FIRE ECOLOGY
SPECIES: Washingtonia filifera | California Palm 



FIRE ECOLOGY OR ADAPTATIONS : 
Man-caused and natural fires are important factors affecting California
palm and the oases in which they grow.  A survey of oases along the San
Andreas Fault revealed fire effects on palms at all sites.  Prior to the
nineteenth century, Native Americans practiced fire management in oases,
burning them at intervals of about 4 years [40].  Burning increased the
yield of fruit crops, removed the dead shag from trunks for easier
access to crops, and removed understory phreatophytes competing for
water resources.  Spring flows increased, which temporarily reduced the
high alkalinity of soils and favored California palm seed germination
and seedling growth.  The oases were thusly maintained at pioneer or
early seral conditions [25,40].

Naturally-occurring oases fires are usually ignited by lightning
strikes; natural average fire frequency is undocumented.  Oases fire
records show that fire can occur at any time of year.  Oases fuels are
usually so prodigious and desiccated that lightning readily produces
fire even when occurring in winter during heavy rain [40].  Other
possible causes of natural fire have been suggested, including ignition
from sparks given off by falling rock in canyon sites, and spontaneous
combustion.  Hydric portions of oases support dense growth with heavy
accumulations of litter [39].  Spontaneous combustion occurs naturally
in Lousiana marshes [38], and hydric portions of oases are similar in
composition and environment [40].

California palms are fire resistant.  They are rarely killed by either
the inital burning of their shag or by subsequent burnings.  Burning
experiments show that their fibrous trunks are difficult to ignite and
almost impossible to flame.  Each successive burning kills some outer
vascular bundles and burns off some of the trunk, causing a reduction of
trunk diameter.  Crown fire, a common occurrence, reduces crown size.
Repeated burnings sometimes results in fire-dwarfed trees.  Reduction in
trunk and crown reduces the evapotranspiration rate, making more
effective use of limited water supplies and allowing for a greater
number of palms per oasis.  Wind-blown, advancing crown fire does not
inflict as much damage or kill as many palms as a slow-moving fire
burning in still air [40].


POSTFIRE REGENERATION STRATEGY : 
   Tree without adventitious-bud root crown
   Secondary colonizer - on-site seed
   Secondary colonizer - off-site seed

Related categories for Species: Washingtonia filifera | California Palm