Yellowstone Handbook 2019

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. 152 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