FIRE CASE STUDIES
SPECIES: Juniperus ashei | Ashe Juniper 



CASE NAME : 
Effects of fire on an Ashe juniper community



SEASON/SEVERITY CLASSIFICATION : 
1) Spring/low--followed wet winter and spring
2) Spring/high--followed dry winter and spring


STUDY LOCATION : 
The Beckham Ranch, Callahan County, 14 miles (24 km) southeast of Baird,
Texas.


PREFIRE VEGETATIVE COMMUNITY : 
The natural vegetation of the area consists of mixed-prairie grasses
interspersed with Ashe juniper and several species of oak.  The dominant
decreasers are little bluestem (Schizachyrium scoparium) and sideoats
grama (Bouteloua curtipendula).  Important increasers are buffalograss
(Buchloe dactyloides), vine-mesquite (Panicum obtusum), Texas
wintergrass (Stipa leucotricha), tall grama (B. pectinata) and meadow
dropseed (Sporobolus asper var. hookeri).


TARGET SPECIES PHENOLOGICAL STATE : 
Large Ashe juniper trees were bulldozed and piled in 1965 (burning took
place in 1970 and 1971).  Small Ashe junipers that escaped the
bulldozers and new seedlings were also present.


SITE DESCRIPTION : 
Average annual precipitation is 24 to 28 inches (600-700 mm).  The
topography of the area is level to undulating with some slopes greater
than 20 percent.  Elevation is 1,198 to 1,394 feet (365-425 m).  The
average minimum January temperature is 23 degrees Fahrenheit (-5 deg C),
and the average maximum July temperature is 95 degrees Fahrenheit (35
deg C).  The average growing season is 232 days.

Sandy loam sites in the study area have deep soils with fine sandy loam
surfaces 6 to 14 inches (15-36 cm) thick, and sandy clays and sandy loam
subsoils.  The soils are slowly to moderately permeable.  The low stony
hill site consists of very shallow, moderately permeable, calcareous,
stony clay soils.  Depth ranges from 6 to 12 inches (15-31 cm) with
limestone rocks and boulders present on the surface and in the profile
in various amounts.

All three sites were sampled for herbage production and fine fuel
concentration, and individual plots were marked to measure pile
consumption and tree mortality.  The uniformly fine fuels ranged from
686 to 3,186 pounds per acre (768-3,568 kg/ha).  The estimated amount of
heavy fuels (piles of Ashe juniper) varied from 20 to 30 tons per acre
(44.8-67.2 t/ha) and occupied from 0 to 85 percent of the area with
an average cover of 22 percent.


FIRE DESCRIPTION : 
Air temperature:  75 to 86 degrees Fahrenheit (24-30 deg C)
humidity: 25-35 percent
wind speed: 10 to 15 miles per hour (16-25 km/h)

The objectives of the prescribed fires were to consume the piles of dead
trees and to burn the intervening areas where Ashe juniper seedlings had
established.  Fires were conducted in 2 separate years.  In March of
1970, one pasture of 1,013 acres (405 ha) was burned, and in March 1971,
2 pastures for a total of 1,620 acres (648 ha) were burned.  All areas
were burned with headfires.  The ignition pattern was a combination of
perimeter and strip headfiring.

Fire intensities were not reported.


FIRE EFFECTS ON TARGET SPECIES : 
Plots on which fine fuels were 686 and 859 pounds per acre (768 and 962
kg/ha) were not successful in carrying the fire.  On plots where fine
fuels exceeded 1,000 pounds per acre (1,120 kg/ha), 99 percent of the
piles were consumed by fire.  The March 1971 fires followed 6 months of
very dry weather and were conducted under the lowest humidities and
highest winds that could be tolerated for prescribed burning.  Where
large piles were within 40 feet (12 m) of each other, firebrands would
ignite the piles downwind, precluding the necessity of continuous fine
fuel.

Ashe juniper mortality was high where the fine fuels were adequate to
carry the headfire.  Of 368 trees under 6 feet (1.8 m) tall, only one
survived.  Many trees over 6 feet (1.8 m) tall were killed by the fire,
particularly where fine fuels exceeded 2,000 pounds per acre (2,240
kg/ha).


FIRE MANAGEMENT IMPLICATIONS : 
Prescribed burning is a useful method for controlling Ashe juniper
encroachment on grasslands.  It is recommended that the larger trees be
chained or dozed to assure mortality and to concentrate dead stems into
piles.  Fires require a minimum of 1,000 pounds per acre (1,120 kg/ha)
of fine fuels for successful spread, and 2,000 pounds per acre (2,240
kg/ha) is optimal.  Soil moisture should be a primary consideration
before conducting a prescribed fire.  Herbaceous plants require good
soil moisture for rapid recovery after the fire, which helps reduce soil
erosion.  Burning increased the yield of little bluestem and meadow
dropseed after the 1970 fire, which followed a wet winter and spring.
The same species decreased about 50 percent after the 1971 fires
following a dry winter and spring.

Vegetation on the burned juniper pile areas differed from that adjacent
to the piles.  Silver leaf nightshade (Solanum elaeagnifolium) and
Carolina horsenettle (S. carolinense) were dominant on the burned pile
areas, and may need to be controlled with herbicides.  Smoothleaf sumac
(Rhus glabra) also increase in prominence on the burned pile areas.

Related categories for Species: Juniperus ashei | Ashe Juniper