BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Cupressus arizonica | Arizona Cypress 



GENERAL BOTANICAL CHARACTERISTICS : 
Arizona cypress is a native, evergreen tree.  In Arizona, it usually
grows 40 to 50 feet (12-15 m) tall but may be as tall as 90 feet (27 m).
Arizona cypress has a diameter of to 2 to 3 feet (0.6-0.9 m) with a
maximum of 5.5 feet (1.6 m) [24].  In Texas, Arizona cypress usually is
less than 33 feet (10 m) tall but may reach 82 feet (25 m) in height,
and is usually 20 inches (50 cm) or less in diameter [9].  Smooth
cypress is usually 25 to 50 feet (8-15 m) tall, Cuyamaca cypress is
generally 30 to 50 feet (9-15 m) tall, and Piute cypress is usually 20
to 50 feet tall (6-15 m) [22,42].  The short, stout horizontal branches
form a dense, conical or narrowly pyramidal crown, which may sometimes
be broad and flat [64].  The trunk either branches near the ground or is
well developed and branch-free for some length [24].  The largest trees
are seldom more than 700 years old [64].  Two stands examined for age
structure in southeastern Arizona had individuals ranging in age from
approximately 25 to 178.1 years and from 197.6 to 456.7 years [46].

The leaves are all small and scalelike.  The ovulate cones are globose,
with woody, separating scales [24].  In young trees, the bark breaks
into thin, large, irregular scales.  On older trunks and branches the
bark is longitudinally furrowed, fibrous, and shreddy [24,64].

Smooth cypress is distinguished by its habit of shedding the outer bark,
which exposes the smooth inner bark [24].  Cuyamaca cypress has thin
bark that is smooth and exfoliating [42].

A well-defined taproot and numerous lateral roots are formed the first
year [22].


RAUNKIAER LIFE FORM : 
   Phanerophyte


REGENERATION PROCESSES : 
Arizona cypress reproduces exclusively from seed.  Mature cones have
been observed on 14-year-old individuals of Cuyamaca cypress, indicating
that sexual maturity occurred sometime previous [66].  Ovulate cones are
usually abundant each year and contain from 48 to 112 seeds each [64].
The cones are closed; they persist on the tree until opened by the heat
of a fire or desiccation due to age [22,65].  Seeds are shed gradually
over several months after the cones are opened by heat [66].  Detached
cones will open, but they rarely result in seedling establishment,
usually due to the lack of a suitable seedbed [1].  The exception is the
San Pedro Martir cypress, whose cones open and shed seeds in July when
they are ripe [22].  Seeds do not appear to have innate dormancy; they
remain viable for a number of years in unopened cones and germinate when
moistened [64].

Arizona cypress requires bare mineral soil for germination and seedling
establishment, which gives it a competitive advantage over the dominant
plants of adjacent communities.  The presence of a litter layer reduces
germination; 10 percent of seeds germinated on bare mineral soil, but
only 3.7 percent germinated on litter-covered substrate [5,46].
Seedlings are sensitive to excessive moisture [68].


SITE CHARACTERISTICS : 
Arizona cypress occurs in the southwestern United States where the mean
annual precipitation is approximately 16 to 24 inches (400-600 mm).
Precipitation is bimodally distributed; relatively wet in summer and
winter, and dry in the spring and fall [7].

Arizona cypress grows in dry, well-drained soils on cool sites [5,64].
Arizona cypress is usually characterized as a moisture-demanding species
of riparian habitats [6,68].  However, recent findings show that Arizona
cypress can occupy relatively xeric sites, including south-facing
slopes, ridge tops, and convex slopes at higher elevations (around 6,600
feet [2,000 m]).  Arizona cypress occurs in relatively pure, dense
groves of smaller trees on most canyon side slopes and is relatively
less important and represented by fewer, larger individuals in riparian
stands [47].  The Arizona cypress-shrub live oak association is found on
wet, north slopes and generally occurs on the upper portions of slopes,
on soils derived from slate, schist, limestone, and granite parent
materials [7].

Arizona cypress is generally found at elevations from 3,000 to 8,000
feet (900-2,400 m) on gravelly slopes or cuts with northern exposure
[64].  Cuyamaca cypress is found on dry slopes from 3,000 to 4,500 feet
(900-1,400 m) within or adjacent to chaparral [42].  Piute cypress
occurs at elevations between 4,000 and 6,000 feet (1,219 and 1,829 m)
and is associated with foothill woodland and chaparral communities.
Some groves of Piute cypress contain singleleaf pinyon (Pinus
monophylla) and California juniper (Juniperus californica) [66].  Piute
cypress occurs on a variety of soils, including red and black clays,
decomposed granite, and fractured rock.  The best growth is on red clay
with well-developed topsoil [59,60].


SUCCESSIONAL STATUS : 
Facultative seral species

The successional status of Arizona cypress is unclear.  Arizona cypress
communities are considered a topo-edaphic climax in southeastern and
central Arizona [14,29].  However, cypress seedlings are shade
intolerant and survive best in full sunlight on bare mineral soils [66].
Parker [46] studied the age structure of a number of Arizona cypress
communities and concluded that Arizona cypress is an intolerant species
that requires disturbance to expose mineral soils for seedling
establishment.  He designated Arizona cypress a "pseudoclimax" species.
The term "pseudoclimax" indicates that stands appear to be climax but
are eventually replaced by more tolerant species.  Arizona cypress
continues to establish on disturbed sites for 50 to 100 years, thus
establishing an apparently climax population with a number of age
classes.  Recent studies, however, indicate a paucity of seedlings under
these stands, which would indicate that the stands are susceptible to
replacement by other species [12,46,47,49,54].

Alternatively, the lack of regeneration in these stands can be
interepreted as resulting from fire exclusion and the absence of
suitable sites for regeneration; Arizona cypress may therefore be
considered a fire climax.  Parker [46] pointed out that Arizona cypress
seedlings established on sites that had been disturbed by logging.  Moir
[39] reported good regeneration in Texas, where there had been fire as
recently as 1944, and he estimated that recruitment is approximately
equal to mortality in an Arizona cypress/Chisos bluegrass (Poa involuta)
habitat type and in Arizona cypress/bigtooth maple habitats as well.


SEASONAL DEVELOPMENT : 
Both the pistillate and staminate cones of Arizona cypress emerge in
spring [64].  Pollen is shed in October and November by Arizona cypress
and smooth cypress in Placerville, California (cultivated outside their
native range) [22].  Ovulate cones remain closed until opened by heat or
age [68].

Related categories for Species: Cupressus arizonica | Arizona Cypress