FIRE CASE STUDIES
SPECIES: Eragrostis intermedia | Plains Lovegrass 



CASE NAME : 
Huachuca Mts, AZ/Prescr. Fire/Grassland & Oak Woodland Response


REFERENCE : 
Bock, J. H.; Bock, C. E. 1987 [9]
Bock, J. H.; Bock, C. E. 1992 [10]


SEASON/SEVERITY CLASSIFICATION : 
spring/moderate


STUDY LOCATION : 
Prescribed fires were carried out at the Appleton-Whittell Research
Sanctuary of the National Audubon Society in Santa Cruz County, Arizona.
The field site is located in southeastern Arizona on the west side of
the Huachuca Mountains.


PREFIRE VEGETATIVE COMMUNITY : 
Prefire vegetation at the oak woodland site in Lyle Canyon included
Emory oak (Quercus emoryi), Arizona white oak (Q. arizonica), plains
lovegrass (Eragrostis intermedia), sideoats grama (Bouteloua
curtipendula), Texas beardgrass (Andropogon cirratus), Hall's panic
grass (Panicum hallii), longleaf falsegoldeneye (Heliomeris longifolia
var. annua), spreading snakeherb (Dyschoriste decumbens), Louisiana
sagewort (Artemisia ludoviciana), bindweeds (Convolvulus spp.), warty
caltrop (Kallstroemia parviflora), catclaw mimosa (Mimosa biuncifera),
velvet-pod mimosa (M. dysocarpa), and yerba de pasmo (Baccharis
pteronioides).

Prefire vegetation at the grassland site on Bald Hill included plains
lovegrass, wolftail (Lycurus phleoides), threeawns (Aristida spp.),
sprucetop grama (Bouteloua chondrosioides), sideoats grama, spreading
fleabane (Erigeron divergens), shrubby false mallow (Malvastrum
bicuspidatum), dwarf morningglories (Evolvulus spp.), spreading
snakeherb, tanseyleaf aster (Machaeranthera tanacetifolia), catclaw
mimosa, velvet-pod mimosa, and yerba de pasmo.

Prefire vegetation data was collected during August 1983.


TARGET SPECIES PHENOLOGICAL STATE : 
Unknown


SITE DESCRIPTION : 
The study sites have 17 inches (430 mm) average annual precipitation,
with half to two-thirds occurring between July and September.  Elevation
is 4,922 feet (1,500 m).  At the time of the study no fires or grazing
had occurred at the sites since 1969.


FIRE DESCRIPTION : 
There were five burned plots and five control plots each at the
grassland and woodland sites.  All fires were conducted under hot, dry,
relatively calm conditions prior to the onset of summer rains.

Plots in oak woodland were burned between 10:00 a.m. and noon on May 25,
1984.  Air temperatures ranged from 90 to 92 degrees Fahrenheit (32-33
deg C).  Relative humidity varied from 16 to 18 percent.  Winds were
variable, gusting from 5 to 10 miles per hour (8-16 km/hr).  Fine dead
fuel moisture was estimated at between 5 and 6 percent.  In four of the
five burned plots, fires moved slowly (1.6 to 4.9 feet per minute
[0.5-1.5 m/min]) with flame lengths of 0.7 to 1.6 feet (0.2-0.5 m) and
fireline intensities of 8-58 kW/m.  In the fifth plot the fire moved
very rapidly (about 98 feet per minute [30 m/min]) with fireline
intensity of 260 kW/m.

Semidesert grassland plots were burned between 10:00 and 11:30 a.m. on
June 12, 1984.  Air temperatures ranged from 84 to 88 degrees Fahrenheit
(29-31 deg C).  Relative humidity varied from 13 to 16 percent.  Winds
were variable, gusting from 5 to 22 miles per hour (8-35 km/hr).  Fires
moved slowly on all burned plots (3.3-13.1 feet per minute [1-4 m/min])
with flame lengths ranging from 2.6 to 4.6 feet (0.8-1.4 m).  These
fires produced fireline intensities of 160 to 540 kW/m.


FIRE EFFECTS ON TARGET SPECIES : 
Prefire vegetation data were collected on all plots during summer 1983.
Postfire data were collected on the burned plots and their controls
during the summers of 1984 and 1985.  All vegetation sampling was
carried out in August, the time of maximum growth during the summer wet
period.  Density and plant height were recorded within each quadrat each
year, as were bare ground cover and overall aboveground plant biomass.

In oak woodland plots, plains lovegrass densities on burned and control
plots were similar prior to the fires.  Plains lovegrass declined
significantly (p<0.5) in density on burned plots in the first postfire
growing season of 1984, but this difference had disappeared by the
growing season of 1985.

In semidesert grassland plots, plains lovegrass densities on burned and
control plots were similar prior to the fires.  Plains lovegrass
declined significantly (p<.01) in density on burned plots in 1984, the
first postfire growing season, but this difference had disappeared by
the second postfire year.


FIRE MANAGEMENT IMPLICATIONS : 
Plains lovegrass usually declines the first growing season after fire,
but by the second growing season it has regained or exceeded its
original cover.

Related categories for Species: Eragrostis intermedia | Plains Lovegrass