FIRE EFFECTS
SPECIES: Ferocactus wislizenii | Barrel Cactus 



IMMEDIATE FIRE EFFECT ON PLANT : 
Barrel cactus plants more than 1 foot (0.3 m) tall are rarely killed by
fire since only their spines are combustible.  However, plants less than
that height may suffer up to 75 percent mortality as a direct result of
fire damage to the apical meristem, or a combination of fire damage to
the meristem and damage from herbivory [16].

Succculents in general rarely actually burn, but spines may ignite and
carry flames to the apex.  The cactus body may scorch and blister
without pyrolysis, leaving undamaged parts of the plant alive.
Mortality results from death of the photosynthetic tissue and underlying
cambium and phloem.  Cacti may appear completely scorched with no green
tissue visible, yet survive fire.  However, fire can cause delayed
mortality, which may not occur for months or even years [30].  Removal
of the spines also increases subsequent herbivory [23,30].  Survival of
succulents depends primarily on protection of the apical meristem.  If
the apical meristem is undamaged, the cactus will resume growth [30].




DISCUSSION AND QUALIFICATION OF FIRE EFFECT : 
NO-ENTRY


PLANT RESPONSE TO FIRE : 
Average mortalities of 50 to 67 percent have been reported for barrel
cactus within the first 2 years following fire in desert grassland and
desert shrub communities in southern Arizona [13,15,23,32,37].

Two consecutive winters of heavy rain produced enough fuel to carry a
fire in a portion of the Sonoran Desert where fire is usually considered
ecologically insignificant.  Following the Granite Fire in Arizona in
June 1979, large-diameter cacti including barrel cactus had the lowest
mortality rate of all cacti.  Many severely burned plants survived and
produced flowers and seeds.  An average of 20 plants per hectare
occurred on unburned sites, and 15 plants per hectare occurred on burns
in postfire years 1 and 2.  Barrel cactus had an overall mortality rate
of 59 percent in burned areas within the first 19 postfire months [21].

Barrel cactus had an average of 6 percent and 31 percent mortality on
unburned and burned sites, respectively, following fires in semidesert
grasslands on the Buenos Aires National Wildlife Refuge and in the
Sierrita Mountains of southern Arizona.  Plants were counted within 11
to 14 postfire months.  Barrel cactus also had significantly greater
(p<.001) fire mortality when under a mesquite (Prosopis juliflora) canopy
(53%) than in open grassy areas (19%) [31].




DISCUSSION AND QUALIFICATION OF PLANT RESPONSE : 
NO-ENTRY


FIRE MANAGEMENT CONSIDERATIONS : 
NO-ENTRY

Related categories for Species: Ferocactus wislizenii | Barrel Cactus