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Juniper-Pinyon Population Dynamics Over
30 Years Following Anchor Chaining
Richard Stevens
Scott C. Walker
1970; Barney and Frischknecht 1974; Tausch and Tueller
1977; Severson 1986; Tausch and West 1988). Patterns of
tree recruitment and ecology could be better explained if
individual trees were studied over several decades. The few
such investigations have focused on individual tree survival
and growth following mechanical control or related treatments, or destructively sampled trees (Jameson 1965; Tausch
1980; Van Pelt and others 1990). In addition, few studies
have been developed to evaluate the effects of grazing on
pinyon-juniper survival, growth, and reproduction following
control measures.
To obtain a better understanding of tree responses following anchor chaining ofUtahjuniper and pinyon and seeding,
permanent marked trees and vegetative belt transects were
established within five-way exclosures constructed on five
chained big game range rehabilitation projects in Sanpete
County, Utah. Resulting research on these five exclosures
focus on: changes in percent cover of trees, shrubs, grasses,
and forbs (Stevens and others 1977); population dynamics of
pinyon and juniper (Stevens and others 1975) and basin big
sagebrush, black sagebrush, and white rubber rabbitbrush
(Stevens 1986); forage production (Plummer and others
1970a); herbivore effects on seeded alfalfa (Rosenstock and
Stevens 1989); and interaction between native and introduced grasses (Walker and others 1995).
Abstract-Permanent marked trees and vegetative belt transects
were established within five-way exclosures on five chained big
game rehabilitation projects in Sanpete County, Utah. Resulting
research focuses on changes in cover of trees, shrubs, grasses, and
forbs; population dynamics of pinyon and juniper and other plants;
forage production; herbivore effects; and interaction between native
and introduced grasses.
A majority of the winter and spring-fall big game and
livestock ranges in the Great Basin are in Utah juniper
(Juniperus osteosperma), pinyon (Pinus edulis), and sagebrush (Artemisa tridentata) types. Within the Great Basin,
prior to settlement, a majority of the juniper-pinyon stands
were confined to selected areas where understory competition and fire controlled tree density and recruitment. From
the late 1800's to the present, distribution and density of
juniper and pinyon and accompanying understory have been
significantly altered as an indirect response to livestock
grazing. Livestock grazing reduced the density and vigor of
perennial understory, which, in tum, regulated fire, the
establishment of exotic annuals, and tree regeneration.
Adjoining semiarid grass and shrublands underwent similar changes as desirable species were eliminated or reduced
in density and vigor by grazing. The absence offire and the
reduced competition, due to loss ofdominant shrubs, grasses,
and other forbs, allowed for an increase in juniper and
pinyon trees, and substantial tree invasion into many adjoining grass and shrublands (Aro 1971; West 1984b; West
and Van Pelt 1986; Woodbury 1947). The invasion ofjuniper
and pinyon, and thickening of stands have resulted in loss of
big game habitat and livestock forage, and have diminished
watershed resources.
Considerable effort has been given to the development of
practices and techniques to reduce tree density and reestablish desirable understory species. Most control measures do
not result in complete tree eradication, nor completely suppress reinvasion. Many trees have remained or reestablished following fire (Barney and Frischknecht 1974), cabling and chaining (Stevens and others 1975; Van Pelt and
others 1990; West 1984a), or construction activities (Kruse
and others 1979).
Studies related to the recovery, invasion, and stand thickening process have contributed generalized schema or notions of succession and stand growth (Blackburn and Tueller
Areas and Methods
-------------------
The five areas are known as Manti (1 mile south of Manti),
south Mayfield (1 mile south of Mayfield), east Mayfield (2
miles east of Mayfield), South Hollow (5 miles southeast of
Mayfield), and Fountain Green (8 miles east of Fountain
Green). Areas treated and chained vary from 600 to 1,200
acres (1,480 to 2,960 ha) and occur at elevations of 5,750 to
7,000 feet (1,750 to 2,100 m). Long-term average precipitation range from 11.5 to 18 inches (29 to 46 cm). Soils at Manti,
south Mayfield, east Mayfield, and South Holloware limestone-derived, cobbly loams in the Frontreen series. Soils at
Fountain Green are formed from alluvium and colluvium
derived from sandstone, limestone, quartzite, and mixed
igneous rocks in the Deer Creek series (USDA, SCS, USDI,
and BLM 1981).
Prior to tree removal, the sites supported juniper and
pinyon with a scattered understory of Wyoming and basin
big sagebrush (Artemisia tridentata ssp. wyomingensis and
ssp. tridentata) and less abundantly, Indian ricegrass
(Oryzopsis hymenoides), western wheatgrass (Agropyron
smithii), bottlebnish squirreltail (Sitanion hystrix), black
sagebrush (A. nova), white rubber rabbitbrush (Chrysothamnus nauseosus ssp. hololeucus), low rabbitbrush (C.
viscidi{lorus), broom snakeweed (Xanthocephalum
sarothrae), and a number of annual forbs as well as considerable cheatgrass brome (Bromus tectorum). Species
In: Barrow, Jerry R.; McArthur, E. Durant; Sosebee, Ronald E.; Tausch,
Robin J., comps. 1996. Proceedings: shrubland ecosystem dynamics in a
changing environment; 1995 May 23-25; Las Cruces, NM. Gen. Tech. Rep.
INT-GTR-338. Ogden, UT: U.S. Department of Agriculture, Forest Service,
Intermountain Research Station.
Richard Stevens is Project Leader and Research Biologist and Scott C.
Walker is Research Biologist, Utah Division of Wildlife Resources, 540 North
Main, Ephraim, UT 84627.
125
placed in a condition class. Measurements along these
transects have been made at 1- to 7-year intervals for the
past 30 years.
Trees were placed into four condition classes: (1) standing
trees -live trees that had not been tipped over with chaining;
(2) seedlings -young trees 1- to 3-years-old that were present
and alive following chaining; (3) downed trees - live trees
that had been tipped over but not completely uprooted by
chaining; and (4) recruits - seedlings. that appeared after
1964. The total number of reported recruits may not represent all seedlings that emerged along the transects over the
30 years. Some seedling recruits may have appeared and
died between measurement years. Tree number data were
exposed to general linear model analysis of variance by year,
grazing treatment, area, and class. Significant differences
were determined at the P<0.05 level. If differences were
significant from the GLM - ANOVA, Fisher's LSD posthoc
test was used to determine where the differences occurred
(Fisher 1966).
Changes in tree numbers of residuals and recruits are
reported in this paper. Tree size, growth rate, production,
and cover data are on file at Great Basin Experiment
Station, Utah Division of Wildlife Resources, Ephraim,
Utah 84627.
nomenclature follows Plummer and others (1977b). All five
sites were double-chained during October and November:
Manti in 1959; south Mayfield in 1960; east Mayfield, South
Hollow, and Fountain Green in 1961. Between chainings a
seed mixture of native and introduced grasses, forbs, and
shrubs was applied by fixed-wing aircraft. Downed trees
were left in place to enhance seedling establishment and for
watershed protection.
During the summer of 1962, a 300 by 300 foot (91 x 91 m)
five-way exclosure was constructed on each of the five sites.
Five grazing treatments were provided with each exclosure
(fig. 1); (a) control-rabbits, deer, and livestock excluded (no
use); (b) rabbit only access; (c) deer only access; (d) rabbit and
deer access; and (e) accessible to rabbits, deer, and livestock.
Monthly precipitation was recorded at each location beginning in 1962.
At each exclosure a set of five permanent 100 foot (30 m)
long transects were randomly located within each of the five
grazing treatments (fig. 1). Tenend-to-endplots, 10 feet long
by 1 foot wide (3 by 0.3 m), were centered over each 100 foot
(30 m) long permanent transect to measure herbaceous
plant numbers, production, and ground cover. Overlying
these transects, 100 by 4.356 foot (30 by 1.33 m) transects
were established to measure shrub and tree numbers, size,
production, and cover. Every juniper and pinyon within each
transect was marked, mapped, and measured for maximum
crown canopy. Heights and weights were estimated and
Results
I
.Rabb.1 t. Deer.
-Transect
ani Cattle USi
32 inch (81.3 em)
netting fence
8 foot (2.4 em)
netting fence
----------------------------------
No significant difference in tree numbers occurred over
time between grazing treatments and areas. There were,
however, significant changes in total numbers ofjuniper and
pinyon trees in all transects, treatments, and areas. In
1964 there were 61 live pinyon and 152 live juniper trees
(table 1) along the five permanent transects in five grazing
treatments on five areas.
Within all five study sites, there were 61 live pinyon in
1964 (table 1). Of these, 19 were trees that had been tipped
over by chaining but were still rooted by at least one root.
There were 31 live standing pinyon and 11 seedlings (young
plants less than 3 years old). Thirty years later, in 1994,
there were significantly less trees in all three tree classes.
Only 31 of the original 61 (51 percent) trees present in 1964
were alive in 1994. Thirty-two percent of the standing trees,
74 percent of the downed trees, and over half (55 percent) of
the seedlings had died between 1964 and 1994. Total loss was
49 perCent. Four new recruit pinyon seedlings were found
between 1964 and 1993. None of these were alive in 1994.
In 1964, there were 152 live juniper trees (table 1). Between 1964 and 1994,43 percent (65) of these died. Fifteen
(27 percent) of the original 55 standing trees died within the
30-year sampling period. Of the 21 seedlings that were
present in 1964, 13 (62 percent) died by 1994. Forty-nine
percent of the 76 trees that had been tipped over by chaining
died before 1994. Between 1965 and 1994,46 new recruit
juniper seedlings were located along the permanent transects.
Nineteen of these died by 1994. Thus, 27 new juniper trees
were added to the population over the 30 years. Even with
this addition of 27 additional trees there was a significant
loss in numbers ofjuniper trees; 152 in 1964 and 87 in 1994,
a 43 percent loss.
There were 213 juniper and pinyon trees within all
transects in 1964. Of these original trees only 118 (55
percent) were alive in 1994. During this 30 years, 27 new
•
•
... ·150 feet (45.9 m)l_
::::::::::::: 32 1nch (81. 3 em).
1 inch (2.5 em)
chicken net fence
Figure 1-Four-way exclosures and comparable outside areas.
126
Table 1-Number of individual marked pinyon and juniper trees 1964 through 1994.
Pinyon
1994
% Change
1964
Juniper
% Change
1994
Tree type
1964
Standing 1
Seedling2
Downed3
31 A
11A
19A
21B
5B
5B
-32
-55
-74
55A
21A
76A
40B
8B
39B
-27
-62
-49
Total
61 A
31 B
-49
152A
87B
-43
% Change
Total 1965
through 1993
Recruit seedlings4
Total 1965
through 1993
4
',"
..
Alive in
1994
0
0
46
Alive in
1994
27
% Change
+57
% Change
Total trees
1964
1994
Pinyon
Juniper
61 A
152A
31 B
141A
-49
-8
Total
213A
172B
-20
Numbers within a row followed by the same letter are not significantly different (p<0.05).
-"
1Mature vertical trees.
21mmature trees 1- to 3-years-old.
3Live trees that have been tipped over by the chaining process which have at least one major root still in the soil.
4 Recru it seedlings, 1 to 3-years-old. Number may not represent total number of recruit seedlings In all years. Seedlings
may have established and died between sampling years. Numbers represent seedlings encountered in the years counts
were made. Fountain Green: 1965,1967,1972,1977,1982,1987,1994. Manti: 1966, 1967, 1969, 1971, 1972, 1975,
1977,1982,1987,1994. South Mayfield, East Mayfield, and South Hollow: 1967, 1972, 1977, 1982, 1987, 1994.
juniper and no new pinyon seedlings were added to the
population. The total number oftrees in 1994 was 172, which
is an overall 20 percent reduction of the 1964 number.
Discussion
Forty-sixjuniper and only four new pinyon seedlings were
found on the transects in the 30 years. None of the pinyon
and 27 (54 percent) of the juniper seedlings were alive in
1994. These numbers may not represent total number of
recruitment seedling. Some may have established and died
between years when sampling occurred.
The trees in the five communities did increase in size,
which gave the impression of more trees. However, increase
in tree density did not occur. There was, in reality, a decrease
in number of trees. Similar results have also been reported
by Dalen and Snyder (1987); Stevens (1987); and Van Pelt
and others (1990). All four of these studies repudiate the
concern of reinvasion or increase in tree numbers, and need
for retreatment expressed by Evans (1988); Johnson (1987);
Jameson (1987); and Tausch and Tueller (1977).
-------------------------------
Anchor chaining has been used on hundreds of thousands
of acres to reduce juniper and pinyon density and facilitate
seedlings, shrubs, forbs, and grasses. Percent tree kill from
chaining has depended on size and age of trees in the
community, soils, and chain type, weight, and chaining
techniques (Stevens 1987).
A majority of trees on the five sites were uprooted and
killed by chaining. Some of the trees that were tipped over
but were still partially rooted initially survived. Among
these, there was a considerable loss; 84 percent of the pinyon
and 48 percent of the juniper. Some of the trees that remained upright and rooted were apparently injured, probably from cambial injuries or root exposure. Fifty-five percent of the pinyon, and 62 percent of the juniper that were
left standing, died within the 30 years. Deer, rabbit, cattle,
and sheep grazing use, or lack of use, over 30 years did not
adversely affect number of juniper and pinyon trees.
Most trees that remain alive on a chained area will
increase in size, become more visually apparent, and may
even give the false impression of reinvasion. Some recruitment of new seedlings will occur. Total number of trees on
the permanent lines in the five exclosures decreased by 20
percent over 30 years from 171 trees per acre in 1964 to 138
per acre (340 per ha) in 1994. There was no reinvasion or
thickening of the stands. Recruit seedlings did appear.
However, reproduction did not keep up with the number of
deaths in the residual population.
Acknowledgments _ _ _ _ _ __
This work was facilitated by Federal Aid to Wildlife
Restoration Pittman-Robertson Wildlife Habitat Restoration Project W-82-R, Utah Division of Wildlife Resources,
and USDA Forest Service Intermountain Research Station.
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