence in the mixed
conifer/pinegrass community. Pinegrass and elk
sedge, the most palatable plants, decrease with
increasing tree cover. Interpretation of range trend
must separate changes in ground vegetation caused by
tree cover from those caused by livestock impacts.
Interpretation of trend is our best means of
appraising current livestock management--we strive
for no downward trend in good range condition or
upward trend in fair or poor condition.
I suspect a selective inhibitory substance in
ponderosa pine litter that is destroyed with periodic underburning. Without fire, this substance is
free to build up in the soil and reduce pine growth.
Measurements on underburned stands have suggested
increased diameter growth of pine compared to
unburned controlled plots. A somewhat analogous
situation has been found in France with Norway
spruce. Under dry summers and buildup of tree
litter, manganese reaches concentrations that prevent regeneration of spruce. It does not prevent
regeneration of beech and maple. Consequently, the
land manager in France must grow alternate rotations of spruce and hardwoods or destroy the toxic
manganese in litter by scarification (Duchaufour
and Rousseau 1959). In this country, pine litter
has been shown to influence root growth of various
grasses and forbs (Jameson 1968, McConnell and
Smith 1971).
On forest areas, condition of the rangeland
must be related to tree cover instead of climax
ground vegetation dominance. The climax condition
under 100 percent fir cover is not a suitable benchmark for estimating how much pinegrass and elk sedge
should occur under a 50 percent crown cover of pine.
Range condition guides must relate tree cover to
composition, density and productivity of ground
vegetation.
77
Big-game animals, deer and Rocky Mountain elk,
suffer the same reduction in forage as livestock.
In addition, variety of palatable plants is significantly reduced. In the ponderosa pine/pinegrass
fire community, five to eight plants contribute
significantly to deer and elk forage. In the dense
fir/pinegrass-arnica community, only three plants
significantly contribute forage.
Underburning has had a direct effect on ground
vegetation. Fire had to be carried by ground
vegetation. Thus, pinegrass, elk sedge, balsam
woollyweed, vetch, arnica, strawberry, and all
other ground vegetation plants in this community
developed genetically under 100 percent utilization
every few years. Those plants best able to compete
and colonize the site became dominant. Nature
selected these plants genetically in the same way
we breed and select pasture or hay grasses.
Various species and varieties are mowed at two- or
three-inch stubble heights to evaluate their performance under use. Those Which perform best are
selected to produce pasture or hay. Periodic
burning has endowed pinegrass and elk sedge with
the ability to withstand utilization by livestock.
They can persist and increase under natural range
conditions with 25 to 40 percent utilization every
single year.
Some plants often found in this plant community,
like the shrub ceanothus, need fire for continued
survival. Ceanothus seeds require heat treatment by
underburn or conflagration fire to trigger
germination (Hickey and Leege 1970). With fire
suppression, many stands of ceanothus have not
regenerated. This shrub is desirable because it
provldes cover and essential early spring, late
fall and winter forage for game animals, and it
adds nitrogen to the soil. The current means of
maintaining ceanothus is logging and use of fire
for residue reduction.
climax? Fire suppression was initiated about eighty
years ago which hardly seems long enough for a climax to have developed.
Another tmplication of climax is that greatest
species diversity occurs in this condition (Odum
1971). Vegetational succession in the mixed conifer/
pinegrass type clearly suggests decreasing species
diversity as climax status is approached. For example,
under pine canopies of 50 percent·, 15 ground vegetation species constantly occur and three tree species
can regularly be found. Under climax conditions,
white fir clearly dominates to the exclusion of ponderosa pine and generally Douglas-fir, and only 7
ground vegetation species constantly occur, none of
which are legumes or shrubs. As a result, wildlife
diversity is also reduced. As noted earlier, 5 to 8
species are palatable to deer and elk under open
pine While only 3 contribute under dense fir.
Climax has also been described as a "stable
state" (Daubenmire and Daubenmire 1968, Odum 1971,
Oosting 1958)• This concept ·suggests that, barring
some natural disturbance, the plant community is
stable. The tussock moth epidemic, which occurred in
the Blue Mountains in the early 1970's, indicates that
climax is most unstable (Brooks, et.al. 1978). Total
stand death only occurred where white fir was the
sole tree species -- climax. Total stand death never
occurred with a mixture of species -- successional
pine-fir/pinegrass. A similar climax vs. successional
relationship is occurring today with a western pine
beetle epidemic. Apparently climax is a condition
where plant succession is very slow but is it also a
condition highly susceptable to disturbance. An
interesting combination of successional "stable
state'' with a disturbance "unstable state".
WILDLIFE
Underburning has affected wildlife in several
ways: stocking level control of trees, encouragement
of successional vegetation and high forage production. Previous discussions have pointed out the
decrease in both herbage production and plant species
diversity as mixed conifer/pinegrass changes form
open pine to dense fir. This change decreases forage
for wildlife and also changes wildlife habitat. Under
fire, recently burned areas were foraging spots due
to legumes and the sttmulation of palatability, tall
trees produced thermal cover, and occasional patches
of regeneration afforded hiding cover (Thomas 1979).
Climax stands seem to have uneven-aged structure
which provides cover but little forage.
Use of prescribed fire in mixed conifer/pinegrass has produced other results. In no case has a
species been eliminated by burning; instead from
one to three new species appear, particularly
legumes such as lupine and vetch. In all cases,
herbage production has increased the year following
burning ranging from 20 to 35 percent and persisting for another 1 to 3 years. And palatability of
pinegrass is increased when fire is hot enough to
burn at least half the duff layer. Cool fire, burning the leaf litter and no duff, does not effectively stimulate legumes, herbage production or
palatability.
ECOLOGY
Past fire has been particularly tmportant to the
pileated woodpecker. This 14-inch~long bird prefers
a ponderosa pine or western larch tree about 24
inches in diameter where it excavates its nest hole,
usually over 40 feet above the ground which requires
a tree about 30 inches DBH. Large, tall, successional
trees suitable for pileated use were produced by
underburning which encouraged pine and larch and also
maintained stocking level control necessary for
growing large diameters. But these circumstances
were not optimum because underburning that produced
large trees also burned up snags housing carpenter
Effects of underburning on both trees and
ground vegetation has raised some interesting
ecological questions. For example, what is climax:
pristine, fire maintained ponderosa pine/pinegrass
or the newly developing white fir/pinegrass-arnica
kind of plant community? Classification and study
of plant communities often uses climax as a point
of reference (Daubenmire and Daubenmire 1968, Odum
1971, Oosting 1958). But how can "climax" without
fire be estimated if most stands have never been in
78
ants used as a staple winter forage supply. And
the burning also tended to prevent an understory
of trees characteristic of most-used pileated woodpecker nesting habitat. Optimum habitat is large,
overstory pine or larch with an understory of trees
less than 50 feet tall and a suitable supply of
heart-rotted snags housing carpenter ants (Thomas
1979). This condition is presently common due to 80
years of fire suppression and seems to represent
a mid-successional optimum for pileated woodpeckers.
Climax without pine or larch is sub-optiomal as is
fire maintained ponderosa pine/pinegrass.
from burning two tons per acre is easily dissipated
through the open crown cover of pine. With a change
from pine to fir, pine trees die and fall to the
ground greatly increasing fuel and crown cover
closes.
A near climax stand appears to have both overstory and understory fir with crown closure exceeding
100 percent. Cover greater than 100 percent is possible When cover of overstory and understory are
measured separately. Up to 30 tons of moderate to
heavy fuel cover the ground. When lightning strikes
in this stand, the fire does not move quickly
through light, flashy fuel but tends to burn hotter
and slower in tree needles, twigs and old trees.
This heavier fuel produces more heat and the closed
crown canopy does not permit heat to escape. The
result, volatilization of flammable oils in tree
needles which suddenly ignite in an explosion to
create a catastrophic crown fire. This phemonenon
was precisely the cause of conflagration fire in
Mitchell Creek during those terrible Wenatchee,
Washington, fires of 1970. Mitchell Creek is primarily mixed conifer/pinegrass. It was totally
consumed by fire.
Livestock grazing has suggested another specter
of traditional thought. Wildlife are considered to
have developed concurrently with vegetation and
climate. In so doing, they have generally filled
most habitat niches by one or more species (Moen
1973). Livestock currently fill a niche apparently
unoccupied prior to White settlement. Historical
reports of elk and deer suggest current populations
are greater than under pristine conditions. In
addition, livestock produce as much red meac today
as all the deer and elk harvested in the Blue
Mountains. At 6.1 million pounds, one might consider this a significant niche.
SUMMARY
SOIL
We have seen that underburning was common in
mixed conifer/pinegrass. By deduction, it would
seem that soils have developed under periodic underburns in this plant community. For years, these
soils caused consternation to soil scientists
trying to classify them by European or eastern
United States nomenclature. The mixed conifer/pinegrass plant community occurs in a northern type of
environment characterized by snow cover during the
winter (Montane Forest Formation) (Lutz and Chandler
1946, Oosting 1958). In Europe and the eastern
United States, montane forests invariably grew on a
podzol or podzolic soil. A podzol has a very dark
A-1 horizon one to three inches thick, a White A-2
horizon three to six inches thick, and below that a
B horizon of brown to dark brown. Mixed
conifer/pinegrass soils do not show this sequence.
Instead they gradually grade from dark to light
brown. These have been referred to by Canadians as
gray wooded or brown forest soils (Spilsbury 1963).
They occur in the West under forest/grass plant
communities that have been periodically
underburned. Underburns consumed litter contributing
to podzol development. Abundant grass roots have
carried a brown to moderately dark brown color well
down into the soil profile. Brown forest soils
developed under periodic burning and are capable of
withstanding periodic burning. In fact, if our supposition is correct that ponderosa pine litter inhibits ponderosa pine growth, it would seem desirable
to consider periodic burning.
Interpreatation of underburning effects in mixed
conifer/pinegrass vegetation of the Blue Mountains
in eastern Oregon suggest that: underburning occurred
at about 10-year intervals; ponderosa pine is being
replaced by Douglas-fir and White fir; ponderosa
pine stands did not develop according to the "normal
stand development" concept; stocking level control
is required to avoid stagnation; range grasses
decrease with increasing tree cover as pine is
replaced by fir regardless of livestock use, thereby
complicating interpretation of range trend; range
condition guides can not be based on climax, instead
they must be tied to tree crown cover in successional stands; pinegrass is capable of sustaining
livestock use because it developed under periodic
100 percent use by fire; livestock are filling a
large animal "niche" unoccupied by wildlife and
account for as much animal production as all the
deer and elk in the Blue Mountains: some plants seem
dependent on fire for their survival, such as
ceanothus and some legumes; species diversity, both
plant and animal, is greater in successional pinfir/pinegrass that in climax; use of climax for ecological interpretation seems tenuous since most
stands have never been in a non-fire climax; soils
developed under periodic fire and should be considered
"brown forest" rather than "podzolic"; burning
apparently does not damage soils since total herbage
production is always greater following fire; underburning has influenced wildlife, such as the
pileated woodpecker, in which successional trees
were encouraged and stocking level control was maintained to produce large diameter trees; and fire
hazard is changing from light, flashy fuel under
open tree canopy to heavy fuels under a nearly
closed canopy.
FIRE HAZARD
Ftre hazard is directly correlated with changes
in tree cover and ground vegetation. In open
pine/pinegrass, about two tons of needle litter can
develop in ten years between fires While herbaceous
flashy fuel is only about a thirn of a ton. Heat
79
Control of underburning in the mixed
conifer/pinegrass community has created an
increased fire hazard in a known fire environment.
We have changed from a fire-resistant plant community to a fire-susceptable plant community. We
may NOT be able to manage for fir in this environment due to fire hazard. We may not have a choice
about burning -- only a choice of how to burn:
prescribed fire or wildfire.
LITERATURE CITATION
Anon. 19(3. National Forests fire report. USDA,
Forest Service.
Arno, Stephen F. 1980. Forest fire history in the
northern Rockies. Jour. For. 78(8):460-465.
Brooks, Martha H., R. w. Stark, and Robert w.
Campbell. 1978. The Douglas-fir tussock moth; a
synthesis. USDA, Forest Service, Tech. Bull.
1578, Washington D.C. 331 pp. illustr.
SPECIES LIST
PLANTS
Arnica
Arnica cordifolia
Balsam woollyweed
Hleracium scouleri
Ceanothus
Ceanothus species
Douglas-fir
Pseudotsuga menziesii
Elk sedge
Carex geyeri
Firs
Abies grandis and Pseudotsuga
menziesii
Heartleaf arnica
Arnica cordifolia
Lodgepole pine
Pinus contorta
Lupines
Lupinus spp.
Mixed conifer
Pinus ponderosa, Pseudotsuga
menziesii, Abies grandis
Norway spruce
Picea excelsa
Pinegrass
Calamagrostis rubescens
Ponderosa pine
Pinus ponderosa
Strawberry
Frageria species
Vetch
Vicia americana
Western larch
Larix occidentalis
White fir
Abies grandis
Daubenmire, R. and Jean B. Daubenmire. 1968. Forest
vegetation of eastern Washington and northern
Idaho. Wash. Agr. Exp. Stat., Tech. Bull. 60,
Wash. State Un., Pullman, WA 104 pp., illus.
Duchaufour, PR. and L.A. Rousseau. 1959. Phenomena
of Poisoning of Conifer Seedlings by Manganese
in Forest Humus. Revue Forstiere Francaise,
December, 1959.
Dyksterhuis, E.J. 1949. Condition and Management of
Range Lands Based on Quantitative Ecology.
Jour. Range Mgmt. 2(3): 104-105.
Ellison, L. 1951. Indicators of Condition and Trend
on High Range Watersheds of the Inter-mountain
Region. USDA, Agricultural Handbook No. 19. 66
PP• illust.
Hall, Frederick c. 1973. P.lant Communities of the
Blue Mountains in Eastern Oregon and
Southeastern Washington. USDA Forest Service,
Pacific Northwest Region, R6 Area Guide 3-1. 62
PP•; illust.
Hansen, Henry P. 1942. Ebst-Mount Mazama Forest
Succession on the East Slope of the Central
Cascades of Oregon. Amer. Midland Naturalist
27(2): 523-534.
Hickey, William o. and Thomas A. Leege. 1970.
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Review. Idaho Dept. Fish and Game, Wildlife
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Jameson, Donald A. 1968. Species Interactions of
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Arizona. U.S.D.A., Forest Service, Rocky
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Note RM-113.
ANIMALS
Deer
Odocoileus hemionus
Rock Mountain Elk
Cervus canadensis
Pileated woodpecker
Dryocopus pileatus
Lutz, Harold J. and Robert F. Chandler, Jr. 1946.
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N.Y. 514 pp., illustr.
McConnell, Burt R. and. Justin G. Smith. 1971. Effect
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Meyer, Walter H. 1961. Yield of Evenaged Stands of
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80
LITERATURE CITED
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and Co., San Francisco, 458 pp., illust.
Thomas, Jack Uard. 1979. Wildlife Habitats in
Managed Forests. The Blue Mountains of Oregon
and Washington. U.S.D.A., Forest Service, Agr.
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Odum, Eugene P. 1971. Fundamentals of ecology, W.B.
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~Ieaver,
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81