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Wildlife, Animals, and Plants
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Introductory
SPECIES: Juniperus monosperma | Oneseed Juniper
ABBREVIATION :
JUNMON
SYNONYMS :
NO-ENTRY
SCS PLANT CODE :
JUMO
COMMON NAMES :
oneseed juniper
one-seed juniper
one-seeded juniper
red cedar
cherry-stone juniper
western Texas juniper
sabina
redberry juniper
TAXONOMY :
The currently accepted scientific name on oneseed juniper is Juniperus
monosperma (Engelm.) Sarg. Oneseed juniper has been placed within the
section Sabina [77]. It is known to hybridize with alligator juniper
(J. deppeana); these two species form hybrid swarms from central Mexico
through southern Colorado [28]. Redberry juniper (J. pinchotii) is
reportedly the product of a stabilized hybrid of oneseed juniper and
alligator juniper [28,53]. Hybrid swarms between oneseed juniper and
redberry juniper occur in parts of the Southwest [28,47].
Two varieties, based on certain morphological differences as well as
geographic distibution, are generally recognized [81] :
Juniperus monosperma (Engelm.) Sarg. var. monosperma
Juniperus monosperma (Engelm.) Sarg. var. gracilis Martinez
LIFE FORM :
Tree
FEDERAL LEGAL STATUS :
No special status
OTHER STATUS :
NO-ENTRY
COMPILED BY AND DATE :
D. Tirmenstein, January 1989
LAST REVISED BY AND DATE :
NO-ENTRY
AUTHORSHIP AND CITATION :
Tirmenstein, D. A. 1989. Juniperus monosperma. In: Remainder of Citation
DISTRIBUTION AND OCCURRENCE
SPECIES: Juniperus monosperma | Oneseed Juniper
GENERAL DISTRIBUTION :
Oneseed juniper occurs from central Colorado, southern Nevada, Arizona,
and New Mexico to western Texas and southward into northern Mexico
[47,48,75]. This species along with true pinyon (Pinus edulis) is the
dominant tree on 60 million acres (24,281,238 ha) of the Southwest [15].
The variety gracilis is restricted to parts of Mexico [81].
ECOSYSTEMS :
FRES21 Ponderosa pine
FRES28 Western hardwoods
FRES29 Sagebrush
FRES32 Texas savanna
FRES34 Chaparral - mountain shrub
FRES35 Pinyon - juniper
STATES :
AZ CO KS NV NM OK TX MEXICO
ADMINISTRATIVE UNITS :
BAND BIBE CACA CHCU CHIR CORO
FOBO GRCA GUMO LAME LAMR MOCA
ORPI PEFO WACA WUPA
BLM PHYSIOGRAPHIC REGIONS :
7 Lower Basin and Range
11 Southern Rocky Mountains
12 Colorado Plateau
13 Rocky Mountains Piedmont
KUCHLER PLANT ASSOCIATIONS :
K011 Western ponderosa pine
K018 Pine - Douglas-fir forest
K019 Arizona pine forest
K023 Juniper - pinyon woodland
K031 Oak - juniper woodlands
K037 Mountain mahogany - oak scrub
K038 Great Basin sagebrush
K055 Sagebrush steppe
SAF COVER TYPES :
237 Interior ponderosa pine
239 Pinyon - juniper
240 Arizona cypress
241 Western live oak
SRM (RANGELAND) COVER TYPES :
NO-ENTRY
HABITAT TYPES AND PLANT COMMUNITIES :
Oneseed juniper is an indicator in a number of pinyon-juniper shrubland
and desert grassland classification systems. This species frequently
occurs as a codominant with ponderosa pine (Pinus ponderosa), pinyon, or
Utah juniper (Juniperus osteosperma) in woodland habitat or community
types [23,24,44].
Published classifications listing oneseed juniper as an indicator are
listed below.
Forest vegetatoin of the White River National Forest in western
Colorado: a habitat type classification [31].
Phyto-edaphic communities of the Upper Rio Puerco Watershed, New Mexico [23].
Plant associations of Region Two [44].
Preliminary habitat types of a semiarid grassland [24].
VALUE AND USE
SPECIES: Juniperus monosperma | Oneseed Juniper
WOOD PRODUCTS VALUE :
The relatively small stature and multiple stems of oneseed juniper limit
its usefulness as a timber species. The wood currently has little
commercial value but was formerly used locally for fenceposts, poles,
railroad ties, and mine timbers [16]. Oneseed juniper wood is described
as strong and long-grained [28].
IMPORTANCE TO LIVESTOCK AND WILDLIFE :
Pinyon-juniper woodlands provide good habitat for mule deer, bighorn
sheep, bison, wild horses, pronghorns, coyotes, bobcats, badgers,
porcupines, rabbits, mice, voles, woodrats, squirrels, and numerous
birds [16]. The foliage and berries of oneseed juniper provide food for
many species of birds and mammals.
Browse: The foliage of oneseed juniper appears to be of little value to
domestic livestock. Sheep and goats may browse this species to a
limited degree in some areas [13,35]. Oneseed juniper browse may induce
abortions in domestic livestock under certain circumstances [73].
Deer utilize the foliage to at least a limited extent [13,35,52].
Mahgoub and others [51] observed fairly heavy utilization in parts of
south-central New Mexico where juniper can represent up to 20 percent of
the annual diet of mule deer. Oneseed juniper foliage is reported to be
a major mule deer food item from January through March in parts of
southeastern New Mexico [63]. Pronghorns also browse oneseed juniper,
and in some areas, winter use may be fairly heavy [10,74]. Bighorn
sheep and elk consume at least small amounts of juniper browse in
certain locations [63].
Fruit: The berrylike fruits of oneseed juniper serve as an abundant and
readily available food source for a wide range of wildlife species. The
bright berries tend to remain on the tree and can provide food
year-round [16]. Fruits are initially plump and juicy but become dry
and leathery by the second winter [65]. Berry ripening usually
corresponds with the arrival of winter residents to the pinyon-juniper
woodlands [64].
Oneseed juniper berries represent an extremely important food source to
a number of bird species. Berries are abundant, easily acessible, and
nutritious [64]. It is estimated that avian population densities may be
70 percent greater during years with abundant juniper berry crops
(generally every 2 to 5 years) [5]. Studies with captive birds have
revealed that an average Townsend's solitaire can consume approximately
240 berries per day, or 36,000 to 84,000 per winter [5,64]. In some
areas at least 97 percent of the Townsend's solitaire's winter diet may
be made up of oneseed juniper berries [65]. Robins also consume large
numbers of juniper berries. An individual bird can eat 220 berries per
day or 33,000 per winter [5]. Balda [5] reported 20,000 berries per
cubic meter of juniper foliage in 1973, but by September 1974, birds and
other dispersal agents had reduced berry numbers to 300 per cubic meter.
Birds and mammals serve as important dispersal agents for seeds of
oneseed juniper. Many bird species disperse seed up to 6.3 miles (10 m)
or more from the seed source [5]. Sheep and domestic cattle can also
facilitate the dispersal of oneseed juniper [40]. A number of the
following species known to consume oneseed juniper are important
dispersal agents [64]:
food source probable role
northern flicker berry disperser
Steller's jay berry disperser
mountain chickadee flesh ---
plain titmouse flesh ---
sage thrasher berry disperser
American robin berry disperser
Townsend's solitaire berry disperser
western bluebird berry disperser
evening grosbeak seed probable
Cassin's finch seed probable
desert cottontail berry disperser
black-tailed jackrabbit berry disperser
cliff chipmunk seed probable
rock squirrel seed probable
golden mantled ground
squirrel seed probable
deer mice seed probable
Mexican woodrat seed probable
coyote berry disperser
gray fox berry disperser
Other wildlife species known to consume oneseed juniper berries include:
mule deer, western chipmunk, antelope ground squirrel, squirrels, bear,
javelina, pocket mouse, rabbits, and raccoon [40,63,72,73].
PALATABILITY :
The fruits of oneseed juniper are sweet tasting and highly palatable to
many birds and mammals [64]. They appear to remain palatable even when
dry. The foliage is relatively unpalatable to most species, although it
is reported to be somewhat more palatable than most other junipers [13].
The palatability of oneseed juniper to livestock and wildlife species in
two western states has been rated as follows [14]:
CO UT
Cattle poor poor
Sheep poor fair
Horses poor poor
Pronghorn ---- fair
Elk ---- fair
Mule deer ---- fair
Small mammals ---- good
Small nongame birds ---- good
Upland game birds ---- good
Waterfowl ---- poor
NUTRITIONAL VALUE :
Oneseed juniper is rated as poor in overall protein and energy value
[14]. However, many species of birds apparently obtain at least
moderate energy value from the berries [5]. These fruits provide a
comparatively rich source of carbohydrates for a number of birds [64].
Caloric value of oneseed juniper berries is as follows [64]:
size mg/unit cal/mg cal/unit
berries 6.6 mm diameter 107.49 4.57 490.82
seeds 4.9 x 3.6 mm 37.52 4.66 174.85
flesh --- 69.97 4.52 315.97
COVER VALUE :
Oneseed juniper provides good cover for a number of birds and mammals
including quail, wild turkeys, deer, and songbirds [63]. The degree to
which oneseed juniper provides environmental protection during one or
more seasons for wildlife species is as follows [14]:
CO UT
Pronghorn ---- good
Elk ---- good
Mule deer fair good
White-tailed deer fair ----
Small mammals good good
Small nongame birds good good
Upland game birds ---- good
Waterfowl ---- poor
VALUE FOR REHABILITATION OF DISTURBED SITES :
Oneseed juniper is rated as having low overall value for short-term
rehabilitation but high value for long-term rehabilitation [14]. It has
not been widely used in the past for rehabilitation projects due to
unreliable seed germination caused by inhibitors in the seed coat and
dormancy [21]. Fertilizers, wood chip or straw mulch, plastic mesh for
protection against rodents, and drip irrigation can all contribute to
increased survival on disturbed sites [20,21]. Oneseed juniper has been
successfully planted on a number of surface coal and uranium mines in
the Southwest [20]. Improved techniques have resulted in survival rates
of 70 percent to 99 percent [20,21].
On certain New Mexico sites, drip irrigation is somewhat more effective
than mulch, while triple-superphosphate aids growth more than
slow-release fertilizers [20]. Seed germination can be enhanced by
leaching seeds with water at 68 to 75 degrees Fahrenheit (20-24 deg C)
and cold stratification for 90 days, or seeds should be treated with
water and GA3 or ethephon only, applied 30 days prior to cold
stratification [21]. Planting dates can significantly influence
seedling survival. On the New Mexico test sites, July planting dates
produced best results at higher elevations, whereas August plantings
were most successful on low-elevation sites [20]. Seedling survival at
several New Mexico sites was as follows [20,21]:
Raton, NM Site Grants, NM Site
planting % survival treatment % survival
July 73 mulched 96
May 55 non-mulched 89
August 48
treatment % survival
May-fertilized 22
May-unfertilized 88
July-fertilized 62
July-unfertilized 86
August-fertilized 3
August-unfertilized 95
Coal mine site
planting % survival 2 years after planting
August 47
September 16
November 14
Transplanting containerized seedlings onto disturbed sites has also been
successful [20,21]. Survival of transplants is apparently dependent on
moisture availability [21]. In New Mexico, survival is best when trees
are planted after the June drought but before the ground freezes
[20,21]. Mulch which aids in water conservation can enhance survival on
dry sites, and on extremely arid sites, drip irrigation may be necessary
[20,21]. Fertilizer may improve survival on some sites particularly
when combined with irrigation [20]. Applications of fertilizer should
be made near the base of the tree but not in the same hole in which the
tree was planted [20].
OTHER USES AND VALUES :
Native American peoples historically used oneseed juniper for a variety
of purposes. Wood was used for bows and arrows by the Kiowa, Commanche,
Cheyenne, and Apache [28]. A number of North American peoples ate the
fruit or ground them into flour for bread [73]. Prayer sticks were made
from wood, and a green dye, fibrous mats, and saddles were fashioned
from the bark [73]. Parts of the tree were also used as building
materials and for medicinal purposes [40].
During historic times, oneseed juniper was used as a fuel source, as
fenceposts, charcoal, mine timbers, posts, cellulose, and in a number of
chemical products [40]. Springfield [71] noted that many species of
juniper may have potential value for the production of charcoal, pulp,
particleboard, chip products, fiber, or in certain chemicals. Oneseed
juniper was first cultivated in 1900 [42].
MANAGEMENT CONSIDERATIONS :
Pinyon-juniper woodlands have been increasing in extent since settlement
times. In many parts of Southwest, oneseed juniper and other species
have encroached into adjacent grasslands [35,56,80]. A decrease in fire
frequency has often been cited as the probable cause of this increase
[79], but overgrazing offers another possible explanation. Past
management efforts have largely focused on halting the juniper invasion
through mechanical or chemical means. Little regard was given to
possible wildlife use of these areas, or to potential wood products
value of these species. These factors should be considered when
attempting to devise and implement management strategies in
pinyon-juniper woodlands. Strategies aimed at preserving wildlife
habitat while allowing carefully managed grazing opportunities should be
favored. In many cases juniper removal alone does little to increase
long-term forage potential.
Mechanical control: A number of methods of mechanical removal have been
used with varying success. Cabling, chaining, bulldozing, and various
means of hand removal have been used in attempts to convert these
woodlands to grasslands. Generally, cabling or chaining is most
effective on even-terrain sites with approximately 250 trees per acre or
less, and with at least half of those trees greater than 10 feet (3.1 m)
[4,41,71]. Neither the single chaining nor double chaining method
effectively kills trees less than 10 feet (3.1 m) in height [71].
In many areas, junipers and pinyons start to resume dominance as soon as
28 years after cabling [69]. Oneseed juniper seeds remain viable buried
in the soil on-site or are dispersed from off-site by birds and mammals
[69]. In many areas, particularly with many young tree prior to
treatment, reinvasion is rapid, and results do not appear to justify
these relatively expensive attempts at control [61]. Junipers may
become dominant particularly rapidly on sites with deeper soils [68].
Poor results have also been obtained on rocky soils, which seldom
produce good graminoid cover after juniper removal [67]. Stands should
have few young trees and at least 15 percent residual grass cover for
these mechanical treatments to be effective in promoting increases in
forage [67]. Some researchers recommend using fire or herbicides as a
second treatment approximately 5 years after cabling to increase tree
kill [67].
Bulldozing is most effective on sites with small- to medium-sized trees
and tree densities of 100 to 150 per acre [41,71]. Severson [70]
reported poor results after pinyon-juniper woodlands in New Mexico were
thinned and bulldozed. Differences in densities between most treated
and untreated areas were not detectable 13 to 18 years later [70]. No
significant differences were observed between bulldozed and
untreated/thinned treatments [70].
Crushing even-aged mature stands and hand removal of individual trees
have been tested, although both methods are expensive and have somewhat
limited utility [3,41]. Mechanical removal of oneseed juniper has not
produced increased water yields in experiments [19].
Chemical control: The foliage of junipers tends to be resistant to
herbicides, and leaves have little surface area for absorption [41].
Junipers can reportedly be killed by chemicals such as arsenite,
ammonium sulfate, esters of 2,4-D, and 2,4,5-T, polychlorobenzoic acid,
and picloram. See Springfield [71] and Johnsen [41] for details.
Range condition: Many pinyon-juniper ranges are now in relatively poor
condition. The following species are indicative of range condition on
certain Arizona oneseed juniper sites [32,33]:
excellent: black gama (Bouteloua eriopoda), Indian ricegrass (Oryzopsis
hymenoides), blue grama (B. gracilis), winterfat (Eurotia
lanata), cliffrose (Cowania spp.), and fourwing saltbush (Atriplex
canescens).
good: Indian ricegrass, black grama, blue grama, needlegrass
(Stipa spp.), and spike muhly (Muhlenbergia wrightii).
fair: blue grama, bare soil.
poor: broom snakeweed (Gutierrezia sarothrae), ringgrass
(Muhlenbergia torreyi), often much erosion.
Production: Herbage production values are variable in pinyon-juniper
woodlands. Springfield [71] reported an inverse relationship between
tree canopy and average herbage production as follows:
tree canopy average herbage production
0% 600 lbs per acre
20% 300 lbs per acre
80% 50 lbs per acre
Several studies have examined the influence of oneseed juniper canopy on
understory vegetation. Results suggest fairly distinct vegetative zones
surrounding oneseed junipers. Relatively little vegetation grows
closest to the tree where litter accumulation is greatest and shading
most extreme [1,66]. Generally such species as blue grama, sand muhly
(Muhlenbergia arenicoloides), skunkbush sumac (Rhus trilobata), and
algerita (Berberis trifoliata) occur here [1]. The second zone, which
extends outward beneath the canopy, is represented by creeping muhly
(Muhlenberiga repens), broom snakeweed, galleta (Hilaria jamesii),
sideoats grama (Bouteloua curtipendula), blue grama , and western
wheatgrass (Pascopyrum smithii) [1]. Production here was found to be
approximately 293 pounds air-dry herbage per acre [2]. Blue grama,
galleta , wolftail (Lycurus phleoides), mat muhly (Muhlenbergia
richardsonis), scarlet globemallow (Sphaeralcea coccinea), dropseed
(Aristida spp.), and hairy grama (Bouteloua hirsuta) are often most
prevalent in the outer zone or in tree interspaces [1]. In some areas,
western wheatgrass and broom snakeweed are well represented in
interspaces which receive full sunlight [2]. Generally, cool-season
grasses such as prairie junegrass (Koeleria cristata), western
wheatgrass, bottlebrush squirreltail (Sitanion hystrix), and mutton
bluegrass (Poa fendleriana) occur more abundantly under the canopy of
oneseed juniper than in the interspaces [1,17]. Schott and Pieper [66]
reported that oneseed juniper canopy crown diameter is negatively
correlated with the basal area of grasses. Such factors as shading,
decreased soil moisture due to absorption by oneseed juniper roots, and
possible chemical properties of oneseed juniper litter, all effect the
composition of understory vegetation [2,38,66].
Fertilization: The diameter of oneseed juniper was found to be largely
unaffected by the addition of nitrogen fertilizer in a New Mexico study,
although the growth of lateral branches and the apex was enhanced [63].
BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Juniperus monosperma | Oneseed Juniper
GENERAL BOTANICAL CHARACTERISTICS :
Oneseed juniper is a native, perennial evergreen which grows as a shrub
or small tree [73]. Although it can grow up to 49 feet (15 m) in
height, 7 to 13 feet (2-4 m) is more typical [75,78]. In extremely arid
areas trees may reach only 3 to 4 feet (0.9-1.2 m) at maturity [40].
Most oneseed junipers have multiple stems at or below ground level [75].
Oneseed juniper is characterized by a rounded or low spreading bushlike
crown [73,75].
Branches are stout and grayish to reddish-brown [27]. Gray to brown
twigs are scaly or shreddy [75]. The bark is ashy gray to gray, thin,
fibrous, and furrowed or shreddy [27,75,78]. The inner bark is
reddish-brown [82]. Foxx and Tierney [22] reported the following
rooting depths:
average rooting depth (cm) range (cm)
2,438 579-6,096
The relatively deep root system is well adapted for growth on sites with
low soil-water content [28].
Foliage is described as "bunched" [3]. The yellow-green, scalelike
leaves are mostly opposite, although sometimes occur in whorls of three
3 [75,82]. Juvenile leaves are sharp and awl-shaped [78].
Oneseed juniper is dioecious with small glaucous, brown, globular
staminate cones, and subglobose ovulate cones [75]. Mature cones are
dark blue to purple or brownish, and succulent, or at least somewhat
fleshy [27,75,78]. Seeds are generally one per fruit, more rarely two,
reddish-brown and ovoid to globose [27,75].
Oneseed juniper is a slow-growing species. Lymbery and Pieper [49]
reported an increase in height of approximately 6.3 inches (16 cm) per
decade, with a corresponding increase in stem diameter of 0.5 inch (1.2
cm). Growth rate tends to vary according to site characteristics,
however. On a hilly site in southwestern Texas, a oneseed juniper 35
years of age was 14 feet (4.3 m) in height with a diameter of 0.5 inch
(1.3 cm) [11]. The taproot extended to 3.5 feet (1.1 m) in depth [11].
Oneseed juniper has the ability to stop active growth when moisture
conditions are limited but can resume growth when moisture availability
improves [30]. This growth pattern may represent an important
adaptation allowing junipers to survive on harsh, arid sites. Although
small trees may be killed by drought, mature oneseed junipers are quite
resistant to drought [40].
RAUNKIAER LIFE FORM :
Phanerophyte
REGENERATION PROCESSES :
Oneseed juniper is dioecious with seed persisting for 1 to 2 years
[40,42]. Trees first produce seed at 10 to 30 years of age, although
maximum seed production generally does not occur until 50 to 200 years
of age [42,67]. Trees as short as 18 inches (46 cm) in height can
produce seed [40]. Oneseed juniper typically produces large seed crops
at 2- to 5-year intervals [42].
Germination of most species of juniper is relatively poor [59]. Seeds
generally require a specific period of rest and afterripening [59].
Pack [59] found that high temperatures, alternating temperatures,
freezing and thawing, removal of the seedcoat, application of hydrogen
peroxide, dilute acids, carbon dioxide, or light had little influence on
the germination of juniper seeds. Juniper seeds are described as having
a semipermeable and thick seed coat with a dormant embryo [59].
Oneseed juniper seed should generally be cold-stratified prior to
planting [42]. Germination was found to improve after a 48-hour water
soak and stratification at 41 degrees Fahrenheit (5 deg C) for 30 to 120
days [21]. Under laboratory conditions germination results were best
when seeds were exposed to an 8-hour photoperiod; 16 hours at 68 degrees
Fahrenheit (20 deg C), and 8 hours at 106 degrees Fahrenheit (30 deg C)
[21]. Seed should be leached with water at 68 to 75 degrees Fahrenheit
(20-24 deg C) and cold stratified for 90 days, or treated with water and
GA3 or ethephon applied 30 days prior to cold stratification [21].
Exposure to sunlight appears to have relatively little effect on
germination [40]. Johnsen [40] observed average germination of 44
percent for seeds grown in the dark, and 52 percent for seeds exposed to
sunlight [40]. Soil moisture may be an important factor influencing
germination. Germination appears to be best in moist but not saturated
soil [40]. Seeds of oneseed juniper do not germinate well on the soil
surface which is subject to rapid desiccation. Seed emergence by depth
is as follows [40]:
depth % emergence
(inches) uncovered covered
0 0 44
1/4 44 40
1/2 52 38
1 48 48
2 28 30
4 0 0
Juniper seeds appear to be resistant to drought when buried in the soil
[39]. Buried seeds can often retain viability and germinate when
moisture conditions become favorable [39]. Approximately 54 percent of
oneseed juniper seed stored for 21 years germinated [39]. Natural
germination generally occurs during the first spring after dispersal
[75].
Seedling establishment is often very poor even when good germination
occurs [69]. Researchers in some areas have found that only
approximately 3 percent of juniper seeds develop to the seedling stage
[36]. Shade may be important for good early growth of oneseed juniper
[36]. Emergence appears to be somewhat greater under trees or shrubs
than in interspaces where humidity and temperature fluctuations are more
extreme [40]. In some areas, small junipers are particularly numerous
under the canopy of pinyon or other species [36,67]. Most seedlings
occur some distance from the parent tree, although most seeds are
located beneath the source tree [64]. Seedlings seldom establish
beneath mature junipers, and an autopathic effect from litter is
suspected [67].
Dispersal of oneseed juniper may occur through water, gravity, or by any
of a number of birds and mammals [3]. Animal dispersal may be
particularly important, as digestive processes may actually actually
enhance germination [5]. Most berries occur on the outer edges of trees
where they are most visible and accessible to birds [64]. The brightly
colored highly visible berries remain on the trees for much of the year
and provide a constantly available food source for animals [5,16]. It
is estimated that on certain sites in New Mexico, 90 to 95 percent of
juniper reproduction could be attributed to bird dispersal [25,60].
Domestic sheep and cattle also aid in seed dispersal [40]. Trampling by
livestock can apparently reduce competition with grasses and help to
"plant" the seeds [40].
Although oneseed juniper is generally described as a nonsprouter [83].,
limited sprouting, mostly from older trees, has been observed in some
areas [12,76]. Approximately 10 percent of living oneseed junipers
sprouted from the base following an Arizona fire [76].
SITE CHARACTERISTICS :
Oneseed juniper is an important species throughout much of the
pinyon-juniper woodlands of the Southwest [8,49,]. It forms woodlands
with true pinyon, singleleaf pinyon (Pinus monophylla), Mexican pinyon
(P. cembroides), Utah juniper , and alligator juniper throughout much of
its range [54,82], and occasionally occurs in pure stands at lower
elevation sites too dry for pinyon [47,80].
Oneseed juniper typically occupies fairly xeric sites in semiarid
climatic zones [19,28]. The distribution of this tree may be largely
confined to the Arizona monsoon area or regions which receive summer
rains [57]. A typical Arizona-Utah site occupied by oneseed juniper
receives 10 to 15 inches (25-38 cm) of precipitation annually, and has
an average growing season of approximately 120 days [80]. Tree density
is believed to be related to leaf water potential [6]. Unlike several
related species, the distribution of oneseed juniper does not appear to
be limited by temperature inversions [35].
Oneseed juniper grows on dry, rocky, open flats, and slopes [27,29]. It
commonly occurs in canyons or on middle elevation foothills [27,80]. In
many areas this juniper occurs in a zone below ponderosa pine or
alligator juniper, but above oak (Quercus spp.)-mountain-mahogany
(Cercocarpus spp.) shrublands [58,80]. Common shrub, forb, and grass
associates of oneseed juniper include: skunkbush sumac , turbinella oak
(Quercus turbinella), broom snakeweed, mountain-mahogany, big sagebrush
(Artemisia tridentata), black sagebrush (A. nova), antelope bitterbrush
(Purshia tridentata), winterfat, rabbitbrush (Chrysothamnus spp.),
mesquite (Prosopis glandulosa), Mormon-tea (Ephedra spp.), yucca (Yucca
spp.), pricklypear (Opuntia spp.), scarlet globemallow, blue grama,
sideoats grama, bottlebrush squirreltail (Sitanion hystrix), prairie
junegrass, western wheatgrass, muhlys (Muhlenbergia spp.), and galleta
[3,45,55,69].
Because soil moisture is so limited on many oneseed juniper sites,
competition with others species may significantly influence the
occurrence of this tree on a particular site. Grasses can compete
effectively with oneseed juniper seedlings for moisture and can limit
its distribution in some areas [40,83]. A number of oaks also compete
for soil moisture, although oneseed juniper appears to be capable of
outcompeting them on shallow soils [67].
Oneseed juniper grows on a variety of soil textures including gravelly,
rocky, or sandy soils [27]. Parent materials include basalt, limestone,
and sandstone [19]. Generalized growth potential by soil type is rated
as follows [14]:
gravel: fair
sand: fair to poor
sandy loam: good
loam: good
clay loam: fair to good
clay: good to poor
dense clay: fair to poor
organic: poor
acidic: poor
saline: fair
sodic: poor
sodic-saline: poor
Soil characteristics, temperature, and topography combine to influence
the upper and lower elevational extent of oneseed juniper [80].
Elevational range of oneseed juniper by state is as follows [14,49]:
from: 2,951 to 6,885 feet (900-2,100 m) in Arizona and New Mexico
4,000 to 7,600 feet (1,220-2,318 m) in Colorado
3,500 to 3,500 feet (1,068-1,068 m) in Utah
SUCCESSIONAL STATUS :
The successional status of oneseed juniper has not been well documented.
This long-lived species apparently occurs as climax vegetation in some
areas [12,31] but as a seral species in others [12,23,67,68]. According
to some researchers, oneseed juniper is the most water-stressed plant in
certain climax communities of New Mexico, and although it persists, it
typically does not replace itself [67,68]. In these communities it is
probably best thought of as a late seral species [67,68]. Francis [23]
reported that oneseed juniper occurs in a variety of low to high seral
communities of New Mexico, suggesting that this species may have a wide
successional role in some areas of the Southwest.
Topographic factors can significantly influence the successional role of
oneseed juniper. Nonsprouting junipers such as oneseed juniper are
susceptible to fire and are consequently not considered to be a climax
species in grasslands subject to frequent fires [83]. On rocky breaks
or escarpments where fires do not occur or are infrequent oneseed
juniper grows as a climax species [83].
SEASONAL DEVELOPMENT :
Annual leader elongation of oneseed juniper generally begins in April.
Detailed phenological development is as follows [30]:
Phenological state Date
bark begins to slip March 25
pollen shedding and female flowers open March 25
approximate start of leader elongation April 20
1st conspicuous formation of male flowers April 19
leader elongation ceases October 26
Flowering varies with geographic location but can occur from January
through June [21]. Flowering generally occurs in March or April
[27,42]. Fruit matures in one season and ripens from August through
November [40]. Most fruits ripen in August or September [42]. Seed may
remain on the tree for 1 to 2 years with dispersal in October or
November [42]. Lymbery and Pieper [49] reported that in the northern
Sacramento Mountains, flowering occurred from March to April, fruit
ripening from August to September, and seed dispersal from October to
November.
FIRE ECOLOGY
SPECIES: Juniperus monosperma | Oneseed Juniper
FIRE ECOLOGY OR ADAPTATIONS :
Oneseed juniper is considered susceptible to fire [83]. Fire mortality
is generally high for both young and old trees [43], although the
thicker bark of older trees may afford some protection [12]. Older
trees often have very little understory vegetation beneath the crown and
fuels are quite limited [12]; consequently, they frequently limit the
rate of spread [76]. A history of heavy grazing can also reduce the
flammability of mature oneseed juniper stands by reducing fine fuels
[4]. In some locations, mature stands may not burn due to a lack of
fuels [41].
In some areas, juniper is protected from fire by site factors. For
example, oneseed juniper frequently grows on rocky breaks or escarpments
where fire frequency is very low [83]. Wright [83] reported that
fire-intolerant plants such as oneseed juniper often occupy isolated
topographic breaks which may be surrounded by grasslands that burn at
fairly frequent intervals [83]. Oneseed juniper is described as a
climax species on such rocky terrain not subject to frequent fires [83].
Postfire reestablishment is primarily through seed and is relatively
slow [39]. Most establishment is from seed dispersed from off-site by
birds and mammals, but some establishment may occur from seeds buried
on-site and protected from the heat of fire by overlying soil layers.
Establishment may be relatively poor even when good germination occurs,
and growth is typically very slow [67].
Oneseed juniper is usually described as a nonsprouter [83], but older
trees have been known to sprout infrequently after fire [12,76]. This
mode of regeneration appears to be relatively unimportant, however.
POSTFIRE REGENERATION STRATEGY :
Secondary colonizer - on-site seed
Secondary colonizer - off-site seed
FIRE EFFECTS
SPECIES: Juniperus monosperma | Oneseed Juniper
IMMEDIATE FIRE EFFECT ON PLANT :
Oneseed juniper is generally damaged or killed when aboveground foliage
is consumed [43]. Trees less than 4 feet (1.2 m) in height are
particularly susceptible to fire mortality [15]. The length of exposure
to fire required to kill trees generally increases with size [37].
Average mortality following a low-intensity June wildfire in oak-juniper
woodlands of Arizona was 76 percent [43]. Researchers observed 92
percent mortality after a stand of small, bushy oneseed juniper were
burned [9]. Springfield [71] noted that typically 70 to 100 percent of
oneseed junipers less than 4 feet (1.2 m) in height are killed by fire.
Mortality rates are apparently somewhat more variable among larger
trees. Kills ranging from 30 to 100 percent have been reported in trees
5 to 6 feet (1.5-1.8 m) in height [71].
Relatively little is known about the ways in which fire intensity,
specific weather conditions, understory vegetation, and season of burn
influence the effect of fire on oneseed juniper. In general, fires of
greater intensity appear to be most damaging to oneseed juniper.
Researchers have found that 100 percent mortality results when 60
percent of the crown is scorched [37]. Temperatures lethal to oneseed
juniper tissue are also related to the degree of desiccation [34], and
thus season of burn may also influence the amount of damage the plant
sustains. Laboratory experiments have shown that lethal temperatures
tend to be lowest during late spring and summer [34].
DISCUSSION AND QUALIFICATION OF FIRE EFFECT :
Fires which occur during late spring or summer may be most damaging to
oneseed juniper. Lethal temperatures have been reported as follows
[34]:
Lethal temperatures (degrees C) at various dates _
1957 1958
March 5 80.0 January 7 69.4
April 3 73.8 February 7 70.6
April 29 71.2 April 12 70.6
May 29 72.5 May 1 67.5
June 27 71.2 May 23 66.2
July 29 72.5 June 24 62.5
August 19 71.2 July 21 61.8
September 17 71.2 August 19 65.0
October 17 76.2 September 18 70.6
November 7 76.2 Average 67.6
December 10 73.8
Average 73.6
PLANT RESPONSE TO FIRE :
Regeneration of oneseed juniper is generally through seed when
aboveground vegetation has been killed or seriously damaged by fire.
Older oneseed junipers can occasionally sprout from the base after fire
[12,40]; approximately 10 percent of oneseed junipers sprouted after a
June wildfire in Arizona. However, in most cases, sprouting appears to
be a relatively unimportant mode of regeneration.
The length of time required for postfire recovery of oneseed juniper has
not been well documented. However, researchers have observed that
following other types of disturbance such as mechanical removal, oneseed
juniper only rarely becomes established within the first few years after
the disturbance [69]. A similar response is probable after fire.
Oneseed juniper did not become prominent after an intense wildfire in
Utah until postfire year 40. This species did not regain dominance on
this site until approximately 70 years after the fire [76]. Evidence
suggests that factors such as soil type and preburn community
composition may significantly influence the length of time required for
recovery [69]. Seedling establishment may be favored in the shade of
dead vegetation, including oneseed junipers [12]. Once established,
oneseed juniper can bear seed as early as 10 years of age on some sites
[69].
DISCUSSION AND QUALIFICATION OF PLANT RESPONSE :
In some intance, oneseed juniper can survive when partially defoliated
by fire [15]. Often the extent of damage is not evident until postfire
year 1 or 2 [15]. The status of oneseed junipers 2 years after a fairly
low-intensity April fire on blue grama-pinyon-juniper range was as
follows:
total trees 120
composition 69.8%
kill 24.2%
unharmed 13.3%
partial defoliation 62.5%
average % defoliation
(all trees) 44.6%
FIRE MANAGEMENT CONSIDERATIONS :
Oneseed juniper has been invading grasslands of the Southwest during
much of the past century [35]. In some locations grasslands or open
woods have been replaced by thick stands of pinyon and juniper.
Historically, fire is believed to have played an important role in
maintaining juniper savannas, and grasslands [40,79]. Fire suppression
is believed to have contributed to the relatively recent spread of
oneseed juniper. Mueggler [56] reported that a fire-free period of 85
to 90 years may be required for the formation of a "well-developed"
juniper woodland.
Oneseed juniper can be burned individually, grasslands burned, or
pinyon-juniper woodlands broadcast burned. However, not all methods are
equally applicable to all sites, and it is important to tailor the
method chosen to the density of the stand, tree age, fuel levels, and
weather conditions [3,61,71,76,83].
Attempts have been made to enhance forage production through the use of
fire. In some instances, forage production has increased after oneseed
juniper and other species were removed by fire. Aro [4] reported
increased forage production of up to 500 pounds per acre following fire
in some pinyon-juniper sites in Arizona. However, in other instances
little long-term increase in forage production has been noted. The
presence of a good stand of residual grasses prior to burning may be
important for a favorable reponse.
Removing oneseed juniper by burning individual plants appears to be most
applicable to smaller trees less than 10 feet (3.1 m) in height, in
stands of up to 100 per acre [37,71]. Small junipers reportedly burn
rapidly [37,71]. Larger trees frequently take a considerable length of
time to burn, making this method prohibitively expensive [37].
Light surface fires have been used in attempts to eliminate young
oneseed juniper which have invaded nearby grasslands. Adequate fuel is
generally available in these areas and young seedlings and saplings 3.2
to 6 feet (1-1.8 m) or less in height are readily killed [9,76].
Fire-induced mortality in larger trees may be somewhat variable, however
[35]. In some areas grazing should be deferred for a time to allow for
sufficient buildup of fuels [71]. Oneseed juniper does not survive in
grasslands where fires occur frequently [83].
Fire may be used in pinyon-juniper woodlands in which oneseed juniper is
well represented when weather conditions are favorable and sufficient
fuels are present. Dense stands of approximately 400 or more trees per
acre, with a flammable understory, are most suitable for broadcast
burning [76]. In areas with a past history of heavy grazing where
little fuels remain and few residual grasses occur, burning may be
difficult and ineffective. Burns tend to be most successful when
carried out in June when temperatures are high and the humidity low
[4,61]. Unfortunately, the risk of escape may be great during this time
period [4], and the window for burning very narrow [61].
FIRE CASE STUDIES
SPECIES: Juniperus monosperma | Oneseed Juniper
1. Galleta-blue grama range
2. Pinyon-juniper/blue grama
1st CASE NAME :
Galleta-blue grama range
REFERENCE :
Jameson, D. A. 1962 [35]
SEASON/SEVERITY CLASSIFICATION :
(1) Winter/low
(2) Spring/not recorded
(3) Summer/not recorded
STUDY LOCATION :
All three burn sites were located approximately 25 miles (40 km) north
of Flagstaff, Arizona. The January and March burns occurred on lands
administered by the Coconino National Forest. The June wildfire took
place in the Wupatki National Monument.
PREFIRE VEGETATIVE COMMUNITY :
Galleta (Hilaria jamesii) and black grama (Bouteloua eriopoda) dominated
the preburn community. Oneseed juniper had been steadily invading the
area during the past century and by 1956, numbered approximately 60
trees per acre. Other common preburn species included: threeawns
(Aristida spp.), needlegrasses (Stipa spp.), blue grama (Bouteloua
gracilis), Russian-thistle (Salsola kali), specklepod loco (Astragalus
lentiginuosus), broom snakeweed (Gutierrezia sarothrae), and gray
rabbitbrush (Chrysothamnus nauseosus).
TARGET SPECIES PHENOLOGICAL STATE :
(1) January 4, 1956 - dormant
(2) March 19, 1956 - not recorded
(3) June 28, 1956 - not recorded
SITE DESCRIPTION :
Elevation - 5,900 feet (1,798 m)
Parent material - basic basalt exposed along ridges, covered
by cinders 1 to 4 inches (2.5-10.2 cm) deep
on uplands and deeper in drainage areas.
Calcareous silt tends to cement the cinders.
Moisture patterns - little surface runoff, low evaporation,
subsurface is often moist.
Average annual precipitation - 11.6 inches (30 cm) (60 percent as
summer thunderstorms).
Grazing history - badly overgrazed by 1907. Levels reduced in recent
years. (1) January and (2) March burn sites -
light sheep grazing for at least 20 years prior to the
study. (3) June burn site - lightly grazed by cattle
in winter.
FIRE DESCRIPTION :
(1) January 5 fire: Air temperature - 49 to 54 degrees Fahrenheit (9-12
deg C).
Relative humidity - 44 percent at 49 degrees F (9
deg C).
Wind - from northeast, gusts to 6 to 8 miles per hour
(10-13 km/hr).
Fires were set from 12:45 to 3:45 p.m., burned 60 out
of 90 acres. Fire slowed down or died as it moved
toward the junipers.
(2) March 19 fire: Air temperature - 70 degrees Fahrenheit (21 deg C).
Relative humidity - 44 percent.
Wind - from southwest at 15 to 20 miles per hous
(24-32 km/hr).
Fire burned close to trees because prevailing winds
had piled tumbleweed and other debris under the
larger trees. The southwest wind caused debris to
ignite.
(3) June 28 fire: Fire was started by lightning, conditions were very
dry.
Wind - from the southwest at 10 to 15 miles per hour
(16-24 km/hr).
Air temperature - 97 degrees Fahrenheit (36 deg C)
(interpolated).
Relative humidity - 17 to 25 percent.
FIRE EFFECTS ON TARGET SPECIES :
Oneseed junipers less than 18 inches (46 cm) in height appeared to be
badly damaged immediately after the fires. Large junipers which had
tumbleweeds piled beneath the canopy also appeared to be badly damaged.
Most other large oneseed junipers were only partially damaged. Two
years later, the junipers were discovered to have been much more
seriously damaged than had previously been believed. Three hundred and
eighty randomly located oneseed junipers were examined. Mortality of
trees less than 4 feet (1.2 m) in height ranged from 70 to 100 percent
on all three burn sites. Approximately 30 to 40 percent of the trees 5
to 6 feet high (1.5-1.8 m) were killed. The March and June burns
resulted in the deaths of 60 to 90 percent of the oneseed junipers 8 to
10 feet (2.4-3.1 m) in height. Much of the mortality observed in large
oneseed junipers was attributed to the presence of tumbleweeds and other
flammable debris. When the fires moved with the prevailing winds,
tumbleweeeds ignited and tree mortality was relatively high (60-90%).
When fires moved against the prevailing winds, flammable understory
debris did not ignite and few (<10%) large oneseed junipers were killed.
FIRE MANAGEMENT IMPLICATIONS :
The amount of flammable material present at a given site and wind
conditions can greatly influence mortality in larger junipers.
Mortality can be relatively high when winds ignite tumbleweed and other
debris which has accumulated beneath the crown. Study results suggest
that a high percentage of smaller oneseed junipers (<4 feet [1.2 m]) can
be killed by fire. Grass fires at frequent intervals can presumably
halt the invasion of oneseed junipers which are less than 4 feet (1.2 m)
in height when the burning regime was implemented. Larger trees are
much more resistant to the effects of fire except where significant
amounts of flammable material are present beneath the crown.
FIRE CASE STUDIES
SPECIES: Juniperus monosperma | Oneseed Juniper
2nd CASE NAME :
Pinyon-juniper/blue grama
REFERENCE :
Dwyer, D. D.; Pieper, R. D. 1967 [15]
SEASON/SEVERITY CLASSIFICATION :
Spring/low
STUDY LOCATION :
Fort Stanton Experimental Range in south-central New Mexico.
PREFIRE VEGETATIVE COMMUNITY :
The preburn community was mainly a grassland dominated by blue grama
(Bouteloua gracilis). Oneseed juniper and pinyon (Pinus edulis) grew
on rocky ridges. Other common preburn species which occurred primarily
as scattered individual included: winterfat (Eurotia lanata),
apacheplume (Fallugia paradoxa), fourwing saltbush (Atriplex canescens),
algerita (Mahonia trifoliolata), skunkbush sumac (Rhus trilobata), and
walkingstick cholla (Opuntia imoricata).
TARGET SPECIES PHENOLOGICAL STATE :
Not recorded
SITE DESCRIPTION :
Topography - rolling
Slope - 0 to 9 percent
Elevation - 6,014 to 6514 feet (1,829-1,981 m)
Average annual precipitation - 15.5 inches (39 cm), with approximately
61.8 percent occurring from June to
October.
Soils - mostly very fine sandy loam "developed on recent alluvium
derived from the San Andres Formation and mixed material of
Guadalupe age."
FIRE DESCRIPTION :
Fire was started at 1:45 PM.
Relative humidity - low
Wind - warm, dry, from the south, (speed not recorded)
Soil, litter, and grass fuel - very dry.
Rate of spread - 1,250 feet per hour (381 m/hr)
Available fuel in open grasslands - 750 pounds per acre (670 kg/)
Fire did not travel through the tree crowns.
FIRE EFFECTS ON TARGET SPECIES :
All oneseed junipers less than 4 feet (1.2 m) in height were killed by
fire. The foliage of many of these smaller trees extended close to the
ground and ignited readily. Larger junipers were found to be somewhat
more resistant to ground fires of this type. Many trees did not show
the extent of fire damage until 1 or 2 years after the fire. Overall,
approximately 24 percent of oneseed junipers were killed by fire. Some
larger oneseed junipers partially defoliated by fire still survived 2
years after the burn. Many of these plants presumably recovered from
the effects of fire.
2 years after the burn -
total number of oneseed junipers 120
composition % 69.8
kill % 24.2
unharmed % 13.3
partial defoliation % 62.5
average % defoliation
(all trees) 44.6
FIRE MANAGEMENT IMPLICATIONS :
Study results suggest that low intensity ground fires may be effective
in reducing small (< 4 feet [1.2 m] in height) oneseed junipers.
Frequent fires can maintain grasslands subject to oneseed juniper
invasion if the fire regime is begun while trees are still in the
seedling or sapling stages. Larger oneseed junipers are somewhat
resistant to low intensity grass fires. Fine fuels tend to be sparse
under larger junipers.
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[2611]
Index
Related categories for Species: Juniperus monosperma
| Oneseed Juniper
|
 |
