BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Cercocarpus ledifolius | Curlleaf Mountain-Mahogany 



GENERAL BOTANICAL CHARACTERISTICS : 
Curlleaf mountain-mahogany is a native, xerophytic, evergreen shrub or
small tree growing up to 35 feet (10.6 m) tall and 3 feet (0.9 m) in
diameter [9,33,57].  The thick, tortuous, leaf-scarred branches [37]
arise from a short trunk [33] and form a round or umbrella-shaped crown
[14,33].  Leaves are broadly elliptic to lanceolate, 0.48 to 1 inch
(12-25 mm) long, leathery, somewhat resinous, and curled under at the
margins [64,33,37,57].  Flowers are borne singly or in rows of three in
the leaf axils [37,64].  Achenes retain their long, plumose styles [30].

The roots of curlleaf mountain-mahogany play a key role in its ability
to inhabit water- and nutrient-deficient substrates.  Dealy [66]
suggested that a combination of initial rapid root growth and slow top
growth may help curlleaf mountain-mahogany outcompete its associates.
Average root growth rates of 24 seedlings in a growth chamber were as
follows:

	Average Root Extension		Number of Days
		
	13.6 inches (0.34 m)		      25
	23.2 inches (0.58 m)		      62
	30.4 inches (0.76 m)		      92
	39.2 inches (0.98 m)		     120

The six longest roots reached a mean depth of 3.7 feet (1.13 m).
Curlleaf mountain-mahogany is able to extend its taproot into cracks in
bedrock, tapping into otherwise unavailable water supplies [26].
Curlleaf mountain-mahogany roots form nodules in association with
nitrogen-fixing, filamentous bacteria which increase available soil
nitrogen [33,35,62].  In the San Bernadino Mountains of California, the
soil in limber pine stands associated with curlleaf mountain-mahogany
contained higher nitrogen concentrations than soils beneath similar
stands lacking curlleaf mountain-mahogany [35].
     
Curlleaf mountain-mahogany can be extremely long-lived.  On western and
central Nevada sites, Schultz [49] discovered curlleaf mountain-mahogany
trees that were approximately 1,350 years old.  In Idaho curlleaf
mountain-mahogany plants at least 150 years old were found; older stems
had rotten cores which made accurate aging impossible [47].  The average
age of curlleaf mountain-mahogany on sites in southwestern and central
Montana was only 22 years but ranged from 5 to 85 years [14].



RAUNKIAER LIFE FORM : 
   Phanerophyte


REGENERATION PROCESSES : 
Curlleaf mountain-mahogany reproduces by seed.  Curlleaf
mountain-mahogany can grow vigorously after pruning, but its ability to
sprout after top-kill has been described as weak or non-existent in the
literature [4,5,8].

The minimum fruit-producing age of curlleaf mountain-mahogany is
approximately 15 years [12].  Seed production may be sporadic or cyclic.
Few seeds were found in central and southwest Montana curlleaf
mountain-mahogany stands in 1973, but seed production was high in 1974
[14,75].  Observations of two stands in central Oregon over 12 years
revealed only 3 years of high seed production [66].  High seed
production occurred in different years in the two stands and the seed
production of individual trees varied from year to year.  Wind-drifted
seeds occasionally piled up to 10 inches (25 cm) deep in rocky pockets
under and around the edges of curlleaf mountain-mahogany stands.

Curlleaf mountain-mahogany seeds are primarily wind dispersed [52].  The
pointed basal end of the achene and corkscrew-like tail enable it to
penetrate the ground [30].

Germination requirements for curlleaf mountain-mahogany are not well
understood.  Bradley and others [4] suggested that curlleaf
mountain-mahogany is dependent on fire because it needs mineral soil for
germination.  However, Schultz [49] encountered curlleaf
mountain-mahogany seedlings growing in deep plant litter under curlleaf
mountain-mahogany canopies.  Germination experiments on seed collected
in central Oregon indicated that stratification increased germination
[66].  Incubated seeds having no stratification did not germinate, but
stratification for 170 days at 4 deg C resulted in 98 percent
germination.  Experiments performed on seed collected from sites in
Utah, Idaho, and Nevada demonstrated that the chilling requirements for
curlleaf mountain-mahogany seeds are variable [31].  Curlleaf
mountain-mahogany seed may remain viable for a number of years; in Utah
seeds stored in an open, unheated, uncooled warehouse for 7 years
germinated at a rate of 76 percent [55].

Curlleaf mountain-mahogany seedlings are sensitive to drought, frost,
and browsing [10,47,52].  First-year seedling survival in a curlleaf
mountain-mahogany stand in north-central Idaho averaged only 29 percent
in the very dry summer of 1968.  Winter mortality was also high; the
average survival of seedlings protected from all browsing was 50
percent.  For seedlings protected from big game and rabbits, survival
was 45 percent.  For completely unprotected seedlings, survival was 25
percent [47].


SITE CHARACTERISTICS : 
Curlleaf mountain-mahogany grows on shallow to moderately deep soil at
middle to high elevations on gentle to steep slopes, rock outcrops, and
ridges.  Curlleaf mountain-mahogany commonly occurs on dry, rocky, sandy
soils [8,11,14,26,44], although it sometimes occurs on clay or loam
soils [10,52].  Elevational ranges for curlleaf mountain-mahogany vary
from 2,013 to 4,528 feet (610-1,372 m) in the northern and northwestern
parts of its range to 9,900 feet (3,000 m) or higher in Arizona,
southern Utah, Nevada, and east-central California [10,30].

Precipitation and growing season information for curlleaf
mountain-mahogany stands in Nevada is available.  At Great Basin
National Park in east-central Nevada, annual precipitation is evenly
distributed throughout the year and averages 13.2 inches (330 mm).
Average yearly minimum and maximum temperatures are 17.96 degrees
Fahrenheit (-7.8 deg C) and 85.46 degrees Fahrenheit (29.7 deg C),
respectively [26].  In the Humboldt National Forest, northeastern
Nevada, the growing period is 49 days.  The mean annual soil temperature
is 42.8 degrees Fahrenheit (6 deg C) [27].


SUCCESSIONAL STATUS : 
Curlleaf mountain-mahogany is somewhat shade tolerant.  It is able to
grow in open coniferous forests; however, it occurs most often and grows
most vigorously on sites without forest canopy.  Seedlings establish
under the canopies of mature curlleaf mountain-mahogany, but canopy gaps
are necessary for long-term survival.

The successional role of curlleaf mountain-mahogany varies with
community type.  Mountain brush communities in which curlleaf
mountain-mahogany is either dominant or codominant are generally stable
[7].  Changes in relative abundance of codominant species may occur;
however, succession rates are extremely slow because vegetation changes
depend on soil development which is also slow [10].  In coniferous
forests and mesic mountain brush communities adjacent to forests,
curlleaf mountain-mahogany is a seral species.  Barring major
disturbance such as fire, mature conifer stands develop and eventually
shade out most curlleaf mountain-mahogany [4,5,7,39].

In western and central Nevada communities in which curlleaf mountain
mahogany occurs, large-scale disturbance was infrequent in presettlement
times.  However, evidence of small-scale disturbance from
lightning, low-severity fire, insects, wind, and snow is abundant.
Small disturbances often create canopy gaps in dense stands of curlleaf
mountain-mahogany.  Gaps allow for the release of young curlleaf
mountain-mahogany [49].

In western and central Nevada, Schultz and others [48] observed
self-tolerance in curlleaf mountain-mahogany seedlings.  Seedlings may
establish under mature curlleaf mountain-mahogany where they remain as
suppressed individuals, often dominating the understory, until canopy
gaps release them.  Suppressed plants eventually die; they are probably
replaced by more seedlings.

In mountain brush communities dominated by curlleaf mountain-mahogany,
interspecific competition is minimal and curlleaf mountain-mahogany may
grow large [48].  Over time, however, intraspecific competition may
result in an overall reduction in the biomass production of the
community [50].  As a result of intraspecific competition, many curlleaf
mountain-mahogany communities are dominated by a few very large, mature
individuals.  Younger, smaller curlleaf mountain-mahogany may live as
understory plants for 100 years or more [9].


SEASONAL DEVELOPMENT : 
Annual growth in curlleaf mountain-mahogany stands in Montana begins
with formation of flower buds in April or May [14].  Flowering generally
occurs in May [12,14,64] but may begin as early as April [26] and
sometimes extends into July [12].  Branch elongation and leaf production
occurred in May through July in eastern Nevada [26].  Seeds are
dispersed during late summer (July or August through September) [12,26].

Curlleaf mountain-mahogany phenology at 4,700 feet (1,433 m) near Silver
Lake, Oregon, was described as follows [21]:

        Month           Growth Stage

        mid-April       few buds
        early May       many buds
        mid-May         anthesis
        late June       early milk (seeds are soft and immature)
        early July      dough (seeds have a dough-like consistency)
        mid-July        dough
        mid-August      mature seed

Related categories for Species: Cercocarpus ledifolius | Curlleaf Mountain-Mahogany