MORTALITY OF ASPEN ON THE 

GROS VENTRE 

ELK WINTER RANGE 

R. G. Krebill 

USDA Forest Service Research Paper INT-129, 1972 

INTERMOUNTAIN FOREST AND RANGE 

EXPERIMENT STATION 

Ogden, Utah 84401 
USDA Forest Service 

Research Paper INT- 129 

November 1972 

MORTALITY OF ASPEN ON THE 

GROS VENTRE 

ELK WINTER RANGE 

R. G. Krebill 

INTERMOUNTAIN FOREST AND RANGE EXPERIMENT STATION 

Forest Service 

U. S. Department of Agriculture 

Ogden, Utah 84401 

Robert W. Harris, Director 
R. G. KREBILL, Plant Pathologist, stationed at the Forestry Sciences 

Laboratory, Logan, Utah, joined the Intermountain Station staff 

in 1962. He holds the bachelor of science degree in forestry 

from the University of California and the doctoral degree in plant 

pathology from the University of Wisconsin. He has published 

many articles on rusts of conifers, and recently has undertaken 

research on diseases of trees and shrubs important to wildlife 

and recreation. 

Special recognition is extended to George E. Gruell, Teton National Forest, and Norbert V. DeByle, Intermountain Station, for their 

encouragement and advice on aspen ecology and the ways of wildlife; to 

Chester E. Jensen, Intermountain Station, for his help in sampling 

design; to T. E. Hinds, Rocky Mountain Station, for training in recognition of aspen diseases; and to Jack D. Rogers, Washington State University, and Flora G. Pollack, USDA. Agricultural Research Service, 

Beltsville, who helped identify specimens of some of the problem fungi. 

To these and other helpful friends, the author is deeply grateful. 
CONTENTS 

INTRODUCTION ................ METHODS ................... RESULTS ................... Age of Overstory Trees ............ Mortality of Overstory Trees ......... Aspen Sprouts ................ Miscellaneous Information on Injury. 

Pathogens. and Insects .......... Associated Understory Vegetation ....... DISCUSSION AND CONCLUSION . . . . . . 

LITERATURE CITED .............. 

Page 

1 

4 

6 

6 

6 

8 
ABSTRACT 

Stands of aspen on the Gros Ventre elk winter range of northwestern 

Wyoming are suffering high mortality and are not regenerating satisfactorily. If the 1970 mortality rate (3.6 percent) continues, about a two-thirds 

reduction in the numbers of tree-sized aspen can be expected by year 

2000. Collected evidence suggests that the mortality rate is unusually 

high because of a combination of pathogenic fungi, injurious insects, and 

physiological stress that follow bark wounding of tree trunks. Elk and 

possibly moose are suspected of causing most of these severe trunk injuries. Sooty bark canker, Cytospora canker, sllld stem-boring insects 

were the most common pests associated with tree mortality. The prospect for aspen on the elk winter range is especially critical because of the 

heavy impact of browsing and pests on aspen sprouts which prohibits 

natural replacement of the dying aspen overstory. 
INTRODUCTION 

Aspen (PopuZus trernuloides) provide beautiful scenery and important wildlife 

habitat on the Gros Ventre elk winter range of the Teton National Forest in northwestern Wyoming. Although aspen occupies only about 4 percent of the winter range, the 

type usually is in a conspicuous position in the lower and middle elevations where it 

often forms transition zones between shrub rangelands and conifer forests. Ecological 

succession has not been satisfactorily documented for the Gros Ventre, but the aspen 

type of the general area is now mostly considered as being sera1 to conifers and to have 

been perpetuated by wildfire (Gruell 1970; and Loope 1971). Fires of the 1870's and 

1880's are thought to have been particularly important in shaping the current vegetation, but more recently "...fire protection has allowed many aspen stands to be invaded 

by conifer species" (Gruell 1970). Some -2,000 to 5,000 elk (Cervus canadensis nelsoni) 

are thought to winter in the Gros Ventre area. Supplemental winter feed is supplied at 

three Gros Ventre stations, but elk also feed on native trees, shrubs, sedges, grasses, 

and forbs. Heavy elk use of aspen has, for several decades, been noted by the occurrence of "highlined" trees and browsed spr0uts.l Elk and also moose (AZces aZces 

shirasi) apparently contribute to the conversion of aspen stands to conifers (Beetle 

1968; and Gruell 1970). These animals cause injuries (fig. 1) that presumably induce 

susceptibility of aspen to disease (Loope 1971) and they consume sprouts that might 

otherwise replace dying overstory trees. In numerous stands, aspen are obviously dying 

at an alarming rate (fig. 2). When conifers are absent, it appears that deteriorating 

aspen stands will retrogress to a treeless rangeland type (fig. 3). 

The study described herein was initiated to provide an up-to-date prediction of 

the future of aspen in the Gros Ventre area. Emphasis was placed on determining the 

rate of mortality of the aspen overstory, its causes, and the likelihood of overstory 

replacement by natural sprouting. Hopefully, these findings will inform resource 

managers about the severity of the aspen deterioration problem so that they might better 

determine whether modifications in current management might be necessary to maintain 

the pleasing diversity of forest types now present in the Gros Ventre. 

llnspection reports of Teton National Forest as relayed by George E. Gruell, 

Wildlife Biologist, Teton NF, Jackson, Wyoming. 
Figure 1 .--Excessive game use of aspen is especiaZly evident in close proximity to elk 

feedgrounds where trees have suffered severe bark damage and sprouts are 

browsed down to the snow ZeveZ. 

-~ .. ~ 

Figure 2.--Late stages of aspen deterioration in a stand south of Upper SZide Lake. 

Areas such as this are currentzy changing from an aspen type to a grass-forb 

parkZand with scattered conifers. Many other deteriorating stands succeed more 

rapidZy toward a conifer type, but some cuZminate in shrub, grass, and forb 

communities. 
Eigure 3.--Deteriorated stand of aspen on Breakneck Ridge east of Upper Slide Lake. 

Although ,it once supported a nearly continuous aspen crmn canopy over several 

acres, this site has reverted to a rangeland dominated by shrubs, forbs, grasses, 

and decaying aspen remnan5s. 
METHODS 

The 84,000 acres of the middle Gros Ventre drainage selected for this study contained most of the aspen stands influenced by wintering elk (fig. 4). Within this area 

100 sample plots were located by a method in which one plot occurred at random within 

each 33.3 acres of the 3,330 acres of aspen type delineated on the Forest Service 1956 

Timber Type Map. Each plot was circular and 1/20 acre in size. Aspen ages were 

estimated by increment cores extracted at the 10-inch height from two trees containing 

wood sound enough for ring analysis and located nearest the plot centers. Ring counts 

were made in the laboratory with the aid of the acid-phloroglucinol staining technique 

of Patterson (1959). All aspen trees (individual stems taller than 10 feet) within 

plots were tallied by 6-inch d.b.h. size classes and condition classes: i.e., live, 

died in the current season, or died before the current season. Trees were assigned to 

current year mortality if unweathered dead leaves still remained in the crown. Dead 

trees that had fallen to the ground were not included in the sample unless they were 

windfall of the current season. 

Sampling began in August 1970 and was completed in September, before fall coloration. This short time span insured a fairly comparable estimation of current mortality 

on all plots. Special efforts were made to record indicators that might suggest the 

cause of mortality in both classes of dead trees and the presence of injury or disease 

on all trees. Aspen sprouts within the plots were tallied, their heights determined, 

and any evidence of injury from browsing, insects, or diseases was recorded. The 

presence and ground coverage provided by young conifers, conspicuous shrubs, grasses, 

and forbs were also noted since understory vegetation can provide clues as to the 

degree of inherent stand stability and disturbance. 
Figure 4.--Boundaries of the Gros Ventre study area, Teton NationaZ Forest, Teton 

County, Wyoming. 
RESULTS 

Age of Overstory Trees 

As determined by ring cou~lts, the trees sampled in the Gros Ventre were relatively 

old; none were less than 40 years of age, and the majority were between 81 and 120 years. 

The following tabulation shows the age distribution of sample trees: 

Age cZass 

Years 

Frequency 

Percent 

Mortality of Overstory Trees 

The combined sample from all plots totaled 2,332 live trees and 1,684 dead trees, 

of which 86 had apparently died during the 1970 season. These data are transformed to 

a per-acre basis (mean number of trees per acre) and presented in greater detail in the 

following tabulation: 

Size cZass, in. d.b. h. Live trees Dead trees Died in 1970 

Combined 
Wind breakage, sooty bark canker, and llbarking" complemented by weak parasites and 

stem-boring insects accounted for most of the aspen mortality on the sample plots, as 

shown in the following tabulation: 

Size class "Barking, " weak 

in. d.b. h. Wind breakage Sooty bark canker parasites, pests, etc. 

Percent Percent Percent 

Combined 2 35 6 3 

Death resulting from wind breakage or windfall was infrequent in small trees but 

rather common in the larger tree classes. 

Cenangiwn singutare, cause of sooty bark canker, was the single most injurious pathogen 

found on dead trees (fig. 5), and it too was especially prevalent in the larger tree 

classes. The third group was composed of trees that seemed to have died from a mixture 

of the following: bark wounding by elk or moose; infestation by stem-boring insects 

(probably species of Agrilus) (fig. 6); infection by bark fungi (including Cytospora 

sp.); suppression; and occasionally,, sunscald. Mortality caused by this mixed category 

was especially prominent among the smaller trees. 

:gure 5. --Sooty bark canker, 

caused by the fungus Cenangium 

singulare in game-wounded portion of the aspen trunk on the 

left. The tree on the right 

was also scarred by game, but 

otherwise has remained healthy 

Note the advanced degree of 

stand deterioration and the 

absence of visible sprouts. 
Figure 6. --GaZZeries of 

stem-boring insects, 

preswnabzy Agrilus sp. 

in cambia2 zone as see 

when dead bark is 

stripped from aspen 

trunk. 

Aspen Sprouts 

Even though generally hidden by grasses, forbs, and shrubs (fig. 7), aspen sprouts 

were found in 96 of the 100 plots. Expanded to a per-acre basis and expressed at the 

0.05 confidence interval, the mean number of aspen sprouts ranges from 463 to 843 per 

acre, but 20 plots had less than 100 aspen sprouts per acre. Sprouts of 84 plots 

showed indications of having been browsed down annually to less than 2 feet in height. 

Sprouts surv'ived and grew beyond a height of 3 feet in only three plots. 

Miscellaneous Information on Injury, Pathogens, and Insects 

Although diagnosis of mortality was emphasized during field evaluation of plots, 

the more obvious injuries, pathogens, and insects were noted and recorded. The 
Figure 7. --Aspen sprout 

browsed off to about 14 

inches high. There were 

an average of 653 sprouts 

per acre on sqZe pZots, 

but most were overtopped 

by forbs as is shown in 

this photo. Although 

aspen sprouts were 

present on 96 pZots, 

they were actuaZZy 

rep lacing dying trees 

on only three plots; 

aZZ other aspen sprouts 

were held in check by 

browsing and pest 

damage. 

incidence of disease and insect problems in stems expressed as a percentage of the 

aspen tree sample (n=4,016) is shown in the following tabulation: 

Prob Zem 

Bark wounds 

Stem-boring insects 

Cytospora canker 

Sooty bark canker 

Cryptosphaeria canker 

Heartrot 

Ceratocystis canker 

Rough stem galls 

Roundheaded borer galls 

Buttrot 

do,. 

Causa Z organism 

Big game and rodents 

Agri Zus spp . Cytospora chrysospema 

Cenangiwn singuZare 

Cryp tosphaeria popu Zina 

Fomes igniarius 

Ceratocystis fimbriata 

Dip Zodia twne faciens 

Saperda sp. 

Fomes app lanutus 

PhoZiota squarrosa 

Plot 

incidence 

2~dentified by symptoms only. 
The incidence of diseases and insects in aspen foliage in 1970 expressed in terms 

of presence in all plots (n=100) is shown in the following tabulation: 

Prob Zern 

Aspen leaf miner 

Aspen leaf blight 

Aspen shoot blight 

Causa Z organism 

PZot 

incidence 

Phy ZZocnistis popuZie ZZa 53 

Marssonina popuZi 13 

PoZZaccia radiosa 8 

Inasmuch as only the more obvious injuries and pests were recorded, the frequency 

and various types of tree Bamage problems probably are underestimated in these tabulations. For example, conks (used to indicate incidence of heart and buttrot) were evident 

on less than 2 percent of the trees sampled, but heartrot was present in 33 percent of 

the increment cores examined for age data. Furthermore, some types of aspen damage in 

the Gros Ventre were not included because they occurred outside the 100 sample plots. 

For example, beaver (Castor canadensis) had damaged trees immediately adjacent to one 

plot but there was no beaver damage in any of the plots. 

Many of the problems listed in the tabulations on pages 9 and 10 are combined in 

the mortality figures shown in the tabulation on page 7. For instance, Fomes appZanatus 

had rotted the roots of at least three trees that succumbed to windfall. Likewise, 

heartrot was present in many other trees that were included in "wind breakage," and at 

least one tree broke off at a Ceratocystis canker. 

In addition to the direct effects of bark injury caused by game and rodents, it 

was also noted that 90 percent of the sooty bark cankers occurred in the lower part of 

trees where the trunks had been scarred by animals. Elk were responsible for most of 

these bark scars, but moose, mice, and hares also contributed. 

Of the foliage pests, shoot blight was limited to sprouts, but leaf blight and 

the aspen leaf miner occurred both on sprouts and on overstory leaves. Aspen leaf 

hoppers were rare, but occurred on sprouts in at least one plot. 

Associated Understory Vegetation 

The mean understory vegetation was composed of about 49 percent forbs, 36 percent 

grasses and occasional sedges, 12 percent shrubs, and 3 percent conifer saplings. Each 

of these groups contained a diversity of species. The frequency of occurrence of the 

more conspicuous trees, shrubs, and forbs are presented in table 1. Grasses and sedges 

were not identified except for pinegrass (CaZamagrostis rubescens), which on an average 

occupied 66 percent of the ground cover in the eight plots in which it occurred. 

Although forbs were present in all plots and grasses or sedges were found in all but 

one plot, shrubs were absent from 10 plots and conifer saplings were missing in 27 plots. 
Table 1.--Constancy of trees, shrubs, and forbs comonZy found in the 200 s

l~he shrubs Lonicera invoZucrata, Prunus virginiana, SaZix scouZeriana, Ribes sp

aZnifoZia, Sambucus sp., and Pachistima myrsinites were present in fewer than five of 

there were 16 species of forbs not listed because they were noted in fewer than 10 pl

possible indicator species such as Frasera speciosa, BaZsamorhiza sagittata, Perideri

PyroZa secunda. There were some forbs in this group (such as AZZiwn sp., Tarmacwn s

gZauca) that probably were more frequent but were inadvertently overlooked because of 

condition at the time of sampling. 

: No. of 

Trees : plots 

Picea engehannii 39 

Pinus f ZexiZis 3 5 

Pinus contorta 16 

Abies Zasiocarpa 16 

Pseudotsuga menziesii 2 

: No. of 

Shrubs : plots 

ROS~ spp. 5 4 

Shepherdia canadensis 53 

Symphoricarpos oreophi Zus 41 

Berberis repens 7 

Artemisia tridentata 7 

PotentiZZa fruticosa 7 

Juniverus communis 5 

ArctostaphzlZos uva-ursi 5 

Forbs 

Geranium richar

Lupinus arqente

ThaZictrwn occi

GaZium boreale 

Fragaria sp. 

AchiZ Zea miZZef

Senecio spp. 

Aster spp. 

Epi Zobiwn angus

Lathyrus sp. an

PotentiZZa grac

PedicuZaris bra

CastiZZe ja suZp

HeZianthe ZZa un
DISCUSSloN AND CONCLUSION 

Since aspen generally are known to be short-lived trees (Strothmann and Zasada 

1957), it is natural that some aspen stands are becoming decadent in the Gros Ventre. 

bleinecke (1929) noted for nearby Utah that senility occurs with aspen at about 120 

years of age and that the "wild aspen forest as a whole does not reach much beyond 

130 years." If this is true for the Gros Ventre, we can expect a marked change in 

much of the aspen type within the next few decades since about two-thirds of the 

sampled trees are already in the 81- to 120-year age class. Furthermore, a drastic 

decline in the aspen type is eminent if game browsing continues to prohibit replacement 

of dying overstory trees and if exclusion of fire continues to allow invasion by 

conifers . 

Even if the aspen senility and decadence situations of Utah do not apply directly 

to the study area, the Gros Ventre mortality data (see page 6, second tabulation) 

provide a dismal view. Using those data we can estimate that in 1970 there were 

approximately 1,500,000 aspen trees in the 3,330 acres of aspen type in the Gros Ventre 

sample area. If the 3.6 percent mortality rate of 1970 remains stable in the future, 

aspen would decline to about 500,000 trees by year 2000, and to only 40,000 by year 

2070. Although the 3.6 percent rate was a fair estimate3 based on the criteria used 

to estimate current year mortality, it probably was conservative since it could not 

have included trees which died in 1970 during winter dormancy. Certainly, these data 

indicate that unless there is replacement of overstory trees, the aspen overstory is 

due for a marked decline. 

Although few comparative data are available, aspen mortality appears to be somewhat 

greater on the Gros Ventre than in other aspen areas. For instance, Hinds (1964) found 

that only 9 percent of the standing trees were dead in sample plots scattered over a 

wide area of Colorado, whereas almost 42 percent in the Gros Ventre sample were dead. 

Assuming that most aspen trees remain standing for about 10 years after death (which 

approximates the measured 1970 Gros Ventre mortality rate), there appears to be less 

35~he confidence interval at the 0.05 level was only 2.6 to 4.6 percent as determined from a standard error computed as described by Freese (1962) for attributes from 

unequal-sized clusters. 
than 1 percent annual mortality in Colorado as compared to the 3.6 percent rate in the 

Gros Ventre. Furthermore, the Gros Ventre rate is perhaps two to four times greater 

than reported recently by Manion and Valentine (1971) in New York. Also, in Ephraim Canyon of central Utah, Dr. K. T. ~ar~er~ found about 2.7 percent annual mortality in 

a sample of 2,091 aspen larger than 4 inches d.b.h. Harper's technique involved reexamination in 1970 of trees originally examined and tagged as being dead in 1969. When 

examining Harper's sample trees in autumn of 1970, we found that many would not have 

been tallied as 1970 mortality by the criterion used in the Gros Ventre study; these 

were trees that had not maintained dead leaves and were assumed to have succumbed during 

the 1969-1970 dormant season. From this we conclude that the 3.6 percent annual mortality measured in the Gros Ventre probably is an underestimate of actual mortality. 

In the Gros Ventre, it appears that increased mortality has been caused by big game 

"barking" combined with pathogens and injurious insects that invade the wounded trees. 

Most of the 1,061 trees included in the "Barking, weak parasites, pests, etc." category 

of the tabulation on page 7 had scars resulting from big game chewing and some had been 

completely girdled. "Barking" damage was most injurious to the smaller trees; this 

partially accounts for the especially high rate of mortality in the 0- to 6-inch class. 

Probably though, the higher mortality in smaller trees was caused mostly by partial 

suppression which reduced their resistance to weak pathogens and stem-boring insects that 

characteristically follow "barking." Cytospora chrysospema probably is a primary 

contributer to the demise of such trees. This fungus was thought to be a major factor 

in the aspen dieback associated with similar elk wounding of .trees in Rocky Mountain 

National Park (Packard 19421, and "...it is generally considered a weak parasite on 

declining or dying trees" (Hinds 1964). Although encountered infrequently, Cryptosphaeria popuZina seemed to replace Cytospora as an invader of wounded bark in the 

dead aspen trees encountered in some of the Gros Ventre plots. It is not known whether 

this fungus is parasitic on aspen, but these observations suggest that it may be a weak 

parasite on this species and similar in aggressiveness to Cytospora. 

The sooty bark fungus (Cenangiwn sing~lZarel is an aggressive pathogen that can 

enter wounded tissues and girdle and kill aspen trees within 2 to 4 years (Hinds 1962). 

In the Gros Ventre, this fungus appears to be frequently aided by AgriZus beetles. 

Although Hinds (1964) found that elk wounds on aspen in Colorado seldom served as 

entrance points for canker organisms, the sooty bark fungus in the Gros Ventre was more 

frequently associated with.big game wounds than would be expected by mere coincidence. 

Perhaps this results from more severe wounding in the Gros Ventre, or possibly wounding 

occurs at a more favorable time for fungus infection. In this respect, it should not 

be overlooked that moose are abundant in the Gros Ventre and might be "barking" some 

aspen trees during the growing season. In this study, a few fresh "barking" wounds 

were found in late September (fig. 8) in an area where only moose sign was fresh. In 

contrast, other observations in the Gros Ventre sample area suggest that most of the 

elk "barking" occurs in winter between December and May. 

Harmful fungi and insects were not particularly severe on aspen foliage during 

1970, but it is suspected that in years when they are epidemic they might complement 

the aggressiveness of other pathogens, or as Mielke (1957) suggested for Marssonina, 

some aspens might even die from heavy attacks. In spite of the appeal of this logic 

the Gros Ventre data failed to support a role by Marssonina in aspen mortality; the 13 

plots showing leaf blight had similar mean numbers of live and dead trees (20.5 and 

14.8, respectively) as did plots without Marssonina (23.7 and 17.1, respectively). The 

hypothesis might better be tested during and after epidemic conditions. 

&personal communication, Dr. K. T. Harper, University of Utah, Salt Lake City, 

based on research while employed by Intermountain Station. 

13 
Figure 8. --Big game scars 

on a 9-inch-diameter 

aspen trunk. The fresh 

toothmarks near the 

center and Zower right 

of this Zate-summer 

photo are suspected to 

have been made by a 

moose. The scar on the 

upper Zeft ZikeZy was 

from elk chewing of the 

previous winter and 

that on the right from 

eZk a year earlier. 

Unfortunately, mortality tends to open the crown canopy which can initiate a chain 

of events that result in rapid stand deterioration. Graham, Harrison, and Westell 

(1963) noted that deterioration following the opening of aspen crown canopies can sometimes render "...within a 5- or 10-year period a valuable stand ... to a worthless 

condition." Presumably, increased exposure to sunlight and associated sunscald that 

results from opening the canopy increases the susceptibility of remaining trees to harmful insects and diseases. This is an alarming hpothesis for the Gros Ventre elk winter 

range where most stands of aspen are already in at least the early stages of deterioration. It also seems reasonable to suspect, as Beetle (1968) suggested, that remaining 

trees become more "vulnerable to wind" as stands are opened up through overstory 

mortality. 

It should not be overlooked that some mortality in a relatively dense aspen overstory might improve wildlife habitat by increasing forage production in the understory. 

Concerning the Coconino National Forest, Reynolds (1969) reported that thinning aspen 

from 229 sq.ft. basal area per acre to 42 sq.ft. per acre significantly increased the 

production of forbs, perennial grasses, and aspen sprouts. In the Gros Ventre, live 

aspens averaged only about 138 sq.ft. per acre in the 1970 plots, but 16 percent of the 

plots had less than half that amount. Natural mortality seldom resulted in fallen trees 

in numbers sufficient to create barriers to animal movement such as Reynolds had noted 

and it is assumed that increased forage is readily available to big game. 
In most Gros Ventre plots there were numerous aspen sprouts (r = 653 per acre), 

but far too few escaped browsing and pests for successful replacement of overstory 

mortality. In fact, replacement was occurring on only three of the 100 sample plots. 

Insects and diseases were injurious to sprouts in addition to the detrimental effect of 

browsing by elk, moose, deer, cattle, and rodents. The aspen leaf miner was prevalent 

and Marssonina leaf blight and leaf hoppers were observed. On some of the wetter sites, 

PoZZaccia shoot blight was devastating. Sprouts that were stripped of leaves by moose 

late in the growing season were particularly sensitive to frost injury, which may partially account for the severe impact of browsing. 

A study of the associated vegetation in the aspen sample plots reinforces the 

conclusion that much of the Gros Ventre aspen is changing. Of the 100 sample plots, 

only 13 plots showed a species composition that was essentially identical to the stable 

PopuZus tremuloides-Symphoricarpos oreophi Zus habitat type described by Reed (1971) . Nevertheless, there is some encouragement from these 13 plots because their 1970 mortality rate was only about two-thirds of that in the remaining 87 plots. Also, these 

plots contained a greater proportion of trees in the smallest size class, in which mortality was only about one-third that of the remaining 87 plots. This supports general 

observations suggesting that some stands of aspen will persist much longer than others. 

Forty-seven of the 100 plots had spruce or fir saplings in their understory; this, and 

the abundance of plants such as buffaloberry (Shepherdia canadensis), indicate that 

perhaps half of the aspen in the Gros Ventre occupy sites that are somewhat like the 

Abies Zasiocarpa-PyroZa secunda habitat type of Reed (1969). It could also be argued, 

however, that the occurrence of plants such as pinegrass, balsamroot (BaZsamorhiza 

sagittata), and sagebrush (Artemisia tridentata), along with the presence of conifer 

saplings in 73 plots, is indicative of a state of browsing disclimax (in the sense of 

Beetle 1968) in otherwise stable aspen. In either case, it is evident that if the 

current trends continue, perhaps one-half to three-fourths of the area now in aspen 

will succeed to conifers. Some of the remaining will go to shrub, grass, and forb 

communities, and at best, only a token amount will remain as a dominant aspen type. 

The high rate of mortality in the aspen overstory on the ,Gros Ventre elk winter 

range appears to be caused mostly by a mixture of pathogenic fungi and insects which 

invade trees wounded by big game. The situation is critical because the combination of 

heavy browsing and pests prevents aspen sprouts from replacing dead trees. If current 

trends continue, most of the aspen type will ultimately be eliminated from the Gros 

Ventre winter range. Additional data about the potential for regenerating these aspen 

stands are needed before an aggressive and intensive management program can be initiated 

to preserve both the aspen type and the big game herds. 
LITERATURE CITED 

Beetle, A. A. 

1968. Range survey in Teton County, Wyoming. Part 111. Trends in vegetation. 

Univ. Wyo., Agric. Exp. Stn., Laramie, Res. J. 26, 16 p. 

Freese, F. 

1962. Elementary forest sampling. USDA Agric. Handb. 232, 91 p. 

Graham, S. A., R. P. Harrison, Jr., and C. E. Westell, Jr. 

1963. Aspens--phoenix trees of the Great Lakes Region. 272 p. Ann Arbor: Univ. 

Mich. Press. 

Gruell, G. E. 

1970. Elk habit investigations, Teton National Forest. In: Jackson Hole Coop. 

Elk Stud. Advis. Counc. Meeting, March 12, 1970, 24 p. 

Hinds, T. E. 

1962. Inoculations with the sooty-bark canker fungus on aspen. Plant Dis. Rep. 

46 :57-58. 

Hinds, T. E. 

1964. Distribution of aspen cankers in Colorado. Plant Dis. Rep. 48:610-614. 

Loope, L. L. 

1971. Dynamics of forest communities in Grand Teton National Park. Naturalist 

22 ~39-47. 

Manion, P. D., and F. A. Valentine 

1971. Diseases of trembling aspen in the Adirondack Region of New York. Plant 

Dis . Rep. 55 : 662-665. 

Meinecke, E. P. 

1929. Quaking aspen--a study in applied forest pathology. USDA Tech. Bull. 155, 

34 p. 

Mielke, J. L. 

1957. Aspen leaf blight in the Intermountain Region. USDA For. Serv. Intermt. 

For. and Range Exp. Stn. Res. Note 42, 5 p. 

Packard, F. M. 

1942. Wildlife and aspen in Rocky Mountain National Park, Colorado. Ecology 

23 ~478-482. 

Patterson, A. E. 

1959. Distinguishing annual rings in diffuse porous tree species. J. For. 57 : 126. 

Reed, R. M. 

1969. A study of the forest vegetation in the Wind River Mountains, Wyoming. 

77 p. Ph.D. thesis, Wash. State Univ., Pullman. 

Reed, R. M. 

1971. Aspen forests of the Wind River Mountains, Wyoming. The Am. Midl. Nat. 86: 

327-343. 

Reynolds, H. G. 

1969. Aspen grove use by deer, elk, and cattle in southwestern coniferous forests. 

USDA For. Serv. Res. Note RM-138, 4 p. 

Strothmann, R. O., and Z. A. Zasada 

1957. Silvical characteristics of quaking aspen. USDA For. Serv. Lake States For. 

Exp. Stn., Stn. Pap. 49, 26 p. 
Headquarters for the Irxtermountain Forest and 

Range Experiment Station are in Ogden, Utah. 

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Bozeman, Montana '(in cooperation with 

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Young University) 

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