Montana Field Guide

This group occurs in the alpine zone and near the treeline in the upper subalpine zone in most of the higher elevation mountain ranges of Montana. The vegetation in this group is generally dominated or composed of a semi-continuous layer of low-growing shrubs including dwarf shrubs and subshrubs as well as krummholz communities. The elevations of these sites range from as low as 6,000 feet in northwestern Montana to 10,500 feet in southwestern Montana. As this group encompasses a variety of communities, site factors such as topographic position, slope, aspect, moisture conditions, parent material and soil characteristics are variable. Communities may be dominated by heath-like, ericaceous, dwarf-shrubs, others by subshrubs in fellfield or turflike conditions, by krummholz communities or rarely by other short-statured shrubs.
Sites dominated by Avens (Dryas) are typical of exposed, drier fellfields on ridges and saddles, while those dominated by dwarf willows vary from fellfield to turf-like communities. Mountain heather and heath communities often occur on level or concave glacial topography with late-lying snow and subirrigation from surrounding alpine slopes. The low shrub communities may form a dense, heath type ground cover less than 0.5 meters (1.6 feet) in height, communities dominated by dwarf-shrubs in fellfield-like habitats or as patches of low-growing shrubs. Some communities within this group are very similar to G314 - Alpine Turf and Fellfields except that they are dominated by dwarf shrubs instead of herbaceous species.

This Group is equivalent to the Alpine Dwarf-Shrubland Ecological System as well as krummholz communities included in the Rocky Mountain Subalpine Woodland and Parkland, and the Spruce-Fir Forest and Woodland Ecological Systems.

Alpine Zone; Vegetation Cover >15%; Dwarf Shrubs, Subshrubs, Krummholz; Short Growing Season; Timberline; Fellfield, Turf and Snowbed Communities.

This group occurs in the higher elevation mountain ranges in Montana that have vegetated, alpine areas above treeline, including the island mountain ranges of central and south-central Montana.

In Montana, G316 is confined to areas within or immediately adjacent to Level IV Ecoregions 15h (High Northern Rockies), 16h (High Idaho Batholith), 17h (Middle Rockies Alpine Zone) and 41b Canadian Rockies Crestal Alpine-Subalpine Zone.

In Montana, G316 occurs within these Major Land Resource Areas: 43A-Northern Rocky Mountains and 43B-Central Rocky Mountains.

Small Patch and Large Patch

This group occurs in the alpine zone and along the treeline in the upper subalpine zone on various topography depending on the specific vegetation community. The elevation ranges from as low as 6,000 feet in northwestern Montana to 10,500 feet in southwestern Montana. The climate is very cold, with heavy snow accumulation and a very short growing season (60 to 90 days). As this group encompasses a variety of communities, site factors such as topographic position, slope, aspect, moisture conditions, parent material and soil characteristics are variable. Sites dominated by Avens (Dryas) are typical of exposed, drier fellfields on ridges and saddles, while those dominated by dwarf willows vary from fellfield to turf-like communities. Mountain heather and heath communities often occur on level or concave glacial topography with late-lying snow and subirrigation from surrounding alpine slopes. These sites are often characterized as snowbed communities, which form in concave, depressional areas that retain snow until mid to late summer and can occur on all aspects but are most common on north and east-facing aspects. Here, the soil temperatures remain colder throughout the growing season than on surrounding slopes and aspects. Soils have become relatively stabilized in these sites and are moist but well-drained and often acidic. Krummholz can occur on a variety of sites near timberline on relatively level to steep slopes.

The vegetation in this group is often composed of a semi-continuous layer of low-growing shrubs including dwarf shrubs and subshrubs as well as krummholz communities. The low shrub communities may take the form of a dense, heath type ground cover less than 0.5 meter (1.6 feet) in height, communities dominated by dwarf-shrubs in fellfield-like habitats, or as patches of low-growing shrubs on alpine slopes. The drier sites are similar to fellfield communities but have a relative dominance of dwarf shrubs. Some windswept and drier sites that are fellfield-like may be dominated by or have a relatively high coverage of Eight-petal Mountain-avens (Dryas hookeriana). The dwarf willows, Arctic willow (Salix arctica) and Net-veined Willow (Salix reticulata) are the relative dominants in dry to mesic sites that are similar to turf and fellfield communities of G314. The ericaceous heaths or mountain heathers (Cassiope mertensiana, Cassiope tetragona, Phyllodoce empetriformis, Phyllodoce glanduliflora) form heath type ground covers or patches in areas near timberline to areas higher in the alpine. Other shrubs that may be found as components of this group include Kinnikinnick (Arctostaphylos uva-ursi) on dry fellfield-like sites, Shrubby Cinquefoil (Dasiphora fruticosa, syn. Potentilla fruticosa), Alpine Bog Laurel (Kalmia microphylla) on mesic sites, Ribes montigenum, Salix vestita, and Grouse Whortleberry (Vaccinium scoparium).

In contrast to the low shrub dominated communities, the Krummholz communities within this group are dominated by stunted trees at timberline, formed by the harsh climate at these high elevations. Communities of this type form a mosaic of dense patches of matted, dwarfed, evergreen conifer trees usually less than 6 feet (2 meters) tall, occasionally with scattered, short, upright trees among the mats. In Montana, Subalpine Fir (Abies lasiocarpa), Engelmann Spruce (Picea engelmannii), and Whitebark Pine (Pinus albicaulis) are the primary krummholz-forming species.

Various alpine forbs and graminoids occur within these communities as scattered individuals or forming patches in a mosaic with the low shrub and krummholz communities. Frequent species include Showy Sedge (Carex spectabilis), Shortstalk Sedge (Carex podocarpa), Rocky Mountain Sedge (Carex scopulorum), Carex nigricans, Hitchcock’s woodrush (Luzula glabrata var. hitchcockii) and Piper’s woodrush (Luzula piperi). Forbs such as Alpine Pussytoes (Antennaria species), Arnica (Arnica species), Indian Paintbrush (Castilleja species), Glacier Lily (Erythronium grandiflorum), Alpine Saint John’s wort (Hypericum formosum), Luetkea pectinata, Luzula piperi, Oreostemma alpigenum, Pedicularis spp., Polemonium viscosum, Polygonum bistortoides, Polygonum viviparum, Sibbaldia procumbens and Rocky Mountain Groundsel (Packera cymbalarioides). Additional floristic information may be found in: Bamberg (1961), Willard (1963), Bamberg and Major (1968), Lewis (1970), Komarkova (1976, 1980), Zwinger and Willard (1996), Cooper et al. (1997), and Billings (2000).

In Montana, this group is represented by 12 Associations grouped into 5 Alliances. These habitats have been well documented and this likely covers all the types expected to occur within this group in the state.

The fire disturbance interval is typically very long within these communities. Historically, stand-replacing fires occur infrequently in adjacent subalpine woodlands (Arno 1979). Lightning strikes can cause fire within these systems, although severity and spread are usually limited.

This system is especially fragile due to the very limited growing season and limited soil development. Species that occur in these systems are generally slow growing and decrease in cover and vigor in areas of trampling.

K.A. Schulz 2015

S. Mincemoyer, L. Vance, T. Luna

11/25/2024