BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Pinus contorta var. latifolia | Rocky Mountain Lodgepole Pine 



GENERAL BOTANICAL CHARACTERISTICS : 
Rocky Mountain lodgepole pine is a small- to medium-sized, coniferous,
evergreen tree.  Mature tree heights range from 50 to 100 feet (15-30 m)
and bole diameters occasionally reach 24 inches (61 cm) [16,40].  Mature
size varies regionally.  In much of the Rocky Mountains, 140-year-old
trees are commonly 60 to 80 feet (18-24 m) tall and 7 to 13 inches
(18-33 cm) d.b.h.  In the Blue Mountains of Oregon, 12-inch (30 cm)
d.b.h. trees are 75 feet (23 m) tall at age 100 years [51].  Mature
Rocky Mountain lodgepole pine have remarkably straight, branch-free
boles and small, open crowns on the upper 25 to 60 percent of the tree
[52].  The trees are short-lived.  Two-hundred-year-old trees are rare,
except around Yellowstone National Park, where pure stands contain 300-
to 400-year-old trees [52].

Growth is greatly affected by stand stocking.  In British Columbia and
Montana, tree size in 90-year-old stands varied under different stand
densities as follows [52]:

   location                     density                 avg. d.b.h.

British Columbia        576 stems/acre (1,423/ha)     9 inches (23 cm)
British Columbia      6,750 stems/acre (16,700/ha)    3 inches (7.5 cm)
Montana                 500 stems/acre (1,235/ha)     7.5 inches (19 cm)
Montana               2,500 stems/acre (6,175/ha)     3.6 inches (9 cm)

With extreme overstocking, growth is stagnated and "dog-hair" stands
develop.  In one 70-year-old stand with 100,000 stems/acre (247,000/ha),
trees averaged only 4 feet (1.2 m) in height and less than 1 inch (2.5
cm) in diameter at ground level [51].

Rocky Mountain lodgepole pine has sharp-pointed, 1- to 3-inch-long
(2.5-7.5 cm), yellowish-green needles in fascicles of two [40].  The
bark is thin (less than 0.5 inch [1.2 cm]), light-colored, and scaly,
except for low-elevation plants in northern Idaho and southern British
Columbia which may have thicker, deeply fissured, black bark [16,40].
The root system is highly variable, and may vary among individuals at a
single location from very shallow to quite deep [52].  Individual trees
may have serotinous or nonserotinous cones.  Cone serotiny is discussed
further under REGENERATION PROCESS.


RAUNKIAER LIFE FORM : 
   Undisturbed State:  Phanerophyte (mesophanerophyte)
   Burned or Clipped State:  Therophyte


REGENERATION PROCESSES : 
Seed and seed production:  Lodgepole pine seeds are among the smallest
in the genus Pinus, averaging 94,000 per pound (207,000/kg) [51].  Seed
production begins at an early age.  Five- to ten-year-old trees
typically bear cones.  Seed production is quite regular.  Good seed
crops are produced at 1- to 3-year-intervals with light crops
intervening [52].

Cone serotiny:  Rocky Mountain lodgepole pine produces serotinous cones
which do not open at maturity because they are sealed shut by a resinous
bond between the cone scales.  These cones remain on the tree for years
and require temperatures between 113 and 140 degrees F (45-60 C) to melt
the resin and release the seed [51].  In nature, temperatures of this
magnitude within a tree's crown are generated only by forest fires.

Individual trees may have serotinous cones, nonserotinous cones, or both
[52].  The percentage of trees in a stand bearing serotinous cones
varies greatly by region and elevation, and with stand age and fire
history.  Young trees produce open cones.  The serotinous cone trait is
not exhibited until trees are 20 to 30 years old [48].  In the Canadian
Rockies, typically 80 to 90 percent of lodgepole pine trees bear
serotinous cones [52].  In eastern Oregon, serotinous cones are uncommon
[51].  In the U.S. Rockies, cone serotiny is quite variable.  Lotan [48]
summarized lodgepole pine serotiny by habitat type for numerous National
Forests of the northern and central Rocky Mountains.  The percentage of
trees bearing serotinous cones in a given stand ranged from 0 to 85
percent and averaged less than 50 percent.  On some forests, cone
serotiny increased with increasing elevation.  On the Colville National
Forest in Washington, for example, about 10 percent of lodgepole pine
trees in low-elevation Douglas-fir habitats had serotinous cones,
compared with 82 percent in high-elevation subalpine fir habitat types.
However, on the Deerlodge National Forest, Montana, cone serotiny varied
between 28 and 47 percent and did not change with elevation.  Type of
stand disturbance also influences cone serotiny.  Stands initiated from
high-intensity crown fires (a process which selects for the closed-cone
trait) have a higher percentage of serotinous trees than stands which
are initiated from nonfire related disturbances [61].  Near West
Yellowstone, Montana, 58 percent of lodgepole pine trees in an
even-aged, fire-origin stand had serotinous cones, while only 38 percent
of the trees in an adjacent uneven-aged stand had serotinous cones [49].

Seedfall and dispersal:  Nonserotinous cones open shortly after
ripening.  Most of this seed is shed in September and October, but small
amounts fall throughout the winter and spring [52].  The winged seeds
are dispersed by gravity and wind.  Nearly all fall within 200 feet (60
m) of the source [16].  In stands with a high proportion of serotinous
trees, annual seedfall is small.  In lodgepole pine stands in Alberta
and Montana, annual seedfall was 10,100 to 28,700 per acre
(25,000-71,000/ha) and 17,400 per acre (43,000/ha) respectively [16].

Seed viability, germination, and seedling establishment:  Seeds remain
viable in closed cones for years.  However, once released, few remain
viable for more than 1 year [50].  Seed soundness is relatively high,
which is attributed to lodgepole pine's relative freedom from cone and
seed insects.  Seed soundness was 75 to 79 percent in southeastern
Oregon, and 65 to 88 percent in Colorado [16].  Germinative capacity is
also high, ranging from 65 to 90 percent under laboratory conditions
[52].  Germination is poor when daytime soil temperatures are below 60
degrees F (15 deg C) and is optimal when daytime soil temperatures range
between 70 and 81 degrees F (21-27 C) [52].  In nature, most germination
occurs within a few weeks of snowmelt, when soils are moist and
temperatures favorable.  Germination and seedling survival are best on
mineral soil.  Duff and litter are generally poor lodgepole pine
seedbeds because they dry out quickly.  Seeds may germinate on duff, but
shallow-rooted seedlings growing here commonly die from drought [51].
Lodgepole pine seedlings are poor competitors.  Establishment is greatly
reduced where grasses are plentiful [52].


SITE CHARACTERISTICS : 
Rocky Mountain lodgepole pine grows across a wide range of environments
in montane and subalpine forests of the West.  With a broad range of
moisture and temperature tolerances, it occupies forests spanning a
range of envirnomental conditions from relatively low-elevation, warm
and dry forests to relatively high-elevation, cold and moist forests
[66].  Elevational ranges for four Rocky Mountain states are as follows
[20,36,56,67]:

    from 6,000 to 11,000 feet (1,830-3,350 m) in Colorado
         4,000 to 7,500 feet (1,220-2,290 m) in Montana
         6,800 to 9,100 feet (2,070-2,775 m) in Utah
         6,560 to 10,500 feet (2,000-3,200 m) in Wyoming

Soils:  Lodgepole pine grows on a wide variety soils but grows best on
moist, medium-textured soils derived from granitic, shale, or
coarse-grained lava parent materials [10,52].  It rarely grows on soils
derived from limestone, except in Canada, where extensive stands occur
on calcareous glacial tills [52].  It is often the only tree that grows
on very infertile soils, which allows it to attain climax [see
SUCCESSIONAL STATUS].

Associated vegetation:  Principal tree associates are indicated under
SAF cover types.  Because of its tolerance of a wide range of
environmental conditions, lodgepole pine grows in association with many
understory species.  The most common understroy associates include
pinegrass (Calamagrostis rubescens), elk sedge (Carex geyeri), Ross
sedge (C. rossii), pachystima (Pachystima myrsinites), twinflower
(Linnaea borealis), beargrass (Xerophyllum tenax), huckleberry or
whortleberry (Vaccinium spp.), serviceberry (Amelanchier alnifolia),
oceanspray (Holodiscus discolor), bitter cherry (Prunus emarginata),
buffaloberry (Shepherdia canadensis), curlleaf mountain-mahogany
(Cercocarpus ledifolius), bitterbrush (Purshia tridentata), and juniper
(Juniperus spp.) [34,67,79].  An association between lodgepole pine and
Vaccinium is especially common, and thrives in cool, moist sites on
infertile, granitic soils [52].


SUCCESSIONAL STATUS : 
Lodgepole pine is an intolerant, seral species throughout the northern
Cascades and much of the Rocky Mountains.  It possesses several
attributes that allow it to pioneer burned-over areas aggressively: (1)
serotinous cones that contain a large seed reserve which is released by
fire; (2) regular and abundant seed production; (3) small seeds that
disperse well; (4) rapid juvenile growth; and (5) adaptability to a wide
variety of sites [16,49].  Most of the extensive lodgepole forests of
the Rocky Mountains are seral and of fire origin.  These stands are
typically even-aged, establishing within 10 to 20 years after fire [86].
Lodgepole pine cannot reproduce in the shade of its own canopy.  Without
another fire, lodgepole stands begin to breakup between 100 and 200
years of age and are eventually replaced by shade-tolerant conifer
associates [17,23,51].  These is most commonly subalpine fir and
Engelmann spruce (Picea engelmannii) at upper elevations, and
Douglas-fir at lower elevations.  Other tolerant associates that may
replace lodgepole pine include grand fir (Abies grandis), white fir (A.
concolor), western redcedar (Thuja plicata), western hemlock (Tsuga
heterophylla), mountain hemlock (T. mertensiana), and ponderosa pine
(Pinus ponderosa) [86].

Under certain situations, lodgepole forests can be persistent or climax.
This occurs on sites where tolerant conifers are unable to grow and thus
lodgepole pine remains as the dominant tree.  Factors that allow
lodgepole pine to be the exclusive tree on a site include [12,67]: (1)
frequent, widespread, stand-replacing wildfires that eliminate the seed
source of shade-tolerant competitors (prolonged seral stages), (2)
frequent, light ground fires that remove tolerant competitors (prolonged
seral stages), (3) exclusively dense lodgepole pine stands that
competitively exclude the regeneration of shade-tolerant competitors
(prolonged seral stages), and (4) sites that are environmentally
unsuitable for the establishment of other conifers (climax lodgepole
stands).

Topoedaphic conditions that exclude other conifers and allow lodgepole
forests to become climax are found on sites having gentle terrain,
droughty soils, and frequent summer frosts [80].  Edaphic conditions
alone, such as infertile soils, may also exclude other conifers [52f].
For example, extensive climax lodgepole forests occur in Yellowstone
National Park on obsidian sands [75].  In climax lodgepole forests, a
high percentage of the trees produce nonserotinous cones [36,37].
Regeneration occurs through gap-phase replacement resulting in
uneven-aged stands [86].  In Yellowstone, the overstory canopy is
apparently open enough for sufficient light to reach the forest floor,
permitting understory pine to survive and eventually replace the
overstory [18].


SEASONAL DEVELOPMENT : 
Lodgepole pine flowering occurs in the spring, but fertilization does
not occur until approximately 13 months after pollination.  After
fertilization, cones and seeds mature rapidly over the summer and are
mature by August or September.  Cone maturity is indicated by a color
change from purple-green to light-brown.  Nonserotinous cones disperse
seeds shortly after ripening.  Most seeds are shed in September and
October, but small amounts fall throughout the winter and spring [52].

In northern Idaho, western Montana, and Yellowstone National Park,
phenological events proceed as follows [76]:  

          east of Continental Divide     west of Continental Divide 
         (Montana and Yellowstone NP)   (northern Idaho & western MT) 

             date of occurrence                date of occurrence
         ---------------------------    -----------------------------
         earliest   latest   average    earliest   latest   average

bark     March 18   May 27   May 14     March 12   May 18   April 26
 slips
shoots   March 18   July 21  May 16     March 31   June 13  May 4
 start 
buds     March 18   June 28  May 30     March 27   June 25  May 17
 burst
pollen   May 17     July 14  June 17    May 1      June 23  June 6
 starts
pollen   June 1     July 27  July 3     May 2      July 12  June 19
 ends
shoots   April 6    Sept 18  July 22    May 31     Sept 17  July 27
 end
bark     July 11    Oct 1    Aug 18     June 2     Oct 2    Aug 24
 sticks
winter   June 6     Sept 19  Aug 3      May 31     Oct 10   Aug 14
 buds formed
cones    July 20    Sept 25  Aug 19     May 26     Sept 18  July 29
 full size
cones    July 18    Oct 31   Sept 3     Aug 8      Oct 7    Sept 7
 open

Phenological events proceed as follows at Kananaskis Provincial Park,
Alberta [78]:

     event               earliest date    latest date    avg. date 

pollen shed begins         May 7             July 3       June 14
pollen shed ends           May 27            July 25      July 1
buds bursting              April 17          May 28       May 10
leaves fully flushed       May 31            July 16      June 13
diameter growth begins     April 21          June 6       May 15
diameter growth ends       June 22           Aug 18       July 24
height growth begins       April 15          May 27       May 2
height growth ends         July 30           Aug 28       Aug 13

Related categories for Species: Pinus contorta var. latifolia | Rocky Mountain Lodgepole Pine