FIRE EFFECTS
SPECIES: Ceanothus leucodermis | Chaparral Whitethorn 



IMMEDIATE FIRE EFFECT ON PLANT : 
Fire-caused mortality of mature chaparral whitethorn is described as
"moderate" [26].  Up to 50 percent of the sprouting population may be
killed by a single fire [22].  Young plants which typically have a
smaller rootcrown, and thus a reduced capacity to sprout from latent
buds, tend to be more susceptible to fire than mature individuals
[15,26].  However, larger underground, burllike structures of mature
chaparral whitethorn often survive despite significant damage.  Keeley
and Zedler [26] observed that less than 20 percent of the "burl" area in
burned chaparral stands was actually killed by fire.  Since plants do
not survive when these underground regenerative structures are
destroyed, overall adult mortality in this stand was approximately 20
percent.

Postfire mortality of mature chaparral whitethorn is typically slight
following prescribed burns of light intensity [29].  However, extremely
hot fires often kill both young and mature plants [42].  In chaparral, a
shorter fire cycle contributes to less intense fires and greater
survivorship whereas a longer fire regime results in higher fire-caused
mortality of sprouting shrubs such as chaparral whitethorn [26].

Large numbers of seed accumulate in the soil during fire-free periods
and many survive most fires.


DISCUSSION AND QUALIFICATION OF FIRE EFFECT : 
NO-ENTRY


PLANT RESPONSE TO FIRE : 
Chaparral whitethorn regenerates vegetatively after fire in some areas,
but is also capable of producing an abundance of seedlings [13,22,43,50].
Both modes of regeneration appear to be important, although the relative
value of each varies significantly according to geographic location and
season of burn [13,43].  Sampson and Jespersen [43] report that chaparral
whitethorn tends to sprout in southern California, but not from Tulare
County northward.  A number of researchers have observed much greater
sprouting than seedling production [19,26], while others have noted
greater relative importance of regeneration through seed [25,50].

Vegetative regeneration:  Chaparral whitethorn often sprouts from the
stump or rootcrown area [15,17], although sprouting from burllike
structures has also been reported [20,26].  Stump-sprouting apparently
occurs when aboveground stems are not seriously damaged by fire.  Old
snags with multiple sprouts "clusterd about the base" are commonly
observed after fire in chaparral communities [19].  It should be noted
that all forms of sprouting are much less likely following fires of
relatively high intensity [42].

Regeneration through seed:  The long-lived seeds of chaparral whitethorn
accumulate in large numbers beneath the parent plant during fire-free
intervals [9].  Seeds buried at depths so that they receive heat
scarification rather than exposure to lethal temperatures, are
stimulated to germinate [1,14,49].  Generally, seedling establishment is
favored by fall burns which provide stratification for seeds [13].
Overall postfire seedling establishment potential is described as
"moderate" [26].  Seedling mortality may be high, particularly during
dry periods [19].  However, seedlings often number more than 886 per acre
(355/ha) within a few years after fire [50].

Postfire recovery time:  Resprouts generally grow much faster than do
seedlings [15].  Typical heights of stump sprouts measured 10 years after
fire ranged from 26 to 29 inches (66-74 cm) in southern California
chaparral, although heights of up to 7 feet (2.1 m) have been reported
on particularly good sites [19].  Comparative postfire growth of sprouts
and seedlings are as follows [19]:

			years after burn - (in inches)
               1     2      3     4       5     7      10      15
sprouts       6.0   21.0   ---   30.0   30.0   50.0   84.0    70.0
seedlings     2.5    8.3   11.6  14.6   15.6   18.0   24.7    30.7

Postfire recovery of this fast-growing shrub is rapid regardless of the
type of primary regenerative strategy employed.


DISCUSSION AND QUALIFICATION OF PLANT RESPONSE : 
Numerous studies have compared the relative importance of chaparral
whitethorn seedlings and resprouts after fire [19,22,25,50].  Preliminary
evidence suggests that resprouts may be relatively more important toward
the southern portion of the shrub's range [43].  However, factors such
as season of burn, community composition, weather conditions, fire
intensity and severity, years since the last fire, and geographically
expressed genetic variation may also represent important determinants of
the type of response.  Pertinent observations are summarized below
[22,25,50]:

		1) location: southern California
		   season of burn:  October 1967, September 1968

            1967 burn   		1968 burn
sprouts     -----	                   2
seedlings   1,556                         670


		2) location:  southern California chaparral
		   season of burn:  September

		     #/ha
resprouts            1,170
seedlings            2,050


		3)  location:  southern California chaparral
		    season of burn:  November
                    intensity: all aboveground vegetation removed

site 1 -		density -10 3/ha      	cover m sq. /ha
	             March          June       March          June
resprouts            ---            2.1         ---            189
seedlings            17.7          88.1          5             109
   		 		 
site 2 -            
resprouts            ---           30.0         ---           1,200
seedlings            85.6          70.5         26              223


FIRE MANAGEMENT CONSIDERATIONS : 
Fuels and flammability:  Chaparral whitethorn tends to be highly
flammable because of its chemical composition and growth form.  It
possesses substantial amounts of fine fuels, a low moisture content, and
high proportions of resin, oil, wax, and volatile products [30].  Leaf
energy content is estimated at 20.16 kJ/g -1 [40].  In addition, plants
tend to have much dead material, and form expansive acreages of dense
shrub growth with interlocking crowns [30].  Thus, fire in shrub
communities dominated by species such as chaparral whitethorn have the
potential to become "huge and violent" in a relatively short period of
time [30].  Natural fire intervals in California chaparral or coastal
sage communities range from 20 to 60 years [11,28,51].  Where chaparral
whitethorn occurs as an important understory species in drier coniferous
forests of California, it can increase overall stand flammabilty as dead
woody material accumulates in the shrub's crown when plants become
decadent [49].

Wildife considerations:  The nutritional value of chaparral whitethorn
may be altered by fire.  Foliar nitrogen concentration of chaparral
whitethorn begins a rapid decline during the first 6 years after fire
[41].  Potassium content is typically elevated during the first few
years after fire, but then begins to decrease [41].

Production:  Postfire production of chaparral whitethorn was found to
average approximately 360 pounds per acre (403 kg/hectare) 5 years after
a fall burn [13].

Related categories for Species: Ceanothus leucodermis | Chaparral Whitethorn