FIRE CASE STUDIES
SPECIES: Juniperus pinchotii | Pinchot Juniper 



CASE NAME : 
Fire-induced mortality of redberry juniper [Juniperus pinchotii Sudw.]

 2.  Wright, H. A.; Bunting, S. C. Neuenschwander 1976 [2622]


SEASON/SEVERITY CLASSIFICATION : 
Spring, 1979
Spring, 1980
Spring, 1981


STUDY LOCATION : 
Masterson Ranch, King County, Texas; Potts Ranch, Motley County, Texas


PREFIRE VEGETATIVE COMMUNITY : 
The preburn community was a Pinchot juniper-mixed grass type.  Pinchot
juniper was the dominant woody species.  Associated shrubs included
skunkbush (Rhus aromatica), littleleaf sumac (R. microphylla), algerita
(Mahonia trifoliolata), lotebush (Ziziphus obtusifolia), catclaw acacia
(Acacia greggii), feather dalea (Dalea formosa), honey mesquite
(Prosopis glandulosa var.  glandulosa), catclaw mimosa (Mimosa
biuncifera), and elbowbush (Forestiera pubescens).  Dominant grasses
were sideoats grama (Bouteloua curtipendula), perennial threeawn
(Aristida wrightii, A. purpurea, A.  longiseta, little bluestem
(Schizachyrium scoparium), silver bluestem (Bothriochloa saccharoides),
tall dropseed (Sporobolus asper var.  asper), slim tridens (Tridens
muticus), hairy tridens (Erioneuron pilosum), and fall witchgrass
(Leptoloma cognatum).


TARGET SPECIES PHENOLOGICAL STATE : 
NO-ENTRY


SITE DESCRIPTION : 
Long-term mean annual precipitation is 23 inches (590 mm), of which 90
percent occurs during the growing season.

Soils on the King County area are shallow, rock Mollisols of the Talpa
series, while those on the Motley County area are deep Alfisols of the
Miles series.


FIRE DESCRIPTION : 
1979 broadcast burn on 2,000 acres (800 ha) in mid-March
1980 broadcast burn on 700 acres (280 ha) in mid-March.  
    Relative humidity: 25 percent
    Air temperature: 68 to 79 degrees Fahrenheit (20 to 26 deg C)
    Wind speed: 7 to 14 miles per hour (12-24 km/h)
    Fine fuel load: 1,607 to 3,125 pounds per acre (1,800-3,500 kg/ha)

The separate 1981 study involved burning Pinchot juniper plants with an
individual plant burner.  Plants in three size classes were randomly
assigned to one of four treatments consisting of a control, light,
moderate, and heavy fine fuel simulated fires.  The burner was
calibrated using time/temperature curves developed for mixed grass fuels
by Wright and others [1976].  Treatments were applied in early April
with air temperatures from 68 to 79 degrees Fahrenheit (20 to 26 deg C)
and relative humidity from 60 to 75 percent.

Pinchot juniper plants on the two broadcast burns (1979,1980) were
seedlings from 3 to 32 inches tall (7-80 cm), residual live stems that
escaped the chaining treatment, and 5- to 6-year-old basal sprouts from
plants that were top-killed by chaining.


FIRE EFFECTS ON TARGET SPECIES : 
Mortality was assessed 6, 18, and 30 months after the prescribed fires
in 1979 and 1980.  Mortality of young Pinchot juniper was 42 percent 6
months after the 1979 fire, 49 percent 18 months after the fire, and 50
percent 30 months after the fire.  This indicates that disease, insects,
and rodents do not interact with fire injury to increase mortality.

Postfire growing conditions appear to affect mortality following a
prescribed fire.  Following the 1979 fire, precipitation was 18 percent
above the long-term average during the growing season.  In 1980,
precipitation was 32 percent below average and summer temperatures were
higher than normal in the growing season following fire treatments.
Mortality following the 1980 fire was higher; there was some effect of a
higher fine fuel load, but this did not appear to have as great an
effect as the drought conditions.

In the 1981 simulated fire study Pinchot juniper mortality increased
across size classes with increased heat treatment.

Location of the bud zone relative to the soil surface was the dominant
variable associated with mortality of Pinchot juniper plants.  Only 1 of
100 marked mature plants (with buried bud zones) was killed by broadcast
burning in 1979, and the bud zone of this plant had been mostly exposed
by the chaining operation 4 years earlier.  In the drought year of 1980,
burning killed approximately 5 percent of the mature plants.  The plants
that were killed typically had a large amount of woody debris from the
caining operation lodged around the base, increasing fire intensity.


FIRE MANAGEMENT IMPLICATIONS : 
Pinchot juniper can be killed by fire if it is burned before the
majority of young plants have their bud zones covered by soil.  On
shallow rocky sites, mortality of Pinchot juniper plants less than 13
years old and 20 inches (50 cm) tall ranged from 33 to 100 percent,
depending on the size of the plants and the conditions of the following
growing season.  Continuing control of Pinchot juniper can be achieved
with a prescribed fire treatment only; chaining is needed only if the
Pinchot juniper on the site is allowed to reach mature heights.
Intervals between prescribed fire treatments should be approximately 7
to 20 years, or when Pinchot juniper on the site reaches 20 inches (50
cm) in height and the bud zone is still exposed.  The age at which the
bud zone is covered with soil varies with site.  On deep soil sites with
gentle slopes the bud zones are protected earlier.  On such sites, the
interval between fires should be shorter to obtain satisfactory control
of Pinchot juniper.

Development of fine fuel loads of 2,680 pounds per acre (3,000 kg/ha)
will improve fire control of Pinchot juniper.  Fires conducted in dry
years will also achieve higher mortality rates, but these conditions
negatively affect herbaceous plant yield.  Good soil moisture reserves
at the time of the fire are recommended to minimize herbaceous plant
yield loss.

Related categories for Species: Juniperus pinchotii | Pinchot Juniper