BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Quercus dumosa | Nuttall's Scrub Oak 



GENERAL BOTANICAL CHARACTERISTICS : 
Nuttall's scrub oak is a native evergreen shrub from 3.2 to 9.6 feet
(1-3 m) in height.  The sclerophyllous leaves are spiny to toothed.
Acorns are small (8-15 mm wide by 5-8 mm deep) [23].  The root system
has been described as deep and extensive [13].


RAUNKIAER LIFE FORM : 
   phanerophyte


REGENERATION PROCESSES : 
Seed:  Acorns mature within a single season [50].  Acorn crops are
generally light, although larger crops are produced at irregular
intervals [27,69].  Production appears to vary by the individual tree.
Some plants consistently bear large numbers of acorns, while others
rarely produce acorns [50].

Seed dispersal:  Acorns are readily dispersed in the fall by gravity or
animals [27,28].  Squirrels and jays are particularly effective
dispersal agents for many California oaks [1].  Mature Nuttall's scrub
oak acorns rarely remain on the ground for long [50].  Many are eaten
immediately, but small mammals and birds frequently cache acorns for
winter use [73,74].

Germination and viability:  The acorns germinate readily without
scarification or other special treatment [27].  They occasionally begin
germinating prior to dispersal from the parent plant [28].  Germination
generally begins within 1 month after dispersal although it may be
delayed on xeric sites [35].  Some studies have related germination of
Nuttall's scrub oak to time of seed harvest and exposure to certain
charrates [28,35,49,52].

Acorns are susceptible to heat and are generally killed by fire even
when protected by overlying soil or litter.  A longer period of exposure
to lower temperatures is more damaging than short bursts of higher
temperatures [28].  Acorns are also vulnerable to mold and rot [35].
Mortality of planted acorns ranged from 4 to 42 percent in laboratory
tests [23].  Results of germination tests are as follows [43]:

         cold stratification       temperature F      duration    germination
         (in days)               day      night       (days)      capacity (%)
         30 to 90                86        68           28        80 to 90

Acorns which have been harvested 1 1/2 to 2 months prior to maturity
exhibit good germination if the tip of the pericarp is removed before
seeds are planted [11,49,52].  Germination by harvest date was reported
as follows [49]:

                 percent germination by harvest date -
              8/17     8/31      9/14       9/28       10/12
intact acorns  15       4          0         20          90
tips removed   50      89         86        100          95

Acorns of Nuttall's scrub oak are relatively short-lived, and when dried
to room temperature, most remain viable for less than 9 months [28].
Properly stored seed can remain viable for up to 8 months, but viability
is much reduced after 15 months [49,52].  Acorns stored for 6 to 12
months frequently exhibit varying degrees of damage or deformity.
Temperatures just above freezing and a moisture content of 60 percent of
the fresh weight appear most conducive to long viability [49].

Seedling establishment:  Establishment of Nuttall's scrub oak through
seed appears to be uncommon despite consistent acorn production
[27,31,54,49].  Seedlings sometimes establish under the oak canopy, but
it is doubtful whether many are actually recruited into the population
[29].  Seedling establishment probably only occurs during years of ample
precipitation [54,73].  Where establishment from seed does take place,
seedlings generally emerge during the first growing season, although a
few may emerge during the second growing season [73].

Vegetative regeneration:  Nuttall's scrub oak typically sprouts
vigorously in response to fire, mechanical injury, or other types of
disturbance [5,9,46].  Several types of vegetative response have been
well documented for this species.  Nuttall's scrub oak commonly
stump-sprouts when portions of the stump remain undamaged [10,39,44].
It also sprouts from the root crown after the trunk or aerial crown is
damaged [9,20,50].  It does not produce a lignotuber [27], but
occasionally old root crowns which have been burned repeatedly develop
into massive structures at the ground surface [20].  These swollen root
crowns have the ability to sprout from latent buds but are not
considered to be lignotuberous [25].


SITE CHARACTERISTICS : 
Nuttall's scrub oak generally occurs on sandy soils near the coast.
Parent material is often sandstone.  It grows at elevations less than
660 feet (200 m) [23].


SUCCESSIONAL STATUS : 
Nuttall's scrub oak is an important species in some chaparral
communities of California [12].  These communities depend on fire for
their continued existence.  Succession here may perhaps best be viewed
as a process by which senescent individuals are replaced by new
individuals of the same species [20].  A dense cover of Nuttall's scrub
oak generally develops within 5 to 10 years after fire in oak chaparral
[41].  In many areas Nuttall's scrub oak, along with ceanothus
(Ceanothus spp.), assumes dominance as early as the fourth year after
fire [30].  In coastal chaparral communities of southern California,
Nuttall's scrub oak generally becomes dominant during the second decade
after fire, and within 30 to 40 years oak chaparral communities on
north-facing slopes have closed canopies.  The vegetative composition of
these sites remains essentially unchanged without further disturbance,
with Nuttall's scrub oak continuing to dominate [20].  Nuttall's scrub
oak's prolific sprouting ability makes it a prominent component of early
seral communities.


SEASONAL DEVELOPMENT : 
Hanes [15] observed that the cambial activity of Nuttall's scrub oak in
California chaparral began in March and peaked in May.  The oak was
inactive from late July through February [22].  Immature acorns which
have been damaged by wind, rain, hail, or insects begin to fall in May
[37].  Ripe acorns are dispersed in fall [28].

Related categories for Species: Quercus dumosa | Nuttall's Scrub Oak