FIRE CASE STUDIES
SPECIES: Juniperus monosperma | Oneseed Juniper 



1. Galleta-blue grama range
2. Pinyon-juniper/blue grama

1st CASE NAME : 
Galleta-blue grama range


REFERENCE : 
Jameson, D. A. 1962 [35]

SEASON/SEVERITY CLASSIFICATION : 
(1) Winter/low
(2) Spring/not recorded
(3) Summer/not recorded


STUDY LOCATION : 
All three burn sites were located approximately 25 miles (40 km) north
of Flagstaff, Arizona.  The January and March burns occurred on lands
administered by the Coconino National Forest.  The June wildfire took
place in the Wupatki National Monument.


PREFIRE VEGETATIVE COMMUNITY : 
Galleta (Hilaria jamesii) and black grama (Bouteloua eriopoda) dominated
the preburn community.  Oneseed juniper had been steadily invading the
area during the past century and by 1956, numbered approximately 60
trees per acre.  Other common preburn species included: threeawns
(Aristida spp.), needlegrasses (Stipa spp.), blue grama (Bouteloua
gracilis), Russian-thistle (Salsola kali), specklepod loco (Astragalus
lentiginuosus), broom snakeweed (Gutierrezia sarothrae), and gray
rabbitbrush (Chrysothamnus nauseosus).


TARGET SPECIES PHENOLOGICAL STATE : 
(1) January 4, 1956 - dormant
(2) March 19, 1956 - not recorded
(3) June 28, 1956 - not recorded


SITE DESCRIPTION : 
Elevation - 5,900 feet (1,798 m)
Parent material - basic basalt exposed along ridges, covered
                  by cinders 1 to 4 inches (2.5-10.2 cm) deep
                  on uplands and deeper in drainage areas.  
                  Calcareous silt tends to cement the cinders.
Moisture patterns - little surface runoff, low evaporation,
                     subsurface is often moist.
Average annual precipitation - 11.6 inches (30 cm) (60 percent as
                                 summer thunderstorms).
Grazing history - badly overgrazed by 1907.  Levels reduced in recent
                  years.  (1) January and (2) March burn sites -
                  light sheep grazing for at least 20 years prior to the
                  study.  (3) June burn site - lightly grazed by cattle
                  in winter.


FIRE DESCRIPTION : 
(1) January 5 fire:  Air temperature - 49 to 54 degrees Fahrenheit (9-12
                                       deg C).
                     Relative humidity - 44 percent at 49 degrees F (9
                                         deg C).
                     Wind - from northeast, gusts to 6 to 8 miles per hour
                            (10-13 km/hr).
                     Fires were set from 12:45 to 3:45 p.m., burned 60 out
                     of 90 acres.  Fire slowed down or died as it moved
                     toward the junipers.

(2) March 19 fire:  Air temperature - 70 degrees Fahrenheit (21 deg C).
                    Relative humidity - 44 percent.                    
                    Wind - from southwest at 15 to 20 miles per hous
                           (24-32 km/hr).
                    Fire burned close to trees because prevailing winds
                    had piled tumbleweed and other debris under the
                    larger trees.  The southwest wind caused debris to
                    ignite.
 
(3) June 28 fire:  Fire was started by lightning, conditions were very
                   dry.
                   Wind - from the southwest at 10 to 15 miles per hour
                          (16-24 km/hr).
                   Air temperature - 97 degrees Fahrenheit (36 deg C) 
                                     (interpolated).
                   Relative humidity - 17 to 25 percent.


FIRE EFFECTS ON TARGET SPECIES : 
Oneseed junipers less than 18 inches (46 cm) in height appeared to be
badly damaged immediately after the fires.  Large junipers which had
tumbleweeds piled beneath the canopy also appeared to be badly damaged.
Most other large oneseed junipers were only partially damaged.  Two
years later, the junipers were discovered to have been much more
seriously damaged than had previously been believed.  Three hundred and
eighty randomly located oneseed junipers were examined.  Mortality of
trees less than 4 feet (1.2 m) in height ranged from 70 to 100 percent
on all three burn sites.  Approximately 30 to 40 percent of the trees 5
to 6 feet high (1.5-1.8 m) were killed.  The March and June burns
resulted in the deaths of 60 to 90 percent of the oneseed junipers 8 to
10 feet (2.4-3.1 m) in height.  Much of the mortality observed in large
oneseed junipers was attributed to the presence of tumbleweeds and other
flammable debris.  When the fires moved with the prevailing winds,
tumbleweeeds ignited and tree mortality was relatively high (60-90%).
When fires moved against the prevailing winds, flammable understory
debris did not ignite and few (<10%) large oneseed junipers were killed.


FIRE MANAGEMENT IMPLICATIONS : 
The amount of flammable material present at a given site and wind
conditions can greatly influence mortality in larger junipers.
Mortality can be relatively high when winds ignite tumbleweed and other
debris which has accumulated beneath the crown.  Study results suggest
that a high percentage of smaller oneseed junipers (<4 feet [1.2 m]) can
be killed by fire.  Grass fires at frequent intervals can presumably
halt the invasion of oneseed junipers which are less than 4 feet (1.2 m)
in height when the burning regime was implemented.  Larger trees are
much more resistant to the effects of fire except where significant
amounts of flammable material are present beneath the crown.



FIRE CASE STUDIES
SPECIES: Juniperus monosperma | Oneseed Juniper 



2nd CASE NAME : 
Pinyon-juniper/blue grama


REFERENCE : 
Dwyer, D. D.; Pieper, R. D. 1967 [15]

SEASON/SEVERITY CLASSIFICATION : 
Spring/low


STUDY LOCATION : 
Fort Stanton Experimental Range in south-central New Mexico.


PREFIRE VEGETATIVE COMMUNITY : 
The preburn community was mainly a grassland dominated by blue grama
(Bouteloua gracilis).  Oneseed juniper and pinyon (Pinus edulis) grew
on rocky ridges.  Other common preburn species which occurred primarily
as scattered individual included:  winterfat (Eurotia lanata),
apacheplume (Fallugia paradoxa), fourwing saltbush (Atriplex canescens),
algerita (Mahonia trifoliolata), skunkbush sumac (Rhus trilobata), and
walkingstick cholla (Opuntia imoricata).


TARGET SPECIES PHENOLOGICAL STATE : 
Not recorded


SITE DESCRIPTION : 
Topography - rolling
Slope - 0 to 9 percent
Elevation -  6,014 to 6514 feet (1,829-1,981 m)
Average annual precipitation - 15.5 inches (39 cm), with approximately
                               61.8 percent occurring from June to
                               October.
Soils - mostly very fine sandy loam "developed on recent alluvium
        derived from the San Andres Formation and mixed material of
        Guadalupe age."


FIRE DESCRIPTION : 
Fire was started at 1:45 PM.  
Relative humidity - low
Wind - warm, dry, from the south, (speed not recorded)
Soil, litter, and grass fuel - very dry.
Rate of spread - 1,250 feet per hour (381 m/hr)
Available fuel in open grasslands - 750 pounds per acre (670 kg/) 
Fire did not travel through the tree crowns.


FIRE EFFECTS ON TARGET SPECIES : 
All oneseed junipers less than 4 feet (1.2 m) in height were killed by
fire.  The foliage of many of these smaller trees extended close to the
ground and ignited readily.  Larger junipers were found to be somewhat
more resistant to ground fires of this type.  Many trees did not show
the extent of fire damage until 1 or 2 years after the fire.  Overall,
approximately 24 percent of oneseed junipers were killed by fire.  Some
larger oneseed junipers partially defoliated by fire still survived 2
years after the burn.  Many of these plants presumably recovered from
the effects of fire.

                2 years after the burn -
        total number of oneseed junipers        120
        composition %                           69.8
        kill %                                  24.2
        unharmed %                              13.3
        partial defoliation %                   62.5
        average % defoliation
                (all trees)                     44.6


FIRE MANAGEMENT IMPLICATIONS : 
Study results suggest that low intensity ground fires may be effective
in reducing small (< 4 feet [1.2 m] in height) oneseed junipers.
Frequent fires can maintain grasslands subject to oneseed juniper
invasion if the fire regime is begun while trees are still in the
seedling or sapling stages.  Larger oneseed junipers are somewhat
resistant to low intensity grass fires.  Fine fuels tend to be sparse
under larger junipers.

Related categories for Species: Juniperus monosperma | Oneseed Juniper