BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Larix lyallii | Alpine Larch 



GENERAL BOTANICAL CHARACTERISTICS : 
Alpine larch is an intolerant, native, deciduous, coniferous tree
[2,13].  Dominant alpine larch usually live 400 to 500 years, but many
trees reach 700 years, and the oldest individuals may live up to 1,000
years [1].  Alpine larch generally has one erect bole, with a braided
stem.  It rarely grows as krummholz because its leaves are deciduous and
its buds are woody and protected [2,18].  Young alpine larch have very
flexible boles, which allow them to occupy snowslide and snow creep
sites [3].  As a high-elevation species, it averages 40 to 50 feet
(12-15 m) in height and 12 to 24 inches (30-60 cm) in d.b.h. on
north-facing slopes.  The largest recorded alpine larch, found in the
Cascade range of Washington, is 95 feet (29 m) tall and 79 inches (201
cm) d.b.h.

Alpine larch produces a coating of white tomentum on its growing shoots.
This 'wool' remains present for at least 1 year and is believed to
decrease water loss from these shoots by increasing the boundary layer
[25].  The leaves are grouped into clusters of 30 to 40 rigid needles,
borne on short, light bluish-green spurs, 1 to 2 inches (2-4 cm) long.
The bark is thin (generally less than 1 inch), initially smooth,
becoming more deeply furrowed with age.  Cones are reddish-yellow to
purple-green and 1 to 2 inches (3-5 cm) long.  The bracts are much
longer than the cone scales [22].  Alpine larch trees are generally
deeply rooted on poor soils.  They are well anchored by a large taproot
and long, continuous lateral roots [3].


RAUNKIAER LIFE FORM : 
   Phanerophyte (mesophanerophyte)
   Phanerophyte (microphanerophyte)
   Therophyte


REGENERATION PROCESSES : 
Flowering and fruiting:  Alpine larch can begin producing cones when
they are 100 years old, but generally do not produce seed in quantity
until they reach 200 years of age [3].  Alpine larch are monoecious.
Pollen is wind-dispersed from the male strobili in June, and by
September, small purplish cones 1.5 to 2.0 inches (4-5 cm) long emerge.
Low cone production can be attributed to late season frost damage.
Other factors limiting fertilization, pollination, and seed maturation
are unknown [2].

Seed production and dissemination:  Large seed crops are infrequent,
occurring only 1 year out of 10 in Montana.  Seeds are winged and are
usually wind-disseminated in September.  Snowslides have been known to
transport seeds to lower elevations [7].  Cleaned seed number between
105,000 and 163,000 per pound (231-359 500/kg).  Seed destruction by
fungi and larvae are discussed under management considerations.

Seedling establishment:  Studies have shown that without seed
scarification, germination rates are poor.  Dry winds and high
temperatures on southern slopes probably contribute to poor germination
[3].  Soaking seeds for 24 hours in 3 percent hydrogen peroxide solution
can improve seed germination [3,26].  Alpine larch seedlings generally
have five cotyledons, although four or six may appear.  They are narrow,
pointed, and 0.4 to 0.6 inch (1.0-1.5 cm) long.  Germination is epigeal.
Successful germination takes place mostly on moist mineral soil surfaces
on northern aspects.  Richards [25], however, found that height and
diameter growth for young alpine larch was 1.5 times greater on southern
exposures than on northern.  Seeds of alpine larch germinate in July,
soon after snowmelt; they require full light and low temperatures for
germination [2].

For the first 20 to 25 years, growth is typically very slow.  This
strategy allows for extensive establishment of the root system and
decreases the probably of top-kill from windthrow or heavy snowpack [2].
Alpine larch apparently become deeply rooted; thus, soil moisture near
the surface seems to have no influence on their growth [3].  Seedlings
16 to 25 years old and only 8 to 16 inches (20-40 cm) tall had taproots
penetrating 16 to 24 inches (20-40 cm) and laterals 8 to 24 inches
(20-60 cm) beneath the surface [25].  Alpine larch seedlings and
saplings up to 3 or 4 feet (1.00-1.25 m) tall exhibit evergreen basal
limbs.  This foliage lasts for two summers and helps establish alpine
larch on severe sites [3].

Hybridization is known to occur between alpine larch and western larch
[17].  Areas most likely to support hybrid populations are those that
have experienced natural disturbances, such as snow or rock slides.  The
creation of such microsites may allow these species to intermingle
because of their varying successional adaptabilities [17].

Vegetative reproduction:  Alpine larch does not reproduce from sprouts.
Layering has been known to occur only in a few severely stunted trees or
krummholz [3].


SITE CHARACTERISTICS : 
Climate:  Alpine larch is most commonly found in very cold, moist, high
altitude sites.  Altitudinal limits are approximately 5,800 to 9,900
feet (1,770-3,010 m) [3,16].  The mean temperatures are below freezing
for 6 months [2].  Mean annual precipitation on most alpine larch sites
is between 32 and 75 inches (800 and 1,900 mm), occurring principally in
the form of snow and sleet.  Periods of drought do occur in late summer
but have minor effects on tree vigor.  Violent winds are very common,
often reaching hurricane velocity of 73 miles per hour (117 km/h).

Soils:  Alpine larch commonly grows on slopes covered with granite or
quartzite talus, not previously occupied by vascular plants.  This tree
will also establish itself in cracks between big boulders [2].  Soil
development on alpine larch sites is extremely poor due to low
temperatures and short growing seasons, which retard microbial and
chemical activity [2,3].  The rocky shallow soils are generally very
gravelly loams, ranging in pH from 3.9 to 5.7 [24].  General
classification of apline larch soils are in fragmental, and loamy
skeletal families within the order Entisols (cryorthents) [27].


SUCCESSIONAL STATUS : 
Alpine larch is an intolerant seral species that will decrease when
shaded by more shade-tolerant conifers [11].  This long-lived dominant
often forms pure stands 500 to 1,000 feet (150-300 m) above the
elevational limits of other conifers.  Alpine larch is generally
classified as an associate species within the whitebark pine, Engelmann
spruce, subalpine fir, and mountain hemlock (Tsuga mertensiana) habitat
types.  In higher elevation sites, alpine larch is classified under the
alpine larch/subalpine fir hts; while in lower elevation sites, it is
categorized more broadly into the subalpine fir/smooth woodrush hts
[2,23].

Alpine larch can be thought of as a pioneer species, establishing itself
on rocky surfaces.  It also proliferates after fire, avalanche, or other
site disturbances.  On some occasions, alpine larch will regenerate on
burned areas within the subalpine fir zone, 330 to 490 feet (100-150 m)
below its usual elevational limits [2].  This regenerative trend is more
dominant on northern exposures and at high elevations [3].  At the
highest timberline elevations, alpine larch fills a vacant niche
representing the potential climax.  Its ability to grow at higher
elevations than other conifers relates to its superior resistance to
winter dessication [2].


SEASONAL DEVELOPMENT : 
The growing season for alpine larch lasts approximately 90 days.  Bud
development is triggered by rising mean air temperature to about 39
degrees Fahrenheit (4 deg C) and can be normally expected to begin the
end of May.  Shoot growth occurs mostly in July and progresses rapidly.
The height growth of a small alpine larch will average approximately 0.6
inch (1.5 cm) a year during the first 25 years.  Leaf fall and dormancy
are controlled by photoperiod.  Late summer drought, however, has been
shown to induce early yellowing [3].  Alpine larch far outlives its
associated conifer species and usually dies as a result of being
windblown after pronounced heart rot.  If lower limbs remain on the
stump, the tree can remain alive for many more decades [3].

Related categories for Species: Larix lyallii | Alpine Larch