BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Sorbus sitchensis | Sitka Mountain-Ash 



GENERAL BOTANICAL CHARACTERISTICS : 
Sitka mountain-ash is a native, deciduous shrub 4 to 8 feet (1.2-2.4 m)
tall, or a small tree up to 20 feet (4.5-6.0 m) tall and 6 inches (15
cm) d.b.h.  On rocky alpine sites at higher elevations Sitka
mountain-ash is often only 1 to 2 feet (0.3-0.6 m) tall.  Leaves are
pinnately compound and are 4 to 8 inches (10-20 cm) long with 7 to 11
leaflets.  Sitka mountain-ash bark is thin and smooth.  Flowers are
borne in terminal corymbs with 15 to 60 flowers per head.  Fruits are
small pommes [39].


RAUNKIAER LIFE FORM : 
   Phanerophyte


REGENERATION PROCESSES : 
Sitka mountain-ash mainly propagates by seed [32,38].  Mountain-ashes
(Sorbus spp.) begin producing seed at about 15 years of age and usually
produce a good seed crop every year.  Seeds are mainly dispersed by
birds.  Seedlings are hardy and are not very susceptible to insects or
disease, but may be injured by deer browsing [14].

Cooper [7] reports that American mountain-ash (S. americana), a closely
related species, sprouts from the stump when top-killed.

Propagation:  Cleaned seeds have been stored for 2 to 8 years without
loss of viability.  Seeds sown in the spring require 60 or more days of
previous stratification at 32 to 41 degrees Fahrenheit (0-5 deg C) in
moist sand, moss, soil, or other medium.  Unstratified seed should be
sown in the fall or early winter.  Germination is slower and not as
successful if seeds are not removed from the berries before sowing [14].


SITE CHARACTERISTICS : 
Sitka mountain-ash occurs in dry to moist, well-drained sandy loam or
other soils [38].  In southern and southeastern Alaska, Sitka
mountain-ash is an uncommon to rare forest tree, occurring from sea
level to timberline along the coast [39].  In coastal British Columbia,
Sitka mountain-ash is an indicator of moderately dry to fresh,
nitrogen-poor soils.  It is common but scattered in British Columbia,
where it is found in montane to subalpine, open-canopy coniferous
forests.  Its occurrence there increases with increasing precipitation
and elevation [22].  In the Pacific Northwest, it occurs in mid- to
upper-elevation coniferous forests and forest openings, and is
particularly widespread from 3,000 to 5,000 feet (900-1,515 m) on the
western slope of the Cascade Range [35].  Sitka mountain-ash is found at
elevations from 3,400 to 6,700 feet (1,030-2,030 m) in Montana [9].  In
the Bitterroot Mountains of west-central Montana, it is most often found
in moist, deep soils along creeks or streams [24].


SUCCESSIONAL STATUS : 
Facultative Seral Species

Sitka mountain-ash is shade intolerant and persists in clearings [22].
It is present in many climax forests and plant associations
[2,3,12,15,34,36].

Sitka mountain-ash may inhibit growth of other vegetation [8].


SEASONAL DEVELOPMENT : 
Sitka mountain-ash flowers from June to July.  Fruits ripen from
September to October and persist through late winter [14,39].

Related categories for Species: Sorbus sitchensis | Sitka Mountain-Ash