BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Pinus monticola | Western White Pine 



GENERAL BOTANICAL CHARACTERISTICS : 
Western white pine is a native, evergreen, long-lived (400+ years),
monoecious tree [9,11,16,44].  It can reach 200 feet (60 m) in height
and 8 feet (2.4 m) in d.b.h.  The needles, 2 to 4 inches (5-10 cm) long,
are in bundles of five.  The bark on young trees is smooth and grayish
green but on mature trees becomes grayish brown, scaley, and separated
into rectangular plates [16].  The crown is narrow and composed of
regularly spaced branches [1].  In dense stands western white pine
self-prunes well, leaving a long, clean bole [16].

The root system consists of a taproot and lateral roots which can spread
up to 26 feet (8 m).  Most (75 percent) of the lateral roots are in the
upper 24 inches (60 cm) of soil [11].

The male strobili are yellow, and the female strobili are reddish
purple.  Mature female strobili are 5 to 15 inches (12-38 cm) in length
[44].

The early growth of western white pine is not rapid, but it is the
fastest growing sapling and pole-sized tree in the Northern Rockies
[8,13].


RAUNKIAER LIFE FORM : 
   Phanerophyte


REGENERATION PROCESSES : 
Western white pine can begin producing strobili at 7 years of age [11],
but production can be limited by moisture stress and timing.  Moisture
stress in the early summer of the year strobili mature leads to
abortion, while moisture stress in the early summer of the first and
second years prior to strobili emergence causes an increase in the
number of strobili.  Moisture stress in the late summer prior to
strobili emergence causes a decrease in strobili numbers [47].

A good crop of female strobili is about 40 per tree [1].  During fair to
poor crop years cone beetles (Conophthorus spp.), cone moths (Dioryctria
abietivorella and Eucosma rescissorianna), red squirrels, and deer mice
can cause partial or complete crop failures [11].

Seed production requires 3 years from the onset of bud initiation.  Good
seed crops occur every 3 to 4 years.  The mean number of seeds per pound
is 27,000 (59,000/kg).  The seed can be dispersed by wind up to 2,620
feet (800 m) from the parent tree.  Seeds remain viable in the duff for
up to 4 years, but the germination rate decreases.  After 2 years the
rate is 25 percent, and after 4 years the rate is 1 percent.  Western
white pine's seed requires cold moist stratification of 30 to 120 days
to germinate; germination is epigeal [11].  Moisture and soil
temperature are believed to control the onset of germination.  The
perferred germination substrate is mineral soil, but seeds will also
germinate in duff [8,11].

Seedling mortality is quite high in the first year due to snow mold
(Neopeckia coulteri), rodents, late season drought, and elevated soil
temperatures on dry sites [11].  On dry sites seedling establishment is
favored by partial shade, while on moist sites full sunlight favors
establishment [11,15].

Vegetative reproduction:  Western white pine does not naturally
reproduce by sprouting or layering.  However, cuttings from young trees
treated with rooting hormones (indolebutyric acid) have rooted with fair
success [11].  Williams [69] describes the process and considerations
for rooting cuttings from older trees (25 years).  He obtained a mean
success rate of 37 percent.


SITE CHARACTERISTICS : 
Western white pine is restricted to climates characterized by dry
summers and a predominance of winter precipitation [72].  The most
extensive and best stands of western white pine are found in the river
bottoms and less steep lower slopes of the Priest, Coeur d'Alene, St.
Joe, and Clearwater River basins [72].  In British Columbia, western
white pine is a minor species on moderately dry to wet, nutrient-medium
to nutrient-rich sites in the maritime and submaritime climates [23].
Here, western white pine requires sites fairly rich in calcium and
magnesium [25].  However, in the coastal Northwest, western white pine
becomes abundant only on poor sites, where it can outcompete Douglas-fir
(Pseudotsuga menziesii) and other conifers.  It does well on
unproductive, gravelly soils in the Puget Sound area and reportedly
thrives at the edges of bogs on the Olympic Peninsula [1].

Soils:  Western white pine grows on a wide variety of soils within its
range, the majority of which have been classified as Spodosols [11].
Along the West Coast, it attains best development on deep, porous soils,
but it is most common on poor, sandy soils.  In northern Idaho and other
inland sites, it is found on shallow to deep soils, with the surface
layers composed of loess or loessial-like material.  Parent materials
include granite, shist, basalt, and sedimentary rocks.  The pH ranges
from 4.5 to 6.8 with a mean of 5.4 [11].

Elevation and topography:  Western white pine is generally a montane
species, but grows at a wide range of elevations [11,72].  Elevational
ranges vary as follows [11]:

Area                         Feet                   Meters

British Columbia            0 to 1,480              0 to 450
Vancover Island, BC         0 to 3,940              0 to 1,200
California              6,000 to 10,990         1,830 to 3350
Idaho                   1,540 to 5,910            500 to 1,800
Montana                 1,540 to 5,910            500 to 1,800
Oregon                  6,000 to 7,020          1,830 to 2140
Washington                  0 to 6,070              0 to 1,850

Associated species:  In Washington, Oregon, and the Inland Empire,
western white pine grows in communities that are rich in other woody and
herbaceous flora, but in the Sierra Nevada associated vegetation is
usually sparse [11].  In addition to those previously listed under
Distribution and Occurrence, overstory associates include Pacific silver
fir (Abies anabilis), noble fir (A. concolor), whitebark pine (Pinus
albicaulis), foxtail pine (P. balfauriana), limber pine (P. flexilis),
sugar pine (P. lambertiana), Jeffrey pine (P. jeffreyi), quaking aspen
(Populus tremuloides), and paper birch (Betula papyrifera) [11].

Understory associates include Pacific yew (Taxus brevifolia),
huckleberry (Vaccinium spp.), willow (Salix spp.), honeysuckle (Lonicera
spp.), currant, Rocky Mountain maple (Acer glabrum), snowberry
(Symphoricarpus spp.), ocean-spray (Holodiscus discolor), serviceberry
(Amelanchier alnifolia), pachistima (Pachistima myrsinites), sedges
(Carex spp.), pinegrass (Calamagrostis rubescens), false-solomons-seal
(Smilacina), wild ginger (Asarum caudatum), and queencup beadlily [11].


SUCCESSIONAL STATUS : 
Obligate Initial Community Species
Facultative Seral Species

Western white pine is classified as shade intolerant to very intolerant
[24].  It is usually seral to fir (Abies spp.), spruce (Picea spp.), or
hemlock (Tsuga spp.) [5,9].  Stickney [59] classified western white pine
as a colonizer.

Western white pine does not respond favorably after release from 30 to
60 years of suppression [5,6].


SEASONAL DEVELOPMENT : 
Height and diameter growth starts from May to late June depending on
elevation, aspect, and latitude [11].

Strobili buds emerge in June.  The buds are differentiated in July and
August of the year preceding emergence.  Pollen dispersal lasts for a
mean of 8.5 days and usually starts the last week in June.  Time of
flowering varies over a period of 20 days and is strongly controlled by
temperatures during the preceding weeks.  It is delayed for 5 days for
every 1,000 feet (300 m) gain in elevation, and 6 days per degree
Fahrenheit below normal temperatures for May and June.  The female
strobili ripen from August to September of the second year after bud
emergence [11].

The mean phenological development dates for western white pine in
northern Idaho were as follows [53]:

Bark    Shoots  Buds    Pollen  Pollen  Shoots  Winter  Cones   Cones
Slips   Open    Burst   Starts  Ends    End     Buds    Full    Open
                                                Formed  Size    

Apr 28  May 6   May 21  Jun 11  Jun 28  Aug 11  Aug 13  Aug 1   Sep 8 

Related categories for Species: Pinus monticola | Western White Pine