FIRE CASE STUDIES
SPECIES: Diospyros texana | Texas Persimmon 



CASE NAME : 
Welder Wildlife Refuge fire temperature study


REFERENCE : 
White, R. S. 1969 [46]

SEASON/SEVERITY CLASSIFICATION : 
Spring/variable severity


STUDY LOCATION : 
The study was conducted on the Welder Wildlife Refuge in San Patricio
County, Texas, about 20 miles (32 km) north of Corpus Christi.


PREFIRE VEGETATIVE COMMUNITY : 
Two plant communities are present in the study area:
chaparral-bristlegrass (Setaria spp.) and honey mesquite (Prosopis
glandulosa var. glandulosa)-buffalograss (Buchloe dactyloides).
Collectively, these communities are dominated by leguminous shrubs
interspersed with grasses.  Honey mesquite and huisache (Acacia
farnesiana) dominate the shrub layer, and seacoast bluestem
(Schizachyrium scoparium var. littoralis) is the most abundant
graminoid.


TARGET SPECIES PHENOLOGICAL STATE : 
At the time of the fire, Texas persimmon (Diospyros persimmon) was
semidormant.  A few old leaves were present on some plants.  Two weeks
after the fire, leaf buds began to open on unburned plots.


SITE DESCRIPTION : 
The study is located on the Gulf Coastal Plain so presumably the
topography is flat or rolling.  The soil is a clay in the Vertisols
order.  The climate is subtropical; rainfall averages 30 inches (760 mm)
a year.



FIRE DESCRIPTION : 
The 10-acre (4 ha) study site was divided into four subplots; one was
burned on March 8 and the remaining three on March 12.  Fire weather and
site conditions for the March 8 fire were as follows:  air temperature
60 degrees Fahrenheit (16 deg C), relative humidity 90 percent, wind
velocity 10 miles per hour (16 k/h), soil moisture 40 percent, and
herbaceous fuel moisture 9 percent.  Conditions for the March 12 fire
were as follows:  air temperature 55 degrees Fahrenheit (13 deg C),
relative humidity 45 percent, wind velocity 20 to 30 miles per hour
(32-48 k/h), soil moisture 37 percent, and herbaceous fuel moisture 7
percent.  Both fires were wind driven.  The March 12 fire was hotter
than the March 8 fire primarily because of lower humidity and higher
wind velocity.
 
Forty to fifty percent of the study site did not burn.  Fire carried
well through the tall seacoast bluestem but burned poorly in areas
dominated by shorter grasses.  Surface temperatures during the fires
were extremely variable.  Maximum surface temperatures ranged from 480
to 1,350 degrees Fahrenheit (249-732 deg C).  Temperature showed a weak
(P<0.10) correlation with fuel quantity.  Flame height was about 7 feet
(2.1 m) on March 8 and 8 feet (2.4 m) on March 12.


FIRE EFFECTS ON TARGET SPECIES : 
Although 50 Texas persimmon plants were originally tagged for postfire
study, only 17 plants were analyzed because of incomplete burning.
Percent partial and complete top-kill of Texas persimmon at different
fuel loads follows:

           Fuel         Partial Top-kill	Complete Top-kill
        (lbs/acre)         (percent)                (percent)

          0-2,000              67                       33
        2,000-4,000            25                       75
          > 4,000               0                      100

Regardless of fuel load, no Texas persimmon was completely killed.

Fire damage to Texas persimmon was inversely related to its size when
fuel loads were less than 2,000 lbs per acre.  Of six individuals less
than 1 inch (2.5 cm) in basal diameter, three individuals were partially
top-killed and three were completely top-killed.  Of six individuals
greater than 1 inch (2.5 cm) in basal diameter, five were partially
top-killed and only one was completely top-killed.


FIRE MANAGEMENT IMPLICATIONS : 
Spring fire was effective at top-killing Texas persimmon, but did not
result in mortality.  For useful brush control, fire must be applied a
number of times over a period of years.  To achieve maximum results,
fire should be prescribed when the plants are young and the fuel load is
high.

Related categories for Species: Diospyros texana | Texas Persimmon