A Comparative Study of the Vegetation of Grazed and Ungrazed Canyons of the Wasatch
Range, Utah
Author(s): Walter P. Cottam and Frederick R. Evans
Reviewed work(s):
Source: Ecology, Vol. 26, No. 2 (Apr., 1945), pp. 171-181
Published by: Ecological Society of America
Stable URL: http://www.jstor.org/stable/1930822 .
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A COMPARATIVE STUDY OF THE VEGETATION OF
GRAZED AND UNGRAZED CANYONS OF THE
WASATCH RANGE, UTAH 1
WALTER
P.
COTTAM
AND FREDERICK
R.
EVANS
Universityof Utah, Salt Lake City, Utah
CLIMATIC, PHYSIOGRAPHIC, AND
GEOLOGIC FEATUREIS
INTRODUCTION'
The past twodecades have beenmarked
by intensifiedgovernmentaleffortsin
rangerehabilitation. These efforts
have
been handicapped by lack of definiteinformationabout the pristinenature of
grazed lands as well as about quantitative and qualitative changeswhichgrazing has doubtless induced in the plant
cover. The meagernessof the historical
recordconcerningthevegetationoverthe
vast grazingareas ofthe West at the time
of settlement,togetherwith the almost
totalabsenceofpreservedprimitiveareas,
makes the problemof reconstructing
the
originalplant cover difficultthough not
impossibleto solve. In these problems
ecologyfindsboth a duty and a privilege
to serve the land-useprogram.
The Wasatch Mountains east of Salt
Lake City,Utah, affordedan opportunity
to ascertainsomeoftheeffectsofnearlya
centuryof intensive,unregulatedgrazing
and otherhumaninfluenceson the native
vegetationand soil of various elevations
and slope exposures. This study was
confined to vegetational problems of
Emigration and Red Butte canyons,
while the resultsof parallel but independent soil investigationswerereportedby
Croftet al ('43) of the same and other
areas of the Wasatch Mountains. Emigration and Red Butte canyons were
selected forstudy because of theircomand
parabilityin position,physiography,
historicaluse.
1 Acknowledgmentsare due the Intermountain
Forest and Range Experiment Station, Ogden,
Utah, for valuable suggestionsand financialaid
in the pursuit of this study.
The WVasatchMountains constitute
the northeasternrimof the Great Basin.
They rise abruptly as an escarpment
froma desert floorwith an elevation of
4500 feet up to altitudes of 12,000 feet.
The range is deeply dissectedby numerous canyons having a general east-west
direction,of which Red Butte and Emigrationcaynons are typical. These two
canyons are parallel to each other with
their mouths directlyeast of and adjacent to Salt Lake City and discharge
their streams westward into Salt Lake
Valley. Red Butte Canyon, which lies
one mileto the northof EmigrationCanyon, drains an area of approximately25
square miles. EmigrationCanyondrains
an area ofapproximately40 square miles.
It is characteristicof the canyons of
the Wasatch Mountains that the southfacing slopes are less precipitous than
their north-facingcounterparts. Since
the drainage area of Red Butte Canyon
is less and its lengthshorterthan those
of Emigration Canyon while both canyons at theirmouthsare approximately
the same depth,both slopes of Red Butte
Canyon are in generalsteeperthan those
of EmigrationCanyon.
In soil and geological features these
two canyonsshow importantdifferences.
EmigrationCanyon is composed principally of Jurassic limestone while Red
Butte Canyon consistsin part of a complex mixtureofTriassic shale, sandstone,
and limestone. Considering the great
differencein grazing use, it was suggested by Croft,Woodward,and Anderson ('43) that the soils of Red Butte
171
172
WALTER
P.
COTTAM
AND
FREDERICK
Canyon erode much moreeasily than do
thoseof EmigrationCanyon. It is generallyrecognizedalso thatsandstonesoils
are basically less favorable for plant
growththan are limestonesoils (Hilgard,
'06). These factswould seem to favora
moreabundantvegetationin Emigration
Canyonand are importantin theanalysis
of vegetationin this paper.
The Wasatch front, because of its
westernexposureand itsabruptrisefrom
the desert, is considerably more xeric
than the canyons that dissect it. Precipitation,which averages 16.13 inches
annually at Salt Lake City, increases
with elevation to a maximumof about
40 inches at 9000 feet. The growing
season shortens with higher altitude;
Salt Lake Valley has a frostlessperiodof
about 160 days while BrightonCanyon,
10 miles south of Emigration Canyon,
with an elevation of 8700 feet, has an
averagegrowingseason ofabout 90 days.
HISTORY OF RANGE USE ANDOWNERSHIP
Soon afterthe settlementof Salt Lake
Valley in 1847,both Red Butte and Emigrationcanyonscame underprivateownershipand both were utilizedforgrazing
purposes. In 1888 the United States
governmentbegan the purchase of Red
Butte Canyon forthe purpose of establishingFort Douglas at its mouth,and by
1909 had acquired titleto the entirewatershed. Protectionfromgrazingprobably commencedwith the firstpurchase
of the land. Even then,however,gully
erosionwas manifestin the canyon. It
is assumed that depletion of the plant
coverwas responsiblebecause, underprotection,gullieshave become revegetated
and severeerosionat presentis only half
thatfoundin EmigrationCanyon. Ring
counts fromtrees growingon these old
erosionscars place theirage at approximately 40 years, a date which coincides
with the purchaseof Red Butte Canyon
by the War Department.
As a result of a policy to protect its
watershed,Salt Lake City has acquired
R.
EVANS
Ecology, VTol,26, No. 2
title to most of the land in Emigration
Canyon. However,some of the canyon
is includedin the Wasatch National Forest, and a fewsectionsstillremainunder
privateownership. Because the permanent stream in Emigration Canyon is
small and uncertain,the water is not
used by Salt Lake City fordomesticpurposes,and littleattentionhas been given
to grazing or erosion problems. City
propertyis still leased to private stockmen, and grazingin this canyon, therefore, has continued without regulation
since the time of settlement.
In addition to the grazing abuses alreadyrecounted,EmigrationCanyon for
a distance of six miles is used as a stock
trail to and from the higher summer
rangesoftheWasatch and Uintah Mountains. The number of sheep passing
over this trail varies fromyear to year.
In thespringof 1935,forexample,97,550
sheepand 200 cattle used thistrail;in the
fallof the same year 123,000sheep were
herdeddown the canyon. By comparison, the spring drive of 1931 included
145,510sheep,and the fallflockstotaled
209,203 sheep. Trailing here is said to
have begun in the early "fifties." Each
flockhas the freedomofthecanyonup to
the six-milepoint wherethe trail passes
over Little Mountain into Parley's Canyon. It is not uncommonfor a single
flockto remaina week withinthe lower
reachesof EmigrationCanyon.
Many summerhomeswith theirassociated fenced enclosures are located in
Emigration Canyon along the stream
course,and the canyon is much used for
campingand generalsummerrecreation.
On the other hand, civilians have been
rigidlyexcludedfromRed Butte Canyon
since the turnof this century.
Fires at the mouths of both canyons
are not uncommon. Especially is this
trueof Red Butte Canyon wherevegetationis purposelyburnedto clear the land
for target ranges. Both canyons have
sufferedfrominadvertentburns at various places and timesat higherelevations.
April, 1945
EARLY
CANYON
DESCRIPTIONS
VEGETATION
OF
OF VEGETATION
No recordsare extantwhichreferparticularlyto the vegetationof Red Butte
Canyon, and but fewreferto the vegetation of Emigration Canyon in 1847.
However, it is significantthat available
referencesdescribe Emigration Canyon
as denselyvegetated. William Clayton
('21), an early Mormon historian,stated
that it was necessary, because of the
dense growthof vegetation,forthe pioneersto reconstructa road throughEmigration Canyon which had apparently
been used by the Donner partyonly the
year previous. In July, 1847, Erastus
Snow and Orson Pratt traveled through
Emigration Canyon in advance of the
main pioneer party. Snow said that
"The thicketdown the narrowsat the
mouth of the canyon was so dense that
we could not penetrate through it. I
crawled forsome distance on my hands
and knees throughthis thicket until I
l:
WASATCH
RANGE,
UTAH
173
was compelledto return." (Quoted from
Linn, '02.) Clayton ('21), in describing
the pioneertrekdown EmigrationCanyon,said, "The grass on the creekgrows
fromsix to twelvefeethighand appears
veryrank." (Doubtless Elymuscondensatus.2) At theirlast encampment,a position six miles fromthe mouth of this
canyon, he wrote, "The grass here appears even thickeron the ground than
where we left this morning. The soil
looks indeed rich, black and a little
sandy. The grassis about fourfeethigh
and very thick on the ground and well
mixedwithrushes." At thepresenttime
thevegetationin EmigrationCanyon has
no suchappearance,but, in general,these
2 Authorityforplant names is Tidestrom,Flora
of Utah and Nevada, with the followingexceptions: grasses, Hitchcock's Manual of the grasses
of the United States; Populus tremuloidesvar.
aurea, Pseudotsuga taxifolia,Berberisrepens,and
Sisymbriumaltissimum, Kearney and Peebles,
Floweringplants and fernsof Arizona.
I
FIG. 1. A typicalview midwayup Red Butte Canyon showingthe dense vegetationin the
bottomof thecanyon. Note theabundanceofcow parsnip(Heracleum
lanatum),a palatableweed
rarelyseenin EmigrationCanyon.
174
FIG. 2.
WALTER
P. COTTAM
AND
FREDERICK
R. EVANS
Ecology, Vol. 26, No. 2
EmigrationCanyon contrastsunfavorablywithcorrespondingareas in Red Butte Canyon.
Note the hedgednatureof the haw shrubs(Crataegus rivularis) and the low ruderalvegetationin
the foreground.
thecanyon,thoughits exact positionwas
placed at random. From this point the
centerofeach succeedingtransectwas establishedin the bottomof the canyon at
exactlythree-mileintervalsby speedometerreading. Each transectconsistedof
40 plots evenlyspaced along a compass
line and so distributedthat 20 plots lay
on each hillside. The firstplot of each
transectlay 100 feetfromthestreambed,
and the twentiethplot lay on or near the
canyonridgetops. Plots wereseparated
by a distanceof 200 feet,makingthe entire transectof 40 plots 8000 feet long.
Each plot was circularin shape and 100
square feetin area.
FIELD PROCEDURE
transectsand plotswere
Corresponding
The lengthof EmigrationCanyon to established for Red Butte Canyon, but
the main tributariesof its drainage was since this canyon is not as long as Emifound by speedometermeasurementsto grationCanyon, altitudes at the stream
be approximately12 miles. In orderto bed wererecordedby meansofan aneroid
sample adequately the vegetationin this barometerforeach transectin Emigracanyon,fourtransectsdrawnat rightan- tion Canyon and the same altitude was
gles to thedirectionofdrainageand equi- used to locate the correspondingtransect
distantfromoneanotherwereestablished. in Red Butte Canyon. AltitudinalposiTransect I was located at the mouth of tionsforcorrespondingtransectsin each
descriptionsapply to Red Butte Canyon
as it appears today (figs.1, 2).
Three moreor less distinctbeltsofvegetationhave been recognizedon the Wasatch front. A grass-sagebrushclimax
extendsfromthe valley floorto an average elevation of 5000 feet. Above this
to about 7500 feet scrub oak (Quercus
gambeli)dominatesthe landscape, while
stillhigherthereis a belt ofaspen (Populus tremuloides
var. area) and conifers
consistingof white fir (Abies concolor),
Douglas fir (Pseudotsugataxifolia),and
blue spruce (Picea pungens).
April, 1945
CANYON
VEGETATION
OF WASATCH
RANGE,
UTAII
175
canyonat thestreambed wereas follows:
1, 5000 feet; Il, 5350 feet; 111, 5600 feet;
IV, 6800 feet. The point-observationplot methodof vegetationalanalysis devised by Stewart and Hutchings ('36)
was adopted forthis study.
The surveywas made in thesummerof
1935 (late June, July). Each summer
since then the authorshave made a cursory study of the two canyons. Conditions at presentare essentiallythe same
as thoseat thetimeoftheoriginalsurvey.
ANALYSIS
OF VEGETATION
Data gatheredin this study permita
comparativeanalysisofthevegetationin
Red Butte and Emigrationcanyonswith
respectto the densityof the plant cover
as a whole and of the individualspecies,
and grazingcapacity.
Comparativedensities: Graphic comparisonsof plant densitiesof Red Butte
and Emigrationcanyonsare shownin figures 3 and 4. The densityof the plant
cover of Red Butte Canyon is approximatelytwicethatofEmigrationCanyon.
The distributionof plant densities by
transectsin the two canyons (fig.4) presents several interestingfacts. (1) The
canyons are nearly equal in the total
amountof vegetationon transectI. (2)
/5
k~~~~~~~~
~~~~~~.04
n
0: .03
PO
0"
Al.-
.0/
FIG. 3. Comparison of the density of plant
cover and forage acre factor of Red Butte and
Emigration canyons. Solid bars = Red Butte
Canyon; cross-hatchedbars = Emigration Canyon.
rA7NSECrS
1II
FIG. 4. Comparison of densities of all vegetation in each transect of Red Butte and Emigration canyons. Solid bars = Red Butte Canyon;
cross-hatchedbars = Emigration Canyon.
Except at the mouth,Red Butte Canyon
shows plant densitiesfarin excess of the
correspondingareas in EmigrationCanyon. (3) The vegetation midway up
Red Butte Canyon (transectII1) is less
dense than on adjacent areas below and
above (transect II and IV) in the same
canyon. Field observationsclearly reveal the reasonforthis in the prevalence
of rockoutcroppingsand poorsoil chiefly
on the south slope of the canyon. (4)
Except at the mouth, EmigrationCanyon varies but slightlyin the densityof
vegetationof all transects.
Vegetation
types:Red Butte and Emigrationcanyons are both dominatedby
scrub oak (Quercusgambeli). Figure 5
gives a graphic comparisonof the two
canyonswithrespectto total amountsof
weeds,3shrubs,and grassesin each of the
fourtransects. Some outstandingfacts
are illustrated by these graphs. (1)
Shrub densities exceed the combined
densitiesofweeds and grassesin all areas
above the mouth in both canyons. (2)
The mouthof Red Butte Canyon has a
grass-weedaspect, while the mouth of
Emigration Canyon is dominated by
3 The Forest Service classificationof vegetation
is used in this study. Weeds include all nongrassyherbaceous plants whilethe term"ruderal"
is reserved for plants falling under the popular
concept of "weed."
176
WALTER
P. COTTAM
AND
FREDERICK
R. EVANS
Ecology,Vol. 26, No. 2
/4 _
i0
TRANSECTS:
I
H
RED
surrT
T
U
II
Zf
EMICRAA
KE
r/Ov
FIG. 5. Comparison of densities of shrubs, weeds, and grasses in each transect of Red Butte
and Emigrationcanyons. Solid bars = shrubs; cross-hatchedbars = weeds; stippledbars = grasses.
shrubs. The grassyslopes of Red Butte parison of the vegetation of these two
Canyon are burned by firemuch more canyons. An analysis of the vegetation
oftenthan are the correspondingslopes from the standpoint of livestock influof Emigration Canyon. (3) The pro- ences involved a re-examinationof the
portionsof shrubs,weeds,and grasseson vegetation in each canyon on the basis
the various transectsof each canyon are, of the palatability forsheep and cattle.
in general,similar. Accordingto strati- In this analysis the authorsfollowedthe
graphicmaps of the area, the portionof Forest Service practice of determining
Red Butte Canyon in the vicinity of the forageacre factorforthe sectionsof
transectIII possesses,in additionto lime- each canyon throughwhichthe transects
stone, some shale and sandstone, prob- passed. The forageacre factoris a fracably accounting in part for the fewer tional unit of measurementfromwhich
shrubs on that transect. Other differ- actual stock-carrying
capacity of a given
ences in proportionsof the three plant rangeis estimated. The amount of fortypes (for example, on transect II of age on any given acre of range is depenEmigrationCanyon) may be accounted dent on two importantmeasurable facfor chieflyby the influenceof grazing, tors: first,the density of each forage
although the greater excess of shrubs species, and second, the utility (palata(chieflyscruboak) overweedsand grasses bility)4of each foragespeciesto livestock.
at the head of Red Butte Canyon is
Many laymen and even stockmenare
doubtless due to the fact that at this proneto accept quantityofvegetationas
altitudeclimateand topography(steeper the sole criterionof grazing capacity.
slopes) favor the maximum growth of The errorin not consideringquality of
shrubs.
vegetation as well as quantity is illusGRAZING CAPACITIES
Differencesof grazing use to which
Red Butte and Emigrationcanyonshave
been subjected constitute a variable
which should prove significantin a com-
I Palatability tables used in this study were
secured fromthe U. S. Forest Service. A palatability rating is given for each species of plant.
Palatability is definedas the per cent of current
growth of a given species of plant utilized by
stock when the range is properlygrazed.
April, 1945
CANYON
VEGETATION
OF
WASATCH
'.11
RANGE,
UTAH
177
triplants as big sagebrush (Artemnisia
dentata), rabbit brush (Chrysothamnus
speciosus),and barberry(Berberisrepens),
all oflow palatabilityto livestock. None
of these plantswas encounteredin measurable quantities at the mouth of Red
Butte Canyon.
DISCUSSION
rRANsrcrs
1
FIG. 6.
Comparison of forage acre factors of
each transectof Red Butte and Emigration canyons. Solid bars = Red Butte Canyon; crosshatched bars = Emigration Canyon.
trated in figures3, 4, and 6. The total
densityofvegetationof EmigrationCanyon is 55 per cent of that of Red Butte
Canyon,but the actual amountof forage
is only42 percentas much (fig.3). This
fact stands out even more in comparing
specificareas of the two canyons. The
density of vegetation at the mouthof
EmigrationCanyon is 87 per cent of that
at the mouthof Red Butte Canyon (fig.
4). Owing to the quality of the plant
cover,however,the amount of forageat
the mouthof EmigrationCanyon is only
45 per cent of that at the mouthof Red
Butte Canyon (fig.6).
The difference
betweenthe forageacre
factorand the densityof plant cover in
Red Butte and Emigration canyons is
much greaterat the mouths than elsewhere. This may be explained by the
fact that at the mouth of Emigration
Canyon therehas been a greaterchange
of vegetational types. It is here that
the competitionbetweengrassand shrub
types is in most delicate balance in the
undisturbedrange. These facts would
seemtosupporttheconclusionofPickford
('32) and theunpublishedobservationsof
othersthat the foothillvegetationof the
mountainson theeasternrimoftheGreat
Basin at the timeof the firstwhitesettlementwasthegrasstype. Approximately
one-thirdof the vegetationat the mouth
of EmngrationCanyon consists of such
In the absence of detailed historical
data it was impossibleto ascertainwith
accuracy the floristicchanges which occurred in the vegetation of Emigration
Canyon (lue to grazingand otherfactors.
That the vegetationin Red Butte Canyonwas richbothin quantityand quality
offoragewas evidentto thewritersat the
outset of this study, and the foregoing
analysisgivessome numericalidea of the
differencesbetween the two canyons.
The followingmore detailed consideration of the data on grasses,weeds, and
shrubs points to the great probability
that grazingis chieflyresponsibleforthe
impoverishmentand the retrogressive
succession of vegetation which has occurredin EmigrationCanyon.
Grasses: The density of palatable
grasses, including Agropyronspicatum,
A. pauciflorum,A. dasystachyum,
BroB. carinatus,Poa pramus brizaeformis,
tensis, and P. secunda, is five times
greater in Red Butte Canyon than in
Emigration Canyon. The density of
an introducedspecies,
Bromus tectorum,
is one and one-halftimesgreaterin Red
Butte Canyon than in EmigrationCanyon. This grass,thoughpalatable fora
short time early in the growingseason,
has a low palatabilityratingmost of the
summer. The successfulinvasionofthis
species in Red Butte Canyon (table I) is
doubtlessdue to the frequentburningat
is priits mouth. That Bromustectorum
marilya grassofthefoothillenvironment
oftheintermountain
westis generallyobserved and specificallyshown for both
Red Butte and Emigrationcanyons.
are most
Grasses (except B. tectorum)
abundant at lower elevations in Red
Butte Canyon, but in EmigrationCan-
178
WALTER
P. COTTAM
AND
FREDERICK
R. EVANS
Ecology,Vol. 26, No. 2
TABLE
I. A comparison of densities in per
cent of Broiiius tectorum and combined native
grasses in the various transectsof Red Butte and
Emigrationcanyons
gration Canyon is seen in the following
significant
data: (1) The densityof weed
vegetationwith low palatabilityis twice
as greatin EmigrationCanyon as in Red
Red Butte Canyon
Emigration Canyon
Butte Canyon. The densityofmorepalatable species,on the otherhand, is only
IralsectsBromus Brms Combined
BromCsombined
Brms
native
native
one-fifth
as great in EmigrationCanyon
tectorum
tectorum
grasses
grasses
as in Red Butte Canyon. (2) HerbaceI
2.01
0.85
1.62
0.11
ous vegetationoflow palatabilityis twice
II
0.86
0.66
0.08
0.09
as dense as palatable weeds in EmigraIII
0.21
0.18
0.25
0.01
tion Canyon; in Red Butte Canyon the
IV
0.06
0.08
0.11
0.14
densityof palatable weeds is five times
that of unpalatable weeds. (3) Highly
yonthereverseis true(table I). Several palatable species of weed vegetation,
factors are probably responsible. Red probably once abundant in Emigration
Butte Canyon with its more precipitous Canyon, are on the verge of extinction
slopes and its less open upperdrainageis (table II).
morefavorableto shrubsand less favorable to grasses. This phenomenon is TABLE II. Percentagepalatabilityof important
specieswithcomparative
in per cent
densities
common to narrowcanyons of the Wain RedButteand Emigration
canyons
satch Mountains. The near absence of
native grasses midway up Emigration
Density
PalataCanyon (table I, transectI I I) is explained
bility
Red
Emiby the fact that the sheep trail passes
Butte gratin
over Little Mountain near this point,
Grasses:
and, consequently,grazingis heaviest in
80
0.23
Agropyron spicatum ..........
0.03
Bromus tectorum.............
15
0.78
0.50
this vicinity. Despite grazing, grasses
Poa longiligula ..............
85
0.15
0.02
are moredense in theupperareas ofEmi- Weeds:
Achillea lanulosa ............
0.12
40
0.04
gration Canyon (table I, transect IV)
Balsamorhiza sagittata........
40
0.90
0.18
Geranium
45
0.22
fremoniii
0.04
..........
than at the correspondingelevation of
20
0.25
Lathyrus leucanthus ..........
0.14
50
0.25
0.07
Red Butte Canyon. This observation Leptotaenia multifida.........
15
1.11
Wyethia amplexicaulis ........
0.28
gives credence to the probabilitythat
grass was abundant in EmigrationCan- Shrubs:
Amelanchier alnifolia .........
75
0.39
0.19
Artemisia tridentala..........
0
0.04
0.53
yon in pioneerdays.
Berberis repens..............
0
0.13
0.14
0
trace
Chrysothamnus speciosus......
0.55
Ten native grasseswere foundin Red
20
4.51
2.56
Quercus gambeli.............
50
Rosa spp ...................
0.64
0.16
Butte Canyon whichwere not observed
50
0.80
0.21
Symphoricarpos vaccinioides. ..
in EmigrationCanyon (table III). Conversely,all but one of the native grasses
Mule's ear ( Wyethiaamplexicaulis),an
encounteredin the plots of Emigration
Canyon appeared in Red Butte Canyon. herb of low palatability(15 per cent), is
These factswould seem to emphasizethe much moreabundant in Red Butte Canof rare yon than in EmigrationCanyon (table
dangerof completeextermination
and highlypalatable speciesinovergrazed II). A possibleexplanationis that stock
areas. A comparisonof the palatability in EmigrationCanyon is forcedto suband density of three principal grasses siston plantsof low palatabilityand that
(table II) leaves little doubt as to the sheep are fond of the seed heads and
with the natural reprodamaging influenceof severe grazingon therebyinterfere
ductive processesof the plant.
palatable grasses.
Shrubs: Scrub oak is by far the most
Weeds:The-influenceof heavy grazing
on the native herbaceousflora5 of Emi- common shrub in both canyons. Dei All species of weeds whichaveraged in density
at least one-eighthof one per cent per plot and
whichweregiven palatability ratingsby the U. S.
Forest Service are included in the data.
CANYON
April, 1945
TABLE
III.
RANGE,
179
UTAH
List of grasses occurringin plots of Red Butte and Emigrationcanyons. Presence of a
species is indicatedby a plus sign and absence by a zero sign
Species
Species
|
Agropyrondasystachyum
A gropyronpauciflorum
Agropyronsmithiimolle
Agropyronspicatum . .....
Agropyronsubsecundum+..
*Agrostisalba .+
Agrostisexarata.+
Agrostisidahoensis.
*Agrostisverticillata.
Aristida longisetarobusta . +
*Bromusbrizaeformis
.+
Bromus carinatus.+
*Bromustectorum
.+
Catabrosaaquatica .+
.0
*Dactylisglomerata
Deschampsia caespitosa ..+
Elymus condensatus.+
*
OF WASATCH
VEGETATION
Red
Butte
+
+
+
4-I
0
+
?+
?+
Emigration
+
+
0
+
0
+
0
+
0
Q
+
+
+
0
+
+
+
SeisRed
Species
Festuca kingii.
Festuca subulata.
Glyceriaelata.+
Glyceriastriata.
Hordeumjubatum.+
Koeleria cristata.+
Melica bulbosa.+
*Munroa squarrosa.0
Oryzopsishymenoides.
*Phleum pratense.
*Poa annua .0
*Poa compressa.+
Poa longiligula.+
*Poa pratensis.+
Poa secunda.+
*Setaria viridis.
Stipa columbiana.+
Butte
+
+
+
+
+
0
Emigration
+
0
0
0
+
0
+
+
0
+
+
0
+
+
+
+
+
Introducedspecies
spite the fact that this shrubhas a palatabilityrating of only 20 per cent, the
densityof scrub oak in EmigrationCanyon is but half of that in Red Butte
Canyon. The densityofotherspecies of
shrubswithhighpalatabilityis less than
one-thirdas muchin EmigrationCanyon
as in the other. Sagebrush and rabbitbrushwithlittleforagevalue have a density 13 timesgreaterin EmigrationCanyon than in Red Butte Canyon.
Ruderals: The ruderal flora of Red
Butte and Emigrationcanyons includes
the followingspecies: Ambrosia psilostachya,Asclepias speciosa,Bromustectorum, Caulanthushastatus,Camelina microcarpa,Chenopodium
album,Helianthus
annuus, Lactuca scariola,Lepidium apetalum,Lepidiumperfoliatum,
Marrubium
vulgare,Polygonumdouglasii,Salsola pestifer,Sisymbrium
altissimum,Sophia parviflora,and Zygadenuspaniculatus.
Most ruderalsare practicallyvalueless
as forageand many are exotic annuals.
They appear either as pioneers on denuded areas or as the last stage in retrogressivesuccession. In Red Butte
Canyon, with the exception of Bromus
tectorum,
they are confinedto the lower
elevations of the canyon where fireor
disturbedsoil about Fort Douglas permit
their growth. In Emigration Canyon,
however,a major highway,a long-used
sheep trail, heavy grazing,and summer
homesall contributeto conditionsfavorable to an abundant ruderalflora. The
densityof ruderalsin Red Butte Canyon
is 12 per cent less than in Emigration
Canyon (fig.7). ExceptingBromustectorum,the densityof ruderalsin Emigration Canyon is seven timesas greatas in
Red Butte Canyon. These ruderalsare
most abundant in burnedareas on transect I, along the denuded sheep trail,and
in fencedareas nearsummerhomeswhere
Z.00
-
100
k.50
rRA NS ECTs
I
FIG. 7. Comparison
ofdensitiesofruderalsin
each transectof Red Butteand Emigration
canyons. Solid bars = Red Butte Canyon; crosshatchedbars = EmigrationCanyon.
180
WALTER
P. COTTAM
AND
FREDERICK
R. EVANS
Ecology, \Tol. 26, No. 2
.. .. .
FIG. 8.
Barren areas along the sheep trail in Emigration Canyon constitute
a flood hazard to Salt Lake City
thenativevegetationhas been destroyed.
Owing to the decrease of native vegetation on heavily grazed slopes, ruderals
occur in all areas of EmigrationCanyon
in contrastto the very small amount of
these plants in the miidand upper areas
ofRed Butte Canyon. Only one ruderal
was found in
species, Bromus tectorum,
plots on transects III and IV of -Red
Butte Canyon.
EROSION
alarming impoverishmentof the plant
cover, and sheet erosion is generallyin
evidence. Advanced gullyerosionis especiallynoticeableon the slopes of Little
Mountain where the trail passes out of
EmigrationCanyon. Here barrenareas
(fig. 8) more than ten acres in extent
furnishrunoffwhich reaches flood proportions when snows melt and heavy
rains fall. A cloudburstin this vicinity
mightresultin a floodthatwoulddestroy
homes of Salt Lake City lying directly
in its path. That this menace is a very
real one is evidenced by the fact that
such a floodhas already occurredin Dry
Canyon which lies about one and onehalf miles to the north (Alter, '21).
There the drainage area is not nearlyas
largeas that in EmigrationCanyon, and
the plant cover is considerably more
dense.
For more than half a century,from
100,000 to 200,000 sheep have trailed
throughEmigrationCanyonto themountain summerrangeseach springand have
returnedthroughthiscanyon to the desert winterranges each fall. Each herd
leisurelygrazes in the canyonforseveral
days in transit. Besides thisabuse, private flocksgraze on the upper areas of
EmigrationCanyon duringthe summer.
SUMMARY
Cattle also graze in the canyon during
1. Two canyons,Red Butte and Emithe summermonths.
Such overuse of thesegrazinglands in gration,extendingparallelto each other,
Emigration Canyon has resulted in an adjacent and generallysimilarin geogra-
April, 1945
CANYON
VEGETATION
OF
phy,slope exposure,and elevation,were
compared in respect to quantity and
quality of plant cover.
2. In theirpristinecondition,because
of morefavorablesoil types,Emigration
Canyon probablycontaineda vegetation
equal to or surpassingthat which now
existsin Red Butte Canyon.
3. For a periodofat least 40 yearsRed
Butte Canyon has been protectedagainst
grazing. EmigrationCanyon has been
grazed heavilysince settlementin 1847.
4. Palatable vegetation has probably
decreased, and unpalatable vegetation
has probably increased in Emigration
Canyon. Only 42 per cent as much forage is producedhere as in equal areas in
Red Butte Canyon.
5. Ten native grasses found in Red
Butte Canyon were not encounteredin
EmigrationCanyon, suggestingthe danger of completeexterminationof highly
palatable species throughgrazingabuse.
6. Evidence points to the probability
of the completesubstitutionof the original grass type with unpalatable shrubs
plus Bromus tectorumat the mouth of
EmigrationCanyon.
7. Some highly palatable shrubs in
EmigrationCanyon have a density less
than one-thirdthat in Red Butte Canyon. Othershrubsoflow palatabilityin
WASATCHI
RANGE,
181
UTAII
Emigration Canyon have 13 times the
densityof the same shrubsin Red Butte
Canyon.
8. The densityof ruderalsin EmigrationCanyon is 12 percentgreaterthanin
Red Butte Canyon. ExceptingBromus
the densityof ruderalsin Emitectorum,
grationCanyon is morethan seven times
greaterthan in Red Butte Canyon.
9. Sheet erosionis generalthroughout
EmigrationCanyon and advanced gully
erosionis commonalong a sheep trail.
LITERATURE
CITED
Alter,J. Cecil. 1921. Forests in relationto cli-
mate and water supply. Trans. Utah Acad.
Sci. 2: 195-198.
Clayton, William. 1921. Journal of William
Clayton. Deseret News, Salt Lake City,
Utah.
Croft, A. R., Lowell Woodward, and Dean A.
Anderson. 1943. Measurements of accelerated erosion on range-watershed land.
Jour. Forestry41: 112-116.
Hilgard, E. W. 1906. Soils. 593 pp. The
Macmillan Co., New York.
Linn, W. A. 1902. Story of the Mormons.
The Macmillan Co., New York.
Pickford, G. D. 1932. The influenceof continued heavy grazing and promiscuous burning on spring-fallranges in Utah. Ecology
13: 159-171.
Stewart,George,and S. S. Hutchings. 1936.
The point-observation-plot(square-foot-density) method of vegetation surveys. Jour.
Anmer.Soc. Agron. 28: 714-722.