![]() | Yellowstone Handbook 2019Vegetation |
Yellowstone Resources and Issues Handbook. Published by the National Park Service (NPS).
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VE G E TAT I O N
More than 1,300 plant taxa occur in Yellowstone National Park. The whitebark pine, shown here and found in
high elevations in the Greater Yellowstone Ecosystem, is an important native species in decline.
Vegetation
The vegetation communities of Yellowstone National
Park include overlapping combinations of species
typical of the Rocky Mountains as well as of the
Great Plains to the east and the Intermountain region
to the west. The exact vegetation community present in any area of the park reflects the consequences
of the underlying geology, ongoing climate change,
substrates and soils, and disturbances created by fire,
floods, landslides, blowdowns, insect infestations,
and the arrival of nonnative plants.
Today, the roughly 1,386 native taxa in the park
represent the species able to either persist in the area
or recolonize after glaciers, lava flows, and other
major disturbances. Yellowstone is home to three
endemic plant species, at least two of which depend
on the unusual habitat created by the park’s thermal
features. Most vegetation management in the park
is focused on minimizing human-caused impacts on
their native plant communities to the extent feasible.
Vegetation Communities
There are several vegetation communities in
Yellowstone: higher- and lower-elevation forests
and the understory vegetation associated with them,
sagebrush-steppe, wetlands, and hydrothermal.
Quick Facts
Number in Yellowstone
Native plant taxa: more than 1,300:
•
Hundreds of wildflowers.
•
Trees: nine conifers (lodgepole
pine, whitebark pine, Engelmann
spruce, white spruce, subalpine
fir, Douglas-fir, Rocky Mountain
juniper, common juniper, limber
pine) and some deciduous species,
including quaking aspen and
cottonwood.
•
Shrubs: include common juniper,
sagebrush (many species), Rocky
Mountain maple.
•
Three endemic species (found only
in Yellowstone): Ross’s bentgrass,
Yellowstone sand verbena,
Yellowstone sulfur wild buckwheat.
Nonnative plant species: 225.
Characteristics
•
Vegetation in Yellowstone is typical
of the Rocky Mountains.
•
Elements of the Great Plains and
Great Basin floras mix with Rocky
Mountain vegetation in the vicinity
of Gardiner and Stephen’s Creek.
•
Hydrothermal areas support
unique plant communities and rare
species.
Management Issues
•
Controlling nonnative species,
which threaten native species,
especially near developed areas;
some are spreading into the
backcountry.
•
Park partners are monitoring
whitebark pine and forest insect
pests.
•
Biologists survey areas for sensitive
or rare vegetation before a
disturbance such as constructing a
new facility.
•
Park managers are restoring areas
of disturbance.
Vegetation
143
VE G E TAT I O N
Vegetation Communities in Yellowstone National Park
0
10 Kilometers
Lodgepole
pine
forests
Dominate more than 80% of the total forested area.
Can be seral
(developing)
or climax.
0
10 Miles
Climax forests underlain by rhyolite.
Spruce-fir forests
Engelmann spruce/subalpine fir dominate older forests.
Usually found on moist and/or fertile substrates.
Climax forests underlain by andesitic soils.
Whitebark pine forests
Major overstory component above 8,400 feet.
Major understory component of lodgepole-dominated
forests from 7,000 to 8,400 feet.
Seeds are ecologically important food for a variety of
wildlife species.
Douglas-fir forests
Associated with the Lamar, Yellowstone, and Madison
river drainages below 7,600 feet.
Often fewer than 20 inches annual precipitation.
More frequent historic fire interval (25–60 year) than
other forest communities in the park.
144
Yellowstone Resources and Issues Handbook, 2019
Non-forest
North
Includes grasslands, sagebrush, alpine meadows, talus,
and hydrothermal environments.
Encompasses the moisture spectrum from dry
sagebrush shrublands to wet alpine meadows.
Provides the winter and summer forage base for
ungulates.
Á
Other communities not shown on map
Aspen—found in small clones interspersed among the
sagebrush/forest ecotone (transition zone) along the
Yellowstone, Madison, and Snake river drainages.
Wetland—Wetlands include wet meadows, forested
wetlands, springs, and seeps comprised of woody
vegetation, forbs, rushes, sedges, and grasses. Some
are thermally influenced.
Riparian—typically streamside vegetation includes
cottonwoods, willows, and various deciduous shrubs.
More Information
Staff Reviewers
Roy Renkin, Vegetation Management Specialist
Heidi Anderson,Botanist and Wetland Ecologist
Vegetation
145
VE G E TAT I O N
Craighead, J.J. et al. 1963. A Field Guide to Rocky Mountain
Wildflowers from Northern Arizona and New Mexico to
British Colombia. Boston: Houghton Mifflin.
Cronquist et al. (ongoing, currently 6 volumes)
Intermountain Flora. New York Botanical Garden.
Despain, D. 1990. Yellowstone Vegetation: Consequences of
Environment and History in a Natural Setting. Boulder:
Roberts Rinehart.
Dorn, B. 2001. Vascular Plants of Wyoming. 3rd edition.
Elliot, C.R. and M.M. Hektner. 2000. Wetland Resources of
Yellowstone National Park. YNP: Wyoming. Out of print,
available at www.nps.gov/yell
Hitchcock and Cronquist. 1974. Flora of the Pacific
Northwest. Seattle: UWashington Press.
Hitchcock et al. Vascular Plants of the Northwest (5 volumes). Seattle: UWashington Press.
Kershaw et al. 1998. Plants of the Rocky Mountains. Lone
Pine Publishing.
Preston, R.J. 1968. Rocky Mountain Trees: A Handbook of
the Native Species with Plates and Distribution Maps.
New York: Dover.
Romme, W.H. and . Knight. 1982. Landscape diversity:
The concept applied to Yellowstone National Park.
Bioscience. 32:8.
Shaw, R.J. 1964. Trees and Flowering Shrubs of Yellowstone
and Grand Teton national parks. Salt Lake City:
Wheelwright Press.
Shaw, R.J. 1992. Wildflowers of Yellowstone and Grand
Teton national parks. Salt Lake City: Wheelwright Press.
VE G E TAT I O N
Douglas-fir forests occur at lower elevations and are associated with the Lamar, Yellowstone, and Madison river
drainages in Yellowstone National Park.
Forests
Forests cover roughly 80% of the park, and lodgepole
pine makes up nearly all of that canopy. Lodgepole
pine, Engelmann spruce, subalpine fir, whitebark
pine, and limber pine are found at higher elevations.
Douglas-fir forests occur at lower elevations, especially in the northern portion of the park. The thick
bark of Douglas-fir trees allows them to tolerate lowintensity fire. Some of the trees in these forests are
several hundred years old and show fire scars from a
succession of low-intensity ground fires. In contrast,
lodgepole pine trees have very thin bark and can be
killed by ground fires.
At higher elevations, such as the Absaroka
Mountains, older forest is dominated by Engelmann
spruce and subalpine fir, especially in areas that
grow on andesite, a volcanic rock. These forests may
have been dominated by lodgepole pine at one time,
but have been replaced by Engelmann spruce and
subalpine fir in the absence of fire and presence of
non-rhyolitic soil (a non-volcanic soil). Engelmann
spruce and subalpine fir can also be common in the
understory where the canopy is entirely composed of
lodgepole pine.
In rhyolitic soils (another volcanic substrate),
which are poor in nutrients needed by fir and spruce,
lodgepole pine remains dominant. At higher elevations such as the Absaroka Mountains and the
Washburn Range, whitebark pine becomes a significant component of the forest. In the upper subalpine
zone, whitebark pine, Engelmann spruce, and subalpine fir often grow in small areas separated by subalpine meadows. Wind and dessication cause distorted
forms known as krumholtz where most of the “tree”
is protected below snow.
Common Conifers
Higher-Elevation Species
Lodgepole Pine (Pinus contorta)
•
Most common tree in park, 80%
of canopy
•
Needles in groups of twos
•
Up to 75 feet tall
Engelmann Spruce (Picea
engelmannii)
•
Often along creeks, or around wet
areas
•
Blunt, flat needles
•
Cones grow upright, disintegrate
on tree
•
Up to 100 feet tall
Lower-Elevation Species
Douglas-Fir (Pseudotsuga menziesii)
•
Resembles the fir and the
hemlock, hence its generic name
Pseudotsuga, which means “false
hemlock”
•
Cones hang down and remain
intact, with three-pronged bract
between scales
Up to 100 feet tall
Limber Pine (Pinus flexilis)
•
Needles in groups of five
•
Young branches are flexible
•
•
Up to 75 feet tall
•
Often on calcium-rich soil
Rocky Mountain Juniper
(Juniperus scopulorum)
•
Needles scale-like
•
Sharp, square needles grow singly
•
Cones hang down and remain
intact, with no bract between
scales
Whitebark Pine (Pinus albicaulis)
•
Grows above 7,000 feet
Up to 100 feet tall
•
Needles in groups of five
•
Up to 75 feet tall
•
146
Subalpine Fir (Abies lasiocarpa)
•
Only true fir in the park
Yellowstone Resources and Issues Handbook, 2019
•
Cones are small and fleshy
•
Up to 30 feet tall
Description
Lodgepoles are the only pine in Yellowstone whose
needles grow in groups of two. The bark is typically
somewhat brown to yellowish, but a grayish-black
fungus often grows on the shady parts of the bark,
giving the tree a dark cast.
The species is shade intolerant; any branches left
in the shade below the canopy will wither and fall
off the tree. Lodgepoles growing by themselves will
often have branches all the way to the base of the
trunk because sunlight can reach the whole tree.
Reproduction
Like all conifers, lodgepole pines have both male and
female cones. The male cones produce huge quantities of yellow pollen in June and July. This yellow
pollen is often seen in pools of rainwater around the
park or at the edges of lakes and ponds.
The lodgepole’s female cone takes two years to
mature. In the first summer, the cones look like tiny,
ruby-red miniature cones out near the end of the
branches. The next year, after fertilization, the cone
starts rapidly growing and soon becomes a conspicuous green. The female cones either open at maturity
releasing the seeds, or remain closed—a condition
called serotiny—until subjected to high heat such as
a forest fire. These cones remain closed and hanging
on the tree for years until the right conditions allow
them to open. Within a short period of time after the
tree flashes into flame, the cones open up and release
seeds over the blackened area, effectively dispersing seeds after forest fires. Trees without serotinous
cones (like Engelmann spruce, subalpine fir, and
Douglas-fir) must rely on wind, animals, or other
agents to carry seeds into recently burned areas.
VE G E TAT I O N
Lodgepole Pine
The lodgepole pine (Pinus contorta) is by far the
most common tree in Yellowstone. Early botanical
explorers first encountered the species along the
West Coast where it is often contorted into a twisted
tree by the wind, and thus named it Pinus contorta
var. contorta. The Rocky Mountain variety, which
grows very straight, is Pinus contorta var. latifolia.
Some American Indian tribes used this tree to make
the frames of their tipis or lodges, hence the name
“lodgepole” pine.
Lodgepole pine forests are the most common in
Yellowstone. A lodgepole’s serotinous cones need to
be exposed to the high heat of a forest fire for the
seeds to be released. The other cones open when the
seeds within are mature (end of the second summer).
Habitat
Lodgepole pines prefer slightly acidic soil, and will
grow quickly in mineral soils disturbed by fire or by
humans, a road cut for example. Their roots spread
out sideways and do not extend deeply—an advantage in Yellowstone where the topsoil is only about 6
to 12 inches deep, but a disadvantage in high winds.
Lodgepole pines are vulnerable in windstorms, especially individuals that are isolated or in the open.
Besides reseeding effectively after disturbance,
lodgepole pines can grow in conditions ranging from
very wet ground to very poor soil prevalent within
the Yellowstone Caldera. This flexibility allows the
species to occur in habitat that otherwise would not
be forested.
Because lodgepole pines are dependent on sunny
conditions for seedling establishment and survival,
the trees do not reproduce well until the canopy
opens up significantly. In the Yellowstone region,
this allows the lodgepole pine forest to be replaced
by shade-loving seedlings of subalpine fir and
Engelmann spruce where the soil is well-developed
enough to support either of these species. In areas
of nutrient-poor soil, where Engelmann spruce and
subalpine fir struggle, lodgepole pines will eventually
be replaced by more lodgepole pine trees as the forest
finally opens enough to allow young lodgepoles to
become established.
Vegetation
147
VE G E TAT I O N
Whitebark Pine
Whitebark pine (Pinus albicaulis) occurs at high elevations a in subalpine communities in the northern
Rocky Mountains and the Pacific Northwest. It often
grows in areas with poor soils, high winds, and steep
slopes that are inhospitable to other tree species.
White bark pine is a key species in these upper ranges
where it retains snow and reduces erosion, acts as a
nurse plant for other subalpine species, and produces
seeds that are an important food for birds, grizzly
bears, and other wildlife. Whitebark pine produces
wingless seeds and relies primarily on Clark’s nutcrackers (Nucifraga Columbiana) for seed dispersal.
Substantial mortality in whitebark populations has
been documented throughout its range. Decreases
are attributed to the introduced pathogen, white
pine blister rust (Cronartium ribicola); native mountain pine beetle (Dendroctonus ponderosae); historic
wildand fire suppression resulting in more frequent,
larger, and hotter wildfires; and projected environmental factors associated with climate change. These
agents, both individually and collectively, pose a significant threat to the persistence of healthy whitebark
pine populations on the landscape.
A reported 14–16% of whitebark pine trees taller
1.4 meters tall are infected with blister rust in the
Greater Yellowstone region. As of 2017, 1,502 of the
more than 5,300 monitored trees had died, including
67% of those in the >10 cm in diameter size classes.
(The mountain pine beetle prefers larger trees for
laying their eggs; the larvae feed on the inner phloem
of the bark.) In addition, the Greater Yellowstone
Network has estimated that by the end of 2015, 26%
of whitebark pine trees >1.4 meters tall had died.
Aerial surveys, which measure the spatial extent
of mortality rather than the percentage of individual
dead trees counted on the ground, have generally
produced higher whitebark pine mortality estimates
in the Greater Yellowstone Ecosystem. This could be
because larger trees, which occupy more of the area
in the forest canopy visible from the air, are more
likely to be attacked by beetles. In 2013, an aerial survey method called the Landscape Assessment System
was used to assess mountain pine beetle-caused
mortality of whitebark pine across the region. Results
of the one-time study indicate that nearly half (46%)
of the GYE whitebark pine distribution showed severe mortality, 36% showed moderate mortality, 13%
showed low mortality, and 5% showed trace levels of
mortality.
148
Yellowstone Resources and Issues Handbook, 2019
The needles of a whitebark pine are clustered in
groups of five.
Despite the high percentage of large trees that
have died, there are trees that are still producing
cones and regeneration is occurring. The network
estimated an average growth of 51 small trees per 500
meters squared by the end of 2015.
More Information
Gibson, K. 2006. Mountain pine beetle conditions in whitebark pine stands in the Greater Yellowstone Ecosystem,
2006. Missoula, MT: USDA Forest Service, Forest Health
Protection, Missoula Field Office.
Greater Yellowstone Whitebark Pine Monitoring Working
Group. 2017. Monitoring whitebark pine in the Greater
Yellowstone Ecosystem: 2016 annual report. Natural
Resource Data Series NPS/GRYN/NRDS—2017/1453.
National Park Service, Fort Collins, Colorado.
Macfarlane, W.W., Logan, J.A., and Kern, W.R.. 2013. An
innovative aerial assessment of Greater Yellowstone
Ecosystem mountain pine beetle-caused whitebark pine
mortality. Ecological Applications 23(2):421–37
Mahalovich, M. F. 2013. Grizzly Bears and Whitebark Pine
in the Greater Yellowstone Ecosystem. Future Status of
Whitebark Pine: Blister Rust Resistance, Mountain Pine
Beetle, and Climate Change. US Forest Service. Report
Number: 2470 RRM-NR-WP-13-01.
Shanahan, E., K. M Irvine, D. Thoma, S. Wilmoth, A. Ray, K.
Legg, and H. Shovic. 2016. Whitebark pine mortality
related to white pine blister rust, mountain pine beetle
outbreak, and water availability. Ecosphere 7(12)
Shanahan, E., K. Legg, and R. Daley. 2017. Status of whitebark pine in the Greater Yellowstone Ecosystem: A steptrend analysis with comparisons from 2004 to 2015.
Natural Resource Report NPS/GRYN/NRR-2017/1445.
National Park Service, Fort Collins, Colorado.
Tomback, D.F., S.F. Arno, and R.E. Keane. 2001. Whitebark
pine communities: Ecology and restoration.
Washington, DC: Island Press.
Staff Reviewer
Kristin Legg, Program Manager, Greater Yellowstone
Network.
Erin Shanahan, Ecologist, Greater Yellowstone Network.
Forest Insect Pests
The conifer trees of Yellowstone face six major insect
and fungal threats. The fungus is an nonnative species, but the insects are native to this ecosystem. They
have been present and active in cycles, probably for
centuries. A scientist studying lake cores from the
park has found some of their insect remains in the
cores, indicating their presence even millions of years
ago. However, in the last 10 years, all five insects have
been extremely active, which may be due to the effects of climate change.
The primary cause of tree mortality in the
Yellowstone is native bark beetles. The beetles damage trees in similar ways: their larvae and adults
consume the inner bark. If the tree is girdled, it dies.
Their feeding activity can girdle a tree in one summer,
turning the crown red by the following summer. The
needles usually drop within the next year, leaving a
standing dead tree. Isolated pockets of red-needled
trees are scattered throughout the park.
Pest Activity
The severity of insect-caused tree mortality has been
considerable throughout the West for over a decade,
and the insects have spread to previously unaffected
plant communities. Several native bark beetle species
in the Scolytidae family have altered extensive areas
within Greater Yellowstone. Forest structure, tree
health, and climate are the major factors in determining whether an outbreak expands; drought and
warmer temperatures can make forests more vulnerable to infestation.
Recent evaluation has shown decreases in infection and infestation rates since 2001, suggesting
that resistance may be slowly increasing. Although
activity by both Douglas-fir beetle and Engelmann
spruce beetle has declined to endemic (natural to
Yellowstone) levels since 2000, other forest insects of
ecological significance remain active. Mountain pine
beetle activity was largely confined to the northwest
portion of the park, in high-elevation whitebark
pine and lower-elevation lodgepole pine, peaking in
2009 with annual decreases in mortality since then.
Defoliation of Douglas-fir and Engelmann spruce
Forest Insect Pests
Number in Yellowstone
Six forest pests
Mountain Pine Beetle
(Dendroctonus ponderosae)
•
Affects whitebark, lodgepole, and
limber pine.
•
The tree defends itself by increasing
resin (pitch) production, which can
“pitch out” the insect from the tree
and seal the entrance to others.
•
Look for globs of resin, often mixed
with wood borings, on the bark.
•
Adults emerge in mid-summer.
Engelmann Spruce Beetle
(Dendroctonus rufipenni)
•
Affects Englemann spruce, rarely
lodgepole pine.
•
Larvae feed for two years.
•
Look for reddish dust on the bark
and at the base of the tree in early
summer.
Douglas-Fir Beetle (Dendroctonus
pseudotsugae)
•
Affects Douglas-fir.
•
Western Spruce Budworm
(Choristoneura occidentalis)
•
Affects Douglas-fir, true firs,
spruce.
Larvae defoliate trees and can
destroy cones and seeds.
Look for clumps of chewed needles
on branch tips.
White Pine Blister Rust
•
A nonnative disease caused by a
fungus, Cronartium ribicola.
•
Affects whitebark and limber pines.
•
The disease affects the tree’s ability
to transport nutrients and produce
cones, and may eventually kill the
tree.
•
Look for cankers (lesions) on the
bark.
Larvae also consume outer bark.
Western Balsam Bark Beetle
(Dryocoetes confusus)
•
Affects subalpine fir.
•
•
Management Issues
•
Research supported by the National
Park Service will investigate the
interactions between insect
infestations and wildfire.
Vegetation
149
VE G E TAT I O N
Understory Vegetation
Understory vegetation differs according to precipitation, the forest type, and the substrate. Lodgepole
pine forest is often characterized by a very sparse understory of mostly elk sedge (Carex geyeri) or grouse
whortleberry (Vaccinium scoparium). Pinegrass
(Calamagrostis rubescens) occurs frequently under
Douglas-fir forest but is also common under other
forest types, especially where the soil is better developed or more moist. In some areas of the park,
such as Bechler and around the edges of the northern range, a more obviously developed shrub layer
is composed of species such as Utah honeysuckle
(Lonicera utahensis), snowberry (Symphoricarpos
spp.), and buffaloberry (Shepherdia canadensis).
VE G E TAT I O N
by the western spruce budworm is present in the
park throughout the lower Lamar and along the
Yellowstone and Lamar river valleys, but has spread
considerably less in recent years. These trends appeared to continue in 2011, when the park was only
partially surveyed.
Future of Insect Outbreaks in Yellowstone
Landscape-scale drought and the availability of suitable host trees have contributed to the initiation and
persistence of insect outbreaks. Healthy trees can
defend themselves from beetle attack by “pitching
out” adult females as they try to bore into the tree.
Extreme winter temperatures can kill off overwintering broods, and wet summer weather impedes the
insects from invading additional trees. Insect activity also decreases as the larger and more susceptible
trees are killed off. Spruce beetles have declined
because they have killed almost all of their preferred
food source (spruce trees more than 10 inches
in diameter).
Recent and ongoing studies supported by the
National Park Service are investigating the interaction
between insect infestations and wildfire. Researchers
have focused on how bark beetle epidemics may affect fire behavior in lodgepole-dominated forests and
are comparing the resulting fire hazard with that in
Douglas-fir forests.
More Information
Amman, G.D. and K.C. Ryan. 1991. Insect infestation of fireinjured trees in the Greater Yellowstone Area, Edited by US
Department of Agriculture, Forest Service, Intermountain
Research Station.
Christof, B., D. Kulakowski, and T.T. Veblen. 2005. Multiple
disturbance interactions and drought influence fire
severity in Rocky Mountain subalpine forests. Ecology
86(11):3018–3029.
Despain, D.G. 1990. Yellowstone vegetation: Consequences of
environment and history in a natural setting. Boulder, CO:
Roberts Rinehart Publishing Company.
Fleming, R.A., J.-N. Candau, and R.S. McAlpine. 2002.
Landscape-scale analysis of interactions between insect defoliation and forest fire in central Canada. Climatic Change
55(1–2):251–272.
Furniss, M. M. and R. Renkin. 2003. Forest entomology in
Yellowstone National Park, 1923–1957: A time of discovery and learning to let live. American Entomologist
49(4):198–209.
Hagle, S.K. et al. 2003. A Field Guide to Diseases and Insects
of Northern and Central Rocky Mountain Conifers. U.S.
Forest Service Report R1-03-08.
Hicke, J.A. et a.. 2006. Changing temperatures influence
suitability for modeled mountain pine beetle outbreaks
150
Yellowstone Resources and Issues Handbook, 2019
in the western United States. Journal of Geophysical
Research 111:G02019.
Johnson, P.C. and R.E. Denton. 1975. Outbreaks of the
western spruce budworm in the American northern
Rocky Mountain area from 1922 through 1971, Edited
by US Department of Agriculture, Forest Service,
Intermountain Forest and Range Experimentation
Station. Ogden, UT.
Logan, J.A. et al. 2003. Assessing the impacts of global
warming on forest pest dynamics. Frontiers in Ecology
and the Environment 1:130–137.
Lynch, H., R. Renkin, R. Crabtree, and P. Moorcroft. 2006.
The influence of previous mountain pine beetle
(Dendroctonus ponderosae) activity on the 1988
Yellowstone fires. Ecosystems 9(8):1318–1327.
McCullough, D.G., R.A. Werner, and D. Neumann. 1998.
Fire and insects in northern and boreal forest ecosystems of North America. Annual Review of Entomology
43(1):107–127.
Pauchard, A. and Alaback, P. 2006. Edge types defines alien
species invasions along P. contorta burned, highway and
clearcut forest edges. Forest Ecology and Management
223: 327–335.
Renkin, R.A. and D.G. Despain. 1992. Fuel moisture, forest
type, and lightning-caused fire in Yellowstone National
Park. Canadian Journal of Forest Research 22(1):37–45.
Ryan, K.C. and G.D. Amman. 1994. Interactions between
fire-injured trees and insects in the Greater Yellowstone
Area. In D. G. Despain, ed., Plants and their environments: Proceedings of the first Biennial Scientific
Conference on the Greater Yellowstone Ecosystem,
259–271. Yellowstone National Park, WY: US
Department of the Interior, National Park Service, Rocky
Mountain Region, Yellowstone National Park.
Schmid, J.M. and G.D. Amman. 1992. Dendroctonus
beetles and old-growth forests in the Rockies. In M.R.
Kaufmann, W.H. Moir and R.L. Bassett, ed., Old-growth
forests in the Southwest and Rocky Mountain regions,
proceedings of a workshop, 51–59. Portal, AZ: USDA
Forest Service, Rocky Mountain Forest and Range
Experimentation Station.
Schoennagel, T., T.T. Veblen, and W.H. Romme. 2004. The
interaction of fire, fuels, and climate across Rocky
Mountain forests. BioScience 54(7):661–676.
Simard, M. et. al. 2011. Do mountain pine beetle outbreaks
change the probability of active crown fire in lodgepole
pine forests? Ecological Monographs 81(1): 3–24.
Veblen, T. T., K. S. Hadley, E. M. Nel, T. Kitzberger, R. Marion,
and R. Villalba. 1994. Disturbance regime and disturbance interactions in a Rocky Mountain subalpine forest. Journal of Ecology 82(1):125–135.
Staff Reviewer
Kristin Legg, Program Manager, Greater Yellowstone
Network
VE G E TAT I O N
Other vegetation communities in Yellowstone include sagebrush-steppe, wetlands, and hydrothermal
communities. Sagebrush-steppe occurs in the northern range in Yellowstone.
Other Vegetation Communities
Sagebrush-steppe
This vegetation type occurs in the northern range;
in Hayden, Pelican, and Madison valleys; on Swan
Lake Flats; and along many of the rivers and creeks.
Mountain big sagebrush (Artemisia tridentata var.
vaseyana) dominates, along with several other kinds
of sagebrush. Several grass species, such as Idaho
fescue (Festuca idahoensis), also dominate sagebrushsteppe. Other species found in sagebrush-steppe
include mountain brome, needlegrasses, yampah,
sticky geranium, and several species of upland sedges.
The northern range can be spectacular with these
wildflowers in late June and early July.
In 2015, a long-term sagebrush-steppe monitoring
program was inititated to track the changes in plant
cover and species composition over many years with
an emphasis on invasive species. Data loggers will be
used to assist staff with correlating any changes in the
vegetation with climate change.
Wetlands
Where to See
Some wetlands located near roads:
•
Northeast Entrance Road, beginning east of
Yellowstone Picnic Area: listen for frogs in spring;
look for sandhill cranes throughout the Lamar Valley.
•
Firehole Lake Drive: listen for frogs and look for
elephant’s head flowers where the road begins.
•
Dunraven Pass area: look for abundant wildflowers
in high-elevation seep wetlands near the road.
•
Norris Geyser Basin, Back Basin: near Puff ‘n’ Stuff
Geyser, look for dragonflies.
•
All thermal areas: look for seaside arrow grass,
ephydrid flies, thermophiles, and other life forms.
Wetlands
Yellowstone’s wetlands include lakes, rivers, ponds,
streams, seeps, marshes, fens, wet meadows, forested
wetlands, and hydrothermal pools. They occupy
more than 357 square miles (924 km2) in Yellowstone:
44% are lakes and ponds larger than 20 acres or
having water deeper than 6.6 feet at low water; 4%
are rivers and streams; 52% are shallow water systems that dry up most years. Approximately 38% of
the park’s plant species—including half of the rare
plants—are associated with wetlands, and 11% grow
only in wetlands. Wetlands provide essential habitat
for Yellowstone’s rare plants, thermal species, reptiles
and amphibians, and for numerous insects, birds and
fish.
Hydrothermal Communities
Yellowstone is the best place in the world to see
hydrothermal phenomena such as geysers and hot
springs. Fascinating and unique plant communities
have developed in the expanses of thermally heated
ground. Many of the species that occur in the geyser
basins are actually species that tolerate tremendously
different conditions, and thus grow all over the western United States. Other species, however, are typical
of the central Rockies, or are regional endemics.
Hydrothermal plant communities demonstrate in
very short periods of time that change is fundamental
in any natural system. In a few days, the ground can
heat up, perhaps triggered by an earthquake, and
kill plants, while an adjacent area may cool, allowing
plants to invade a previously inhospitable place.
Staff Reviewer
Stefanie Wacker, Vegetation Ecologist
Vegetation
151
VE G E TAT I O N
NPS/D. RENKIN
The appearance of wildflowers announces spring in the park. Enjoy the wildflowers, but don’t pick them.
Wildflowers
Wildflowers such as lupine (Lupinus argenteus) and
arnica (Arnica cordifolia) often grow under the forest
canopy, but the most conspicuous wildflower displays occur in open meadows and sagebrush-steppe.
The appearance of springbeauties (Claytonia lanceolata), glacier lilies (Erythronium grandiflorum), and
steershead (Dicentra uniflora) announce spring in
the park. Soon colors splash the slopes, especially on
the northern range—yellow from arrowleaf balsamroot (Balsamorhiza sagittata), white from phlox
(Phlox multiflora), reds and oranges from paintbrush
(Castilleja), and blue from penstemon (Penstemon
montanus) and lupine. Goldenrod (Solidago missouriensis) and purple asters indicate the coming of fall.
Finding Flowers
Elevation, relative temperatures, soil types, and
precipitation patterns all play a role in what you find
blooming in various areas at different times of the
year. In addition, far-reaching events such as fires can
cause spectacular blooms of species that thrive on the
conditions these events create.
Remember that many of Yellowstone’s wildflowers are also very important parts of animal diets.
The bulbs of springbeauty and glacier lily, for example, are vital spring foods of the grizzly bear. Wild
strawberries are collected by ground squirrels and
chipmunks; the seeds of most wildflowers are used
by birds and insects. Even the petals of many flowers
are eaten by animals. Bees and other insects collect
nectar and pollen.
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Yellowstone Resources and Issues Handbook, 2019
Exotic Species
Exotic plants—escaped domestics and
“weeds”—can be found
in Yellowstone. Look
for them in disturbed
sites such as roadsides where they have
little initial competition
and frequent redisturbance. Dalmation
toadflax (Linarea
dalmatica), yellow
sweetclover (Melilotus
officinalis), ox-eye daisy
(Leucanthemum vulgare), and other exotics
compete unnaturally
with native plants. For
this reason, and for the
contin