CHANGES IN VEGETATION AND
LAND USE AT TWO TOWNSHIPS IN
SKULL VALLEY, WESTERN UTAH
Steven R. Sparks
Neil E. West
Edith B. Allen
ABSTRACT
back to the 1930's. Large vegetation changes had presumably already occurred in some areas by this time.
Anecdotal accounts from Cache (Hull1976), Rush, and
Tooele Valleys (Christensen and Hutchinson 1965), for
example, indicate that there was a massive decrease in
perennial grass cover within 10 to 15 years after settlement. The older the study, the less likely it is to meet the
relatively more rigorous standards of the late twentieth
century for data collection and analysis. "Data" collected
earlier than the 1930's tend to be merely observational
and anecdotal.
Ecologists working in the forests of the midwestern and
northeastern United States have made use of surveyors'
field notes from the General Land Office (GLO) survey of
the late nineteeth and early twentieth centuries (Stearns
1974). These surveyors, during the course of establishing
range and township lines, would also note the species
of trees present. If trees were present at a section or
quarter-section corner, the distances to the nearest large
trees were noted (usually 2-4 trees), as well as the compass direction from the corner to the tree trunk, and the
diameter of the tree trunk. A "blaze" was then carved
into the trunk denoting the position of the tree. These
trees served as "witness trees" or "bearing trees" in case
the position of the corner was ever disputed.
When trees were not present, surveyors tended to
describe other vegetation by such general terms as
"undergrowth," or "brush." Some GLO surveyors in the
Great Basin, however, indicated not only the presence
of juniper trees ("cedars"), but differentiated major species
of shrubs (for example, sagebrush, shadscale, white sage,
mahogany, grease wood), and indicated the presence of
perennial grasses ("bunchgrass"), and recorded the presence of "salt weeds" on the alkali flats (playas) of Great
Basin valleys. These "data," while qualitative, represent
the perceptions of the surveyors as to what the dominant
species of a particular area were. The data were systematically collected and therefore enable us to reconstruct a
general picture of the dominant species in the vegetation
as it existed at the time of the GLO surveys.
Plant species distribution and community composition
at the time of settlement are controversial in several respects. For example, there is some dispute over the relative abundance of shrubs, particularly sagebrush, and
perennial bunchgrasses (West 1983). Understanding
the impact oflivestock grazing requires at least a broad
knowledge of pre settlement (and prelivestock) vegetation
patterns. For instance, presettlement juniper distribution
was apparently more restricted compared to presently
Historical changes in plant dominance, in two townships of Skull Valley, UT, were assessed by repeating the
earlier descriptions made by surveyors from the General
Land Office. Massive conversions to cheatgrass and other
annuals of former sagebrush- and shadscale-dominated
vegetation on bench, foothill, and bajada sites were found.
In addition to unrestricted livestock grazing, wildfires
were identified as the probable triggering factors for
these changes. Both forces were probably required for
conversion to dominance by annuals. Juniper at higher
elevations, lesser grazed areas at mid-elevations, and
greasewood-, salt grass-, and pickleweed-dominated
areas at lower elevations have undergone much less
change.
INTRODUCTION
Substantial changes in plant species distribution and
community composition have occurred in the Great Basin
portion of western Utah since settlement in the latter half
of the nineteenth century (Cottam 1976; West 1989). Excessive grazing by livestock, woodcutting, fire suppression
and other changes in fire patterns, along with the introduction of alien weeds are all mechanisms that have been
suggested by researchers to be responsible for these
changes.
Although we have known for many years that these
changes in plant species distribution and community
composition have been extensive for many areas, it is
more difficult to quantify changes for particular areas,
or to estimate what portions of the landscape have the
most highly altered vegetation. Even long-term studies,
such as the data gathered at the Desert Experimental
Range in southwester.n Utah (Clary 1987), only date
Paper presented at the Symposium on Cheatgrass Invasion, Shrub DieOff, and Other Aspects of Shrub Biology and Management, Las Vegas, NV,
April 5-7, 1989.
Steven R. Sparks was former Postdoctoral Research Fellow, Department of Range Science and the Ecology Center, Utah State University,
Logan, UT 84322-5230, now Ecologist, Forest Fire Laboratory, Pacific
Southwest Research Station, Forest Senrice, U.S. Department of Agriculture, Riverside, CA 92507. Neil West is Professor of Range Science, Department of Range Science and the Ecology Center, Utah State University,
Logan, UT 84322-5230. Edith B. Allen was fonner Research Assistant
Professor, Department of Range Science and the Ecology Center, Utah
State University, Logan, UT 84322-5230, now Research Associate Professor, Department of Biology and Systems Ecology Research Group, San
Diego State University, San Diego, CA 92182-0057.
26
This file was created by scanning the printed publication.
Errors identified by the software have been corrected;
however, some errors may remain.
observed patterns (Murdock and Welsh 1971; Young and
others 1976; Rogers 1982; West 1988; Young in press),
although changes in juniper distribution have been inferred for only a few areas (Tausch and others 1981).
The real extent of this putative juniper expansion and
all the factors controlling it have not been established.
Increases in juniper abundance have important consequences for livestock, wildlife, water yield, and soil erosion (West 1984). Finally, although the great increases
in the distribution and abundance of weedy annuals in
the Intermountain Region, especially cheatgrass (Bromus
tectorum), are well documented (Mack 1986), the pattern
and causes of invasions of annuals and their consequences
are more elusive. Which portions of the landscape are at
greatest risk to invasion by annuals are unknown.
Knowledge of the magnitude of vegetation change in
the Great Basin is important. If we can understand the
causes of these changes, as well as being able to predict
future changes that may result from direct human pressure or global climatic change, we might be more successful at preventing or mitigating future changes and reversing previous change. We therefore elected to reconstruct,
insofar as possible, the past vegetation of two townships
(areas of 36 square miles) with contrasting land use histories, and to describe the present vegetation patterns
as well. We wished to address the following questions:
(1) What are the changes in species distribution and community composition? (2) How are changes in vegetation
influenced by the landscape features? (3) How does human land use intensity influence vegetation change?
GREAT
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UTAH
MATERIALS AND METHODS
Figure 1-Location of the study area.
We chose two townships in Skull Valley, Tooele County,
UT (fig. 1), for which we were able to obtain complete
GLO surveyors' notes through the state office of the
Bureau of Land Management (BLM) in Salt Lake City.
In addition to availability of such records, we chose
these particular townships because (a) they both included
a representative cross-section of the zonation of the lower
elevations of the valley, and (b) they represented extremes
in differences in land use history. Other possible townships within Skull Valley (fig. 1) would likely show intermediate levels of alteration due to human activities.
One township, (T. 3S., R.8W., hereafter referred to
as the Salt Mountain township), one of the first settled
in Skull Valley because of the ready availability of water
for livestock, was surveyed in 1871. The other township
(T.1S., R.9W., hereafter referred to as the Hastings
Pass township), has been less intensively impacted by
livestock because ofthe absence of perennial sources
of water. This township was not surveyed until1913.
Both of these townships are approximately one-third
high-elevation (above about 5,500 ft) juniper (Juniperus
osteosperma) habitat, one-third mid-elevation (originally
shrub dominated), and one-third low-elevation (below
about 4,400 ft) with playas, greasewood (Sarcobatus vericulatus), or saltgrass (Distich/is stricta) habitat. The Salt
Mountain (SM) township is on the eastern side of Skull
Valley, abutting the Stansbury Mountains. The Hastings
Pass (HP) township is on the western side of Skull Valley,
in and below the Cedar Mountains.
Besides the ready availability of perennial sources
of water, the high-elevation, juniper-dominated eastern
third of the SM township has gentler topography than
the analogous high-elevation, juniper-dominated western
third of the HP township. Rugged topography in the
mountainous portion of the HP township, along with its
greater probable aridity, has resulted in much of the
mountainous areas of this township receiving little or
no grazing by livestock.
We visited during 1988 the sites of each of the section
corners and quarter-section corners established by the
GLO surveyors. If junipers were present, we attempted
to locate the original bearing trees. We also established
quadrats, generally 12 m by 40 m (size was varied occasionally for very dense or sparse stands of junipers), and
recorded the number of junipers in each of five size-ageform classes (Blackburn and Tueller 1970; Tausch and
others 1981). Dead trees were also recorded. Based on
the proportion of young to old trees, and on the presence
or absence of suitably sized trees closer to the corner monument than the original bearing trees, we subjectively
classified the sites as either increasing, decreasing, or
static with regard to juniper reproduction.
At each site we also recorded our perceptions of the
dominant or most conspicuous species within view. Our
observations were not strictly comparable to those of the
surveyors, since ours were site-specific, whereas those
27
Number of Cattle, Tooele County
of the surveyors appeared to integrate their perceptions
of the dominant or most conspicuous species along the
entire 114-mile transect since the previous quarter-section
corner. Strict reenactment of the original survey procedures would have taken a crew of six workers to handle
the requisite rods and chains. We lacked the budget to
do so. Because subjectivity was great for both styles of
observation, and because such a study can only show
gross changes in species dominance, we feel the differences in observation styles are unimportant.
Land-ownership histories were documented for both
townships using records in the state BLM office in Salt
Lake City, and in the Tooele County Courthouse, Tooele,
UT. Grazing histories and fire occurrence were inferred
from records of the BLM Salt Lake District Office. Tax
records on livestock numbers were found in the Tooele
County Courthouse. Livestock numbers were also inferred from the Agricultural Census of 1880 found at the
Church of Jesus Christ of Latter-day Saints (LDS) Church
Archives in Salt Lake City.
14000
12000
10000
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10
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8000
6000
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z
4000
2000
0
1880
1900
1920
1940
1960
1980
Year
Number of Sheep, Tooele County
TRENDS IN LIVESTOCK NUMBERS
250
Tax records from Tooele County summarize sheep and
cattle numbers for the entire county as far back as the
late nineteenth century. County summary records prior
to 1900, however, tend to be less trustworthy. In fact, all
tax records can only be used as an index of past livestock
use, since, of course, they do not indicate where the grazing took place, and are of uncertain accuracy.
Sheep numbers in Tooele County apparently fluctuated
tremendously between 1900 and 1915, with some very
high years (over 200,000 sheep) and some rather low
years (less than 100,000) (fig. 2). After World War I,
sheep numbers declined relatively steadily, until they
dropped below 50,000 in 1980. A single-year estimate
for 1880 (from the Agricultural Census of 1880) shows
low (about 65,000) sheep numbers in Tooele County for
that year.
Cattle numbers in Tooele County showed just the opposite trend (fig. 2). Between 1900 and 1915, numbers
remained low (less than 4,500). Beginning with World
War I, numbers increased relatively steadily, with a peak
around 1970 of more than 13,000. The single-year estimate from the Agricultural Census of 1880 shows cattle
numbers in Tooele County to be nearly 14,000 in that
year, however.
Although these estimates of past livestock numbers in
Tooele County are of uncertain accuracy and particular
relevance to Skull Valley, they do show that both cattle
and sheep numbers were at times quite high in the past,
and from this we can reasonably infer that livestock grazing pressure on rangelands has likewise been considerable at times.
s
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1880
1900
1920
1940
1960
1980
Year
Figure 2-Numbers of cattle and sheep on the
tax rolls of Tooele County, UT, 1900-1980.
Between the years of 1887 and 1923 (Atkin 1958), immigrants from Hawaii built and occupied the settlement
ofiosepa in this township, and ran an extensive livestock
operation there. A working cattle ranch continues in the
township today. In addition to the activities of farming
and livestock grazing, considerable woodcutting also took
place in this township. Surveyors even noted the presence of a sawmill in the township in 1871, perhaps to
process logs from both the township and elsewhere. In
recent decades, many juniper-dominated sites have been
chained (West 1984). Of the 35 juniper-dominated sites
visited in the SM township in 1988, seven have been
chained, and eight show signs of considerable woodcutting, both by saw and axe. Human activity continues
at a probably lesser intensity in the township today.
CHANGES IN LAND OWNERSHIP
Ownership records reveal that about 16 percent of the
SM township was homesteaded between 1878 and 1900.
Surveyors' plat maps and field notes indicate that there
were already three or four farms/ranches in the township
in 1871.
28
Although livestock grazing probably occurred in the
HP township well into the last century, apparently no
permanent settlements existed, nor has there ever been
any private land in this township. No chainings or signs
of woodcutting were found in the HP township. Obviously, the presence of perennial streams and springs in the
SM township has resulted in considerably more intensive
human activity there compared to the HP township.
Hastings Pass Vegetation Change
100
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80
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c:
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60
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Q)
GENERAL CHANGES IN
VEGETATION
0)
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40
Ul
~
For data analysis, all the visited sites were grouped into
types depending primarily on their elevational position in
the townships, from the lowest elevation sites ("playa" or
"saltgrass"), slightly higher elevation areas dominated by
greasewood ("sarco"), mid-elevation bench, bajada, or foothill sites ("bench"), and high-elevation sites usually dominated by junipers. High-elevation sites had more variable
topography, and so were further divided into flat or gently
sloping ("flats"), in or adjacent to large canyons or washes
("cyn/wash"), and mountainous sites located on steep
slopes or ridge tops ("mtns") categories.
Figure 3 shows the proportion of total sites for each
type that have changed radically in plant species dominance since 1913 or 1871. Radical changes in species
dominance were defined as the disappearance, or present
inconspicuousness, of a species listed as conspicuous by
the surveyors for a particular area, or conversely, the conspicuous occurrence at a particular site in 1988 of a species not mentioned by the surveyors. More subtle changes
were not considered.
The longer and more intensive use of the SM township
has resulted in more extensive changes in the species of
dominant plants (fig. 3). Most or all of the sites within
each type have undergone significant changes in species
dominance since the GLO surveyors described the area,
with the exception of the playa type. In the HP township,
some sites within each type have undergone significant
changes since 1913, but the mid-elevation zones-bench
and greasewood sites-have changed the most. Within
the mountains, areas of relatively flat topography are
most likely to have undergone significant changes since
1913. Areas of more rugged mountainous topography,
or areas of high salinity and low vegetation cover, have
changed the least.
Besides livestock grazing, signs of which may be found
in both townships in all but the most rugged terrain, fire
is probably the most pervasive factor responsible for vegetation change (fig. 4). In the SM township, fires appear
to have played a lesser role compared to the HP township,
but this is largely because of the way fire signs were evident. Charred shrub skeletons, or at higher elevations,
charred juniper skeletons, were used as indicators of past
fires. Although charred juniper skeletons may persist
for many decades, and perhaps even centuries (Erdman
1970), charred shrub skeletons appear to persist less
than a decade. Subsequent fires may eliminate these
shrub skeletons even sooner. Thus, many sites that
have burned, even recently, may not show direct signs
of what woody species prevailed earlier. Sites with cheatgrass dominance in the mid-elevation bench, foothill, or
bajada types are good candidates for underestimated fire
u;
0
0~
20
0
Playa
Sarco
Bench
Flats Cyn/Wash Mtns
Site Type
Salt Mtn Vegetation Change
100
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20
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Playa
Sarco
Bench
Flats Cyn/Wash Mtns
Site Type
Figure 3-Percentages of various types of the
Hastings Pass (HP) and Salt Mountain (SM) townships experiencing radical changes in plant dominance since 1913 or 1871.
occurrences. Greasewood is the only long-lived shrub in
this area that can resprout following burning.
In the HP township, fires tend to have occurred in
the mid-elevation bench and greasewood types, and
within the mountains in the gentler topography of the
flats, becoming less common in more rugged mountainous
topography. Because of the persistence of charred juniper
skeletons, fires at juniper sites can be categorized as either recent (charred shrub skeletons present), or ancient
(old charred juniper skeletons present in a matrix of
older, mature trees). Recent fires tend to have occurred
at the lower, gentler topography, and tend to become less
common at more rugged sites, such as ridge tops (fig. 4).
29
Hastings Pass Fire Occurrence
HP Playa Sites {N
100
=20)
100
•
a
80
rm
total fires
recent fires
ancient fires
•
•
80
1913
1988
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60
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0
20
20
0 -+---"T'"
Playa Sarco
0
Bench
Flats Cyn/Wash Mtns
ATCO
SAVE
Site Type
DISP
ALSP
ANN.
Plant Species
Salt Mtn Fire Occurrence
SM Playa Sites {N
100
= 9)
100
•
total fires
80
80
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60
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20
Bench
0
Flats Cyn/Wash Mtns
ATCO
Site Type
SAVE
DISP
ATGA
KOAM
Plant Species
Figure 4-Percentage of sites with evidence of
fire in 1988.
Figure 5-Percentages of playa sites dominated
by various plant species in the initial and 1988
surveys in the Hastings Pass (HP) and Salt
Mountain (SM) townships. ATCO = Atriplex
confertifolia; SAVE = Sarcobatus vermiculatus;
ALSP = Allenrolfea spp; DISP = Distich/is stricta;
ANN= various introduced annuals, especially,
Bromus tectorum; ATGA =A triplex gardneri;
KOAM = Kochia americana.
CHANGES IN PLANT DOMINANCE
FOR EACH TYPE
recorded it as "alkali flat." We assume that the term
"salt weeds" likely refers toAllenrolfea spp. and pickleweed (Salicornia spp.), which occur conspicuously on
the playa today. Some areas of the HP township playa
are completely barren today, as they likely were in 1913.
Probably few, if any, changes have occurred within this
type since 1913 (fig. 5).
Playa-Changes in the species dominance on the
playas are the most difficult to evaluate, in part because
of the lack of detail in the surveyors' notes. In the 1913
survey of the HP township, the surveyor referred to the
species growing on the playa as "salt weeds," or simply
30
Large expanses of playa, or alkali flat, do not occur
in the SM township. Instead, playas occur interspersed
in a matrix of greasewood-dominated vegetation. Furthermore, plant cover is generally greater on playas
here compared to the HP township. Again, changes
in plant dominance within this type are difficult to evaluate. The surveyor often recorded greasewood as a conspicuous species at these sites. While that is not strictly
true today on the playa sites, these sites always occur
immediately adjacent to greasewood-dominated communities in the SM township, so the apparent decline in the
proportion of sites with grease wood as a conspicuous species is probably spurious (fig. 5). Salt grass seems to be
conspicuous at the same number of sites as in 1871. In
addition, gardner saltbush (Atriplex gardneri) and green
molly kochia (Kochia americana) are often conspicuous at
these playa sites today. These are small, but ubiquitous
plants, and were likely present in 1871 but simply overlooked and not recorded. So, few changes in species dominance are likely to have occurred in the playa sites of
either township since their respective surveys.
HP Sarcobatus Sites (N
100
•
= 11)
1913
fB 198880
~
60
-
40
.!
en
0
tft
20
0
ATCO
SAVE
ALSP
ANN.
NAT.BG
Plant Species
Sarcobatus Sites-Sites in the HP township that
were dominated by greasewood in 1913 show a continuing
dominance by that species today, although in the interspaces, shadscale (Atriplex confertifolia) has often been
replaced by cheatgrass and other annuals (fig. 6). In
the SM township, 10 of the sites that are dominated by
greasewood today were dominated by sagebrush (Artemisia tridentata, A nova, or both, the surveyors did not
differentiate), in 1871. Since 1871, greasewood has
expanded into many areas formerly dominated by sagebrush, with cheatgrass and other annuals present in the
interspaces. Sagebrush is absent from all of these sites
today. Rickard (1964) observed similar changes in southeastern Washington. A larger proportion of sites also
have shadscale as a conspicuous species today compared
to 1871. Although it also appears thatAtriplex gardneri
and green molly kochia have invaded many of these sites
since 1871, it is more likely that these smaller but more
ubiquitous species were simply overlooked and notrecorded in 1871.
SM Sarcobatus Sites (N
=29)
100
•
1871
B 1988-.
80
60
40
20
0
ATCO
Salt Grass-This type occurs only in the Salt Mountain township, and consists of sites dominated by swards
of often thick and matted saltgrass recorded by the 1871
surveyor as "salt grass meadow." Four of the nine sites
recorded as salt grass meadows in 1871 are still such
today. In addition, at several other sites the surveyor
recorded salt grass as the most conspicuous species, approximately the same number as today. A few sites also
had greasewood and sagebrush listed as conspicuous in
187i, while these species were not conspicuous in 1988.
In general, these salt grass-dominated sites have probably
changed little since 1871, despite apparently heavy grazing pressure.
SAVE
ARTR
ANN.
ATGA
KOAM
Plant Species
Figure &-Percentages of Sarcobatus sites dominated by various plant species in the initial and
1988 surveys in the Hastings Pass (HP) and Salt
Mountain (SM) townships. Taxonomic symbols
the same as figure 5 except: NAT. BG =native
bunchgrass, ARTR =Artemisia tridentata, A.
nova, or both.
portion of sites where shadscale and budsage (Artemisia
spinescens) are conspicuous. The bunchgrasses present
on the benches of the Hastings Pass township today may
be different species from those seen in 1913, since the
genera we see there today-Aristida, Oryzopsis, and
Stipa-are ones normally associated with moderately
heavy livestock grazing histories (West 1988). Surveyors
also noted that grease wood was a conspicuous species in
several bench sites of the HP township in 1913, although
it is conspicuous at none of these sites today.
Bench/Baj ada/Foothill Sites-The greatest changes
in both townships have occurred in the mid-elevation __ _
bench, foothill, and bajada sites, where annuals have
become the dominants at essentially all of the sites
in both townships (fig. 7). In the HP township, this
conversion to dominance by annuals has been accompanied by a small decrease in the proportion of sites with
bunchgrass conspicuous, and a large decrease in the pro31_
HP Bench/Foothill Sites (N
=28)
today, again, as with the HP township, include species
from the generaAristida, Oryzopsis, and Stipa, and so
the bunchgrass species composition may have changed
at these sites since 1871. Even while these bunchgrasses
are conspicuous today in many sites, they are by no
means comparable in cover and dominance to the
introduced annuals, especially cheatgrass. Exotic bunchgrasses (Eurasian Argropyron and Elymus spp.) are also
not abundant on the SM benches today. One site today
has greasewood conspicuous where none was mentioned
in 1871.
100
80
fl)
•
II
1913
1988
60
.!
u;
0
~
0
40
High-Elevation Flats-On sites at higher elevations
with flat or gently sloping topography, the proportion of
sites with junipers tends to have greatly decreased in the
HP township, with a concomitant invasion of annuals,
especially cheatgrass, onto these sites (fig. 8). Bunchgrasses remain conspicuous at all of these sites, however,
and sagebrush remains conspicuous at the same proportion of sites. Many sites where shadscale was conspicuous
in 1913 have apparently lost this species.
Junipers have greatly increased in conspicuousness
at many of these sites in the SM township since 1871.
At several sites within this type where junipers were
not mentioned in 1871, they now grow thickly. There
has been a concomitant invasion of cheatgrass and other
annuals, a decrease in proportion of sites with native
bunchgrasses, and an increase in exotic bunchgrasses
and sagebrush. One site showed greasewood where none
was mentioned in 1871. These increases in juniper dominance occurred despite extensive woodcutting and chaining in this township, particularly within this site type.
In fact, nearly all chained areas now have junipers growing thickly upon them. The chainings, reseeding, and consequent management were not intensive enough, thus
tree regeneration was encouraged (West 1984).
20
0
ATCO NAT.BG EX.BG
SAVE
ANN.
ARSP
Plant Species
SM Bench/Foothill Sites (N = 21)
100
80
fl)
60
.!
u;
0
0~
40
High-Elevation Canyons and Washes-Canyon/
wash sites in the HP township, like the mountain sites,
show little change since 1913 (fig. 9). Junipers were
prominent at all sites in 1913, and remain prominent
at all sites today. All10 sites had evident bunchgrass
in 1913, and nine sites have bunchgrass today. Sagebrush shows a slight increase in the proportion of sites
where this species is prominent. Annuals have invaded
a few sites. Some sites had conspicuous shadscale in
1913, with no sites showing shadscale in 1988.
Like HP township, all canyon/wash sites in the SM
township had highly visible junipers in 1871, and all
sites do in 1988 (fig. 9). There has been a decrease in
the proportion of sites with native bunchgrasses, and
a few sites now have exotic bunchgrass species. Cheatgrass is now evident at several sites, and a few more
sites now have sagebrush as compared to 1871.
20
0
ARTR NAT.BG EX.BG
SAVE
ANN.
JUOS
Plant Species
Figure 7-Percentages of bench/foothilllbajada
sites dominated by various plant species in the
initial and 1988 surveys in the Hastings Pass
(HP), and Salt Mountain (SM) townships. Taxonomic symbols the same as figures 5 and 6,
except: EXBG =exotic bunchgrasses, ARSP =
Artemisia spinescens, and JUOS =Juniperus
osteosperma.
Mountain Sites-The most striking result for rugged
mountainous terrain in the HP township is that few
changes in species composition have occurred since 1913
(fig. 10). Junipers have been removed from only two sites
by fire. Bunchgrasses were conspicuous at all of these
sites in 1913, and are still there today. Even where fires
have occurred, bunchgrassess have retained their dominance, and cheatgrass invasion is minimal. Artemisia
spp. were evident at the same number of sites in 1988
In the SM township, increases in annuals have been
accompanied by a large decrease in the proportion of
sites with sagebrush conspicuous (fig. 7). Only two sites
on these benches had junipers in 1871, and junipers were
absent from all bench sites in 1988. Native bunchgrasses
were apparently not conspicuous on SM sites even in
1871, and they are still not conspicuous there today.
The few sites with native bunchgrasses conspicuous
32
HP High Elev. Flats (N
= 8)
HP High Elev. Cyns/Washes (N
100
=10)
100
•
1913
BJ
1988·
•
80
80
60
60
40
40
20
20
0
II
1913
1988-
0
JUOS ATCO
ART NAT.BG ARSP ANN. SAVE
JUOS
ART
NAT.BG ATCO
ANN.
SAVE
Plant Species
Plant Species
SM High Elev. Flats (N = 17)
SM High Elev. Cyns/Washes (N = 8)
100
100
80
•
1871
1B
1988-
•
60
60
40
40
20
20
0
0
JUOS
ARTR NAT.BG EX.BG
ANN.
1B
80
JUOS
SAVE
ARTR
NAT.BG
1871
1988
EX.BG
ANN.
Plant Species
Plant Species
Figure &-Percentages of high-elevation flat sites
dominated by various plant species in the initial
and 1988 surveys in the Hastings Pass (HP), and
Salt Mountain (SM) townships. Taxonomic symbols as in previous figures.
Figure 9-Percentages of high-elevation canyon
and wash sites dominated by various plant species in the initial and 1988 surveys in the Hastings
Pass (HP), and Salt Mountain (SM) townships.
Taxonomic symbols as in previous figures.
as in 1913. Apparently, however, shadscale was conspicuous in several mountainous sites in 1913, but is not
prominent at any of these sites today. The rugged topography of this type has undoubtedly minimized livestock
access and prevented major changes in species dominance
from occurring.
There are only five sites of the mountainous type in the
SM township, so conclusions must be tenuous (fig. 10).
Junipers were conspicuous at three of these sites in 1871,
and were evident at four sites in 1988. Cheatgrass is now
abundant at four sites. Native bunchgrasses were conspicuous at only one site in 1871, and at none in 1988.
Exotic bunchgrasses are now conspicuous where seeded.
Sagebrush was conspicuous at all five sites in 1871, and
was still conspicuous at four of the sites in 1988.
33
=23)
HP Mountain Sites (N
washes for both townships. Juniper growth and establishment apparently accelerates where soil water may
be more available.
In the HP township, the mountainous types show no
decrease in tree density because they seldom burned.
Fires have caused a decrease in junipers at some flat
or canyon/wash sites here, however. Some recent fires
have killed junipers in the canyon/wash type which, before the fire, was dominated by young trees and were
probably sites with increasing tree density. The mountainous sites of this township are generally static (sites
that probably have not changed substantially in juniper
size or density since the GLO survey).
It might be proposed that, in the absence of disturbance
by livestock and fire, wetter sites might be more conducive to juniper establishment and higher juniper densities
compared to drier sites. This does not appear to be the
case, however. Note that the mountainous sites (fig. 12),
have been divided into two types: sites occurring in the
middle of steep slopes ("midslopes"), and sites occurring
100
80
J
u;
0
'#.
60
40
20
0
JUOS
ART
ATCO NAT.BG
ARSP
ANN.
Plant Species
SM Mountain Sites (N
=5)
100
HP Juniper Site Status
80
100
J
60
so
u;
1:'.!
0
Q,
'#.
Q)
·c::l
40
~
60
•
;:
'i
rn
Q)
5il
20
Increasing
11!1 Static
40
1111
~
Decreasing
Inc., then Dec.
•
Increasing
Static
Decreasing
Inc., then Dec.
0
'#.
20
0
JUOS
ARTR
NAT.BG
EXBG
ANN.
0
Bench
Plant Species
Flats
Cyn!Wash
Mtns
Site Type
Figure 10-Percentages of mountain sites
dominated by various plant species in the
initial and 1988 surveys, in the Hastings
Pass (HP), and Salt Mountain (SM) townships. Taxonomic symbols as in previous
figures.
SM Juniper Site Status
100
so
1:'.!
·c:8..
:l
~
60
;:
JUNIPER REPRODUCTION
II
II
'i
rn
Q)
:=
By comparing the positions of witness trees with
respect to the survey monument at each of the juniperdominated sites, and by noting the presence of similarsized or larger trees closer to the monument, we obtained
a qualitative idea of whether particular sites had shown
increases in juniper size and density since the surveyors
had recorded the witness trees, or whether the sites had
shown a decrease in junipers or were apparently static.
A high proportion of the high-elevation, juniperdominated sites show substantial increases in juniper
size, density, or both, since the GLO survey (fig. 11).
Those sites with increased trees are located mostly in
the high-elevation flats or in and near canyons and
40
~
(f)
0
'#.
20
Bench
Flats
Cyn/Wash
Mtns
Site Type
Figure 11-Percentages of section and quartersection corners where junipers were increasing,
static, or decreasing between the initial and
1988 surveys, stratified by site types in the
Hastings Pass (HP) and Salt Mountain (SM)
townships.
34
HP Juniper Old and Dead Trees
HP Juniper Density
600
50
•
II
500
40
Ill
%Old Trees
%Dead Trees
% (Old & Dead)
-;-
.r.
UiG)
400
[!?
~
30
G)
Q.
~
"2
300
...,;:,
Ill
0
c:
Q)
0~
0
G)
G)
20
200
.=
10
100
0
0
Flats
Cyn/Wash
Midslopes
Flats
Ridges
Cyn/Wash
Midslopes
Ridges
Site Type
Site Type
Figure 12-Mean juniper densities
(trees/ha) in 1988 at various mountainous site types within the Hastings Pass
township. The thin lines centered over
the bars represent one standard error
of the mean.
Figure 14-Mean percentages of old
and dead trees in the total juniper density
found in 1988 at various mountainous
site types within the Hastings Pass
township. The thin lines represent one
on or very near ridge tops. Juniper densities do not appear to be very different among the types in the relatively
undisturbed HP township, although the juniper cover
visually appears to be higher in wetter sites (especially
canyon/wash sites). Nor does the proportion of junipers
in the seedling and young sapling age classes appear
to be significantly different (fig. 13), although there is
a tendency for the proportion to be greatest in the relatively wet canyon/wash sites. What do appear to be different are the proportions of old mature/decadent junipers
and the proportions of dead juniper snags (fig. 14). Decadent trees appear to constitute a higher proportion of the
population at the mountainous sites, such as midslopes
and ridges. They probably escape fires and wood gathering more often there than at other sites, such as canyons
and washes, where fires are common (fig. 4).
HP Juniper Seedlings and Young Saplings
50
40
30
20
10
CONCLUSIONS
0
Flats
Cyn/Wash
Midslopes
1. Large historical changes in plant species distribution
and dominance have occurred in the vegetation of both
study townships in Skull Valley. The greatest changes
have occurred in former sagebrush- and shadscaledominated vegetation on bench, foothill, and bajada
sites where livestock grazing and fires have been most
concentrated.
2. In the HP township, most of the changes have been
concentrated in the mid-elevation bench sites, where
Ridges
Site Type
Figure 13-Mean percentages of juniper
seedlings and saplings in the total juniper
density found in 1988 at various mountainous site types within the Hastings Pass
township. The thin lines represent one
standard error of the mean.
35
areas dominated by shadscale and sagebrush and native
perennial bunchgrass have been converted to cheatgrassdominated sites. At the higher elevations, rugged topography and low water availability have resulted in less
disturbance both by fire and livestock. Where fires have
occurred at higher elevations, bunchgrasses have recovered vigorously and there has been little cheatgrass
invasion.
3. In the SM township, the sites with the greatest
changes are once again the mid-elevation sites, where
essentially all of the areas of former shadscale and sagebrush domination have been converted to cheatgrass
communities. But, in this township, higher elevation
areas have less rugged topography and more water, and
have therefore been exploited more intensively by livestock and humans than high-elevation areas of the HP
township. These areas have undergone considerable
expansion of juniper ranges and increases in juniper
density, despite considerable woodcutting and chaining.
In addition, native bunchgrasses have been largely eliminated and some areas reseeded to exotic bunchgrasses.
4. Greasewood, saltgrass, and playa sites in both townships have seen relatively little change in plant species
dominance over the historical period evaluated.
Hull, A. C. 1976. Rangeland use and management in the
Mormon West. In: Proceedings-symposium on agriculture, food and man-a century of progress; 1976 March
29-April2; Provo, UT. Provo, UT: Brigham Young University, College of Biological and Agricultural Sciences:
1-21.
Mack, R.N. 1986. Alien plant invasion into the Intermountain West: a case history. In: Mooney, H. A.;
[and others], eds. Ecology of biological invasions in
North America and Hawaii. Berlin, Federal Republic
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Murdock, J. R.; Welsh, S. L. 1971. Land use in Wah Wah
and Pine Valleys, western Utah. Sci. Bull. Bio. Ser. Vol.
XII. No.4. Provo, UT: Brigham Young University.
Rickard, W. H. 1964. Demise of sagebrush through soil
changes. BioScience. 14(8): 43-44.
Rogers, G. 1982. Then and now: a photographic history
of vegetation change in the central Great Basin Desert.
Salt Lake City, UT: University of Utah Press. 152 p.
Steams, F. 1974. The use of the American General Land
Office Survey in syndynamical vegetation analyses. In:
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Dr. W. Junk b. v. Publishers: 73-80.
Tausch, R. J.; West, N. E.; Nabi, A. A. 1981. Tree age
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woodlands. Journal of Range Management. 34: 259-264.
West, N. E. 1983. Western Intermountain sagebrush
steppe and Great Basin-Colorado Plateau sagebrush
semi-desert. In: West, N. E., ed. Temperate deserts
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West, N. E. 1984. Successional patterns and productivity
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West, N. E. 1988. Intermountain deserts, shrub steppes,
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West, N. E. 1989. Vegetation types of Utah. In: Johnson,
K. L., ed. Rangeland resources of Utah. Logan, UT:
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Young, J. A.; Evans, R. A.; Tueller, P. T. 1976. Great
Basin plant communities-pristine and grazed. In:
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Young, J. A. [In press.] Intermountain shrubsteppe plant
communities-pristine and grazed. Western Raptor
Management Symposium, Boise, ID.
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36