Montana Field Guide

This ecological system is found at alpine elevations throughout the Rocky Mountains, west into the mountainous areas of the Great Basin, and north into the Canadian Rockies. In Montana, alpine fell-fields are well represented throughout the Northern Rocky Mountains and island mountain ranges. Elevation ranges from as low as 1,981 meters (6,500 feet) in northwestern Montana to 3,200 meters (10,500 feet) in southwestern Montana. These are wind-scoured fell-fields that are often free of snow in the winter, such as ridgetops and exposed saddles, subjecting the vegetation to severe environmental stress. Soils on these windy, unproductive sites are shallow, stony, low in organic matter, and poorly developed; wind deflation often results in a gravelly pavement. This system is characterized by a very cold climate during winter, high winds, high ultraviolet radiation and surface temperatures during summer days, and a very short growing season. Ribbons of nitrogen-fixing arctic dryad (Dryas octopetala), shrubby cinquefoil (Dasiphora fruticosa) and alpine leguminous species occur on slopes subject to downward movement due to frost heaving. These ribbons or stair-step vegetation patterns form perpendicular to the slope. Plant cover can be low to moderate (15 to 50%) with exposed, stable scree and boulders constituting the remainder of cover. Most fell-field plants are highly adapted to this xeric environment and occur within these ribbons or as singular plants among exposed rocks. These species are typically cushioned, matted or succulent, or grow as flat rosettes, often with thick leaf cuticles or a dense cover of hairs. Crustose and foliose lichen species form significant cover on exposed rocks.

Elevation ranges from as low as 1,981 meters (6,500 feet) in northwestern Montana to 3,200 meters (10,500 feet) in southwestern Montana. These wind-scoured fell-fields are often free of snow in the winter, occurring on ridgetops and exposed saddles and subjecting the vegetation to severe environmental stress. Soils on these windy, unproductive sites are shallow, stony, low in organic matter, and poorly developed; wind deflation often results in a gravelly pavement. This system is characterized by a very cold climate during winter, high winds, high ultraviolet radiation and high surface temperatures during summer days, and a very short growing season. Exposed, stable scree and isolated boulders constitute at least half of the cover. Soil development is very limited, and derived from a variety of parent materials. It is usually gravelly or rocky, and can be acidic or calcareous. Organic matter is only found in limited quantities within vegetation ribbons and patches of dwarf, woody species.

Ribbons of nitrogen-fixing arctic dryad (Dryas octopetala), shrubby cinquefoil (Dasiphora fruticosa) and alpine leguminous species occur on slopes subject to downward movement due to frost heaving. Common alpine legumes include silver lupine (Lupinus argenteus), yellow sweetvetch (Hedysarum sulphurescens), alpine milkvetch (Astragaulus alpinus), Bourgov’s milkvetch (Astragaulus bourgovii), boreal crazyweed (Oxtropis borealis), silky crazyweed (Oxytropis sericea), and in southwestern Montana, alpine clover (Trifolium species). These ribbons or stair-step vegetation patterns form perpendicular to the slope. Plants accumulate litter within the mats and improve soil fertility, thus facilitating additional species colonization within the mats. Plant cover can be low to moderate (15 to 50%) but plants are is rarely more than 9 centimeters (3.6 inches) high.

Other forbs can occur with the mats, singly or in small patches among the exposed rocks. In northwestern Montana, common forbs include yarrow (Achillea millefolium), penstemon (Penstemon species), phacelia (Phacelia species), alpine fireweed (Chamerion latifolium), moss campion (Silene acaulis),twinflower sandwort (Minuartia obtusiloba), alpine goldenrod (Solidago multiradiata), sky pilot (Polemonium viscosum), cut-leaf daisy (Erigeron compositus), draba (Draba species), arnica (Arnica alpina), alpine pussytoes (Antennaria species), one-stem fleabane (Erigeron simplex), sibbaldia (Sibbaldia procumbens), diverse leaf cinquefoil (Potentilla diversifolia), moss campion (Silene acaulis), lousewort (Pedicularis species), elegant death camas (Zigadenus elegans), alpine bistort (Polygonum bistortoides), rock jasmine buckwheat (Eriogonum androsaceum), alpine buckwheat (Eriogonum ovalifolium), viviparous bistort (Polygonum viviparum), alpine forget-me-not (Myosotis alpestris) and Siberian aster (Symphyotrichum sibiricus). Many of the cushion species are very long lived, and are often well-adapted to limited available water because of deep, fleshy taproots. These species can persist for decades. Other low, mat forming woody species such as arctic willow (Salix arctica), snow willow (Salix nivalis), rock willow (Salix vestita), and in the island mountain ranges, bearberry (Arctostaphylos uva-ursi), are usually present among the exposed rocks. Several northern Rocky Mountain endemic species, species of concern, and potential species of concern inhabit alpine fell-field communities

Cover of sedges, rushes, woodrushes and grasses is usually lower than forb cover, but often includes species such as Dunhead sedge (Carex phaeocephala), spike sedge (Carex nardina), curly sedge (Carex ruprestris), northern single spike sedge (Carex scirpoidea), black and white sedge (Carex albonigra), spiked woodrush (Luzula spicata), Piper’s woodrush (Luzula piperi), Drummond’s rush (Juncus drummondii), alpine blue grass (Poa alpina), spike trisetum (Trisetum spicatum) and slender wheatgrass (Elymus trachycaulus). In southwestern Montana fell-field communities, other species such as blackroot sedge (Carex elynoides), Parry’s rush (Juncus parryi), Idaho fescue (Festuca idahoenisis), spike fescue (Festuca kingii) and sheep fescue (Festuca ovina) become common (Cooper et al., 1999). Diverse crustose and foliose lichen cover is often high on exposed rocks. Fern allies such as lesser spikemoss (Selaginella densa) can be locally abunant in some areas.

Adjacent to this system is a mosaic of alpine plant communities that vary in composition depending on soil development, snow retention, subterranean hydrology and localized topography. Alpine turf and snow bed communities occur on more level or concave sites with greater soil development adjacent to fell-fields. Alpine bedrock, talus and unstable scree fields and ice fields often occur adjacent to this system around mountain summits. Fell-fields are often bordered by subalpine forest krummolz mats and small patches of subalpine forests growing at their upper elevational limit on protected sites. The most common forest association in Montana is whitebark pine-subalpine fir (Pinus albicaulis-Abies lasiocarpa). In scattered locations on north and east facing aspects, fell-fields can be bordered by small patches of alpine larch (Larix lyallii).