BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Quercus emoryi | Emory Oak 



GENERAL BOTANICAL CHARACTERISTICS : 
Emory oak is a native, monoecious shrub or medium-size tree that can
reach 65.6 feet (20 m) tall and 2.5 feet (0.7 m) in diameter
[18,23,50,57,64].  It has a spreading, rounded crown with bark that is 1
to 2 inches (2.5-5.5 cm) thick [35].  The drought-deciduous leaves are
thick and 1.2 to 3 inches (3-8 cm) long [23,102,104].  Pistillate
catkins are one to two flowered [23,121].  Acorns are solitary or
paired, 0.4 to 0.8 inch (1-2 cm) long [35].


RAUNKIAER LIFE FORM : 
   Phanerophyte


REGENERATION PROCESSES : 
After top removal by fire or cutting, Emory oak vigorously sprouts from
root crowns or stumps [18].  Following harvest in Arizona, Emory oak
regenerated by stump sprouts; there was low seedling survival [102].  A
higher percentage of Emory oak stumps than Arizona white oak stumps
sprouted following harvest of oak woodlands in southern Arizona.  Emory
oak sprouts also grew faster than Arizona white oak sprouts [77].

Emory oak acorns mature in one season [35,105].  Germination occurs
during the summer shortly after maturation [87,93].  There is no seed
dormancy.  Most germination occurs within 30 days after acorns drop from
the tree; acorns are viable for about 60 days [75].  In field trials,
Emory oak acorns had lower viability and germination at the soil surface
(5%) than 3 inches (7.5 cm) beneath the soil (29%) [87].  Emory oak
germination is strongly positively correlated with moisture during the
summer rainy season.  Favorable environmental conditions for Emory oak
germination and establishment occur infrequently, about once in a decade
[87,90].

Acorn production is highly variable.  Large acorn crops, up to 15,500
acorns per tree, alternate with several years of low acorn production
[75].  One study demonstrated that Emory oak recruitment in mature oak
woodlands was not limited by germination [87].

Vertebrates consume from 1 to 65 percent of acorns Emory oak produces,
and invertebrates consume from 1 to 50 percent.  While postdispersal
losses can be high, they are also variable.  Seventy-eight percent of
Emory oak acorns escaped predation in a 1978 oak woodland study in
Arizona.  Two years later, only 25 percent of the acorns escaped
predation [75].  Scrub jays and rodents rarely carry Emory oak acorns
very far from seed trees.  Caching of acorns by jays and rodents at 1.5
inches (3.8 cm) or deeper can provide germination opportunities,
depending upon moisture availability [90].

Emory oak topgrowth is slow, especially in seedlings [35,75].  They may
succumb to drought.  Emory oak mortality resulted from drought in a
pygmy conifer-oak woodland in Arizona [85].  A study evaluating seedling
establishment after fire found that drought rather than predation caused
most of the seedling mortality [90].  Acorns dropping directly below the
canopy may experience moisture deficits, since up to 70 percent of
precipitation may be intercepted by the canopy [45].  However, a field
study showed that significantly (P<0.05) higher germination and
viability of Emory oak acorns occurred under trees than in the open
grassland between trees [86].


SITE CHARACTERISTICS : 
Emory oak occurs in arid to semiarid climates with low amounts of
biseasonal rainfall.  The climate has mild, wet winters and hot, wet
summers [34,66,85,109].

Emory oak is found in canyons at the upper edge of deserts or desert
grasslands [35,64].  Emory oak occurs in open oak woodlands from 4,500
to 5,000 feet (1,400-1,700 m) on hills and mountain slopes up through
Arizona cypress canyon forests and pygmy conifer-oak woodlands at 7,000
feet (2,130 m) [66,85].  It occurs as isolated trees in mesic or
riparian habitats and in xeric pine communities [5,66].  Emory oak is
found on alluvial fans, foothills, bajadas, barrancas, high plains, and
mesas [30,39,47,126].

Emory oak occurs on slopes that vary from flat to steep.  Often these
slopes have northern or western aspects [17,31,76,102,117].  Emory oak
may occur on drier sites than codominants Arizona white oak or Graves
oak [31,83,99,123].  Emory oak is a shrub in the Arizona interior
chaparral, where topography is often rough and highly dissected, with
very rocky loam soils [58].  Emory oak is more abundant and grows to
tree size in deeper soils, often in bottomlands where it forms dense
stands.  Reduced amounts of water prevent typical riparian communities
from forming in these areas [18,64,108].

Emory oak occurs in various soil textures derived from a variety of
parent materials.  Soils may be deep with moderately fine to very fine
textures.  The soils can be acidic and may be old alluvium from mixed
sedimentary and igneous rocks [76,83,105,117,122].  More often Emory oak
is reported on shallow soil with weak profiles, along drainages, or on
rocky slopes with textures of very gravelly sandy loams [25,39,47,85,99].


SUCCESSIONAL STATUS : 
Facultative Seral Species

Emory oak is a climax species in evergreen oak and encinal woodlands
[62].  It is both a seral and climax species in pine-oak woodlands
[8,27,85].  Emory oak is a minor climax species in Chihuahua pine
forests [62].  Four years after cabling in pinyon-juniper woodlands
where Emory oak is one of several important oak understory species, the
oaks reestablished during the perennial grass and forb stage [95].


SEASONAL DEVELOPMENT : 
Emory oak gradually drops leaves in the spring as new leaves form
[64,103].  Emory oak acorns mature annually from June through September,
with a peak in midsummer [35,75,87,121].

Related categories for Species: Quercus emoryi | Emory Oak