Transcript Whitebark pine decline

Fire, birds, bears and trees
Conservation and restoration of
whitebark pine ecosystems
Harsh
Environment
• High elevation
(above 7500 ft)
• Cold, moist
winters with cool
moist summers
• Short growing
season (<60-80
days)
Importance of whitebark pine
Baker Lake, Selway Bitterroot Wilderness Area
• Broad tree crowns act as
snow fences, helping to
slowly release water into
the high mountain streams,
extending the stream flow
to the valleys below into
summer
• Food for wildlife, including
the Clark’s nutcracker and
black and grizzly bears
• Aesthetically pleasing for
humans
Whitebark pine seeds
are important to animals
Clark’s nutcrackers and whitebark
pine co-evolved
• Nutcrackers cache the seeds preferentially in open
and burned areas
• This gives whitebark pine a distinct advantage over
other conifers in regenerating large, burned areas
• Lanner: "the habits of Clark's nutcrackers account
for the distribution, site preference, successional
status, population age structure, and spacing of
whitebark pine".
• Cache seeds 1-3 cm deep
• Each bird can cache as many as 22,000 seeds
each year
Whitebark pine decline
• Whitebark pine has declined
from 34% of potential whitebark
pine habitat historically (~1900)
to 19% currently (~ 1990) in
Idaho and Montana
• Decline due to introduced
disease, fire exclusion and
advancing succession
• Fires allow for mass selection
against the introduced white
pine blister rust
• Whitebark pine is likely to be
sensitive to climate change
Ghost forests
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White pine blister rust
Mountain pine beetle
Fire exclusion
Advancing succession
Reconstructing fire history
We can date fire scars. There
are three fire scars on this
cross-section of a whitebark
pine tree cut from a living tree
in 1988
Sometimes we can map and
date past fires from the age
of trees that grew post-fire
We can also analyze maps
of historical fires
Fire ecology of whitebark pine
• Fires recycle accumulated biomass, recycles
nutrients, rejuvenates vegetation, and maintains the
diversity of landscapes
• WBP is readily killed by fires, but sometimes
survives surface fires
• Fire creates regeneration opportunities
• Clark’s nutcrackers disperse the seeds of whitebark
pine. They prefer to cache them in open and burned
areas -- conditions where whitebark pine thrives.
• In the absence of fire, other trees eventually replace
whitebark pine on most sites
Fire exclusion
• Fires were historically infrequent, and of mixed or
stand-replacing severity
• Large fires historically lasted weeks or months
• Modern fires are usually extinguished at lower
elevations before they spread to whitebark pine
• Subalpine fuels are usually too moist to support
extensive fires until late in the summer during
unusually dry years when fire managers are
unwilling to risk fire spread from drier areas
White pine blister rust
• This Eurasian fungus was introduced to the Pacific
Northwest in 1910
• Whitebark pine is very susceptible, as are all 5needled pines
• It reduces cone and seed production long before it
kills trees
• 3 to 8% of whitebark pine trees are resistant
• Blister rust was found in 59% of the stands sampled
across the Intermountain region, with increasing
incidence and intensity over the last 30 years in the
northern Rockies (Smith and Hoffman 1998).
Human-induced climate change threatens whitebark
• WBP will be lost from Yellowstone National Park
with the warm temperatures and dry summers
predicted with a doubling of the carbon dioxide
content of the atmosphere
• Lightning fires are predicted to occur more
frequently if carbon dioxide content of the
atmosphere doubles
• Fire frequency, extent and severity of fires in
subalpine forests could increase
• The outlook is bleak because of blister rust and
advancing succession
Functionally extinct in some areas
• ~30% of trees are dead and ~70% were infected
with blister rust with an average of 25% crown kill in
and around Glacier National Park
• Moderate to high whitebark pine mortality across
61% of the subalpine forest landscapes in the
600,000-ha Bob Marshall Wilderness area
• In Montana, 42% of all whitebark pine trees on
permanent plots died in the 20 years between 1971
to 1992
Restore natural fire regimes
• Fires recycle accumulated biomass and nutrients,
rejuvenates vegetation, and maintains the diversity
of landscapes
• Fires allow for mass selection of blister-rust
resistant trees
• Using prescribed burning is effective but challenging
because suitable conditions are rare
• Also use wildland fire for resource benefit (“let-burn”
policy)
Challenges
• Harsh, fragile environment
• Long response time
• Most whitebark pine forests are in parks and
wilderness areas
– Subject to fire suppression, may not support wildland fire
use
– Active management, other than wildland fire use, is often
prohibited or discouraged
• Access is often limited