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Introduction

Glacier National Park is located in northwest Montana along the main range of the rocky Mountains south of the Canadian border. The Park adjoins the western edge of the Northern great Plains on the east, while to the west, across the North Fork of the Flathead River, lies the inland maritime Whitefish Range. The Flathead Valley and Flathead Lake, the largest freshwater lake in western North America, are located just tot he southwest. Glacier Park encompasses approximately 2000 km2 (ca. 1,000,000 acres), nearly all of which is mountainous terrain. Mountains rise to elevations of 2450-3500 m (8,000-10,000 ft). there are two north-south mountain ranges in Glacier Park, the Lewis and Livingston ranges. The Livingston range is found in the northwest part of the Park, while the lewis Range traverses the entire east side. The Continental Divide (between the Pacific and Atlantic oceans) follows the crest of the Livingston range in the north and then traverses the crest of the Lewis Range. The Northern Divide (between the Arctic and Atlantic oceans) begins in the center of the Lewis Range at Triple Divide Peak. Valleys are generally 920-1250 m (3,000-4,000 ft) east of the Divide.

Glacier was declared a national park by an act of Congress in 1910. Waterton Lakes national Park, Glacier's sister park, is adjacent to the north in Alberta, Canada. The Bob Marshall Wilderness Complex administered by the U.S. Forest Service is immediately south of the Park, separated by the Middle Fork of the Flathead River and U.S. Highway 2. The Blackfeet Indian Reservation adjoins the Park on the east side, and Flathead National Forest is to the west, separated by the North Fork of the Flathead River and an associated road. Glacier Park's pristine quality and vast biological wealth led the United nations Education, Scientific and Cultural organization (UNESCO) to designate Waterton-Glacier International Peace Park a Biosphere Reserve in 1976, and a World Heritage Site in 1995.

Glacier is primarily a wilderness park. With the exception of the Going-to-the-sun Road crossing the Continental Divide from east to west, roads are found only on the periphery. On the other hand, there are more than 700 miles of trails in the Park. With the exception of reduced fire frequency and introduction of exotic plants, the vegetation of Glacier Park has been little changed by European settlement.

Climate

The climate of Glacier National Park is transitional between northern maritime and northern continental (Finklin 1986). It is most strongly influenced by Pacific storms from the west and arctic air from the north, mediated by the high peaks of the Continental Divide. A strong Pacific storm track follows the jet stream along the Canadian border during much of the year and brings a warm, moist influence to Glacier and the adjacent area. Most of the Pacific moisture falls along or west of the Continental Divide, and little remains by the time the storms reach the east edge of the Park. Cold arctic air masses moving south from continental Canada are usually confined east of the Continental Divide, with some cold air flushing west through mountain passes. These prevailing weather patterns cause a pronounced difference between the east and west edges of the Park, but these differences are lost as one approaches the Continental Divide from either side. Finklin's (1986) weather summary for the Park provides the following data.

Glacier Park temperatures are generally warmer in the western valleys than east of the Divide. January is normally the coldest month, while July is the warmest. Average minimum temperature for january was -11C (12F) at West Glacier and ca. -14C (7F) at St. Mary and East Glacier in 1951-1980. Average maximum for July was 26C (78F) at West Glacier and 24C (76F) and 23C (74F) at St. Mary and East Glacier respectively. Temperatures are generally cooler at higher elevations, averaging 8C cooler per 1000 m (4F per 1000 ft). However, temperature inversions, in which valleys are cooler than peaks, often occur at night during the summer and during the day in the winter.

Annual precipitation is generally similar on the two sides of Glacier Park, but decreases from south to north. West of the Divide, annual precipitation was 75 cm (30 in) and 58cm (23 in) at West Glacier and Polebridge respectively in 1951-1980, while east of the Divide East Glacier, St. mary and Lake Sherburne average 76 cm (31 in), 66 cm (23 in) and 59 cm (23 in) respectively. Precipitation is much higher closer to the Continental divide. Many Glacier, just a short distance west of lake Sherburne and at nearly the same elevation, receives nearly twice the precipitation, and Grinnell Glacier and high elevations along the Divide receive 250 cm (100 in) or more. At least half the precipitation falls as snow near the edges of the Park, while 70% is snow at higher elevations. Snowfall may occur during any month of the year at higher elevations. West of the Continental Divide, average relative humidity remains near 80% over the entire year, while it is below 50% during summer months east of the Divide.

The eastern edge of the Park receives more sunshine and higher winds than the lower elevations west of the Divide. West Glacier average 132 clear days per year, while Browning, just east of East Glacier, averaged 164 during the period of 1921-48. Strong winds are common east of the Continental Divide, while winds west of the Divide are rather calm. Exceptionally strong, warm (chinook) winds occur along the east front of the mountains in winter; wind speeds of 160 km/h (100 mph) have been recorded. Valleys west of the Divide average winds of 10 km/h (6 mph) during winter months, while ease of the Divide wind speeds average twice that. Prevailing wind direction is from the west to southwest.

Warmer, less windy winters coupled with cloudier, more humid summers provide a more temperate climate for vegetation west of the Continental Divide in Glacier. The large winter fluctuations in temperature associated with chinook winds east of the Divide are particularly detrimental to woody plants with living tissue above ground. These differences are less pronounced close to the Continental Divide, where the climate and vegetation of head water basins are similar on both sides of the Divide.

Geology

Glacier National Park is a land of mountains carved by glaciers. Geologic formations in the Park are predominantly sedimentary with minor intrusions of igneous rock. Most of these formations are part of the Belt Series dating from the Precambrian age, 800 million to more than a billion years ago. They include limestones and dolomites of the Altyn and Helena (formerly Siyeh) formations and red and green mudstones (argillites) of the Grinnell and Appekunny formations. Shaly mudstones of Cretaceous age, 70-100 million years old, outcrop along the east and south edges of the park. All of these formations were deposited in shallow seas. These sedimentary deposits were folded and uplifted 65-70 million years ago, and huge areas of old Belt rocks slid as a whole eastward on top of younger Cretaceous formations. Along this overthrust zone, older rocks lie on top of younger, contrary to what is normally expected. A more detailed account of Glacier's geology is given by Raupp et al. (1983).

Geology can influence vegetation where he derived soils are poorly developed and still reflect the chemical composition of the parent rock. some species of plants favor calcium-rich soils, while others prefer more acidic substrates. The limestones and dolomites of the Altyn and Siyeh formations are more calcareous, with a higher pH than that of granitic rocks or most mudstones. Furthermore, the white limestones of the altyn Formation, found around St. Mary, are more calcareous than the dirty yellow or grey Siyeh Formation in the center of the Park. A number of plants occur only on soils derived from the softer, younger, shaly Cretaceous mudstones outcropping in the Marias Pass Area.

The uplifted rocks of Glacier Park have been dramatically carved by the action of ice and water, and this activity continues today. During the last ice age, Glacier Park was almost entirely buried beneath huge valley glaciers. These glaciers carved the sheer cliffs with amphitheater-like cirques at their bases and trough-shaped valleys that characterize the Park today. Glaciers deposited huge bands of rocky debris (moraine) along their edges and across their valleys as they retreated. These moraines sometimes dammed valleys, forming the long finger lakes common on the Park's west side. All of the park's glaciers may have disappeared during a warm period about 8000 years ago (Carrara 1989). There are currently about 40 active glaciers in the Park, but they are small and have been shrinking for at least the past 150 years (Raupp et al. 1983). The glaciers continue to erode small areas, but water, snow and wind now play a more significant role, Streams and river erode their banks, especially during rapid spring snowmelt. Wind causes erosion of sparsely vegetated slopes and ridges. Avalanches are common in the Park and prevent many slopes from developing forest vegetation.

The physiography of Glacier affects the vegetation even more than the geology. The deep glacial valleys with high, steep headwalls near the Continental Divide provide warm, snowy, wet environments typical of more coastal ranges. Rock slides, talus slopes, and avalanche chutes form on steep slopes left by the glaciers. These physically harsh habitats are favorable to some plants and not others. Fresh moraine is home to many early successional species that thrive on moist, poorly developed, gravelly soil.

Vegetation

Vegetation of Glacier national ark is diverse, due primarily to the great variation in elevation that influences many environmental factors affecting plant growth. Temperature generally decreases while precipitation and wind increase with elevation. However, aspect greatly modifies these effects in dissected mountainous terrain. North- and east-facing slopes and valley bottoms are cooler because they receive less direct sunlight and may be wetter when wind redistributes snow to lee slopes. Merriam (1890) recognized that increases in elevation generally result in vegetation changes similar to those found when travelling north in the Northern Hemisphere at the same elevation, and this is the basis of his life zone classification. Four Merriam life zones occur in Glacier Park: Transition, Canadian, Hudsonian, and Arctic-Alpine (Standley 1921). I use a three-zone classification in this book to describe the distribution of plants. It is based on elevation and corresponds to the Merriam system. I further divide the subalpine zone into lower and upper zones that roughly correspond to Merriam's Canadian Hudsonian zones respectively.

This Book Merriam Zones Elevation Range
Montane Transition 915-1675 m (3,000-5,500 ft)
Subalpine   1525-2285 m (5,000-7,500 ft)
   (lower) Canadian  
   (upper) Hudsonian
Alpine Arctic-Alpine >1980 m (>6,500 ft)

The Montane Zone

The climate of the Montane zone is characterized by relatively warm temperatures. Grassland vegetation is common on both sides of the Continental Divide. However, montane forests are rare on the east side where lower subalpine forests extend to valley bottoms on cool slopes, and most warm slopes support grasslands.

Riparian Forests

Riparian forests occur along rivers and major streams and are well developed only in the Montane Zone. Both the North Fork and the Middle Fork of the Flathead River, on the west and south boundaries respectively, are unregulated by dams and display good examples of riparian succession. Black cottonwood (Populus balsamifera ssp. trichocarpa) is the dominant species in young and middle-age stands. It establishes on newly created gravel bars along with willow (Salix exigua, S. drummondiana, S. eriocephala), red osier dogwood (Cornus stolonifera), and a diverse assemblage of colonizing species such as Agrostis stolonifera, Astragalus alpinus, A. vexilliflexus, A. robbinsii, Dryas drummondii, Chamerion latifolium, and Equisetum spp. (Malanson and Butler 1991). Other deciduous shrubs or small trees colonize shortly afterward (Foote 1965). These include mountain maple (Acer glabrum), alder (Alnus incana), hawthorn (Crataegus douglasii), river birch (Betula occidentalis), silverberry (Elaeagnus commutata), and chokecherry (Prunus virginiana). Soil develops as stands age and species of more upland habitats become important. White spruce (Picea glauca), ponderosa pine (Pinus ponderosa ), and western red cedar (Thuja plicata) share the canopy with cottonwood, Herbaceous species such as Aster spp., Cerastium arvense, Galium triflorum, Heracleum spondylium, Osmorhiza chilensis, Poa pratensis, and Smilacina stellata become more common. If flooding or channel migration fails to cause severe disturbance, cottonwood will eventually die out, and forests will resemble mesic upland coniferous forests.

Grasslands

Grasslands are dominated by cool season bunchgrasses. They occur in a broad band along the mountain front east of the Continental Divide,such as along St. Mary Lake, in the Blacktail Hills near marias Pass, and north of Polebridge west of the Divide. Many of these communities have a significant shrub component and could be better thought of as shrublands. Polebridge grasslands have been considered most closely allied to Palouse prairie (Koterba and Habeck 1971), but they are floristically indistinguishable from foothills grasslands common throughout Montana's intermountain valleys east of the Continental Divide (Weaver 1980). Dominant native grasses include rough fescue (Festuca scabrella), Idaho fescue (F. idahoensis), bluebunch wheatgrass (Elymus spicatus), oatgrass (Danthonia intermedia), and needlegrass (Stipa spp.). Lupinus sericeus, Achillea millefolium, Eriogonum spp., Geranium viscosissimum, Geum triflorum, and Arnica spp. are common broad-leaved herbs. Mountain big sagebrush (Artemisia tridentata ssp. vaseyana) is common in the Polebridge grasslands. It is killed by fire, so its abundance is probably determined primarily by fire frequency. Grasslands east of the Divide have varying amounts of shrubs including shrubby cinquefoil (Pentaphylloides fruticosa), serviceberry (Amelanchier alnifolia), Canada buffaloberry (Shepherdia canadensis), and bearberry (Arctostaphylos uva-ursi). These become more common in the subalpine zone. Kentucky bluegrass (Poa pratensis) and timothy (Phleum pratense) are common exotic grasses, especially on the east side of the Park where timothy dominates large areas to the exclusion of most other species.

The mesic grasslands of Glacier Park, especially on the west side, are being invaded by trees, primarily lodgepole pine (Pinus contorta) and aspen (Populus tremuloides). Historically, fires were frequent around Polebridge (Barrett et al. 1991) and on the east side of the Park (Barrett 1993, 1997) and were probably the most important factor in maintaining the prairies, although relatively low precipitation and well-drained soils may also have played a role (Koterba and Habeck 197 1). Fires around Polebridge in 1988 killed sagebrush and returned advancing lodgepole forest to grassland.

Aspen Forest

Aspen forest is common in the montane zone, especially east of the Divide where aspen groves intermingle with grassland to form extensive parklands (Lynch 1955). Many of these groves are probably in the lower subalpine zone, but they are all treated here for convenience. West of the Continental Divide, aspen stands are small and usually associated with stream corridors or depressions on slopes otherwise dominated by conifers. Examples are common along the North Fork Flathead Inside Road. Similar sites support aspen east of the Divide, but there stands may be extensive, occupying depressions and cool slopes in the hills along the cast edge of the Park. Aspen forest is leafless until late spring and canopies are not dense, so a good deal of light reaches the ground. As a result, understory vegetation is usually luxuriant. Driest stands have snowberry (Symphoricarpos spp.), serviceberry, Oregon grape (Berberis repens), and rose (Rosa acicularis) dominant in the understory. Wetter stands east of the Divide often have black cottonwood in the canopy and an understory of tall herbs and grasses such as Elymus glaucus, Bromus spp., Geranium richardsonii, Osmorhiza occidentalis, Heracleum spondylium, and Angelica arguta. A dense flowering of glacier lilies (Erythronium grandiflorum) can be seen in some stands before the trees leaf out.

Aspen stands, especially west of the Divide, often have conifers, such as lodgepole pine, spruce (Picea spp.) and subalpine fir (Abies lastocarpa), mixed in. This indicates that many aspen groves are a successional stage eventually leading to spruce/fir forest (Pfister et al. 1977). Periodic fires maybe maintaining aspen in many areas (Barrett 1993). Around Polebridge numerous aspen sprouts occur around older trees killed by the Red Bench fire of 1988. Fire is considered essential for maintaining aspen farther south in the Rocky Mountains (DeByle et al. 1987), but it may not be so important in the aspen parklands of Canada and Montana (Lynch 1955). Aspen stands may be at least partially defoliated during outbreaks of tent caterpillars (Malacosoma spp.).

Wetlands

Wetlands, such as wet meadows, swamps, marshes, and fens, are usually small but common in the montane zone. These wetlands are associated with glacial ponds and takes and with riparian areas and beaver impoundments. Examples can be seen above Lake McDonald and along the Camas Road. Small wet meadows dominated by Calamagrostis canadensis often occur in depressions in coniferous forest and along lake margins. Swamps dominated by alder and willow (Salix drummondiana, S. geyeriana, or S. bebbiana) occur most commonly along streams or around beaver impoundments. Marsh vegetation develops on saturated to flooded mineral soil, often around the shallow margins of lakes or ponds. Marshes are typically dominated by Carex utriculata and/or Equisetum fluviatile. Fen vegetation develops on wet organic soils of glacial depressions or gentle slopes associated with groundwater seepage. Fens are most common west of the Divide, often on nearly level drainage divides. They are commonly dominated by sedges, especially Carex lasiocarpa, C. buxbaumii, and C. utriculata. Although wetlands occupy only a small amount of surface area in Glacier Park, they provide a large diversity of habitats and support a large number of species not found elsewhere.

Coniferous Forest

Coniferous forest of the montane zone occurs primarily on warm slopes and river terraces along the west and, to a lesser extent, east edges of the Park. The most common montane forests are dominated by Douglas fir (Pseudotsuga menziesii), lodgepole pine, paper birch (Betula papyrifera), and spruce. Western larch (Larix occidentalis) is common west of the Divide. These forests occur on warm slopes along forks of the Flathead River and their larger tributaries and in the lower St. Mary and Two Medicine valleys. The shrub understory includes snowberry (Symphoricarpos albus), Oregon grape, mountain maple, spiraea (Spiraea betulifolia), thimbleberry (Rubus parviflorus), and huckleberry (Vaccinium membranaceum). Calamagrostis rubescens, Aster conspicuous, Thalictrum occidentale, and Arnica cordifolia are common in the ground layer; Linnaea borealis and Clintonia uniflora occur in moister sites. Spruce (Picea engelmannii) and subalpine fir become more common at the upper limits of the montane zone. Forests dominated by Ponderosa pine occur on broad terraces above the North Fork Flathead River south of Logging Creek. Most stands have Douglas fir and western larch younger than the pine and understories similar to typical Douglas-fir forests described above (Lunan and Habeck 1973).

River terraces often support moist to wet forest dominated by spruce (Picea glauca), often with scattered cottonwood, western larch (Larix occidentalis), white pine (Pinus monticola), or Douglas fir. Moist stands support shrubs such as serviceberry, thimbleberry, huckleberry and a rich ground layer often including Cornus canadensis, Linnaea borealis, Clintonia uniflora, and Aralia nudicaulis. Wet stands have standing water between trunks for much of the year. Common understory plants include Cornus stolonifera, Rubus pubescens, Equisetum arvense, E. scirpoides, and Mitella nuda.

Exceptionally warm, moist forests, rich in species, occur along Lake McDonald. Western red cedar and western hemlock (Tsuga heterophylla) dominate these stands, but large white pine, larch, and Douglas fir are also common. Lodgepole pine, paper birch, grand fir, and even cottonwood can be found in these stands (Habeck 1968). Pacific yew (Taxus brevifolia), huckleberry, rose (Rosa gymnocarpa) and spiraea are common shrubs. The ground layer is luxuriant with many species of mosses and vascular plants, including Clintonia uniflora, Cornus canadensis, Linnaea borealis, Aralia nudicaulis, Viola orbiculata, Goodyera oblongifolia, Chimaphila umbellata, and Tiarella trifoliata.

The fire history of montane forests west of the Continental Divide is complex (Barrett et al. 1991). A mixture of crown fires and ground fires predominated in the North Fork Flathead Valley resulting in some stands of old ponderosa pine, larch, and Douglas fir with open understories as well as stands of dense lodgepole pine. However, fire suppression during the past century has allowed young spruce, subalpine fir, and Douglas fir to invade formerly open stands (Lunan and Habeck 1973). The moister forests near West Glacier experienced fewer ground fires and less frequent crown fires. The old western larch, white pine, and Douglas fir in these forests have persisted since just after the last catastrophic fire as the more shade-tolerant spruce, western hemlock, and western red cedar regenerate beneath them.

The Subalpine Zone

Grasslands

Grasslands occur from the montane zone to above treeline east of the Continental Divide in Glacier Park. In fact, along the east front of the mountains north of Two Medicine Lake, grasslands extend unbroken from the plains to the summits of Spot and Mad Wolf Mountains, gradually becoming alpine turf dominated by sedges and forbs above treeline. At subalpine elevations, grasslands are usually restricted to south- or west-facing slopes or areas of great wind exposure. Subalpine grasslands are similar in composition to those described for the montane zone. At higher elevations Festuca idahoensis and Elymus trachycaulus become more common, while Festuca scabrella and Elymus spicatus decrease. Shrubs, such as shrubby cinquefoil and Canada buffaloberry, develop a short stature, and dwarf shrubs, such as bearberry and alpine dryad (Dryas octopetala), become more common.

Meadows

Meadows are usually dominated by broad-leaved herbaceous plants and sedges. Dry meadows occur on steep, usually warm slopes with stony, poorly-developed soil subject to frequent downhill movement. Plant cover is sparse. Phacelia hastata, Penstemon ellipticus, Hedysarum sulphurescens, Cirsium hookerianum, Potentilla glandulosa, Aquilegia flavescens, Epilobium alpinum, and Eriogonum flavum are some of the common forbs. Calamagrostis purpurascens, Trisetum spicatum, and Festuca idahoensis are common grasses, and shrubby cinquefoil is a frequent shrub.

Wet meadows are found on gentle to level terrain with adequate snow cover. Soils are relatively deep with a well-developed organic horizon and remain wet or moist during much of the short growing season. Shortly after snowmelt, the early ephemerals, such as Erythronium grandiflorum, Claytonia lanceolata, and Ranunculus eschscholtzii, begin flowering. Shortly thereafter large, showy wildflowers, such as Arnica spp., Senecio triangularis, Erigeron peregrinus, Mimulus lewisii, Polygonum bistortoides, Valeriana sitchensis, and Castilleja spp., begin flowering and continue through the rest of the summer (DeBolt and Lesica 1986). Carex paysonii, Juncus drummondii, and Phleum alpinum are common grass-like plants in these habitats. High subalpine meadows are common around the visitor's center at Logan Pass.

Warm, moderately steep, subalpine slopes may support extensive meadows dominated by beargrass (Xerophyllum tenax). Extensive meadows of this type occur along the Garden Wall north of Logan Pass. Upon closer inspection, most beargrass meadows are seen to be burned-off forests that are regenerating slowly or not at all due to the harsh environment. Most of the species common in these meadows also occur in open, subalpine forests: huckleberry, thimbleberry, mountain ash (Sorbus scopulina), Arnica spp., Chamerion angustifolium, Veratrum viride, and Thalictrum occidentale. In some years, beargrass meadows provide spectacular wildflower displays.

Avalanche Chutes

Avalanche chutes are common on steep, usually warm slopes in the subalpine zone, especially west of the Continental Divide (Butler 1979) and can easily be seen from Going-to-the-Sun Road. They are formed by large amounts of snow sliding rapidly downhill, often in the spring. Trees with rigid trunks are broken off by the moving snow, so the centers of avalanche paths are dominated by herbaceous plants and shrubs with flexible stems. Avalanche chutes are usually associated with long, steep ravines (Butler 1979) that are moister than the adjacent slopes. Common shrubs include green alder (Alnus virldis), serviceberry, spiraea, thimbleberry, Scouler willow (Salix scouleriana), and elderberry (Sambucus racemosa). Associated with the shrubs are many tall, luxuriant, moisture-loving, herbaceous plants, including Heracleum spondylium, Chamerion angustifolium, Urtica dioica, Veratrum viride, Angelica arguta, and Elymus glaucus. Avalanche chutes gradually merge into subalpine forest at the margins (Malanson and Butler 1984).

Forests

Forests of the subalpine zone are the most common habitat in Glacier National Park. Subalpine forests are dominated by subalpine fir, Engelmann spruce, and/or lodgepole pine. Lower subalpine forests may also have Douglas fir, western larch, and white pine, while higher forests often have whitebark pine (Pinus albicaulis). These mesic forests usually have abundant shrubs in the understory, including fool's huckleberry (Menziesia ferruginea), thimbleberry, mountain ash, spiraea, and huckleberry. Common ground layer species include Arnica cordifolia or A. latifolia, Chimaphila umbellata, Linnaea borealis, and Thalictrum occidentale. Relatively warm, moist stands, usually at lower elevations, are characterized by the shrubs Utah honeysuckle (Lonicera utahensts), fool's huckleberry, and mountain lover (Paxistima myrsinites), as well as the herbaceous plants Clintonia uniflora, Tiarella trifoliata, and Trisetum cernuum. As stands become colder and drier, often at higher elevations, these species decrease while the whortleberries (Vaccinium myrtilloides, V scoparium), Hieracium albiflorum, and Xerophyllum tenax increase. Forests near timberline that receive heavy snowfall have open canopies with dense ground layers dominated by Phyllodoce spp., Xerophyllum tenax, Erythronium grandiflorum, and Luzula hitchcockii.

Subalpine larch (Larix lyallii) dominates scattered, small stands on cool, snowy, high-elevation sites with stony soil (Arno and Habeck 1972). These trees do not become stunted, even at the highest elevations. Subalpine fir and Engelmann spruce often occur in these stands as well. The understory usually has Xerophyllum tenax, Luzula hitchcockii, Juncus drummondii and Carex nigricans. Most stands are near or west of the Continental Divide in the north half of the Park, although one stand occurs as far east as the east side of Waterton Lake. The discontinuous distribution of subalpine larch in the Park is anomalous.

Subalpine fir, spruce, and whitebark pine become stunted and dwarfed at upper treeline due to ice-scouring wind or heavy snow accumulations (Arno and Hammerly 1984). These "krummholz" forests are usually sparse and discontinuous, interspersed with alpine tundra or heath. Tree cover breaks the strong, high-elevation wind, allowing snow accumulation and providing plentiful moisture where there is adequate soil. Typical subalpine forest plants, such as Thalictrum occidentale, Senecio triangularis, Xerophyllum tenax, Erigeron peregrinus, Valeriana sitchensis, Gentiana calycosa, Erythronium grandiflorum, and Luzula piperi are common in the ground layer of these protected sites (Habeck 1969). Heath, dominated by the dwarf shrubs Phyllodoce spp. and Salix arctica, develops under sparse krummholz where snow accumulations are deeper. Good examples of moist krummholz occur around Logan Pass. Krummholz developed on skeletal soils of very wind-exposed sites often has an understory of dwarf shrubs such as alpine dryad and bearberry and dwarfed plants of common juniper (Juniperus communis), shrubby cinquefoil, and Canada buffaloberry. These drier elfin forests are most abundant east of the Continental Divide and can be seen along the trail to Scenic Point above Two Medicine.

Fire has influenced the composition and structure of subalpine forests in Glacier Park. This influence has generally been greater in the lower subalpine zone. Testimony is given by the large areas dominated by lodgepole pine along the North Fork of the Flathead River and the extensive brush fields on steep, warm slopes such as those west of Logan Pass or along the Middle Fork of the Flathead. Large areas of lower subalpine forest are strongly dominated by lodgepole pine, a short-lived tree that usually requires fire to open cones and release seeds to germinate in recently burned soil (Muir and Lotan 1985). Engelmann spruce and subalpine fir can invade these forests and would eventually come to dominate, but short fire intervals maintain the lodgepole dominance. Unlike the coniferous trees that are killed by fire, nearly all the understory shrubs and herbaceous plants can survive and resprout from stems or roots protected underground. So while fire drastically changes the overstory, the understory recovers quickly and stays much the same. Subalpine forests demonstrate a pattern of mixed-severity fires with stand-replacing fires predominating in most areas (Barrett 1993,1997).

Large areas of the Park have burned during the past century. Upper subalpine forests have longer fire-free intervals, but the infrequent fires that do occur promote whitebark pine by providing sites for recruitment and reducing competition from subalpine fir (Arno 1986). Whitebark pine, in turn, provides a more benign microclimate for the establishment of subalpine fir.

Disease and insects have also played an important role in shaping Glacier's forests. Mountain pine beetles (Dendroctonus ponderosae) generally attack stands of lodgepole pine that are 80 or more years old, killing most trees. Fallen and standing dead lodgepole increase the likelihood of fire. Mountain pine beetles will also attack whitebark pine, especially trees weakened by disease or competition from fir trees (Keane and Arno 1993). A more serious threat to whitebark pine is the introduced fungal disease white pine blister rust (Cronartium ribicola). Blister rust has spread rapidly in the Northern Rockies in the past 20 years (Keane and Arno 1993). The majority of the whitebark trees in the Park are infected, and many have already died (Kendall 1998). As a result, upper subalpine forests show increasing dominance by subalpine fir.

The Alpine Zone

Although nearly one third of Glacier Park is above treeline, there is relatively little alpine vegetation because most of this zone is too steep or too snowy for soil development. Sites are too cold in the summer, too windy, or too snowy to support forests. Scattered trees can be found in the shelter of boulders or steep slopes. The few recognizable plant communities that repeat across the landscape are highly variable. Sparsely vegetated habitats are better thought of as loose assemblages rather than communities.

Fellfields

Fellfields dominated by alpine dryad are the most extensive alpine vegetation in the Park. These low plant communities develop on stony, usually calcareous soils of exposed slopes and ridges. Plant cover is low. Alpine dryad often occurs on slopes subject to downward movement due to frost heaving. It tends to form stripes and a stair-step ground pattern perpendicular to the slope (Bamberg and Major 1968, Zwinger and Willard 1972). These patterns are seen clearly at Siyeh and Piegan passes. The willows Salix arctica and S. reticulata are other common dwarf shrubs in this vegetation. Carex nardina, C. rupestris, and Poa alpina are common sedges and grasses. Minuartla obtusiloba and Silene acaulis are common cushion plants. Other common broad-leaved species include Hedysarum sulphurescens, Polygonum viviparum, Potentilla diversifolia, and Smelowskia calycina.

Turf

On more protected slopes, soils become deeper and fellfields grade into turf. Vegetation is relatively dense, similar to grassland vegetation, but plants are rarely greater than 12 cm (5 in) high. Dry turf communities are dominated by grasses or sedges including Festuca brachyphylla, Poa alpina, Carex phaeocephala, Luzula spicata, and L. piperi. Arnica mollis, Cerastium arvense, Potentilla diversifolia, Ranunculus eschscholtzii, Silene acaulis, and Solidago multiradiata are common broad-leaved species. The dwarf willow Salix arctica may also be common. Moist slopes with subirrigated, highly organic soil may develop below permanent snowfields. These relatively rare sites support moist turf dominated by the dwarf shrubs, alpine dryad, and the willow Salix reticulata among the sedges Carex scirpoidea, C. rupestris, C capillaris, C paysonis, and Kobresia simpliciuscula. Polygonum viviparum, Solidago multiradiata, and Anemone parviflora are common broad-leaved species.

Snow Fields

Two minor types of alpine vegetation are associated with late-persisting snow fields: heath and sedge snowbed. Alpine heath often occurs on shallow soil of rock ledges (Choate and Habeck 1967). It is dominated by ericaceous, dwarf shrubs: Phyllodoce empetriformis, R glanduliflora, Cassiope tetragona, and Kalmia microphylla. The dwarf willow, Salix arctica, is also common. Carex paysonis and C. podocarpa are common sedges. The forbs Erythronium grandiflorum, Arnica latifolia, Senecio cymbalarioides, and Hypericum formosum may be scattered throughout the heath. Sedge snowbeds occur in relatively level areas where snow lies the latest. This vegetation is species-poor and strongly dominated by Carex nigricans. juncus drummondii and Deschampsia atropurpurea are other common grass-like plants. Sibbaldia procumbens and Hieracium triste may occur in openings in the sod.

Talus

Talus and scree slopes are common above treeline in Glacier Park. Because these slopes are near the angle of repose, the surface is always shifting, making it difficult for most plants to take root. However, plants that can grow downslope with the surface rock experience a surprisingly benign environment, especially on warm slopes. Most talus slopes have a surface layer of loose rock over deep, mineral soil. The surface rock allows rain and snowmelt into the soil below but acts as a mulch by preventing evaporation and keeping the soil moist and warm. Plant cover is usually very sparse and the vegetation is better considered an assemblage rather than a community. Nonetheless, several distinctive species, such as Crepis nana, Erigeron lanatus, Eriogonum androsaceum, Stellarza americana, Polemonium viscosum, Claytonia megarhiza, and Chamerion latifolium occur only on talus slopes (or river gravels). Alpine dryad, Saxifraga bronchialis, Potentilla glandulosa, and Eriogonum ovalifolium are also common on shifting talus but are found in other habitats as well.

History of Botanical Exploration

Botanical exploration of Glacier Park's rugged terrain was minimal before the beginning of the twentieth century. R. S. Williams lived in Columbia Falls and Great Falls and helped survey the east boundary of Glacier National Park in 1897. He collected vascular plants as well as mosses in what was to become the Park and the surrounding area in 1887 and from 1892 to 1897. He later moved east to work for the New York Botanical Garden. Levi M. Umbach of Northwestern University in Illinois collected plants in Glacier Park from 1901 to 1903. Many of the trails were not maintained at that time, so Umbach collected mainly around the towns of East Glacier and West Glacier. He also visited the high country near Sperry Glacier and the Two Medicine Valley. Also in 1901 Frederick K. Vreeland, an electrical engineer from New York City and P. A. Rydberg's companion during his Colorado explorations, collected plants around Lake McDonald and donated them to the New York Botanical Garden. Marcus Jones, one of the West's most famous botanists of the early twentieth century, spent the summers of 1908 and 1909 in western Montana and collected plants near Sperry Glacier and north of Logan Pass (Jones 1910). Morton Elrod, a biology professor at the University of Montana in Missoula, established a biological research station on Flathead Lake, just south of Glacier, in 1899. From then through 1928 he collected plants in Glacier Park in addition to working there as chief naturalist for eight summers. Joseph E. Kirkwood, another professor at the University of Montana, collected plants in the Park in 1910. Joseph Blankenship, the botany professor at Montana State University in Bozeman, collected plants for a short while in the Park in 1903. A. S. Hitchcock, one of the country's foremost agrostologists, spent three weeks in 1914 collecting grasses in Glacier. A summary of early botanical exploration in Glacier Park is given by Standley (1921).

The most significant Glacier Park plant collections were made by Paul Standley during the summer of 1919 while working for the Smithsonian Institution. He spent most of that summer on the east slope, working out of the Many Glacier Valley. Standley spent only three weeks west of the Divide in the vicinity of West Glacier and Lake McDonald (Standley 1921) because access by road was poor or nonexistent at the time. In spite of having to do field work during a drought year, Standley collected ca. 1000 specimens and catalogued the vast majority of species currently known to occur in the Park. His book, Flora of Glacier National Park, Montana, was published in 1921 by the Smithsonian Institution (Standley 1921) and is still a useful reference.

Publication of Standley's book sparked interest in the Park, and many academic botanists began to visit. Bassett Maguire, curator of the herbarium at Utah State University, spent time in Glacier National Park in 1932 and again in 1934. He collected around many of the low-elevation lakes on both sides of the Divide and found many aquatic and wetland plants previously unrecorded for the Park (Maguire 1934, 1939). William T. McLaughlin of Northwestern University collected plants in the Park from 1930 to 1934 and found a few plants previously unreported (McLaughlin 1935). C. Leo Hitchcock collected plants in Glacier Park during the summer of 1933 while he was a professor at the University of Montana in Missoula. LeRoy H. Harvey was professor of Botany and curator of the herbarium at the University of Montana in Missoula from 1946 through 1977. He collected hundreds of specimens throughout Glacier Park, mainly in the 1950s, in preparation for writing a flora that was never completed (Harvey 1954). Frederick J. Hermann, curator of the U. S. Forest Service Herbarium and author of a manual on Rocky Mountain sedges, collaborated with Harvey, collecting vascular plants (mainly sedges) in the Park in 1955 (Hermann 1956). Alfred Schuyler, a curator at the Academy of Natural Sciences of Philadelphia, collected wetland and aquatic plants on the west side of the Park during the summers when he taught summer classes at the University of Montana Biological Station in 1978-1995 (Schuyler 1980, 1982). Several students, including Sam Bamberg, Richard Pemble, Irene Sammons, and Christian Damm, made plant collections as part of their graduate work (Bamberg and Pemble 1968).

Many of Glacier Park's biologists, rangers, and naturalists have also made significant plant collections, most of which are housed in the herbarium at West Glacier. Mona Myatt made numerous plant collections while working on a project to map Glacier's vegetation and fire history during the mid1970s. J. L. McMullen was an interpretive naturalist for five summers during 1947-54; three of those were spent in the Two Medicine Valley where he took some of the first collections from that area. Dave Shea, a ranger in the northeast portion of Glacier Park for many years, found a number of Park records. Jerry DeSanto was a ranger in the Park for over 20 years. He found several species previously unreported and deposited many collections in the Park herbarium (Lesica et al. 1993). He also wrote and privately published a book on the Park's alpine flora (DeSanto 1989).

Fred Hermann returned to Glacier Park in 1962, 1966 and 1968 to collect mosses and publish a checklist (Hermann 1969). Bruce McCune, Roger Rosentretter, and Ann DeBolt collected lichens in the Park during the 1970s and 80s and published an annotated checklist (DeBolt and McCune 1993).

Many Glacier Park plant collections made by Elrod, Harvey, C. L. Hitchcock, Jones, Kirkwood, McMullen, Pemble, Sammons, Schuyler, Umbach, and Williams are deposited at the University of Montana herbarium (MONTU). Collections of A. S. Hitchcock and Standley are at the Smithsonian.

Methods

I began work on this book in 1984 when I spent three months in West Glacier working in the herbarium, compiling an inventory of specimens and preparing a checklist of vascular plants (Lesica 1985). I have continued to collect published information on the Park's flora. Since then I have hiked nearly every trail in Glacier Park with a good deal of bushwhacking as well, collecting hundreds of specimens and taking notes on the flora and vegetation. Other botanists and I collected many new records for the Park during this time (Lackschewitz et al. 1988; Lesica 1991; Lesica et al. 1986, 1993, 1998; Lesica and Stickney 1994), leading to a revised checklist (Lesica 1996). I have observed nearly all of the plants treated in this book in the field, in or near the Park.

Only taxa for which there is a verified specimen are included in this book as part of the Glacier Park flora. Most taxa are verified by specimens at the Glacier Park herbarium or the herbarium at the University of Montana. Literature reports by knowledgeable botanists that are supported by vouchers were accepted at face value. I attempted to verify dubious reports, and in some cases these turned out to be erroneous and were not included.

Morphological descriptions were taken from monographic treatments and then revised using herbarium material collected in and around Glacier Park. I examined and took measurements from approximately 5,000 specimens. Habitat information and distribution within the Park were taken from these specimens and personal experience. "East" and "West" refer to east and west of the Continental Divide respectively. Global distribution information was taken from a number of floristic monographs and is the range of the species as a whole. Ethnobotanical information was obtained from Johnston (1987). Infraspecific taxa (i.e., subspecies, varieties) are mentioned in the second paragraph of the species description. Morphological, ecological, or distributional differences are described when they are thought to be significant in the area.

Original illustrations were prepared from living and pressed specimens collected in or around Glacier National Park. Nearly 350 species are illustrated, approximately one-third of the flora. Most genera in the Park are represented by at least one illustration. In addition, we have tried to illustrate the most common species, those most likely to be seen by short-term visitors to the Park. Illustrations can sometimes be used to help determine the family or genus of an unknown plant, making identification a much easier task.

Taxonomic Philosophy

Application of molecular genetics and methods of modern cladistics to plant systematics has resulted in a good deal of recent change in taxonomic nomenclature. In most cases I have not had the time or competence to evaluate the primary literature justifying these changes. Rather, I have chosen to follow treatments provided in recently published floristic monographs (e.g., Cronquist et al. 1986-97, Hickman 1993, Flora of North America Editorial Committee 1993-2000) or by experts participating in the Flora of North America project. These treatments are cited following the family or genus descriptions. In a few cases I have chosen to follow a treatment at odds with that currently in favor based on my knowledge of the literature and the plants in the field.

I have attempted to include taxonomic synonyms used by floristic manuals pertinent to Glacier Park, including Standley (1921), Hitchcock and Cronquist (1973), Dorn (1984), Moss and Packer (1983), and Kuijt (1982). I hope that including these synonyms will help relieve the distress felt by many of us who have trouble keeping up with the rapid taxonomic flux. When both a varietal and subspecific epithet were available for a particular taxon, I usually chose to use the subspecies. I have included one or more common names only when I believe they are truly in vernacular use.

How to Use This Book

All vascular plants currently known to occur in Glacier National Park are included in this manual's keys and descriptions. I attempted to broaden the applicability of the book by including brief mention of species not currently known from Glacier but known to occur in adjacent mountainous areas. To this end I consulted Kuijt's (1982) Flora of Waterton Lakes National Park and a checklist of vascular plants for Flathead National Forest prepared by Maria Mantas (1999). These additional species are usually listed following genus descriptions. The vast majority of plants occurring in the mountains of southeast British Columbia, southwest Alberta, and much of Flathead National Forest in northwest Montana are included here. Many plants occurring at low elevations in the Flathead Valley or on the Great Plains of the Blackfeet Indian Reservation will not be found in this book. As a general rule, this manual will be less useful the farther one travels from Glacier Park.

The book is organized phylogenetically by four major groups of vascular plants: Pteridophytes (ferns and allies), Gymnosperms (conifers), Dicot Flowering Plants, and Monocot Flowering Plants. Families within these four major groups are arranged alphabetically. Genera and species are arranged alphabetically within families. Plants can be identified by means of "dichotomous keys." The first "couplet" (a pair of identical numbers) consists of two alternate, mutually exclusive statements. The reader must choose the statement that best describes the plant in hand. Following the correct statement is either the name of the family, genus or species to which the plant belongs, or the number of another couplet. For example:

1. Plants slender, trailing subshrubs,- flowers nodding....................................Linnaea
1. Plants shrubs with erect stems ............................................................................... 2

If the first (1) is correct, then the plant is in the genus Linnaea. If the second (1) is correct, then the reader must go to the second couplet (beginning with 2) and again choose the correct statement and continue until a name rather than a number is obtained. The key to the families is used to determine the correct family. Under the description for that family will be a key to the genera used to determine the correct genus. Under the genus description will be a key to the species that finally gives the name (scientific binomial) of the plant. The illustration may aid in this process. A small number of abbreviations are used in the keys and descriptions: ca. (circa), approximately; >, greater than; _>_ greater than or equal to;_<_, less than; <, less than or equal to.

Once the name of the plant is obtained, the description for that species in the text should be checked against the plant in hand to make sure it is correctly identified. Characters common to all members of a family or genus are given under the descriptions for that family and genus and are usually not repeated in the species descriptions, so it is a good idea to read descriptions for the family and genus as well as species. Unfamiliar botanical terminology is defined in the glossary. Geographic ranges are given for the species as a whole, not just the variety or subspecies occurring in the Park.

Floristic Synopsis

Families 86  
Genera 345
Species 1132
Taxa (subspecies, varieties) 1182
Introduced species 127
Native species 1005
Largest families: Native Introduced
Asteraceae 124 26
Cyperaceae 96 0
Poaceae 88 18
Rosaceae 46 0
Brassicaceae 40 12
Scrophulariaceae 39 10
Ranunculaceae 32 0
Saxifragaceae 31 0
Fabaceae 29 0
Onagraceae 26 0
Annuals and biennials 88 61
Herbaceous perennials 804 64
Shrubs and vines 93 1
Trees 20 1

Floristic Plant Geography

A primary goal of biogeography as well as ecology is understanding the distribution of organisms across landscapes and continents. Methods range from molecular genetics to analysis of fossils (Myers and Giller 1988, Axelrod and Raven 1985 ). A common method in plant geography has been floristic analysis: the classification of the flora into groups sharing distinct geographic patterns (Hult6n 1937, McLaughlin 1989). These patterns generally correspond to "floristic regions, ' areas with a distinct flora thought to have evolved under relatively static climatic and soil conditions over long periods of time (Gleason and Cronquist 1964). A species whose geographic range largely corresponds to one of these patterns is considered to have affinities with that floristic region and is assumed to have evolved primarily with other species of the same affinity. It is assumed that plants came to be in a given area by either migrating there or evolving in place. Knowing the geographic patterns underlying a local flora provides clues to evolution and important historic migrations (Hulten 1937, Cain 1944). Compiling a floristic monograph of Glacier Park provides an opportunity to analyze the flora quantitatively and gain new understanding of the evolution of Park's vegetation.

Geographic Patterns in Glacier National Park

Much of the flora of Glacier National Park can be classified into one of four broad geographic patterns: Arctic-alpine, Boreal, Cordilleran, and Great Plains. Delineation of floristic provinces follows Gleason and Cronquist (1964). Within three of these provinces, I recognize subprovinces that roughly correspond to floristic areas described by McLaughlin (1989). There is usually little overlap between provinces; however, there is often a good deal of overlap among subprovinces within a province. Nonetheless, the majority of species can be placed in a subprovince with little uncertainty. There are, however, many species too widespread to discern a geographic affinity; i.e., they are common throughout two or more broad phytogeographic provinces. There are 224 such widespread species in Glacier's flora. In addition, there are 127 species thought to be introduced in the Park; these are addressed later.

Cordilleran Floristic Province 385
    Cascade Mountains Subprovince 77
    Rocky Mountain Subprovince 274
    Southern Rocky Mountain Subprovince 4
    Northern Rocky Mountain Subprovince 30
Boreal Floristic Province 305
    Circumboreal Subprovince 148
    American Boreal Subprovince 157
Arctic-alpine Floristic Province 82
    Circumpolar Arctic-alpine Subprovince 49
    American Arctic-alpine Subprovince 33
Great Plains Floristic Province 9

Cordilleran Flora

Cordilleran species (385) occur in the mountainous regions of western North America from Alaska south to California, New Mexico, Arizona, and sometimes northern Mexico. This region is characterized by bunchgrass grasslands at the lowest elevations, coniferous forest at mid-elevations, and alpine tundra above treeline. Cascade Mountains species (77) occur primarily west of the Rocky Mountains from Alaska or British Columbia south to California and east occasionally to northern Idaho and northwest Montana. Rocky Mountain species (274) are distributed along the main chain of the Rocky Mountains from Alaska or British Columbia and Alberta south to Colorado and Utah. The geographic center of Southern Rocky Mountain species (4) is in Utah and southern Wyoming south to Arizona and New Mexico. Northern Rocky Mountain species (30) are endemic to southeast British Columbia, eastern Washington, northeast Oregon, southwest Alberta, western Montana, and northern Idaho. It is likely that some of these species evolved in the area of Glacier Park.

The Cordilleran Flora is the most well represented in Glacier Park. This is not surprising since the Park lies in the center of the western North American Cordillera. Over two-thirds of these species have a Rocky Mountain Cordilleran distribution. More than three-quarters of the species with Cordilleran affinity occur in the montane zone; nearly half can be

Table 1. Percentage of native species with Cordilleran, Boreal, and Arctic-alpine floristic affinities found in three vegetation zones in Glacier National Park (percentages add to > 100 because some species occur in more than one zone). Species with widespread and Great Plains distributions are not included except in the overall "Park" statistics.


Zone Cordilleran Boreal Arctic-alpine Park
  (385) (305) (82) (1005)

Montane 81% 94% 8% 83%
Subalpine 48% 41% 17% 38%
Alpine 30% 17% 99% 27%

Table 2. Percentage of native species with Cordilleran, Boreal and Arcticalpine floristic affinities found in five habitat types in Glacier National Park (percentages add to > 100 because some species occur in more than one zone). Species with widespread and Great Plains distributions are not included except in the overall "Park" statistics. "Rocky" refers to cliffs, talus, and fellfields.


Zone Cordilleran Boreal Arctic-alpine Park
  (385) (305) (82) (1005)

Forest 40% 40% 1% 34%
Grass/Turf 50% 24% 80% 48%
Wetland 16% 49% 7% 28%
Riparian 14% 22% 7% 17%
Rocky 20% 9% 51% 17%

found in the subalpine; and nearly one-third occur near or above treeline (Table 1). Half of the Park's Cordilleran species occur in grassland or turf Dominant montane grassland species include Elymus spicatus, Festuca idahoensis, Bromus carinatus, Stipa nelsonii, sagebrush (Artemisia tridentata), Geranium viscosissimum, Arnica sororia, and Balsamorhiza sagittata. Forty percent of Cordilleran species can be found in forests, including many of the Park's most common such as subalpine fir (Abies lasiocarpa), Engelmann spruce (Picea engelmannii), whitebark pine (Pinus albicaulis), ponderosa pine (P. ponderosa), lodgepole pine (P. contorta), and Douglas fir (Pseudotsuga menziesii). Many Cordilleran shrubs are common in the forest understories. Included are Rocky Mountain maple (Acer glabrum), Utah honeysuckle (Lonicera utahensis), fool's huckleberry (Menziesia ferruginea), huckleberry (Vaccinium membranaceum), whortleberries (V myrtillus, V scoparium), mountain ash (Sorbus scopulina), and spiraea (Spiraea betulifolia). Many Cordilleran plants are common in the forest ground layer as well, such as Osmorhiza occidentalis, Aster conspicuus, A. engelmannii, Senecio triangularis, Aquilegia flavescens, Thalictrum occidentale, and Prosartes trachycarpa. Relatively few Cordilleran species occur in wetland habitats compared to the Park flora as a whole (Table 2).

Like the Cordilleran Flora as a whole, the Cascade Mountain Flora is best represented in low-elevation forests, with 83% of the species occurring in the montane zone and 66% being found in forests. On the other hand, only 10% of Cascadian species occur above treeline, and only 23% are associated with grassland or turf vegetation. Many of these plants find suitable habitat in the relatively warm, moist valleys west of the Divide, where a humid maritime climate prevails. These forests are often dominated by Cascadian species such as western red cedar (Thuja plicata), western hemlock (Tsuga heterophylla), western white pine (Pinus monticola), and western larch (Larix occidentalis). Other Cascadian species, such as baldhip rose (Rosa gymnocarpa), and oceanspray (Holodiscus discolor), are common shrubs, and Viola orbiculata, Tiarella trifoliata, and Clintonia uniflora are abundant in the understory. Cascadian species found in subalpine forests include subalpine larch (Larix lyallii), Veratrum viride, and Xerophyllum tenax.

Relatively few of Glacier's plants are endemic to the Northern Rocky Mountains even though the Park is in this floristic subprovince (McLaughlin 1989). In contrast to Cascadian species, members with this geographic pattern are most likely found in open, high-elevation habitats. Over half of the species occur near or above treeline and one-third are restricted to the alpine. Only 16% of the Northern Rocky Mountain endemics are found in forests, while two-thirds occur in the shallow soil of cliffs, fellfields, talus or stony slopes, and nearly as many occur in grasslands and turf. Aquilegia jonesii, Antennaria aromatica, Arnica alpina, Eriogonurn androsaceum, and Papaver pygmaeurn are found in alpine fellfields, while Erigeron lanatus and Stellaria americana specialize in talus.

Very few plants have a clearly discernable affinity with the southern Rocky Mountains. Most are rare in the Park and occur near Marias Pass or along the east front of the Mountains. These are Carex elynoides, Saxifraga subapetala, and Valeriana edulis.

Boreal Flora

Boreal species (305) are found in the northern coniferous forests of Canada and adjacent U. S., between the treeless arctic to the north and the Deciduous Forest and Great Plains floristic provinces to the south. These species commonly occur well south of Canada in the coniferous forests of the continent , s mountain ranges. Circumboreal species (148) are found in the northern coniferous forests of Europe and Asia as well as North America, while American Boreal species (157) occur only in North America, across Canada or nearly so.

Plants with a Boreal distribution are very common in Glacier Park. Boreal species occur most frequently in forests and wetlands of the montane zone. Over 90% of these plants are found in the montane zone, while only 17% occur above treeline (Table 1). Nearly half of the Park's Boreal species occur in wetlands, and 40% are found in forests (Table 2). Only a few of the Park's Boreal species are trees; white spruce (Picea glauca) and black cottonwood (Populus balsamifera) are found on riparian terraces, while aspen (P. tremuloides) and paper birch (Betula papyrifera) are early successional forest species. On the other hand, many of the Park's forest understory shrubs have Boreal affinities. These include common juniper (Juniperus communis), green alder (Alnus viridis), serviceberry (Amelanchier alnifolia), buckthorn (Rhamnus alnifolia), snowberry (Symphoricarpos albus), swamp currant (Ribes lacustre), Canada buffaloberry (Shepherdia canadensis), and elderberry (Sambucus racemosa). The ground layer of many forests is also dominated by Boreal plants, especially ferns and ericaceous species such as Lycopodium spp., Athyrium filix-femina, Dryopteris spp., Gymnocarpium disjunctum, Polystichum lonchites, Chimaphila Umbellata, Orthilia secunda, and Arctostaphylos uva-ursi. The majority of Circumboreal plants occur in wetlands such as marshes, lake shores, and fens. Equisetum spp., Potamogeton spp., Sparganium spp., and 20 species of wetland sedges (Carex) are all widespread in the Boreal zone around the world.

Fens are wetlands with perennially saturated organic soil. They are uncommon in Glacier Park and occur primarily west of the Divide. Ninety-seven species of plants commonly occur in Glacier's fens, and over 80% of these have a Boreal distribution. Thirty species are restricted to fens in Glacier Park, and only 3 of these do not have Boreal affinities. Obligate fen species are among Glacier's rarest plants; they include Carex chordorhiza, C. limosa, C. livida, C. paupercula, C. rostrata, C. tenuiflora, Dulichium arundinaceum, Eriophorum spp., Scheuchzeria palustris, and the carnivorous plants Drosera spp. and Utricularia spp.

Arctic-Alpine Flora

Arctic-alpine species (82) are widespread near or north of the Arctic Circle (67 north latitude), north of the general distribution of forest in northern Canada, Greenland and Alaska. They also occur near or above treeline in the mountains of eastern and/or western North America. Dominant vegetation is tundra. Circumpolar Arctic-alpine species (49) have an Arcticalpine distribution in Europe and Asia as well as North America, while American Arctic-alpine species (33) occur only in North America or sometimes adjacent Asia.

Nearly all species with an Arctic-alpine distribution occur near or above treeline in Glacier Park. Plantago canescens occurs in the arctic and along the east front of the Canadian Rockies in exposed montane grasslands rather than alpine turf. Nearly half of Arctic-alpine species are found only along or east of the Continental Divide, while only one (Gentiana glauca) is found exclusively west of the Divide. Alpine dryad (Dryas octopetala) and dwarf willows (Salix arctica, S. reticulata), the dominant subshrubs in Glacier's alpine vegetation, have a circumpolar distribution. Minuartia obtusiloba, Ranunculus eschscholtzii, Silene acaulis, Oxyria digyna, Polygonum viviparum, Carex nigricans, Festuca brachyphylla, and Poa alpina are common herbaceous Arctic-alpine species.

Great Plains Flora

Great Plains species (9) are found primarily in the Semi-arid grasslands at the center of the continent, east of the Rocky Mountains and west of the Mississippi River. Although Glacier is directly adjacent to the Great Plains Floristic Province, few Great Plains species occur in the Park because the mountains rise abruptly, and the Park receives much more precipitation than the Great Plains grasslands that dominate just a few miles to the cast. The few plants with a Great Plains distribution in Glacier occur along the east edge of the Park. They are rare or uncommon, and all but one (Carex sartwellii) are found in montane grasslands. Examples include Rosa arkansana, Liatris punctata, Astragalus flexuosus, and Carex heliophila.

Summary

Glacier Park's flora is dominated by species with Cordilleran and Boreal distributions. Cordilleran plants are well distributed at all elevations and in all habitats; however, Cascadian species are prevalent in moist, low-elevation forests west of the Divide, while Northern Rocky Mountain endemics are most abundant in open habitats at higher elevations east of the Divide. Boreal plants are best represented in forests and especially wetlands. Not surprisingly, Arctic-alpine plants are found mainly above treeline, with more species east than west of the Divide.

Local Plant Geography

In the Northern Rockies, the Continental Divide sharply demarcates the boundary between the semi-arid continental climate of the Great Plains Floristic Province and the temperate maritime climate of the Northern Rocky Mountains to the west. The west side is generally more humid and less windy than east of the Divide. Paul Standley (1921) was the first to describe how these environmental differences affected the floras between the two sides of the Park. There are 154 plant species known to occur only on the west side of the Continental Divide in Glacier Park and 227 on the east side or along the Divide. The distribution of these species suggests that Boreal and Cascadian montane forest and wetland plants are more prevalent west of the Divide, while Arctic-alpine and Northern Rocky Mountain endemics of open habitats are more common on the east side.

Over one-third of the westside-restricted species have a Boreal distribution, but only 1% are Arctic-alpine, and only 9% occur above the montane zone. Nearly half of them occur in forests, and over one-third are found in wetlands; however, only 21% occur in grasslands or turf, and only 4% are found in rocky cliff, talus, and fellfield habitats. Plants restricted to the east side of the Park generally have a different ecology and phytogeographic affinity. Only 9% of these are found in forest, but two-thirds occur in grassland and turf, and nearly one-quarter in rocky habitats. Plants with an arctic-alpine or boreal distribution each account for 15% of these eastside-restricted species. Circumboreal plants are well represented on both sides of the Divide; however, the distribution between floristic subprovinces is very different. There are 26 species of Cascadian plants restricted to the west side, but only 7 east of the Divide. On the other hand, there are 15 Northern Rocky Mountain endemics restricted to the east side but only 3 on the west side.

Historical Plant Geography

Boreal, Cordilleran, and Arctic-alpine floras had achieved much of their modern character by the end of the Tertiary, before the start of the Pleistocene (Axelrod and Raven 1985, L6ve and L6ve 1974, Davis 1981, Hult6n 1937). Glacier Park lies along the main chain of the Rocky Mountains in the middle of the Cordilleran Floristic Province and just southwest of the Boreal Floristic Province, so it is not surprising that Glacier's flora is dominated by species with Cordilleran, Boreal, and Arcticalpine distributions. It is the Northern Rocky Mountain endemics that raise the most interesting questions. Why are there so few endemics? Why do they have such limited distributions? Why do so many occur in open, high-elevation habitats?

Endemism, the occurrence of species with an exclusively local geographic distribution, generally declines from southwest to northeast in Montana (Lesica et al. 1984). Much of northern Montana and the Northern Rocky Mountain Floristic Province, including Glacier Park, was almost completely covered with ice during the Pleistocene glaciations (Perry 1962). Presumably all the vegetation including narrowly endemic species was destroyed by the glaciers, and during warmer interglacial periods the barren landscapes were recolonized by more widespread plants that survived south or perhaps north of the glaciers (Davis 1981, Hult6n 1937). The low number of Northern Rocky Mountain endemics in Glacier Park is likely attributable to glaciation.

Some of the Northern Rocky Mountain endemics may be relics of a much larger distribution, while others have likely evolved in the Northern Rockies and never had a larger distribution (Cain 1944). Papaver pygmaeum is part of an ancient circumpolar arctic-alpine complex of very similar species (Welsh et al. 1987). Presumably Glacier's pygmy poppy is an isolate from this complex that survived only in and around the Park. On the other hand, several Northern Rocky Mountain endemic genera have actively spawned many local endemics throughout the western Cordillera. These include Allium, Antennaria, Astragalus, Calochortus, Erigeron, Eriogonum, Lomatium, and Penstemon. Northern Rocky Mountain species in these genera likely evolved relatively recently and have had little chance to attain a larger geographic distribution.

The few extant Northern Rocky Mountain endemics must have survived glaciation near the glacial front, perhaps in an ice-free area just cast of the Park (Perry 1962, Carrara 1989). Paleoecologists believe that the environment near the ice front was cold with stony, poorly developed soil, similar to that of modern-day arctic tundra (Davis 198 1). Plants adapted to this environment would have a better chance of persisting, so it is probably no accident that all but one of the 30 endemics in Glacier Park (Table 3) are found in cold grassland, turf or talus, cliffs, fellfields, or gravelly streambanks. Trisetum orthochaetum, a forest plant, is a rare hybrid likely of recent origin (Hitchcock et al. 1969).

Introduced Plants

More than half of the Park's introduced plants are in five families, and these are among the ten largest families in the native flora. Although similar to natives at the family level, 60% of Glacier's introduced plants belong to alien genera. Whereas annuals or biennials are poorly represented in the native flora (9%), they account for nearly half (47%) of the introduced species. On the other hand, woody plants are poorly represented in the exotic (2%) compared to the native (11%) flora. Only four introduced species occur in the subalpine, and none have been collected above treeline,

Table 3. Plant species endemic to the Northern Rocky Mountains.


Allium fibrillum Hedysarum sulphurescens
Antennaria aromatica Lathyrus bijugatus
Angelica dawsonii Lomatium sandbergii
Aquilegia jonesii Papaver pygmaeum
Arnica alpina Penstemon albertinus
Astragalus bourgovii Penstemon ellipticus
Astragalus vexilliflexus Penstemon lyallii
Calochortus acicularis Phacelia lyallii
Carex platypuses Physaria didymocarpa
Conimitella williamsii Physaria saximontana
Douglasia montana Senecio megacephalus
Epilobium suffruticosum Stellaria americana
Erigeron lackschewitzii Suksdorfia violacea
Erigeron lanatus Townsendia parryi
Eriogonum androsaceum Trisetum orthochaetum

a typical pattern for the Northern Rockies (Forcella and Harvey 1983). Half of the introduced species known in the Park have been found only west of the Continental Divide, while only 10% have been collected only on the east side.

The introduction of plants is considered one of the most serious problems faced by Glacier Park managers (Lange 1991). Although 126 species of exotics have been recorded, only a handful have caused significant adverse effects. Most exotics (60%) have been found only in disturbed habitats such as along roads or around buildings. Roads are particularly important weed staging habitats because of their disturbed periphery and the number of visitors that use them each year (Tyser and Worley 1992, Lesica et al. 1993). Of the remaining 50 species that do occur in native vegetation, only 10 are thought to be able to invade undisturbed communities and replace native species. Grasslands are the most vulnerable vegetation type. Large infestations of spotted knapweed (Centaurea maculosa), leafy spurge (Euphorbia esula), and St. Johnswort (Hypericum perforatum) occur in montane grasslands, while meadow hawkweed (Hieracium caespitosum), dalmatian toadflax (Linaria dalmatica), and sulphur cinquefoil (Potentilla recta) are locally common. Spotted knapweed is currently the most widespread and troublesome weed in the Park (Tyser and Key 1988).

Three other species invade wetlands and riparian areas: Canada thistle (Cirsium arvense), tall buttercup (Ranunculus acris), and common tansy (Tanacetum vulgare). Only Canada thistle is widespread. I have observed this plant, which has light, wind-born seeds, on fresh beaver dams far from roads or even a trail. Reed canarygrass (Phalaris arundinacea) is native in the Northern Rockies; however, invasive domestic cultivars capable of replacing native vegetation may also have been introduced (Merigliano and Lesica 1998).

There are currently no serious infestations of exotics in the closed-canopy coniferous forests that dominate Glacier's landscape and much of the Northern Rockies (Forcella and Harvey 1983, Weaver and Woods 1986). However, Veronica officinalis, a lawn weed with creeping stems, thrives in dense shade and occurs in undisturbed moist, montane forest in many places west of the Divide in northwest Montana and Glacier Park. It is similar in appearance to our common native, Linnaea borealis, and may be able to compete with it in these habitats.

Timothy (Phleum pratense), Kentucky bluegrass (Poa pratensis), and smooth brome (Bromus inermis) are also common in the Park's grasslands, especially on the east side. These exotics have been seeded along roads (Tyser and Worley 1992) and were also probably intentionally introduced by outfitters in the early half of the twentieth century to increase forage for horses. Infestations of these plants may be due more to overgrazing and seeding than to their inherent invasiveness.

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