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Return Interval for Pinyon-Juniper Following
Fire in the Green River Corridor, Near Dutch
John, Utah
Sherel Goodrich
Brian Barber
Abstract - Colorado pinyon (Pinus edulis Engelm.) and Utah
juniper (Juniperus osteosperma [Torr.] Little) are returning, following three fires, in the Green River corridor, Daggett County, Utah.
It will take several decades to over a century before pinyon-juniper
will dominate plant communities following fire. Recognizing this
interval can facilitate planning and management for a diversity of
successional stages across the landscape of the Green River corridor. The long return interval indicates a rather small burning
program could sustain diversity. The long return interval indicates
long-term benefits and thus higher economic return for burning
compared to treatments of shorter return interval for pinyon and
juniper.
The Green River corridor in Daggett County, Utah, represents the northern limit for Colorado pinyon (Pinus edulis
Engelm.) near the Utah-Wyoming line. North of the Green
River corridor, Colorado pinyon is uncommon and it is
known to extend only a few miles into Wyoming. Utah
juniper (Juniperus osteosperma [Torr.] Little) extends well
into Wyoming where it forms stands without Colorado
pinyon. In the Green River corridor, the two species commonly grow together, but Colorado pinyon often replaces
Utah juniper over time especially on cool aspects where to
some extent it is able to regenerate under its own shade or
at least in small openings created by the death of old trees.
In the Green River corridor 'as elsewhere in their range,
Colorado pinyon and Utah juniper have great capacity to
drive plant community dynamics. Without disturbance they
displace other communities and form close stands across
nearly all soil types and all geologic substrates within the
thermal belt to which they are well adapted. Management of
pinyon-juniper areas can be facilitated by an understanding
of the return interval of these highly competitive plants
following fire or other disturbance. Return of pinyon and
juniper in three burns in the Green River corridor indicate
the return interval following fire.
The three burns are at Mustang Ridge (13 ha or 32 acres),
Dripping Springs (56 ha or 138 acres), and Dutch John
Canyon (82 ha or 203 acres). The burn at Dripping Springs
In: Monsen, Stephen B.; Stevens, Richard, comps. 1999. Proceedings:
ecology and management of pinyon-juniper communities within the Interior
West; 1997 September 15-18; Provo, UT. Proc. RMRS-P-9. Ogden, UT: U.S.
Department of Agriculture, Forest Service, Rocky Mountain Research
Station.
Sherel Goodrich is Forest Ecologist, Ashley National Forest, Vernal, UT
84078. Brian Barber at the time of his recent retirement was Fire Management Officer, Flaming Gorge District, Ashley National Forest, Dutch John,
UT 84023.
USDA Forest Service Proceedings RMRS-P-9. 1999
was aerially seeded with a mix of grasses of which crested
wheatgrass established throughout the burn. The other two
burns were not seeded. These burns are all within a radius
of 4.8 km (3 miles) of the town of Dutch John where mean
annual precipitation at the Flaming Gorge Weather Station
is 31.75 cm (12.50 inches) (Ashcroft and others 1992).
Methods and Results
A search of files at the Supervisor's Office, Ashley National Forest, Vernal, UT, indicated the Mustang Ridge fire
burned about 1950 (Plummer 1965, 1972; Webster 1972),
and the Dripping Springs fire burned in 1959 (Plummer
1965). The burn in Dutch John Canyon was older. It was not
included in notes by Plummer or Webster cited above. This
burn was visited in 1996, and a search was made for fire
scars on pinyon trees that had survived the fire. A number
of fire-scared pinyon trees were found. Cross sections were
taken by chain saw from three of the scared trees. One tree
was near the bottom ofthe canyon. One was from about midslope on the east side ofthe canyon, and the other was taken
from near the top ofthe east side ofthe canyon. All were from
the margin of the burn. No live, scared trees were found
toward the center ofthe burn. This was a stand replacing fire
with few or no survivors except at the margin of the burn.
Also, cross sections of a few trees that had obviously regenerated since the fire were taken between ground level and
about 30 em (1 foot) above ground level.
With the aid ofa 7-30 power binocular scope, annual rings
of the cross sections were counted. Rings from the scar
outward to the cambium were used to indicate the year ofthe
fire. Ring counts from the three scared cross sections indicated the fire had burned 101, 102, and 103 years before
1996. These dates were close enough together to consider a
single burn for the area ofjust over 100 years ago. Growth of
the trees might have been suppressed for a year or two
following the fire. However, the fire is indicated to have
burned in the 1890's. Procedures for dating the fire from
annual rings of trees with fire scares is similar to those
discussed by Arno and Sneck (1997). Annual rings from cross
sections indicated live trees within the burn were 30 to 95
years old. There were smaller trees present than the one
dated at 30 years, but the 95 year old tree was one of the
largest ones in the burn. Since the cross section was taken
above ground level, this tree was somewhat older than 95
years. It was adjacent to the burnt stump of a large tree
burned in the fire. It is highly unlikely that it was a survivor
from the fire. This tree also indicates the fire to have been in
the 1890's.
391
Return of trees to these burns was determined by measurements, ocular estimates, and by photographs. Counts in
six 1.83 by 50.78 m (0.0093 ha) plots in 1997 indicated
between 287 and 358 trees per hectare in some places in the
Mustang Ridge Burn. However, these plots indicated only
71 to 143 trees per hectare were over 1 m tall. The large
n umber of seedlings and small trees indicate am uch greater
dominance of pinyon-juniper in the next few decades. In
some areas of the Dripping Springs and Mustang Ridge
burns, tree density was less than five trees per hectare at 38
and 47 years postfire, respectively. After about 100 years,
density of trees in the Dutch John Canyon Burn varied from
few to many per hectare depending on location within the
fire. Size and age structure of these trees indicated recruitment of all ages within the burn. Overall canopy cover of
pinyon and juniper was less than 1 percent 38 years post fire
at Dripping Springs, about 2 percent -47 years postfire at
Mustang Ridge, and between 5 and 15 percent about 100
years postfire at Dutch John Canyon.
Discussion -------------------------------A slow return rate is indicated for the first 40 to 50 years
with an apparent accelerated rate in later years. A slow rate
of return is also indicated by Despain (1987) in the first 20
to 30 years following burning and seeding in Arizona. Also,
Ronco (1987) suggested stand density of pinyon-j uni per does
not increase appreciably until 45 years after disturbance.
The successional patterns of the Green River corridor appear similar to the model of Erdman (1970) which shows
shrub/open tree communities at 100 years postfire.
Nearly all pinyon-juniper trees within the perimeter of
these fires were killed. There were a few islands of survivors
in the Dutch John Canyon fire on rocky outcrops and at
topographic breaks. It appears that few seeds of either
species survived the fires, or they failed to germinate or at
least failed to establish. However, the 95 year old tree that
had regenerated in the burn indicates at least a few trees
established soon after the fire. Return of trees to the burns
appears to be a largely a function of seed spread from the
edge of the burns, and as indicated by Balda (1987), they are
heavily dependent on birds to disperse their propagules.
This appears to be a major factor in return of these trees to
the center of large burns. Also, the few trees that establish
soon after fire appear to be a source of seed within burns.
This discussion is most applicable to burns over 8 ha (20
acres). Return of pinyon and juniper to smaller burns and
especially the margins of burns could be more rapid. Huber
and others (these proceedings) found a stand with crown
cover of pinyon-juniper at about 60 percent. This appeared
to be at the margin of a small burn of about 140 years old
where seeding establishment was rapid.
Return of trees to the burns at Dripping Springs, Mustang
Ridge, and Dutch John Canyon indicates it will take 100 years
or more for plant communities to progress to a shrub/open tree
status. Also indicated is 150 to 200 years to achieve preburn
density oftrees and greater than 200 years to achieve mature
and old stages of succession. For north-central Arizona, Tress
and Klopatek (1987) estimated 215 years to complete a sere in
pinyon-juniperwoodlands. Erdman (1970) indicated 300 years
from fire to climax forest. Barney and Frischknecht (1974)
392
found woodlands well developed 85 to 90 years after fire in
the Great Basin. However, well developed in this case seems
to apply to young stands with aspect dominance but not the
end of a sere.
Management Implications
The burns reported in this paper and other wildfires and
prescribed burns of the Green River corridor were stand
replacement fires. Underburning does not seem a realistic
option. The stands are difficult to burn until conditions are
severe enough to create crown fires. Recognizing the return
interval for pinyon-juniper after stand replacement fires can
facilitate management oflandscapes where certain levels of
different successional stages are desired across a landscape.
Under a draft concept of "properly functioning condition,"
Amundson and others (1996) indicated a proper landscape
mix of successional stages for pinyon-juniper woodlands in
the Intermountain Region of the Forest Service as follows:
10 percent grass/forb, 10 percent seeding/sapling, 20 percent
young forest, 20 percent mid-aged forest, 20 percent mature
forest, and 20 percent old forest. For the Green River corridor, it appears that it would require a fire frequency of
greater than 200 years to achieve closed, mature pinyonjuniper stands in burns of greater than about 8 ha (20 acres).
Fire interval would have to exceed 100 years to achieve and
maintain scattered trees in plant communities. Fire intervals of 10 to 30 years would not allow for succession beyond
a grass/shrub stage in which trees over 1 m tall would be
mostly excluded.
The rate of succession indicates maintenance of earlier
successional stages can be achieved with a small annual
burning program. For a 8,100 ha (20,000 acre) landscape
with a fire interval of 100 years, only 80 ha (200 acres) of
burning per year could maintain the landscape in early to
mid-seral stages. If 40 percent of the landscape was desired
with mature and old stands, an average of 50 ha (120 acres)
of burning per year is indicated to maintain this condition.
The long return interval greatly facilitates economic return
for prescribed fire, and it indicates a relatively small burning program to achieve a desired mix of successional stages.
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functioning condition. Draft Process - Version. Ogden, UT: U.S.
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