BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Adenostoma sparsifolium | Red Shank 



GENERAL BOTANICAL CHARACTERISTICS : 
Red shank is a native arborescent shrub growing from 6 to 18 feet (2-6
m) tall [7,16,33].  It has a rounded growth form with thick multiple
branches that ascend several feet without foliage before multiple
smaller branches display leaves [15,22].  Red shank is classified as a
broad-leaved sclerophyll [15].  Its leaves are covered with a sticky
resin that may serve to reflect excess radiation [39].  The bark
exfoliates freely, peeling off in long strips [8,15,33].  Red shank has
a large lignotuber; the lignotuber of one individual in the Santa Monica
Mountains measured 12 inches (30 cm) in diameter.  The root system has
not been well studied but appears to be predominatly lateral with masses
of small roots.  Two plants excavated in the Santa Monica Mountains had
thick, woody, multiple roots rapidly branching into succulent fibrous
roots at 1 to 4 feet (0.3-1.2 m) below the soil surface.  A few roots
were found below 6 feet (1.8 m) [15].  The inflorescence is an open
panicle; the fruit is an achene [7,33].  Red shank may live over 100
years [21].


RAUNKIAER LIFE FORM : 
   Phanerophyte


REGENERATION PROCESSES : 
Red shank primarily reproduces vegetatively.  The roots and lignotuber
store carbohydrates and other nutrients necessary for sprout development
from adventitious buds of the lignotuber [23].  Sprouting continues
throughout the life of the plant until senescence, but die-off of young
stems appears to be great.  Growth-ring analysis of red shank in the
Palomar Mountains of San Diego County revealed that most stems were
either less than 5 years of age or greater than 30 years of age, with
few in between [25].  Sprout viability may be enhanced in the first few
years following top-kill by fire or other means because of lack of
competition from older stems.

Seedling recruitment is rare.  Limited research suggests that this is
due to three factors:  low seed set, low seed viability, and rapid loss
of viability in seed that is sound when fresh.  Microscopic examination
of red shank seed collected over the range of red shank's distribution
showed that much of the seed was unfilled.  Heat treatment and
subsequent sowing of the seed resulted in 0 percent germination [15].
Red shank's congener chamise produces two physiologically distinct types
of seed.  One type has a hard seedcoat that requires heat scarification
prior to germination.  This seed can remain viable in the seedbank for
decades before fire breaks dormancy.  The other type is nondormant and
loses viability rapidly [42].  Although red shank has been reported as
producing hardcoated, dormant seed [21], it probably does not.  One
investigation indicated that red shank produces only one of the two
chamise seed types:  nondormant, short-lived seed.  Seed crops are
usually scant.  Hanes [15] searched for red shank seedlings in or near
mature red shank stands from San Luis Obispo County to Baja California.
He found only one site, in the Santa Monica Mountains, that supported
seedlings.  This site was not a burn but had been bulldozed the year
prior to seedling recruitment.  The year following establishment, 50
percent of seedlings died during summer drought.  Hanes suggested that
lack of seedling recruitment accounts for red shank's limited
distribution.


SITE CHARACTERISTICS : 
Red shank grows on dry, well-drained slopes and mesas at elevations from
1,000 to 7,000 feet (305-2,134 m), with most populations found from
1,500 to 5,000 feet (457-1,524 m) elevation [7,15].  It may occur on any
aspect [15], but shows definite slope association in some locations.  In
the Santa Monica Mountains, red shank occurs primarily on north-facing
slopes [3], while in San Diego County, red shank is found on southern
aspects [29].  All red shank populations except one in the Santa Monica
Mountains occur more than 50 miles (80 km) inland [15].

Soils supporting red shank are typically shallow.  They may be coarse in
texture [15], but red shank's shallow, succulent roots are best adapted
to fine-textured soils because of the superior water-retaining capacity
of such soils [2].  Red shank grows in soils derived from granite or
loosely-cemented Miocene sandstone [15].  A soil pH of 6.6 was reported
beneath red shank stands in the Los Padres National Forest, Santa
Barbara County [9], and of 6.3 beneath stands in the Palomar Mountains,
San Diego County.  Where coexisting with chamise, red shank occupies the
more mesic and fertile sites [26].  Soil moisture, organic matter,
sulfate, and ammonium levels are significantly higher (p<0.01, 0.01,
0.05, and 0.05, respectively) on red shank-occupied soil than on
chamise-occupied soil.  Magnesium levels, percent coarse fraction, and
soil pH are significantly lower (p<0.05 in all cases) on red
shank-occupied soil [3].

The climate in which red shank grows is Mediterranean, characterized by
wet, mild winters and hot, dry summers [16].  Santa Ana foehn winds may
occur at any time of year, but are most common in fall [32].



SUCCESSIONAL STATUS : 
Facultative Seral Species

Red shank is a survivor in disturbed communities, establishing from
sprouts following top-kill.  It is usually not replaced by other species
at any stage of chaparral succession.  Red shank is shade intolerant
[15].

Development of new red shank communities during secondary succession is
rare.  When this does occur, seedlings establish during the first few
postdisturbance years, competing with the herbaceous species which also
establish at this time.  Herbs diminish in number as the community
matures, occupying spaces between red shank [15,16].  Red shank stands
attain maximum canopy coverage at about postdisturbance year 25 [17].


SEASONAL DEVELOPMENT : 
Red shank growth begins in February.  The period of most active growth
is from June to mid-August [46].  Flowering occurs in late August and
continues through September [8,33,46].  Stem die-off and abscission
occurs during summer and fall drought.  Plants on the Murphy Ranch in
the Santa Monica Mountains dropped 32.5 percent of randomly tagged stems
during the dry season of a year of normal precipitation [15].

Related categories for Species: Adenostoma sparsifolium | Red Shank