Determining the relationship between whitebark pine stand-level health and seed dispersal by Clark's nutcracker

Material Information

Determining the relationship between whitebark pine stand-level health and seed dispersal by Clark's nutcracker
Barringer, Lauren Elizabeth
Publication Date:
Physical Description:
xi, 82 leaves : ; 28 cm

Thesis/Dissertation Information

Master's ( Master of science)
Degree Grantor:
University of Colorado Denver
Degree Divisions:
Department of Integrative Biology, CU Denver
Degree Disciplines:
Integrative biology


Subjects / Keywords:
Clark's nutcracker ( lcsh )
Whitebark pine -- Diseases and pests ( lcsh )
Whitebark pine -- Seeds -- Dispersal ( lcsh )
bibliography ( marcgt )
theses ( marcgt )
non-fiction ( marcgt )


Includes bibliographical references (leaves 74-82).
General Note:
Department of Integrative Biology
Statement of Responsibility:
by Lauren Elizabeth Barringer.

Record Information

Source Institution:
|University of Colorado Denver
Holding Location:
Auraria Library
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
656564707 ( OCLC )
LD1193.L45 2010m B37 ( lcc )

Full Text
Lauren Elizabeth Barringer
B.S. Appalachian State University, 2002
A thesis submitted to the
University of Colorado Denver
in partial fulfillment
of the requirements for the degree of
Master of Science
Integrative Biology

This thesis for the Master of Science
degree by
Lauren Elizabeth Barringer
has been approved
Diana F. Tomback
to 16

Barringer, Lauren Elizabeth (M.S. Integrative Biology)
Determining the Relationship between Whitebark Pine Stand-level
Health and Seed Dispersal by Clarks Nutcracker
Thesis directed by Professor Diana F. Tomback
Whitebark pine (Pinus albicaulis) in the northern Rocky Mountains
is declining from infection by the exotic pathogen Cronartium ribicola,
which causes white pine blister rust, and from outbreaks of mountain
pine beetles (Dendroctonus ponderosae). Previous studies
demonstrated that as whitebark pine stands are progressively
damaged or killed by blister rust and beetles, Clarks nutcrackers
(Nucifraga columbiana), the main seed dispersers for whitebark pine,
make fewer stand visits when cones are produced and seeds are ripe.
The goal here was to test these observations further by examining
relationships between whitebark pine forest health and nutcracker
visitation with a different study design. I hypothesized that relatively
few nutcrackers visit whitebark pine stands with low live whitebark pine
basal area, high blister rust infection rate, and thus lower cone
production. If this hypothesis is supported by data, what are the

implications for whitebark pine seed dispersal and regeneration? In
2008, I established ten 1 km x 30 m transects and two forest health
plots per transect in Yellowstone, Grand Teton, Glacier, and Waterton
Lakes National Parks. I gathered data on tree health, cone counts, and
nutcracker occurrence in 2008 and 2009 from these transects and
plots. MANOVA results indicated that park was a significant predictor
of variation in health and nutcracker visits. However, logistic
regression analysis failed to isolate a single variable or combination of
variables associated with nutcracker occurrence; several models were
identified as comparable in predictive strength. In comparison to
previous findings, we found a somewhat lower cone production
threshold predicting the probability of nutcracker occurrence. This
finding offers more hope for areas with fewer living trees or heavily
damaged trees. Otherwise, if nutcrackers stop visiting whitebark pine
stands with high damage and mortality, natural regeneration will
diminish greatly. For example, areas burned by wildfire may not
regenerate. If nutcrackers are not dispersing seeds from damaged
stands, then seed or seedling planting may be highly appropriate
restoration strategies for these areas.

This abstract accurately represents the content of the candidates thesis. I
recommend its publication.
Diana F. Tomback

I dedicate this thesis to my parents for their support of my graduate
education and for instilling me with an appreciation for life-long learning.

I thank my advisor, Diana F. Tomback, for her guidance and knowledge
throughout my research. I also thank Michael Wunder for his extremely
valuable help with statistics. Additionally, I wish to thank all the members
of my committee for their participation and insights. I would have been
lost, or at least unsafe, in bear country, without my field assistants, Katie
Chipman, Taylor Turner, Brad Van Anderson, Lisa Bate, Nancy Bockino,
Cyndi Smith, and Myles Carter.
Additionally, the research could not have taken place without the funding
agencies that supported me: U.S.D.A Forest Service, Forest Health
Protection, Whitebark Pine Restoration Fund; Jerry O'Neal fellowship,
National Park Service Rocky Mountains Cooperative Ecosystem Studies
Unit; Technical Assistance Grant, National Park Service, Rocky Mountains
Cooperative Ecosystem Studies Unit; Global Forest Science; and park
personnel for their support of the research and help in selecting good
locations for the transects.

1. INTRODUCTION AND BACKGROUND...................................1
Significance of study.........................................1
Background and significance..................................1
Questions addressed in this study............................2
Background information........................................4
Natural history and ecosystem function.......................4
Clarks nutcracker...........................................7
Blister rust................................................11
Mountain pine beetle........................................12
Ecosystem level..............................................14
Significance of declines....................................14
2. METHODS......................................................18
Study design.................................................18
Study areas and transect sites..............................18
Transects and health plots..................................27

Data Collection................................................30
Health plot and nutcracker data...............................30
Cone count and nutcracker point count data....................31
Data analysis..................................................34
Statistical analysis..........................................34
3. RESULTS........................................................38
Transect Site Characteristics..................................38
Site Characteristics..........................................38
Health plot variables..........................................44
Individual variables..........................................44
Data analysis results..........................................53
Simple Linear Regression......................................56
Logistic Regression and AIC analysis..........................56
Cone threshold comparison.....................................59
4. DISCUSSION.....................................................63
Summary of conclusions.........................................70

1. Whitebark and nutcracker distribution..............................7
2. Study sites.......................................................24
3. Cone counts from 2008 and 2009...................................50
4. Observed nutcracker numbers by park..............................53
5a. Boxplots of variable distributions...............................55
5b. Boxplots continued...............................................56
6. Simple linear regression of nutcracker and cone counts...........60
7. Simple linear regression comparison...............................61
8. Observed vs. predicted proportion of observation hours...........62

1. Transect descriptions...............................................25
2. Health plot characteristics.........................................26
3. Transect health plot variables......................................51
4. Cone counts, nutcrackers, and squirrel observations.................52
5. MANOVA p-values.....................................................54
6. Proportion of variable weights (MANOVA).............................58
7. Top models as determined from AIC analysis..........................58

Significance of study
Background and significance
Whitebark pine (Pinus albicaulis) is a keystone and foundation
species of high elevation ecosystems in the western U.S. and Canada
(Tomback et al. 2001a, Ellison et al. 2005). In the northwestern U.S.
and throughout much of its Canadian distribution, whitebark pine is
declining rapidly from a combination of white pine blister rust infection
(caused by the invasive pathogen Cronartium ribicola) and mountain
pine beetle (Dendroctonus ponderosae) outbreaks. Whitebark pine is
highly susceptible to blister rust, and only a small percentage of trees
(usually <5%) show resistance (Hoff et al. 1980). Mountain pine
beetles kill both blister rust-resistant and non-resistant trees, thus
reducing the rate of spread of resistant genes for blister rust
resistance. Therefore, the combination of an introduced pathogen and
native pest infestations poses serious challenges to maintaining
healthy whitebark pine ecosystems. Currently, whitebark pine losses

are greatest in the northern Rocky Mountains of the U.S., the inter-
mountain region, and adjacent regions in southern Canada, where
blister rust infection levels are high, and outbreaks of mountain pine
beetle have been rapidly expanding (Kendall and Keane 2001,
Schwandt 2006, Gibson et al. 2008).
Dispersal of whitebark pine seeds is primarily accomplished by
Clarks nutcrackers (Nucifraga Columbiana), which harvest and cache
seeds throughout mountain terrain. The coevolved, mutualistic
relationship between whitebark pine and the Clarks nutcracker is an
integral part of the natural history of the northern Rocky Mountains
(Lanner 1982).
This interaction now appears threatened as whitebark pine
succumbs to blister rust and mountain pine beetles. Previous work
shows that nutcrackers are sensitive to the number of seeds available
within a stand and are efficient foragers (e.g., Tomback 1978, Vander
Wall 1988). McKinney and Tomback (2007) and McKinney et al.
(2009) show that nutcrackers may be less likely to visit blister rust-
diseased whitebark pine trees, which often have fewer cones than
healthy trees because of crown damage. With little to no seed
dispersal, natural whitebark regeneration is anticipated to decline

throughout regions with damaged stands and high mortality. In
particular, whitebark pine regeneration in burned areas near these
stands may be delayed or greatly reduced. Whitebark pine is typically
a post-fire pioneer in the subalpine zone (Arno and Hoff 1990,
Tomback et al. 2001b).
Restoration of whitebark pine through planting blister rust
resistant seedlings, and protection of potentially blister rust resistant
trees against mountain pine beetle, are management strategies
advocated by the U.S. Forest Service and supported by several
national parks (Tomback et al. 2001a, Schwandt 2006). Given that
limited funding is available for restoration, it is critical that restoration
be prioritized for areas where whitebark is in the worst shape. Results
from this study, which relates nutcracker occurrence to stand health,
could provide useful information for the prioritization process used by
Questions addressed in this study
Overall, I am interested in determining whether living whitebark
pine stand density and health, and thus cone production capacity,
predicts the occurrence of nutcrackers in whitebark pine communities.
If so, identifying the variables associated with badly damaged stands

which are unlikely to have nutcrackers visit (even if some cones are
being produced) has important management applications.
Here, the following specific questions are asked: 1) What are
the differences in whitebark pine health, stand composition, and basal
area (abundance) within plots at study sites among four national
parks? 2) Are there differences in cone numbers among parks and
from year to year? 3) Are there differences in observed squirrel
numbers (they are influential seed predators on whitebark cones)? 4)
Are there differences in observed nutcracker numbers observed from
park to park? 5) Are there differences in whitebark pine regeneration
(seedlings) from park to park? 6) Is there an overall relationship
between cone numbers and nutcracker occurrence? 7) Are there
variables that predict nutcracker occurrence within and across parks?
8) How does the relationship between cone production and proportion
of observation hours with one or more nutcracker sightings relate to
the relationship observed by McKinney et al. (2009)? How did the cone
production threshold determined from this study relate to the threshold
observed by McKinney et al. (2009)? 9) What cone production
threshold can be used to prioritize whitebark pine stands for

Background information
Natural history and ecosystem function
Whitebark pine is one of five species of bird-dispersed pines in
the genus Pinus (Family Pinaceae), subgenus Strobus (the white
pines), section Strobus, subsection Cembrae (the stone pines). Only
whitebark pine is found in North America; the other four stone pines
occur in Europe and Asia (Price et al. 1998). Whitebark pine is
distributed at treeline and subalpine elevations across eastern and
western montane regions in the western U.S. and Canada. In the
Rocky Mountains, it ranges from the Wind River and Salt River Ranges
of western Wyoming north to about 54 N in Alberta and British
Columbia. It is also distributed from the southern Sierra Nevada and
Cascades north through the Coastal Mountains of British Colombia to
55 N. Isolated stands occur in the northern Great Basin (Nevada), as
well as other areas (Critchfield and Little 1966, McCaughey and
Schmidt 2001) (Figure 1).
McCaughey and Tomback (2001) provide an overview of cone
development and seed production. As is typical in stone pines, trees
grow slowly and the first production of male and female cones begins
around age 20 to 30 years, although large cone crops are not

produced until age 80 to 120 years. Seed and pollen cone formation
occurs from mid-July to mid-September. After ovenwintering, both male
and female cones begin development in April and May. Mature cones
produce two large, wingless seeds on each cone scale (on average, 75
seeds per cone). The cones of whitebark pine are indehiscent, which
means that cones remain closed even after seeds ripen. Thus,
whitebark pine depends on nutcrackers to remove seeds from cones
and disperse them. Consequently, whitebark pine occurs completely
within the range of the Clarks nutcracker (see Figure 1 below). Cone
production in whitebark pine varies from to year to year and is
influenced by tree canopy cover and size, and climatic conditions, as
well as insect and disease presence. Good cone crops are typically
produced every three years (McCaughey and Tomback 2001).
Whitebark pine cone production peaks on average at 250 years of age
(Amo and Hoff 1990).
Whitebark pine occurs across a continuum of community types
(Arno and Hoff 1990, Arno 2001). On favorable sites in the lower
upper subalpine, it occurs as a serai species. After disturbance, and
particularly wildfire, whitebark pine is one of the first conifers to
regenerate, because of rapid seed dispersal by Clarks nutcrackers
and seedlings tolerant of harsh conditions (McCaughey and Tomback

2001, Tomback et al. 2001b). Because whitebark pine is a poor
competitor and moderately shade-intolerant, it declines in these serai
communities over time as faster-growing, shade-tolerant conifers
colonize and continue to regenerate. On harsh sites, usually at higher
elevations, its competitors are often suppressed by wind and exposure.
Whitebark thus can occur as a dominant climax species under these
conditions. In treeline communities, whitebark often assumes a
krummholz growth form (a stunted, low growing tree) due to exposure
(Arno and Hoff 1990).
Historically, whitebark pine has been a prominent subalpine
and treeline species in Glacier National Park and adjacent Waterton
Lakes National Park, as well as in the Greater Yellowstone Area,
including Grand Teton and Yellowstone National Parks (Arno and Hoff
1990). This long-lived conifer plays an important role in the high
elevation ecosystem. It is considered a keystone and foundation
species for numerous reasons: it stabilizes soil at treeline; pioneers
after fire or other disturbance, paving the way for community
development; grows in terrain that may otherwise prove inhospitable
due to harsh environments; and provides an important, high quality
food source for various small granivorous birds and mammals. Thus,
whitebark pine both stabilizes high elevation communities, and

enhances community biodiversity (Arno and Hoff 1990, Tomback et al.
2001a, Tomback and Kendall 2001, Ellison et al. 2005).
Figure 1. Whitebark (cross-hatched) and nutcracker (grey) distribution range
(Ridgely et al. 2005, U.S. Geographical Survey 1999)
Clarks nutcracker
Clarks nutcracker (Family Corvidae) is distributed throughout
high elevation forest habitats in the western United States and Canada
(Figure 1). Nutcrackers are pale grey birds with black and white
markings on wings and tail. They are sexually monomorphic, but males

are often larger than females (Mewaldt 1958). Clarks nutcrackers are
morphologically adapted to a diet of fresh and stored conifer seeds.
Their long, sharp bills are used to dig into unripe, closed cones to
extract seeds (VanderWall and Baida 1977, Tomback 1978). They are
opportunistic conifer-seed specialists that vary their diet based on cone
availability from various conifers from year to year (Tomback 1983,
1998, Lanner 1996). Nutcrackers have a coevolved mutualistic
relationship with whitebark pine (e.g., Tomback 1978, 1982, 1983,
Lanner 1980, 1996, Tomback and Linhart 1990). The large, wingless
seeds of whitebark pine are dependent upon Clarks nutcrackers for
dispersal (Hutchins and Lanner 1982, Tomback 1982). In turn, when
whitebark pine seeds are available, they comprise an important part of
the Clarks nutcracker diet (Giuntoli and Mewaldt 1978, Tomback
1978). Before whitebark pine seeds ripen (in mid to late August),
Clarks nutcrackers act as seed predators and shred cones as they
remove pieces of seeds. This activity leaves obvious signs of harvest
(Tomback 1998). Later, as seeds ripen, Clarks nutcrackers act as
seed dispersers. At this time, nutcrackers fill their throat pouch
(sublingual pouch) with seeds for transport to cache sites. This
behavior is easily observed in the field and is equated with seed
dispersal (Tomback 1978, 2001). These birds can differentiate

between healthy and unhealthy pine seeds (Vander Wall and Baida
1977), and also move from regions where cone production has failed
to regions that produce good cone crops (see review in Tomback
Nutcrackers cache an estimated 35,000 to 98,000 whitebark
pine seeds per individual per year, which are later used as food for
themselves and their young (Hutchins and Lanner 1982, Tomback
1982). Nutcrackers typically cache seeds within a few hundred meters
from their harvesting site, but longer caching distances range from 1-
3.5 km (Hutchins and Lanner 1982, Dimmick 1993). Caches are buried
1-3cm deep in soil or gravel substrate. Mean cache size is 3.2-3.7
(Hutchins and Lanner 1982, Tomback 1982). Cache sites can be in a
variety of habitats (i.e. burned areas, open and closed forests,
meadows, dry slopes) and can even be placed above ground in logs,
rocks, or trees. Ground caches are concealed with substrate and
smoothed over (Tomback 1978). Nutcrackers have a well-developed
spatial memory that allows them to accurately locate caches (in a
laboratory setting) for up to 270 days (Kamil and Baida 1985).
Whitebark pine seed caches are recovered from February through July
(Tomback 1978, Vander Wall and Hutchins 1983). Unrecovered
caches often germinate after snowmelt or rain. In whitebark pine

communities, Stellers jays (Cyanocitta stelleri), mountain chickadees
(Poecile gambeli), common ravens (Corvus corax), pine grosbeaks
(Pinicola enucleator), red crossbills, deer mice (Peromyscus
maniculatus), chipmunks (Tamias spp.), and pine squirrels
(Tamiasciurus hudsonicus) also consume whitebark pine seeds
(Tomback 1978, Hutchins and Lanner 1982). Pine squirrels
(Tamiasciurus hudsonicus and T. douglasi) are the dominant
predispersal seed predator of whitebark pines. They frequently out-
compete nutcrackers for seeds by cutting cones down from trees to
store in middens, which further reduces seed dispersal by nutcrackers
and results in fewer nutcrackers visiting areas where pine squirrels are
present (Tomback 1978, Siepelski and Benkman 2008). Squirrel
predation of whitebark seeds has serious consequences. Selection by
whitebark pine against squirrel predation weakens the selection by
nutcrackers for large seeds and high numbers of seeds per cone. Pine
squirrels have also been shown to reduce whitebark stand density
(Siepelski and Benkman 2008).
In the Rocky Mountains, both grizzly (Ursus arctos) and black
bears (Ursus americanus) consume whitebark pine seeds taken from
cones in squirrel middens (or even from trees); these seeds are an

important pre-hibernation food for bears in the Greater Yellowstone
Area and Rocky Mountain Front (Mattson et al. 2001).
Blister rust
White pine blister rust is now present nearly rangewide in
whitebark pine (Kendall and Keane 2001, McDonald and Hoff 2001).
The only regions reporting low to no infection levels in whitebark pine
are the interior Great Basin and the southern Sierra Nevada (Schwandt
2006). Blister rust originated in Asia and became established in
eastern North American around 1890. It was introduced several times
to the Pacific Northwest, U.S. and Canada by 1910. By 1970, blister
rust distribution had reached as far south as southern New Mexico
(Hawksworth 1990). Blister rust reached northern Colorado by 1998
and had reached southern Colorado by 2003 (Johnson and Jacobi
2000). It was found in the Jarbidge Wilderness of Nevada in 2002
(Vogler and Charlet 2004). Susceptible hosts include five-needled
white pines such as eastern white pine (Pinus strobus), western white
pine (Pinus monticola), sugar pine (Pinus lambertiana), whitebark pine,
limber pine (Pinus flexilis), Rocky Mountain bristlecone pine (Pinus
aristata), Great Basin bristlecone pine (Pinus tongaeva), foxtail pine

(iPinus balfouriana), and southwestern white pine (Pinus strobiformis)
(McDonald and Hoff 2001).
The rust fungus requires two hosts, a pine and an alternate host
plant, to complete its life cycle (McDonald and Hoff 2001). Known
hosts include Ribes spp. (currants and gooseberries), Castilleja sp.
(Indian paintbrush), and Pedicularis sp. (lousewort) (McDonald et al.
2006). Attempts to control the disease by eradicating the alternate
hosts have been unsuccessful (Benedict 1981). The life cycle is
summarized in McDonald and Hoff (2001): Basidiospores from an
alternate host enter whitebark pine through needle stomata in late
summer or early fall. The infection begins as a yellow or red spot on
the needles and may progress to a swollen area on a branch or trunk.
Two to three years after infection, this swollen area becomes a canker
that produces aeciospores. The canker eventually kills cone-bearing
branches by girdling them, thus reducing seed production, and kills
trees by weakening them or girdling the trunk. Aeciospores are wind-
dispersed and can travel up to 500 km (McDonald and Hoff 2001).
Mountain pine beetle
Also threatening whitebark pine forest health are outbreaks of
the mountain pine beetle, a native insect that can use any pine species

as host. Mountain pine beetles attack live conifers by tunneling into the
bark, forming vertical tunnels, and laying approximately 75 eggs per
female. When the eggs hatch, the larvae tunnel away from the
hatching site and produce characteristic horizontal tunnels visible
under the bark. Larvae overwinter under the bark and emerge in early
summer as adults (Leatherman et al. 2007).
Mountain pine beetle outbreaks have occurred intermittently
throughout the 20th century, probably driven by warm, dry weather
conditions and host availability (Logan and Powell 2001). Outbreaks
occurred from about 1910 to the 1930s and again throughout the
1970s and 80s. Large areas of long dead trees are referred to as
ghost forests. Whitebark ghost forests are still present in many areas
today as a result of past beetle kill (Kendall and Keane 2001). The
current outbreak began approximately 10 years ago.
Mountain pine beetle typically attacks whitebark pine that is
experiencing stressful growing conditions (Leatherman et al. 2007).
Stress is currently caused by drought (water stress) from warmer
temperatures (Logan and Powell 2001, Gibson et al. 2008). Healthy
trees produce pitch tubes (visible on the trunk) in defense against the
beetles. These resin tubes are produced in an attempt by the tree to
expel the beetles from its bark. However, under drought or other

stressful conditions, trees may not be able to produce pitch tubes
(Leatherman et al. 2007). Because pine beetles prefer older whitebark
trees, which tend to produce a lot of cones, beetle outbreaks can
drastically decrease seed production in an area. Trees that are
infected with blister rust can be more vulnerable to a successful beetle
infestation as well (Six and Adams 2007, Bockino 2008). Mountain
pine beetle outbreaks now range from British Columbia to California
and east throughout the Rocky Mountains. Infestations of mountain
pine beetle are killing great numbers of whitebark pine in the GYA, the
northwestern U.S., and western Canada (Gibson et al. 2008).
Ecosystem level
Significance of declines
Fewer than 5% of whitebark pine are genetically resistant to
blister rust disease (Hoff et al. 1994). In some forests in the northern
Rocky Mountains, especially in Glacier National Park, blister rust
infection levels can be as high as 90-100% (Kendall et al. 1996,
Kendall and Keane 2001, Smith et al. 2008). The study areas used
here, Waterton Lakes and Glacier National Parks in the northern
Rocky Mountains and Yellowstone and Grand Teton National Parks in
the Central Rocky Mountains, represent two extremes on the whitebark

pine blister rust infection continuum. Recent assessments in Glacier
and Waterton Lakes National Parks (Smith et al. 2008) and the Greater
Yellowstone Area (GYA) (GYWPMWG 2008) indicate mean blister rust
infection levels to be 67%, 71.5%, and 26%, respectively. Glacier
National Park, the contiguous Waterton Lakes National Park in
Canada, and the contiguous Blackfeet Reservation have the highest
mean blister rust infection and mortality levels known rangewide for
whitebark pine (with mortality from all factors ca. 50%) (Smith et al.
2008). Farther to the south, in Yellowstone and Grand Teton national
parks, blister rust infection levels and damage are much lower, but
appear to have increased recently, reaching an overall average of
about 20% (GYWPMWG 2008).
The rust pathogen has been present in northwest Montana
since 1927 and on the continental divide in Glacier National Park since
1939 (Mielke 1943). In contrast, blister rust has been slow to invade
the GYA; surveys for blister rust in Yellowstone National Park in 1970
indicated no occurrence in 26 of 29 whitebark pine stands surveyed,
and extremely low incidence (1 or 2%) in three stands. A second
survey eight years later indicated infections in a few stands previously
without blister rust and some increase in two stands to 5-6% (Carlson
1978). Carlson (1978) suggested that both the ecological conditions in

the GYA, e g., less susceptible alternate host species, and climate
were unfavorable to the spread of the blister rust pathogen, but blister
rust levels are clearly increasing. Thus, blister rust continues to spread
into new regions where hosts are present, and intensify in areas where
it is already present.
Whitebark is declining nearly rangewide from the combination of
blister rust infection and pine beetle infestation. As a result, the
nutcracker-whitebark pine relationship may be threatened in areas with
high blister rust infection and mountain pine beetle outbreaks.
Mountain pine beetles kill both blister rust-resistant and non-resistant
trees, thus greatly reducing the possibility that natural selection can
spread resistance to blister rust fast enough. Therefore, the
combination of introduced pathogen and native pest infestations pose
serious challenges to maintaining healthy whitebark pine ecosystems
in the future. McKinney and Tomback (2007) and McKinney et al.
(2009) have shown that nutcrackers make fewer visits to forest stands
with high levels of blister rust damage and mortality. Nutcrackers are
energy-sensitive foragers, meaning that they select areas for seed
harvest based on rates of energy intake (Tomback 1978, Tomback and
Kramer 1980, Vander Wall 1988). Thus, they may be less likely to visit
blister rust-diseased or damaged whitebark pine trees, which have

fewer cones than healthy trees because of crown damage (McDonald
and Hoff 2001, McKinney and Tomback 2007, McKinney et al. 2009). If
cone decline continues, seed dispersal by nutcrackers could be
reduced, disconnecting the mutualistic relationship between
nutcrackers and whitebark pine (McKinney et al. 2009, Tomback and
Achuff in press). With little to no seed dispersal, natural whitebark
regeneration will decline throughout regions with highly damaged
stands; in particular, burned areas near these stands are unlikely to
regenerate with whitebark pine, which is typically a post-fire pioneer in
the subalpine zone (Arno and Hoff 1990, Tomback et al. 2001b,
Tomback and Achuff in press).
Restoration of whitebark pine through planting of rust- resistant
seedlings and protection of healthy trees are management strategies
advocated by the U.S. Forest Service and supported by different
national parks (Schwandt 2006, Tomback and Achuff in press). Glacier
National Park and adjacent national forests, and national forests in the
Greater Yellowstone Area have implemented some restoration projects
(Schwandt 2009). Given that limited funding is available for restoration,
it is critical that areas for restoration be prioritized and restoration

Study design
Study areas and transect sites
Research sites. Dates of all fieldwork are as follows: July 4 to
August 1 and August 23 to September 3, 2008; July 10 to 24 and
August 26 to September 8, 2009. All research took place in study sites
in Grand Teton, Yellowstone, Glacier, and Waterton Lakes National
Parks. From this point forward, National Park will be abbreviated NP.
Research study areas are mapped in Fig. 2 and major characteristics
are listed in Table 1.
Grand Teton NP. Grand Teton NP is located entirely in
Wyoming, only 30 km south of Yellowstone NP (Figure 2). The park is
1,253.5 sq km in area. Spruce-fir forests are dominant in Grand Teton
NP, although lodgepole pine (Pinus contorta) is the most common
conifer. Whitebark pine grows above 2438 ft. Also present are
Douglas-fir (Pseudotsuga menziesii), subalpine fir (Abies lasiocarpa),
Engelmann spruce (Picea engelmannii), and blue spruce (Picea

pungens) (Crandall 1977). Research transects in Grand Teton NP are
on Teewinot Mountain and below Amphitheater Lake. Both transects
are located in the Teton Mountain Range, and both are accessed from
trailheads adjacent to the Lupine Meadows parking area, located in the
central part of the park.
The Teewinot transect is placed along the Apex trail (a rough
climbers trail), which has steep switchbacks. The transect began
approximately 4 km east of the trailhead. The Amphitheater Lake
transect is accessed from the more widely used Garnett Canyon
trailhead, and placed off a switch-backing trail just below Amphitheater
Lake. Elevation ranged from 2738 to 2867 m. The transect began
approximately 5 km from the trailhead.
Yellowstone NP. Yellowstone NP comprises 8,992.5 sq km with
96% in northwestern Wyoming, 3% in southern Montana, and 1% in
eastern Idaho. Greater than eighty percent of the park is forested.
Whereas subalpine forests of Engelmann spruce and subalpine fir)
comprise the main climax forest vegetation, representing about 77% of
the Parks forest cover, lodgepole pine forms the dominant
successional subalpine forest communities, and is the most common
tree in the park. The remainder of forest is whitebark pine and
Douglas-fir Whitebark pine becomes the dominant canopy species

above 2560 m elevation (Renkin and Despain 1992). I set up research
transects in upper subalpine forests where whitebark pine ranged in
importance from co-dominant to a dominant forest species.
The study sites in Yellowstone NP were located near Craig
Pass, Dunraven Pass, and Avalanche Peak (Figure 2). Craig Pass is
located in the southwest part of the Park. It is accessed from the road
between West Thumb and Old Faithful, adjacent to a parking pullout
just at the Craig Pass Divide (2518 m). This area represented a
suitable but different whitebark pine community type from anywhere
else in this study, but no trails were present in this area.
Consequently, the transect was routed through open forest, accessed
due south from the pullout area. The transect ran along a slight ridge
through open forest (Table 1).
Dunraven Pass is located on Mt. Washburn (Washburn Range)
in the north central part of the Park (Figure 2), accessed either from
the Canyon or Roosevelt Junctions. The transect begins approximately
0.4 km up a trail from the parking area. The transect heads cross-
country along a ridge. It was not placed on trail, which was an old, wide
road not trending through much whitebark pine habitat initially. The
transect ranged in elevation from 2805 m to 2838 m.

Avalanche Peak is located in the east central part of the park in
the Absaroka Mountain Range (Figure 2). The transect followed the
Avalanche Peak hiking trail. There were many dead and downed trees
around the transect.
Glacier NP. Glacier NP, located in the northwest corner of
Montana, is 4,100 sq km in area, and extends to the Canadian-U.S.
border (Figure 2). Fifty-five percent of Glacier National Park is
forested, but with a diversity of forest types, including several Pacific
Northwest forest communities west of the continental divide. Spruce-fir
forests consist of lodgepole and whitebark pine, subalpine fir,
Engelmann spruce, and western larch (Larix occidentalis). Above
1,829 ft in elevation, krummholz conifer growth forms become
common. The west side of the park is mixed conifer forest (Gadd 1995,
Rockwell 2007).
Transect placement in Glacier NP is below Siyeh Pass, above
Scenic Point, and on Elk Mountain (Figure 2). All transects are located
within the Lewis Range. Siyeh Bend trailhead is located east of Logan
Pass in the central part of the park, accessed from Going to the Sun
Road. The transect begins approximately 4 km from the trailhead at
the Siyeh Pass/Piegan Pass trail junction within an extensive forested
area below Mount Siyeh.

The Scenic Point Trail starts from a small parking area in the
southwestern Two Medicine area, on the east slope of Glacier NP. The
transect, which is generally straight, begins approximately 6.4 km from
the trailhead, on the southwest aspect of Scenic Point peak within a
treeline community.
The Elk Mountain transect was located in the Livingston Range
in Glacier NP. Elk Mountain (2388 m) lies along the southernmost
edge of the park and is accessed by US Highway 2. The transect
upper end was approximately 5 km from the trailhead and
approximately 1 km from the summit.
Waterton Lakes NP. Waterton Lakes NP, which is contiguous
with Glacier N P, begins at the Canadian border in southern Alberta
(Figure 2). Together, both parks comprise part of a single ecosystem.
Administered by Parks Canada, Waterton Lakes NP is 505 sq km in
area. Spruce-fir forest and pine/aspen (Populus tremuloides) forests
comprise the majority of the forested area (Gadd 1995, Rockwell
Transects in Waterton Lakes NP were established near Summit
Lake and below Rowe Lake. Transects were located within the Lewis
Range. The Carthew-Alderson Trial led from the trailhead at Cameron
Lake to Summit Lake. The trailhead lies at the end of the Akamina

Parkway, on the north side of Cameron Lake. The transects upper end
was approximately 4.3 km from the Cameron Lake parking lot. It was
established beyond Summit Lake and just off a gradually sloping trail.
The Rowe Lake trail was accessed from the Rowe Lake
trailhead, on the west side of the Akamina Parkway. The upper end of
the transect was approximately 5.4 km from the trailhead, and was
established below Rowe Lake just off the hiking trail.

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Table 1. Transect description. Elevation is the high point of each transect, and latitude/longitude is from GPS readings
at the upper end of the transect. TH=trailhead
Transects Elevation Latitude/Longitude Habitat Access
Grand Teton National Park
Amphitheater Lake (AL) 2867 43 43.738, 110 46.330 Subalpine forest Garnet Canyon TH
Teewinot Mountain (TM) 2837 43 44.569, 110 45.050 Subalpine forest Apex TH
Yellowstone National Park
Craig Pass (CP) 2626 44 25. 564,110 40.060 Subalpine forest Road
Dunraven Pass (DP) 2838 44 47.327, 110 26.992 Mixed subalpine meadow and open forest Mt. Washburn TH
Avalanche Peak (AP) 2900 44 28.697, 110 08.070 Subalpine forest Avalanche Peak TH
Glacier National Park
Siyeh Pass (SP) 2185 48 42.819, 11338.813 Subalpine forest Siyeh Pass TH
Scenic Point (SCP) 2216 48 29.112, 113 19.074 Subalpine/treeline Scenic Point TH
Elk Mountain (EM) 2182 48 18.137, 113 26.566 Subalpine/treeline Elk Mountain TH
Waterton Lakes National Park
Summit Lake (SL) 1945 49 00.478, 114 01.493 Subalpine/open canopy forest Summit Lake TH
Rowe Lake (RL) 2170 49 03.159, 110 03.547 subalpine/open canopy forest Rowe Lake TH

Table 2. Health plot characteristics. Elevation and aspect are at center of plot (25 m point on plot).
Transects Elevation (m) Aspectn Mean DBH (cm) Percent whitebark pine overstory
Grand Teton National Park
Amphitheater Lake (AL) 2823 20 33.9 39.3
2738 185 24.9 37.5
Teewinot Mountain (TM) 2836 5 38.9 56.7
2783 5 37.1 40
Yellowstone National Park
Craig Pass (CP) 2612 38 14.1 90
2626 24 8.3 30
Dunraven Pass (DP) 2868 155 16.9 55.9
2801 210 19.3 71.4
Avalanche Peak (AP) 2728 190 36.4 28.2
2740 165 23.9 9.1
Glacier National Park
Siyeh Pass (SP) 2167 232 33.5 0
2145 210 25.5 4
Scenic Point (SCP) 2089 210 11.4 29
2183 210 4.4 73
Elk Mountain (EM) 2182 220 20.3 25
2123 219 7.3 21
Waterton Lakes National Park
Summit Lake (SL) 1945 190 1.8 0
1923 155 15.9 5
Rowe Lake (RL) 2182 200 17.4 5
2196 160 22.7 10

Transects and health plots
Transect establishment. Two 1 km x 30 m belt transects were
established through forest communities with mature whitebark pine in
Grand Teton NP, three in nearby Yellowstone NP, three in Glacier NP,
and two in nearby Waterton Lakes NP during July 2008, with the help
of field assistants (D. F. Tomback and Katie Chipman).
One transect (Dunraven Pass) in Yellowstone NP was accessed
from the Dunraven Pass Mt. Washburn trailhead, but started off trail
and headed cross-country upslope. A second transect, Craig Pass,
also in Yellowstone NP started 25 m from one of the main roads in
Yellowstone. The other eight transects were established parallel to
existing trails.
Transect placements were dependent on the following
constraints: transects were placed in areas with at least 1 km of
continuous whitebark habitat and accessible (round trip) in one day, on
foot. The field team worked in conjunction with park staff and scouted
possible areas in which to place transects. In all cases, placement of
transects was coordinated with park resource managers, to make
certain that the transects were not readily apparent to park visitors but

accessible enough to facilitate efficient sampling by park staff in
subsequent years.
These constraints limited areas where transects could
potentially be placed. Once a transect area with suitable whitebark
habitat was chosen, the transects were measured out with a 50 m
transect tape. The field team would measure out 100 m, and then
move 5 m to 10 m off trail to mark each 100 m section, for the entire
total 1 km distance. The start, finish, and pathway of each transect
were georeferenced using a Garmin GPS 12 XL unit and marked on
topographical maps. Because existing trails and roads were used for
access and because of the scattered locations of continuous whitebark
habitat, transects were not placed at random, but the starting points
were randomized. Each 100 m section was numbered (1 through 11).
Health plot set up. Two 50 m x 10 m plots were established
within each transect. The locations of the two plots along a given
transect were randomized as follows: a random numbers table was
used to select two consecutive numbers, from 0 to 9, representing
specific 100 m sections along the transect. Once the 100 m section
points were identified, the field team would randomly choose a start
point and establish the health plot parallel to the transect line (when
slope steepness or habitat did not preclude this option). From that

point, 50 m would be measured out using a meter tape. A second
meter tape was used to measure a 5 m on each side of the 50 m tape.
Pin flags in open ground and surveyors tape in trees were used to
demarcate the belts. Once the health plot was created, data (as
described below) were gathered within the plot limits. The start and
end points of each plot were georeferenced and marked by tree tags
and/or rebar. Notes were taken to ensure that the health plot could be
recreated on later visits. Once data were gathered, transect tapes and
pin flags were removed. Occasionally, randomly selected section
numbers placed the plots on very steep terrain or in unsuitable habitat.
When this occurred, we chose the next number on the random number
table. Survey methods followed Tomback et al. (2005) and
GYWPMWG (2008).
Point count station set up. Each transect had six point count
stations, one every 200 m (every other section point, starting at 0 m)
along the 1 km. Point count stations were georeferenced. They were
also marked with tree tags and, temporarily, by surveyors tape.

Data Collection
Health plot and nutcracker data
Whitebark pine stand data. The health plots were created in
July, 2008, to survey stand structure and composition, whitebark pine
diameters at breast height or 1.4 m (dbh), blister rust infection level
and canopy damage, mountain pine beetle symptoms, tree mortality
and cause, whitebark pine regeneration, and cone numbers. All
canopy level trees were counted to determine stand composition by
species. For all whitebark pine greater than 1 cm at dhb on the plot,
dbh was taken using metal dbh tapes. Diameter was used to calculate
live basal area (LBA). LBA was converted to a measure of tree basal
area density, here based on the 500 sq m of the health plot.
Whitebark pine canopy damage was classified into categories
based on a percentage scale. Canopy kill was first assessed by an
observer as an approximate percentage of the entire canopy with
branches devoid of foliage, and then placed in one of the following
categories: 1 (0-5% dead), 2 (6-15% dead), 3 (16-25% dead), 4 (26-
35% dead), 5 (36-45% dead), 6 (46-55% dead), 7 (56-65% dead), 8
(66-75% dead), 9 (76-85% dead), 10 (86-95% dead), and 11 (96-100%
dead) (Tomback et al. 2005). This set of categories recognizes that

small amounts of canopy kill or living canopy are easier to quantify
than larger. Blister rust infection was classified by location (branch vs.
trunk) and presence of aecia/cankers (active or inactive), as well as the
presence of secondary symptoms (sap oozing, rodent gnawing, and
stripped bark). Only trees with active cankers were classified as being
infected with blister rust. Mountain pine beetle symptoms were
classified as new attacks on trees, older attacked tree, or as beetle
galleries present on dead trees.
All whitebark mortality was noted. If the cause of mortality was
discernable, it was recorded. Dead trees were counted and dbh
measured even if the cause of death could not be determined.
Whitebark pine regeneration, defined here as seedlings <50 cm in
height, was counted by walking methodically through the health plot
and counting using hand held counters. Mountain pine beetle attacks
were updated in late summer, 2008, and again during early and late
summer in 2009.
Cone count and nutcracker point count data
Cone counts. Cone count data were taken on the health plots
during each visit. Early and late season whitebark pine cone counts
were performed from the ground using binoculars with an objective of

at least 10 x 42. All whitebark pine trees larger than saplings were
examined for cone production. Counts were done by at least 2 people
from different vantage points. From multiple cone observations, counts
were averaged. Data collection took place twice per year: in mid to late
July 2008, before seed dispersal began, and again between late
August and early September, once seed dispersal was underway. This
protocol was repeated for 2009. From cone count data, an estimate of
al cones per hectare was later calculated, using the larger of the two
values. To do this, I took the total cone counts (per 1000 m2) and
multiplied them by 10 to estimate number of cones per hectare.
Nutcracker point counts. The point count techniques employed
in this study are based on survey methods outlined in Ralph et al.
(1993). Because the point counts here were primarily for inventory,
point count duration was ten minutes. Counts occurred four times per
summer for 10 minutes each point on six points per transect. Transects
were surveyed by stopping every 200 m at the designated point count
stations for 10 minutes of data collection and slowly walking between
point count stations. Data collected during each point count included
start time and end time, number of nutcracker sightings, nutcracker
activities per observation (e.g., flying over, perching, breaking into

cones, caching, etc), nutcracker vocalizations without sightings, and
squirrel sightings.
Nutcrackers heard, but not seen, on point counts were classified
as an observation. I attempted to avoid counting the same nutcrackers
twice by trying to view nutcrackers counted when possible. When
nutcrackers could only be heard, I did my best to auditorily follow their
call directions and only count them once. The transects were 1 km x
30 m officially, but we did not mark 15 m on both sides of the midline.
When I observed or heard a nutcracker, I had to decide whether it was
counted as on transect or off. This was much easier for visual
observations than for vocalization-based counts. By mistake I may
have occasionally counted birds that were beyond the 30 m transect
width. Squirrel count data were also taken during nutcracker point
counts. Two point counts (am and pm) took place on each visit for a
total of 4 point counts per year per point, or a total of 240 min of time
spent gathering observations per transect. Morning point counts took
place before noon (generally before 10am). Afternoon point counts
occurred between 1 and 6 pm. There was always at least a 2.5 hour
window between counts.
Nutcracker point counts may have been hampered by snowy
weather on the Rowe Lake transect (Waterton Lakes NP) in late