FIRE EFFECTS
SPECIES: Juniperus pinchotii | Pinchot Juniper 



IMMEDIATE FIRE EFFECT ON PLANT : 
Moderate- and low-severity fires can kill Pinchot juniper seedlings and
saplings if the basal bud zone is unprotected by soil.  Mature Pinchot
juniper with a soil-protected basal bud zone is top-killed by fire
[49,50].

Considerable heat is required for ignition, but once ignited, the plant
burns so vigorously that usually all the branches are killed [5].


DISCUSSION AND QUALIFICATION OF FIRE EFFECT : 
NO-ENTRY


PLANT RESPONSE TO FIRE : 
Pinchot juniper will sprout from a basal bud zone when top-killed by
fire [5,25].

Ahlstrand [5] reported that 50 percent of the mature height was regained
during a 3- to 7-year recovery period after a fire.  Kittams [25]
reported that 25 to 50 years may be required for attainment of mature
height, which agrees with Ahlstrand's estimate for attaining the mature
height of the original stand.  

Pinchot juniper sprouts were not producing seed after 3 years of
postfire growth [51].


DISCUSSION AND QUALIFICATION OF PLANT RESPONSE : 
NO-ENTRY


FIRE MANAGEMENT CONSIDERATIONS : 
Prescribed fire can be used to eradicate Pinchot juniper seedlings on
grasslands not already infested with mature Pinchot juniper.
Established or mature Pinchot juniper can be controlled by a combination
of mechanical treatments and prescribed fire [41,42].

Pinchot juniper is difficult to kill with fire unless the basal bud
zones are above the soil, which is usually only true for seedlings and
saplings (not sprouts).  If the bud zones are exposed, prescribed fire
can result in 70 to 75 percent mortality [41,50].  Percent mortality
increases in dry years:  90 percent of Pinchot juniper plants less than
20 inches tall were killed by a prescribed fire when precipitation was
32 percent below normal.  Pinchot juniper fire mortality decreases with
increased precipitation, and plots would need to be burned again sooner
than if originally burned in a dry year [50].  Pinchot juniper sprouts
do not produce seed right away, which decreases the amount of seedling
recruitment on the site [51].  Prescribed fires should be limited to
gently to moderately sloping sites (3 to 12 percent grade) to minimize
potential soil loss [50,51].

Areas burned to remove Pinchot juniper are usually not invaded by other
woody species following fire [41].  Herbaceous plant recovery after
prescribed fire depends on the season of burn and postburn moisture
availability [50].  The benefit of increased mortality of Pinchot
juniper from burning in a dry year is offset by the loss of forage;
productivity can be decreased by 50 percent after prescribed burning in
a dry year.  Most Pinchot juniper-invaded pastures recover to noninvaded
productivity levels within 3 years of a prescribed fire (after earlier
mechanical treatment) [50].  After early spring fires, managers are
advised to wait until mid-June before stocking [41].  A 10- to 20-year
burning cycle can keep pasture in a productive state for both wildlife
and livestock, reducing the need for chemical or mechanical control
[41,50].

Rangeland sites with shallow loamy soils over limestone will respond
differently than sites with deep or clay soils.  On deep, heavy soil
sites, tobosa grass (Hilaria mutica) may be the dominant grass.
Following burning, sites with deep soil tend to be more stable with
regard to production and species composition [41].  Pinchot juniper may
become more fire resistant earlier (i.e. the basal bud zone buried
sooner) on sites with deep soil.  On deep-soil sites, a shorter fire
interval (7 to 10 years) may be needed to maintain control of Pinchot
juniper [41,49,50].

Control methods:  Mechanical treatment kills large plants and
concentrates fuels.  Prescribed fire following such treatment removes
woody debris (cover reduction from 25 percent to less than 2 percent)
and kills Pinchot juniper seedlings and plants that escaped mechanical
treatment [51].

Treatment of mature juniper involves chaining or using bulldozers to
push over and pile large trees to concentrate Pinchot juniper fuels and
allow an increase of fine fuels (pastures should be rested or undergo
light grazing only).  The prescribed fire should be conducted 3 to 5
years after the chaining treatment to allow fuels to dry and to allow
Pinchot juniper seeds to germinate so that the seedlings can be killed.
Managers can expect reductions in woody debris cover to below 2 percent
[51].  Follow-up treatments should not be necessary, except that the
area should be burned again before any Pinchot juniper plants are 4 feet
(1.2 m) tall [41,50].

The ignition time needed to burn green Pinchot juniper foliage is most
closely related to foliage moisture content and average mean daily
temperature (r = 0.73 and r=0.48 respectively).  During dry periods, the
most significant factors are moisture content (r = 0.83) and relative
humidity (r = 0.77). During wetter than average periods, no significant
correlations occur, making fire behavior less predictable [10].

Chained, dead juniper is a highly volatile fuel [41,55].  The prepared
sites can be burned with a headfire into 400 to 500 foot (120-150 m)
firelines prepared earlier in the spring [41,50,59].  The green juniper
seedlings can be burned with a foliage moisture content of between 60
and 80 percent [58].  It is recommended that there be 2,000 pounds per
acre (2,250 kg/ha) of fine fuels present to carry the fire into juniper
piles and to completely burn over the surrounding grasses and Pinchot
juniper seedlings.  It should be noted that if the area is populated by
widely separated bunchgrasses, the fire may achieve only 50 percent
coverage, even with 2,500 pounds per acre (2,800 kg/ha) fine fuels.  If
the area is covered with a sod-type grass, such as buffalograss, 1,000
pounds per acre (1,125 kg/ha) of fine fuels may be sufficient to achieve
70 percent burn coverage [41].  Wright and others [60] have developed an
"expert system" for burning large pastures of dozed Pinchot juniper,
with inputs of windspeed, time of day, air temperature, topography,
green juniper moisture content, fuel type, and nearness of cold front.

Large, mature Pinchot juniper with little understory is difficult and
expensive to control with fire.  It is hazardous to burn because extreme
conditions are needed to achieve moderately complete burns.  There has
been limited success with windrowing techniques; conditions for success
are particular and there is a risk of spot fires.  Cover has to be at
least 35 percent to form a relatively continuous fuel bed.  Crown fires
tend to stop when the distance between trees is greater than 26 feet [41].

Prescribed fire for control of Pinchot juniper can be conducted with
ground ignition for small, easily traversed areas.  Ground ignition can
be difficult on large, rough and dissected areas because of increased
fuel breaks.  Aerial ignition, with a helitorch can be safer and give
more control over the ignition pattern [32,58].  When compared for cost
and efficiency, the helitorch method was found to have an economy of
size, that is, as the size of units to be burned increases or the number
of smaller units to be burned increases, the cost per acre decreases.
Such economy does not occur with ground ignition, the cost per acre
decreases only to a limit of approximately 2,500 acres (1,000 ha), above
which the cost per acre remains the same.  Therefore, it is recommended
that aerial ignition be employed for large units (approximately over
5,000 acres [2,000 ha]) or for the equivalent area of smaller units
[42].

Related categories for Species: Juniperus pinchotii | Pinchot Juniper