BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Cercocarpus montanus | True Mountain-Mahogany 



GENERAL BOTANICAL CHARACTERISTICS : 
True mountain-mahogany is a native, xerophytic, deciduous shrub or small
tree growing up to 19.8 feet (6 m) tall [6,15,26,29].  Leaves are
simple, alternate, lanceolate to roundish, and 0.28 to 2.4 inches (0.7-6
cm) long [40].  Flowers are borne solitarily or in fascicles on short
spur branchlets [29].  Achenes retain their long (up to 4 inches [10
cm]), twisted, plumose styles [6,29].

The stout, lateral roots of true mountain-mahogany arise from a large
root crown.  In alluvial soils, they descend downward to depths of 3.3
feet (1 m) or more.  In shallow soils underlain by tuff, they penetrate
to the depth of the bedrock, grow at right angles until encountering a
crack, and descend downward once again.  Average root depth for true
mountain-mahogany in north-central New Mexico was 3.7 feet (1.13 m)
[67].  Near Colorado Springs, Colorado, true mountain-mahogany roots
reached maximum depths between 4 and 5.6 feet (1.2-1.7 m) on residual
loamy soils [5].  True mountain-mahogany roots may have associations of
nitrogen-fixing endomycorrhizae [56].

True mountain-mahogany is probably long-lived.  In the Uintah Basin of
Utah, some true mountain-mahogany was 54 years old [19].


RAUNKIAER LIFE FORM : 
   Phanerophyte


REGENERATION PROCESSES : 
True mountain-mahogany reproduces vegetatively and sexually.  True
mountain-mahogany sprouts from the root crown following disturbance
[13,15].  In favorable years, true mountain-mahogany produces a good
crop of seedlings [48]; however, seedling establishment can be very
sporadic.  True mountain-mahogany did not reproduce during a 10-year
period from 1965 to 1975 on a northeast-facing slope in Chadron,
Nebraska [69].  Stanton [48] suggested that poor seedling establishment
may be caused by drought or frost.  Woodmansee [71] found that
relatively mesic habitats were critical for true mountain-mahogany
seedling success in New Mexico.  Establishment was dependent on abundant
sheltering and shading and the presence of litter.  Germination occurred
under or near mature true mountain-mahogany.

The germination requirements of true mountain-mahogany may vary with
site climatic factors.  Seeds collected from Utah and Colorado varied in
their chilling requirements; however, true mountain-mahogany probably
does not require extremely long periods of chilling for germination
[27].  Scarifying seeds from a Wyoming collection did not result in
increased germination.  Both vernalization and soaking seeds in
distilled water did increase germination [9].  Monsen and Christenson
[32] recommended a long stratification period.  Smith [46] recommended
after-ripening true mountain-mahogany seeds by storing them at room
temperature for 5 months, dry-storing them for 6 weeks at 41 degrees
Fahrenheit (5 deg C), and wet-prechilling the seeds for 2 to 3 weeks.
Day and night temperatures should alternate between 86 and 68 degrees
Fahrenheit (20.0/30.0 deg C).  Differences in size among seed
collections from northern New Mexico did not explain differences in
germination rates; collections containing mostly large seeds did not
exhibit a greater average germination rate than those with a fewer large
seeds and more small seeds [37].

True mountain-mahogany seeds are wind dispersed [7].  The pointed basal
end of the achene and the corkscrew-like tail enable it to penetrate the
ground [26].


SITE CHARACTERISTICS : 
True mountain-mahogany commonly grows on plains, foothills, moderately
steep slopes, ridges, and bluffs [9,15,46,48].  Its occurrence is not
usually related to a particular parent material [9], but in the Black
Hills, true mountain-mahogany grows only on limestone formations [53].
True mountain-mahogany commonly grows in coarse, shallow, well-drained
residual soils on sunny sites [9,48], and it sometimes grows in the
moist, fertile, relatively deep soil of canyon bottoms [6,48].  The
average pH at sites dominated by true mountain-mahogany in Utah was 7.7
[66].

True mountain-mahogany distribution is dependent on moisture
availability [70].  In Utah true mountain-mahogany communities on
south-facing slopes always occur at higher elevations than those on
north-facing slopes [3,70].  In central and western Colorado, where true
mountain-mahogany occurs in mountain shrub communities from 4,000 to
10,000 feet (1,200-3,000 m) elevation, annual precipitation averages
from 10 to 20 inches (2,540-5,080 mm) [46].  In the Laramie Basin,
Wyoming, true mountain-mahogany stands grow at 7,000 to 8,000 feet
(2,100-2,400 m) elevation, and the average annual precipitation is 10 to
17 inches (2,540-4,318 mm).  Temperatures at Laramie may range from -47
degrees Fahrenheit (-43.8 deg C) in winter to 97 degrees Fahrenheit
(36.1 deg C) in summer [9].

Dittberner and Olson [17] list elevations for true mountain-mahogany as
follows:
	
	Colorado	4,000 to 10,000 feet (1,220-3,049 m)  
	Utah		5,000 to 7,000 feet (1,524-2,134 m)
	Wyoming	        4,400 to 8,500 feet (1,341-2,591 m) 


SUCCESSIONAL STATUS : 
True mountain-mahogany is somewhat shade tolerant.  It is able to grow
in open ponderosa pine and Douglas-fir stands; however, it occurs most
often and grows more vigorously on sites without forest canopy.

The successional role of true mountain-mahogany may vary with community
type.  In north-central Utah true mountain-mahogany communities on xeric
sites are more likely to persist and those on mesic sites are more
likely to be seral [70].  In central Utah Anderson [3] found evidence
indicating succession of true mountain-mahogany stands towards mountain
shrub communities dominated by other species.  Greenwood and Brotherson
[66] observed the establishment of pinyon and juniper in true
mountain-mahogany communities in Utah.  In 11 out of 20 sites where true
mountain-mahogany was the dominant species growing in shallow soil
within slickrock areas, pinyon seedlings grew beneath true
mountain-mahogany shrubs.  The deeper soil and modified habitat around
true mountain-mahogany apparently provided a route for pinyon
establishment.  Juniper seedlings were also present.

In the Black Hills, climax mountain shrub communities dominated by true
mountain-mahogany occur near ponderosa pine communities.  In the
ponderosa pine communities, succession after fire includes a stage of
true mountain-mahogany that may be shaded out by the overstory canopy of
ponderosa pine.  However, true mountain-mahogany is rarely eliminated
from the community.  Some stands are ecotonal between ponderosa pine and
true mountain-mahogany and may remain so indefinitely [23].



SEASONAL DEVELOPMENT : 
The seasonal development of true mountain-mahogany varies by region and
elevation.  In Utah flowering varies from mid-May to late June and fruit
ripens from late July to mid-September [6].  In Idaho true
mountain-mahogany fruits from August to October [48].  Phenological data
from two elevations on the Wasatch Plateau in Utah are presented below
[12]:

Phenological Event              Elevation               Elevation
                            7,480 ft (2,280 m)      7,890 ft (2,405 m)

Flower buds bursting            May 23                  June 2
Leaf buds bursting              April 30                May 3
In full leaf                    May 28          	June 5
In full bloom                   May 28                  June 7
Fruit all ripe                  July 23                 August 2
Fruit all dropped               August 11               August 3
Leaves all dropped              October 14              October 19

Related categories for Species: Cercocarpus montanus | True Mountain-Mahogany