BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Ceanothus leucodermis | Chaparral Whitethorn 



GENERAL BOTANICAL CHARACTERISTICS : 
Chaparral whitethorn is an evergreen shrub which grows from 7 to 13 feet
(2 to 4 m) in height [34,43].  Branchlets are pale green and smooth, but
become gray-white, rigid and spiny-tipped at maturity [7,43].  Roots
tend to be well-developed and reach maximum depths of approximately 21
feet (6.4 m), with radial spreads up to 8.4 feet (3 m) [6,17].  Flowers
are white to pale blue and generally form short, dense clusters
[6,7,34].  Shiny, dark olive to brown, flattened or obovoid seed are
borne in sticky, globose capsules [6,34].

Chaparral whitethorn is capable of fixing atmospheric nitrogen [8].


RAUNKIAER LIFE FORM : 
   Phanerophyte


REGENERATION PROCESSES : 
Chaparral whitethorn regenerates both through seed and by vegetative
means [36].  In many areas, seed production is of primary importance,
although sprouting may sometimes be vigorous [13].  Sampson and Jespersen
[43] report that chaparral whitethorn generally does not sprout after
disturbance from Tulare County northward, although sprouting is commonly
observed to the south.

Vegetative regeneration:  Chaparral whitethorn frequently stump-sprouts
after fire or mechanical removal [7,25,30].  However, sprouting from the
rootcrown or burls, although less common, has also been reported
[17,26].  Sprouting of chaparral whitethorn is typically rapid.
Numerous resprouts were noted during the first growing season after
mechanical removal in chaparral communities of southern California [39].
Stump sprouts often grow quickly and can reach 7 feet (2.1 m) in height
within 10 years [19].

Seed:  Seed of chaparral whitethorn averages 77,000 per pound (170 per
g) [48].  Three shiny dark olive-brown seeds are contained in each
sticky globose capsule [7,22,34].  The capsule matures in summer and
ejects seed explosively as it dries [9,24].

Seed dispersal:  Seed casting of wedgeleaf ceanothus can occur within a
relatively short period.  Approximately 95 percent of the seed was cast
within a 14-day period in the Sierra Nevada Mountains of California [9].
Most seed falls within fairly close proximity of the parent plant.
Evans and others [9] found that approximately 36 percent of all
wedgeleaf ceanothus seed dropped to the ground beneath the canopy of the
parent plant, with 42 percent falling at the plant's edge.  The
remaining 1.9 percent was dispersed outward up to 30 feet (9 m) from the
parent shrub.  Most seeds were cast in a southeasterly direction.  Birds
and rabbits sometimes serve as important dispersal agents for many
species of ceanothus, and ants are also known to transport large numbers
of seed [6,22].

Seed production:  Production fluctuates annually and appears to depend
on flowerbud initiation in the previous year, which is in turn largely
determined by the amount of precipitation and nutrients received during
this time [22,30,36].  McDonald [30] reported annual chaparral
whitethorn seed production of approximately 5.2 million per acre (12.9
million per hectare).  Annual seed production was found to vary from
18,800 to 11,600,000 per acre (47,000 to 29,200,000 per hectare) in
southern California chaparral communities [6].  Research results
indicated the following production and viability estimates [22]:

year	seeds/hectare		seeds/m sq aerial coverage      viability
1973	2.7 x 10 6th			230   			    53%
1974	29.2 x 10 6th                   2,454			    44%
1975	47.6 x 10 3rd			4			    ---

Seed predation by insects and rodents can be heavy.  As much as 80
percent of all seed is removed by insects in some areas [21], and rodent
predation can eliminate up to 90 percent of annual ceanothus seed
production in certain locations [6].

Germination:  Seed of chaparral whitethorn is noted for its pronounced
dormancy mechanisms [30].  Germination is significantly improved by
exposure to heat which ruptures the secondary seed coat allowing water
to enter the seed [14].  In laboratory tests, up to 67 percent of seeds
germinated when heated in water at 158 degrees F (70 degrees C), and
then stratified at 36 degrees F (2 degrees C) for 3 months [48].
Germination dropped to 43 percent when seeds were heated to 194 degrees
F (90 degrees C), and then cooled [48].  

Seed banking:  Chaparral whitethorn is noted for its seed banking
properties which enable it to persist in fire-prone chaparral.  Large
numbers of long-lived seed tend to accumulate in the soil, duff, or
litter beneath the parent plants [9,14,31].  McDonald [30] found an
average of 0.3 million chaparral whitethorn seeds stored within the soil
of 1 acre (0.8 million per ha).  Other researchers have reported an
average of 352,227 per acre (870,000 per ha), with estimated viability
of up to 96 percent [22].  However, seed pool dynamics of chaparral
whitethorn are poorly known [1].  Although seed longevity is
considerable, the amount of seed contributed to the seed bank in any
given year has not been documented [1].

Seedling establishment:  Most seedlings emerge during mid-March and
April [2].  Although germination is often good, mortality of young
chaparral whitethorn plants is generally high.  Seedlings are quite
susceptible to the effects of drought [19] and herbivory.


SITE CHARACTERISTICS : 
Chaparral whitethorn grows on dry, rocky slopes, erosion channels,
gullies, and canyons [34,49].  It is an important component of many
chaparral, coastal sage, and oak (Quercus spp.)  woodlands of southern
California [16,34].  Chaparral whitethorn also grows as scattered
individuals or in patches in dry foothill forests dominated by ponderosa
pine (Pinus ponderosa), Coulter pine (Pinus coulteri), or various
woodland oaks (Quercus spp.)  [16,33,49].

Elevation:  Chaparral whitethorn typically grows at low to middle
elevations, and is generally found below 5,500 to 6,000 feet
(1,678-1,800 m) [7,43].  Hanes [15], notes that the most extensive
stands often occur at higher elevation chaparral sites.


SUCCESSIONAL STATUS : 
Facultative Seral Species

Chaparral whitethorn is generally most abundant in earlier seral stages
of chaparral or coastal sage communities [16].  This relatively
short-lived, rapidly growing shrub disappears in stands which have not
been burned for 40 to 70 years [21,31].  


SEASONAL DEVELOPMENT : 
Flowering of chaparral whitethorn has been reported as early as
February; however, most plants flower from April through June [7,34,48].
Seed is typically dispersed during the summer as capsules mature and
dehisce explosively [24].  Evans and others [9] observed that most seed
casting occured during July, with lesser amounts dispersed in August in
the central Sierra Nevada.  In some parts of California, seed does not
mature until September or October [43].

Related categories for Species: Ceanothus leucodermis | Chaparral Whitethorn