BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Quercus oblongifolia | Mexican Blue Oak 



GENERAL BOTANICAL CHARACTERISTICS : 
Mexican blue oak is a native, evergreen, small tree that grows 16 to 26
feet (5-8 m) tall and 1.5 feet (0.5 m) in diameter with a broadly
spreading crown [12,22,26,37].  At higher elevations, its habit is a
shrub [22,26].  The bark is about 1.2 inches (3 cm) thick [6].  The
leaves are oblong and small, 1 to 2 inches (2.2-5 cm) long, with entire
margins [12,26].  Mexican blue oak has solitary or paired pistillate
flowers; the numerous staminate flowers are in catkins [22,44].  Acorns
are 0.5 to 0.7 inch (1.2-1.8 cm) long [12,37,44].  The acorn shell is
very thin and surrounds one seed [6].


RAUNKIAER LIFE FORM : 
   Phanerophyte
   


REGENERATION PROCESSES : 
Asexual reproduction:  Mexican blue oak sprouts abundantly after the
stem is killed [33].

Sexual reproduction:  No information on Mexican blue oak acorn
production or germination was found in the literature.  Information is
available for two oak species, Arizona white oak and Emory oak, that
often occur with and may be representative of Mexican blue oak.  Annual
acorn production is highly variable for these two species:  0 to 60
percent of the trees may produce acorns during a growing season.  These
oaks have no seed dormancy.  Most germination occurs within 30 days
after the acorns drop.  Buried acorns germinate more successfully than
acorns lying on the soil surface.  Vertebrates and invertebrates may
consume from 30 to 75 percent of the acorns produced [31].

Reproductive rates vary among Mexican blue oak populations.  In riparian
canyons in the encinal region of the Santa Catalina Mountains of
Arizona, a Mexican blue oak population exhibited good reproduction with
size classes from seedlings through 23.6 to 35.4 inches (60-90 cm)
d.b.h. present [33].  In a remnant oak woodland in the San Cayetano
Mountains of Arizona, Mexican blue oak populations were declining.  No
Mexican blue oak seedlings were found, and reproduction was poor.  Of
the trees examined, 94 percent were in older age classes and were
greater than 7.9 feet (2.4 m) tall [2].  Growth rates of southwestern
oak species are usually slow [31].


SITE CHARACTERISTICS : 
Mexican blue oak is common in foothills, mountains, and canyons from the
upper edge of desert grasslands extending up to pine woodlands
[7,26,33,35].  It occurs from 4,000 to 6,000 feet (1,219-1,829 m) in
elevation [7,12,44].  At lower elevations from 2,625 to 3,281 feet
(800-1,000 m), Mexican blue oak fingers into riparian communities
[33,40].

Mexican blue oak occurs in semiarid to arid climates with biseasonal
rainfall [31,33,45].  It is found on soils that are often thin, sandy,
rocky, and poorly developed [15,25,31].  Mexican blue oak may grow on
soils derived from granitic parent materials or mixed alluvium-colluvium
[3,33].  It occurs on 15 to 80 percent slopes of all aspects, depending
on moisture availability [2,3].


SUCCESSIONAL STATUS : 
Obligate Climax Species

Mexican blue oak is a dominant climax species in lower, open oak
woodlands [3,24,33].  It is a climax understory species in pine and
pinyon-juniper communities [24,34].  Mexican blue oak occasionally
occurs in climax riparian communities [40].


SEASONAL DEVELOPMENT : 
Mexican blue oak flowers from March to May as the leaves emerge [6,
12,46].  Fruits mature the autumn after flowering [12].  Leaves persist
during winter and drop in spring when the new leaves open [6].

Related categories for Species: Quercus oblongifolia | Mexican Blue Oak