BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Cercidium microphyllum | Yellow Paloverde 



GENERAL BOTANICAL CHARACTERISTICS : 
Yellow paloverde is a native, monoecious, spiny shrub or small tree that
may grow to 26 feet (8 m) tall [3,37,52,88].  The trunk may be 1 foot
(0.3 m) in diameter; it branches about 8 inches (20 cm) from the ground
into four to six major stems [57].  The crown spreads 12 to 18 feet
(3.7-5.5 m) [32].  The bark is thin and photosynthetic [91].  Yellow
paloverde has numerous flowers in 1 inch (2.5 cm) long clusters [16,37].
It has pinnately compound leaves about 1 inch (2.5 cm) long with minute
leaflets and is drought-deciduous [37,100].  Fruits are 2 to 3 inches
(4-8 cm) long and have one to five seeds with constrictions between the
seeds [16,37,80].

Yellow paloverde lives longer than 72 years [22].

Yellow paloverde is susceptible to freezing [90].


RAUNKIAER LIFE FORM : 
   Phanerophyte


REGENERATION PROCESSES : 
Yellow paloverde reproduces sexually and asexually.  Yellow paloverde
has fair to poor ability to produce sprouts after top removal [11].

Photoperiod initiates fruit and flower production of yellow paloverde.
Subsequent local weather conditions determine whether flowering or seed
set occurs [91].  A seed crop is produced when the spring is wet or very
cool [105].

Yellow paloverde is insect pollinated [44,82].

McAuliffe [47] stated that yellow paloverde pods rapidly abscise as a
mechanism to avoid seed predation by bruchid beetles.  The constricted
fruits of yellow paloverde do not open before dispersing [37].

Seeds germinate during a rainy season after 1 year in the soil.
Seedlings are very susceptible to drought during the first 2 to 3 months
following germination.  During a 9-year study in Arizona, 1.6 percent of
all seedlings that germinated survived [105].

Recruitment of yellow paloverde is very slow.  Additions as low as two
individuals over 30 years or longer have been recorded [22,79].

Herbivory limits yellow paloverde distribution [45].  Bruchid beetles
are seed predators of yellow paloverde [47].  Heteromyid rodents rapidly
cache yellow paloverde seeds.  The cached seeds occasionally germinate
[47,95].

Initial distributions of yellow paloverde seedlings are random.
However, after 1 year, a greater proportion of seedlings in open spaces
were consumed by rabbits and hares than seedlings beneath triangle
bursage.  Recruitment patterns of yellow paloverde show significantly
(P<0.001) positive associations with mature triangle bursage and white
bursage (Ambrosia dumosa) [45,46].  Because yellow paloverde outlives
triangle bursage, large mature yellow paloverde have no association with
triangle bursage [46].

Unpredictable water availability causes low, erratic seedling
establishment [12].  Mature yellow paloverde maintain deep root contact
with wet soil [73,105].  Yellow paloverde self prunes; large branches
die during drought [3,105].  Young plants usually survive drought once
they drop branches which occurs at variable ages [77,105].  Death of
mature yellow paloverde due to drought and subsequent desiccation is
uncommon [45,77,92].  Based on water requirement trials, the water-use
efficiency of yellow paloverde approaches that of perennial grasses
[48].



SITE CHARACTERISTICS : 
Yellow paloverde occurs in arid to semiarid climates with mild winters
and hot summers; precipitation is bimodal, occuring in summer and fall [15,54].

Yellow paloverde is found on lower mountain slopes and alluvial outwash
plains [54,97].  In the most arid parts of its range, yellow paloverde
occasionally occurs in small washes or arroyos [24,59,64,91,97].

Yellow paloverde occurs from 1,000 to 4,000 feet (305-1,219 m) in
elevation throughout its range [19,23,54,97,99].  It grows on very
gradual to steep slopes that may face south or north, but it has been
reported on all aspects [19,24,28,36,60,101].

The sites on which yellow paloverde occurs are well-drained [28].
Surface soils may be 1.6 to 2.8 inches (4-7 cm) thick and subsoils may
be 20 inches (50 cm) thick over caliche [91,101].  The soil temperature
regime is thermic (that is, average soil temperatures are between 59 and
72 degrees Fahrenheit [15-22 deg C]) [51].  Soil textures range from
sand to sandy loam to loam [24].  They may be underlain by clay loam and
clays [23,89].  Parent materials may be basaltic, rhyolitic, granitic,
mixed alluvium, and metamorphic [22,49,59,60,91].

The distribution of yellow paloverde is influenced by the continuum of
soil textures that occurs from upper to lower bajada [5].  It is found
primarily on the upper bajadas [6,7,93,97].  Coarse soil of the upper
bajada has one-half the wilting coefficient (which is an estimate of
plant stress) of the finer soil of the lower bajada [102].  Yellow
paloverde grows infrequently on the middle and lower bajada [97].



SUCCESSIONAL STATUS : 
Facultative Seral Species

Yellow paloverde is a climax species in the Sonoran Desert flora [51,54,61].

Successional sequences have not been completely identified for the
desert scrub communities in which yellow paloverde occurs.  Dominants
such as yellow paloverde are the first to reappear and replace
themselves following disturbance [69].


SEASONAL DEVELOPMENT : 
Yellow paloverde may not flower every year, depending on adequate
moisture availability.  It develops flowers from March to May
[24,31,80,91,100].  Leaf production is erratic [24].  Yellow paloverde
grows drought-deciduous leaves two or more times during the year
following summer and winter rains [77,91].

Related categories for Species: Cercidium microphyllum | Yellow Paloverde