Print Report

A3176 Salix arctica - Salix nivalis - Salix reticulata Alpine Dwarf-shrubland Alliance

Type Concept Sentence: This alliance is characterized by an open to moderately dense dwarf-shrub layer dominated by Salix arctica, Salix nivalis, Salix petrophila, or Salix reticulata with a typically sparse herbaceous layer composed of a variety of subalpine and alpine indicator species such as Carex nigricans, Geum rossii, and Polygonum bistortoides. It occurs in the alpine zone of the Rocky Mountains and the high plateaus and mountain ranges in the Colorado Plateau and Great Basin.

Common (Translated Scientific) Name: Arctic Willow - Snow Willow - Netleaf Willow Alpine Dwarf-shrubland Alliance

Colloquial Name: Rocky Mountain Willow Alpine Dwarf-shrubland

Hierarchy Level:  Alliance

Type Concept: The vegetation is characterized by an open to moderately dense dwarf-shrub layer dominated by Salix arctica, Salix nivalis, Salix petrophila, or Salix reticulata. The sparse to moderately dense herbaceous layer is variable. Associated species include taxa from moist uplands such as Carex albonigra, Carex phaeocephala, Carex nova, Erigeron peregrinus, Hypericum scouleri, Geum rossii, Packera streptanthifolia, Polygonum bistortoides; wet species such as Caltha leptosepala, Carex nigricans, Parnassia fimbriata, Triantha glutinosa, Trollius laxus, Veronica wormskjoldii; and snowbed indicator species Sibbaldia procumbens. This alliance occurs in the alpine zone of the Rocky Mountains and the high plateaus and mountain ranges in the Colorado Plateau and Great Basin. Stands occur on gentle to steep rocky or gravelly slopes and range in elevation from 2900-4000 m. Landforms that support these communities are typically of gentle topography, with northerly aspects. They occur where snow lingers into the spring and summer, in places such as lees of cliffs and boulders, secondary slopes, and shallow depressions. Some stands also occur on moist gravel slopes and terraces or along stony margins of streams or lakes, thriving among coarse rock margins with almost no soil.

Diagnostic Characteristics: This alliance is characterized by an open to moderately dense shrub layer dominated by diagnostic species Salix arctica, Salix nivalis, Salix petrophila, or Salix reticulata. The sparse to moderately dense herbaceous layer is variable. Associated species include taxa from moist uplands such as Carex albonigra, Carex phaeocephala, Carex nova, Erigeron peregrinus, Hypericum scouleri, Geum rossii, Packera streptanthifolia, Polygonum bistortoides; wet species such as Caltha leptosepala, Carex nigricans, Parnassia fimbriata, Triantha glutinosa, Trollius laxus, Veronica wormskjoldii; and snowbed indicator species Sibbaldia procumbens.

Rationale for Nominal Species or Physiognomic Features: No Data Available

Classification Comments: Stands in the drier Great Basin alpine are typically smaller and patchy. This alliance needs to be compared to those from ~North Pacific Alpine-Subalpine Dwarf-Shrubland & Heath Group (G317)$$ and ~Vancouverian-Rocky Mountain Subalpine-Alpine Snowbed, Wet Meadow & Dwarf-Shrubland Group (G520)$$.

The associations in this alliance dominated by Salix arctica, Salix nivalis, Salix petrophila, and/or Salix reticulata, especially ~Salix arctica - Salix petrophila / Caltha leptosepala Dwarf-shrubland (CEGL001429)$$ and ~Salix reticulata / Caltha leptosepala Dwarf-shrubland (CEGL001435)$$, need further review as stands occur in both well-drained, moist uplands and poorly drained, saturated areas as indicated by the presence of Caltha leptosepala and other wet condition indicator species.

Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: This alliance is characterized by the dominance of a dwarf (<5 cm tall), mat-forming, broad-leaved deciduous shrub. The canopy is typically continuous(>75%). The herbaceous layer is relatively spare (10-25% cover) to moderate (25-60% cover) consisting of forbs, grasses, lichens, and bryophytes.

Floristics: The vegetation is characterized by an open to moderately dense (10-60% cover) dwarf-shrub layer dominated by Salix arctica, Salix nivalis, Salix petrophila, or Salix reticulata. Other dwarf-shrubs, including Kalmia microphylla and Phyllodoce glanduliflora, generally have less than 5% cover and are present in a small fraction of the stands, except for Dryas octopetala, which may be present in the dwarf-shrub layer with up to 20% cover, but does not exceed cover of Salix. The herbaceous layer is variable, ranging from sparse to moderately dense, and is composed of a variety of subalpine and alpine indicator species from moist uplands such as Carex albonigra, Carex phaeocephala, Carex nova, Erigeron peregrinus, Hypericum scouleri, Geum rossii, Packera streptanthifolia, Polygonum bistortoides; wet species such as Caltha leptosepala, Carex nigricans, Parnassia fimbriata, Triantha glutinosa, Trollius laxus, Veronica wormskjoldii; and snowbed indicator species Sibbaldia procumbens. A variety of other associates may present and include Arenaria congesta, Artemisia scopulorum, Astragalus kentrophyta, Carex rupestris, Carex scopulorum, Castilleja occidentalis, Cirsium scopulorum, Claytonia lanceolata, Festuca brachyphylla, Luzula spicata, Minuartia obtusiloba, Oreostemma alpigenum, Oreoxis bakeri, Oxytropis deflexa, Phlox pulvinata, Polygonum viviparum, Potentilla diversifolia, Saxifraga rhomboidea, Silene acaulis, Solidago multiradiata, Tetraneuris grandiflora, Trifolium brandegeei, and Trisetum spicatum. Mosses contributing the most cover include Aulacomnium palustre, Philonotis fontana, and various species of Bryum. Lichens may contribute significant cover to the community.

Dynamics:  No Data Available
Environmental Description:  This alliance occurs in the alpine and upper subalpine zones of the Rocky Mountains and the high plateaus and mountain ranges in the Colorado Plateau and Great Basin. Stands occur on gentle to steep rocky or gravelly slopes and range in elevation from 2000-4000 m. Landforms that support these communities are typically of gentle topography, with northerly or easterly aspects. They occur where snow lingers into late June or early July, in places such as lees of cliffs and boulders, and in moisture-receiving positions such as shallow depressions and the toeslopes and lower to midslopes of gentle terrain where soils remain wet-moist throughout the growing season (Kiener 1967). Some stands also occur on moist gravel slopes and terraces or along stony margins of streams or lakes, thriving among coarse rock margins with almost no soil (Cox 1933, Baker 1983a). The soils are extremely rocky and often show indications of frost action (i.e., unsorted nets, frost-boils). They range from well-drained to poorly drained, saturated substrates that include various sedimentary rock types, both calcareous (limestone) and not (siltstones, argillite).
Geographic Range: This alliance occurs in the alpine and upper subalpine zones of the Rocky Mountains and the high plateaus and mountain ranges in the Colorado Plateau and Great Basin.

Nations: CA,US

States/Provinces:  AB, BC, CO, ID, MT, NM, NV, UT, WY


Confidence Level: Moderate

Confidence Level Comments: No Data Available
Grank: GNR

Greasons: No Data Available
Type Name Database Code Classification Code
Class 4 Polar & High Montane Scrub, Grassland & Barrens Class C04 4
Subclass 4.B Temperate to Polar Alpine & Tundra Vegetation Subclass S12 4.B
Formation 4.B.1 Temperate & Boreal Alpine Tundra Formation F037 4.B.1
Division 4.B.1.Nb Western North American Alpine Tundra Division D043 4.B.1.Nb
Macrogroup 4.B.1.Nb.2 Eight-petal Mountain-avens - Blackroot Sedge - Moss Campion Alpine Tundra Macrogroup M099 4.B.1.Nb.2
Group 4.B.1.Nb.2.a Eight-petal Mountain-avens - Mountain-heath species - Arctic Willow Alpine Dwarf-shrubland & Krummholz Group G316 4.B.1.Nb.2.a
Alliance A3176 Arctic Willow - Snow Willow - Netleaf Willow Alpine Dwarf-shrubland Alliance A3176 4.B.1.Nb.2.a
Association CEGL001429 Arctic Willow - Alpine Willow / White Marsh-marigold Dwarf-shrubland CEGL001429 4.B.1.Nb.2.a
Association CEGL001430 Arctic Willow / Ross'' Avens Dwarf-shrubland CEGL001430 4.B.1.Nb.2.a
Association CEGL001431 Arctic Willow - (Alpine Willow, Snow Willow) / American Bistort Dwarf-shrubland CEGL001431 4.B.1.Nb.2.a
Association CEGL001432 Arctic Willow - Snow Willow Dwarf-shrubland CEGL001432 4.B.1.Nb.2.a
Association CEGL001435 Netleaf Willow / White Marsh-marigold Dwarf-shrubland CEGL001435 4.B.1.Nb.2.a
Association CEGL003143 Arctic Willow - Dwarf Bilberry / Shorthair Reedgrass - Rocky Mountain Pussytoes Dwarf-shrubland CEGL003143 4.B.1.Nb.2.a
Association CEGL005878 Arctic Willow / Black Alpine Sedge Dwarf-shrubland CEGL005878 4.B.1.Nb.2.a
Association CEGL005936 Snow Willow / Ross'' Avens Dwarf-shrubland CEGL005936 4.B.1.Nb.2.a
Concept Lineage: Old alliances included in this alliance are IV.B.2.N.b. Salix (reticulata, nivalis) Dwarf-shrubland Alliance (A.1119) and IV.B.2.N.b. Salix arctica Dwarf-shrubland Alliance (A.1117).

Predecessors: No Data Available

Obsolete Names: No Data Available

Obsolete Parents: No Data Available
Synonomy: No Data Available
Concept Author(s): K.A. Schulz, in Faber-Langendoen et al. (2013)

Author of Description: K.A. Schulz

Acknowledgements: We have incorporated significant descriptive information previously compiled by D. Culver.

Version Date: 03-14-14
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