''Pinus albicaulis'', known by the common names whitebark pine, white bark pine, white pine, pitch pine, scrub pine, and creeping pine, is a
conifer tree native to the mountains of the western United States and Canada, specifically
subalpine
Montane ecosystems are found on the slopes of mountains. The alpine climate in these regions strongly affects the ecosystem because temperatures fall as elevation increases, causing the ecosystem to stratify. This stratification is a crucial f ...
areas of the
Sierra Nevada
The Sierra Nevada () is a mountain range in the Western United States, between the Central Valley of California and the Great Basin. The vast majority of the range lies in the state of California, although the Carson Range spur lies primarily ...
,
Cascade Range
The Cascade Range or Cascades is a major mountain range of western North America, extending from southern British Columbia through Washington and Oregon to Northern California. It includes both non-volcanic mountains, such as the North Cascades, ...
,
Pacific Coast Ranges
The Pacific Coast Ranges (officially gazetted as the Pacific Mountain System in the United States) are the series of mountain ranges that stretch along the West Coast of North America from Alaska south to Northern and Central Mexico. Although the ...
, and
Rocky Mountains
The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in straight-line distance from the northernmost part of western Canada, to New Mexico in ...
. It shares the common name "creeping pine" with
several other plants.
The whitebark pine is typically the highest-elevation
pine tree found in these mountain ranges and often marks the
tree line. Thus, it is often found as ''
krummholz'', trees growing close to the ground that have been dwarfed by exposure. In more favorable conditions, the trees may grow to in height.
Identification
Whitebark pine is a member of the
white pine
''Pinus'', the pines, is a genus of approximately 111 extant tree and shrub species. The genus is currently split into two subgenera: subgenus ''Pinus'' (hard pines), and subgenus ''Strobus'' (soft pines). Each of the subgenera have been furth ...
group, the ''
Pinus
A pine is any conifer tree or shrub in the genus ''Pinus'' () of the family (biology), family Pinaceae. ''Pinus'' is the sole genus in the subfamily Pinoideae. The World Flora Online created by the Royal Botanic Gardens, Kew and Missouri Botanic ...
'' subgenus ''
Strobus'', and the section ''
Strobus''; like all members of this group, the
leaves
A leaf ( : leaves) is any of the principal appendages of a vascular plant stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, ste ...
(needles) are in
fascicles (bundles) of five
with a
deciduous sheath. This distinguishes whitebark pine and its relatives from the
lodgepole pine
''Pinus contorta'', with the common names lodgepole pine and shore pine, and also known as twisted pine, and contorta pine, is a common tree in western North America. It is common near the ocean shore and in dry montane forests to the subalpine ...
(''Pinus contorta''), with two needles per fascicle, as well as the
ponderosa pine (''Pinus ponderosa'') and
Jeffrey pine (''Pinus jeffreyi''), which both have three needles per fascicle; all three of these species also have a persistent sheath at the base of each fascicle. Whitebark pine owes its name to the light gray bark of its young specimens.
Distinguishing whitebark pine (''Pinus albicaulis''), from the related
limber pine (''Pinus flexilis''), also a member of the white pine group, is much more difficult, and usually requires seed or pollen
cones
A cone is a three-dimensional geometric shape that tapers smoothly from a flat base (frequently, though not necessarily, circular) to a point called the apex or vertex.
A cone is formed by a set of line segments, half-lines, or lines con ...
. In ''Pinus albicaulis'', the seed-bearing female cones are long, dark purple when immature,
and do not open on drying, but the scales easily break when they are removed by the
Clark's nutcracker
Clark's nutcracker (''Nucifraga columbiana''), sometimes referred to as Clark's crow or woodpecker crow, is a passerine bird in the family Corvidae, native to the mountains of western North America. The nutcracker is an omnivore, but subsists mai ...
to harvest the seeds; rarely are there intact old cones in the litter beneath the trees. Its pollen cones are scarlet.
In ''Pinus flexilis'', the cones are long, green when immature, and open to release the seeds; the scales are not fragile. Their pollen cones are yellow, and there are usually intact old cones found beneath them.
Whitebark pine can also be hard to distinguish from the
western white pine (''Pinus monticola'') in the absence of cones. However, whitebark pine needles are yellow-green
and entire (smooth when rubbed gently in either direction), whereas western white pine needles are silvery green
and finely serrated (feeling rough when rubbed gently from tip to base). Whitebark pine needles are also usually shorter, long,
though still overlapping in size with the larger needles of the western white pine.
Distribution
Whitebark pine (''Pinus albicaulis'') can be found at high elevation in the
Rocky Mountains
The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in straight-line distance from the northernmost part of western Canada, to New Mexico in ...
from central
British Columbia to western
Wyoming.
It occurs in the timberline zone of the
Cascades and coastal ranges from British Columbia to the
Sierra Nevada
The Sierra Nevada () is a mountain range in the Western United States, between the Central Valley of California and the Great Basin. The vast majority of the range lies in the state of California, although the Carson Range spur lies primarily ...
, as well as most high ranges between the Rockies and Cascades, such as the
Blue Mountains.
It is also populous in subalpine forests of Montana and Idaho.
Ecology
The whitebark pine is an important source of food for many
granivorous
Seed predation, often referred to as granivory, is a type of plant-animal interaction in which granivores (seed predators) feed on the seeds of plants as a main or exclusive food source,Hulme, P.E. and Benkman, C.W. (2002) "Granivory", pp. 132 ...
birds and small mammals, including most importantly the
Clark's nutcracker
Clark's nutcracker (''Nucifraga columbiana''), sometimes referred to as Clark's crow or woodpecker crow, is a passerine bird in the family Corvidae, native to the mountains of western North America. The nutcracker is an omnivore, but subsists mai ...
(''Nucifraga columbiana''), the major seed disperser of the pine.
Clark's nutcrackers each cache about 30,000 to 100,000 seeds each year in small, widely scattered caches, usually under of soil or gravelly substrate. Nutcrackers retrieve these seed caches during times of food scarcity and to feed their young. Cache sites selected by nutcrackers are often favorable for germination of seeds and survival of seedlings. Those caches not retrieved by the time the snow melts contribute to forest regeneration. Consequently, whitebark pine often grows in clumps of several trees, originating from a single cache of two to 15 or more seeds.
Other animals also depend upon the whitebark pine.
Douglas squirrel
The Douglas squirrel (''Tamiasciurus douglasii'') is a pine squirrel found in the Pacific Northwest of North America, including the northwestern coastal states of the United States as well as the southwestern coast of British Columbia in Canada ...
s cut down and store whitebark pine cones in their
middens.
Grizzly bear
The grizzly bear (''Ursus arctos horribilis''), also known as the North American brown bear or simply grizzly, is a population or subspecies of the brown bear inhabiting North America.
In addition to the mainland grizzly (''Ursus arctos horr ...
s and
American black bear
The American black bear (''Ursus americanus''), also called simply a black bear or sometimes a baribal, is a medium-sized bear endemic to North America. It is the continent's smallest and most widely distributed bear species. American black bear ...
s often raid squirrel middens for whitebark pine seeds,
an important pre-hibernation food. Squirrels,
northern flickers, and
mountain bluebird
The mountain bluebird (''Sialia currucoides'') is a small migratory thrush that is found in mountainous districts of western North America. It has a light underbelly and black eyes. Adult males have thin bills and are bright turquoise-blue and s ...
s often nest in whitebark pines, and
elk
The elk (''Cervus canadensis''), also known as the wapiti, is one of the largest species within the deer family, Cervidae, and one of the largest terrestrial mammals in its native range of North America and Central and East Asia. The commo ...
and
blue grouse
The genus ''Dendragapus'' contains two closely related species of grouse that have often been treated as a single variable taxon (blue grouse). The two species are the dusky grouse (''Dendragapus obscurus'') and the sooty grouse (''Dendragapus f ...
use whitebark pine communities as summer habitat.
Fallen needles under these trees serve as beds that are used by deer and wild sheep seeking shelter during stormy weather.
Threats
The whitebark pine has been classified as endangered by the
IUCN.
Severe population decline in whitebark pine communities is attributed to various causes, most significantly infection with
white pine blister rust, recent outbreaks of
mountain pine beetle
The mountain pine beetle (''Dendroctonus ponderosae'') is a species of bark beetle native to the forests of western North America from Mexico to central British Columbia. It has a hard black exoskeleton, and measures approximately , about the siz ...
s (2000–2014), disturbances in wildland
fire ecology
Fire ecology is a scientific discipline concerned with natural processes involving fire in an ecosystem and the ecological effects, the interactions between fire and the abiotic and biotic components of an ecosystem, and the role as an ecosystem p ...
(including
fire suppression), forest succession, and climate change. A study in the mid-2000s showed that whitebark pine had declined by 41 percent in the western Cascades due to two primary threats: blister rust and pine beetles.
Whitebark deaths in
North Cascades National Park doubled from 2006 to 2011.
White pine blister rust
Many stands of ''Pinus albicaulis'' across the species' entire natural range are infected with white pine blister rust (''Cronartium ribicola''), a
fungal disease introduced from Europe. In the northern Rocky Mountains of the United States, whitebark pine mortality in some areas exceeds 90 percent, where the disease infests nearly . ''Cronartium ribicola'' occurs in whitebark pine to the northern limits of the species in the coastal ranges of British Columbia and the Canadian Rocky Mountains. The blister rust has also devastated the commercially valuable western white pine in these areas and made serious inroads in limber pine (''Pinus flexilis'') populations as well. Nearly 80 percent of whitebark pines in
Mount Rainier National Park are infected with blister rust.
There is currently no effective method for controlling the spread and effects of blister rust. However, a small number of trees (fewer than 5%) in most populations harbor genetic resistance to blister rust.
Restoration efforts undertaken by the
U.S. Forest Service
The United States Forest Service (USFS) is an agency of the U.S. Department of Agriculture that administers the nation's 154 national forests and 20 national grasslands. The Forest Service manages of land. Major divisions of the agency inc ...
,
Bureau of Land Management
The Bureau of Land Management (BLM) is an agency within the United States Department of the Interior responsible for administering federal lands. Headquartered in Washington DC, and with oversight over , it governs one eighth of the country's l ...
, and
National Park Service in the northern Rocky Mountains involve harvesting cones from potentially and known resistant whitebark pines, growing seedlings, and outplanting seedlings in suitable sites. In
California, where the blister rust is far less severe, whitebark pine is still fairly common in the
High Sierras.
Mountain pine beetle
Unusually large outbreaks of mountain pine beetle (''Dendroctonus ponderosae''), a species of
bark beetle
A bark beetle is the common name for the subfamily of beetles Scolytinae. Previously, this was considered a distinct family (Scolytidae), but is now understood to be a specialized clade of the "true weevil" family (Curculionidae). Although the ...
native to western North America, have also contributed significantly to the widespread destruction of whitebark pine stands. The beetles both lay their eggs and introduce pathogenic fungi into their host trees, which include many other species of pine, and the combination of larval feeding and fungal colonization is typically sufficient to kill old or unhealthy trees. However, the beetles have recently expanded their attacks to younger, healthier trees as well as older trees, and climate change has been implicated as the primary culprit. Since 2000, the climate at high elevations has warmed enough for the beetles to reproduce within whitebark pine, often completing their life cycle within one year and enabling their populations to grow exponentially. Entire forest vistas, like that at Avalanche Ridge near
Yellowstone National Park’s east gate, have become expanses of dead gray whitebarks. Scientists have attributed the recent warming trend to anthropogenic
global warming.
In 2007, the
U.S. Fish and Wildlife Service
The United States Fish and Wildlife Service (USFWS or FWS) is an agency within the United States Department of the Interior dedicated to the management of fish, wildlife, and natural habitats. The mission of the agency is "working with othe ...
estimated that beetles had killed whitebark pines across in the West, while in 2009, beetles were estimated to have killed trees on , the most since record-keeping began.
The pine beetle upsurge has killed nearly 750,000 whitebark pines in the
Greater Yellowstone Ecosystem alone.
Fire suppression
Fire suppression has led to slow population declines over the last century by altering the health and composition dynamics of stands without the fire ecology balancing their habitat and suppressing insect-disease threats. In the absence of low-level wildfire cycles, whitebark pines in these stands are replaced by more shade-tolerant, fire-intolerant species such as
subalpine fir
''Abies lasiocarpa'', the subalpine fir or Rocky Mountain fir, is a western North American fir tree.
Description
''Abies lasiocarpa'' is a medium-sized evergreen conifer with a very narrow conic crown, growing to tall, exceptionally , with a t ...
(''Abies lasiocarpa'') and
Engelmann spruce
''Picea engelmannii'', with the common names Engelmann spruce, white spruce, mountain spruce, and silver spruce, is a species of spruce native to western North America. It is mostly a high-altitude mountain tree but also appears in watered canyon ...
(''Picea engelmannii''). In addition,
senescent and blister rust-infected pine trees are not destroyed by natural periodic ground fires, further diminishing the whitebark pine forest's vitality and survival.
Protective efforts
December 15, 2022, the U.S. Fish and Wildlife Service published its decision to list the whitebark pine as a "threatened" species. The causes for listing are four-fold. White pine blister is "the primary stressor," with mountain pine beetle, altered fire regimes, and "the effects of climate change" also contributing. In June 2012, the Canadian federal government declared whitebark pine endangered in accordance with the
Species at Risk Act
The ''Species at Risk Act'' (SARA) (the ''Act'') is a piece of Canadian federal legislation which became law in Canada on December 12, 2002. It is designed to meet one of Canada's key commitments under the International Convention on Biological D ...
. As such, it is the first federally listed endangered tree in western Canada.
In response to the ongoing decline of the tree throughout its range, the Whitebark Pine Ecosystem Foundation was formed. Their mission is to raise awareness and promote conservation by sponsoring restoration projects, publishing a newsletter called "Nutcracker Notes", and hosting an annual science and management workshop for anyone interested in whitebark pine. This U.S. group collaborates closely with the Whitebark Pine Ecosystem Foundation of Canada.
Uses
Many Native Americans, including the
Salish peoples, have been known to eat the seeds from the cones of this tree.
They were roasted, made into porridge, and mixed with dry berries.
References
Further reading
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{{Authority control
albicaulis
Trees of the Northwestern United States
Trees of the Southwestern United States
Trees of Alberta
Flora of the Cascade Range
Flora of the Rocky Mountains
Flora of the Sierra Nevada (United States)
Natural history of the California Coast Ranges
Endangered flora of the United States
Plants described in 1863
Taxa named by George Engelmann