Common (Translated Scientific) Name: Altai Fescue - White Arctic Mountain-heather Boreal Alpine Tundra Macrogroup
Colloquial Name: Western Boreal Alpine Tundra
Hierarchy Level: Macrogroup
Type Concept: Boreal tundra vegetation comprises this macrogroup. It occurs in high elevations from north-central British Columbia, through Yukon, to Alaska, in areas of continental climate. Typical tundra vascular species include Artemisia arctica, Carex microchaeta, Dryas integrifolia, Festuca altaica, Luzula spicata, Polygonum viviparum, Potentilla diversifolia, Salix phlebophylla, Salix polaris, Salix reticulata, Sibbaldia procumbens, and Silene acaulis. Mosses include Hylocomium splendens, Polytrichum spp., and Stereocaulon spp.; lichens include Flavocetraria nivalis, among others. Tundra encompasses various microsites with different physiognomies from the driest to more mesic: Very dry rocky and wind-blown sites are mostly characterized by sparse vegetation of Dryas integrifolia, Kobresia myosuroides, Oxytropis podocarpa, Potentilla nana, Saxifraga tricuspidata, and Silene acaulis, and lichens such as Flavocetraria nivalis. Drier climate microsites have open graminoid-dominated communities that are characterized by Festuca altaica, Anthoxanthum monticola ssp. alpinum, Carex bigelowii, and Carex microchaeta; other associated vascular species include Artemisia arctica, Festuca brachyphylla, Luzula spicata, Polygonum viviparum, Potentilla diversifolia, and Sibbaldia procumbens. Nonvascular species include Polytrichum spp., and Cladonia spp. Slightly more moist sites with dwarf-shrub alpine heath are dominated by Cassiope mertensiana or Cassiope tetragona with Salix phlebophylla or Salix polaris, or with an ericaceous mix of Vaccinium vitis-idaea, Vaccinium uliginosum, Empetrum nigrum, and Arctostaphylos alpina. Low shrublands with 15-40% cover occur where moisture accumulates, and are mostly dominated by Betula nana, Betula glandulosa, or Salix arctica, with a dense lichen understory, as well as the moss Polytrichum juniperinum. Some of the wettest sites have meadow species, including Aconitum delphiniifolium, Artemisia arctica, Carex macrochaeta, Festuca altaica, Geranium erianthum, Myosotis asiatica, Parnassia fimbriata, Ranunculus occidentalis, Sanguisorba canadensis, Senecio triangularis, Valeriana sitchensis, and/or Veronica wormskjoldii. Lastly, scattered trees or krummholz may occur at the boundary between forest and alpine tundra at lower elevations, and include Abies lasiocarpa, Picea glauca, or Pinus contorta, depending upon the area. Sites occur on gentle to steep slopes (5-50°) on mountaintops and high plateaus of boreal western North America, mostly from 1000-2000 m in elevation but as low as 100 m in Alaska and over 2000 m in British Columbia. The climate is continental, so snowpack tends to be light. The frost-free period is very short; in some locales, frost may occur at any time. Soils are typically shallow, well-drained, and stony, and can be subject to downslope movement, solifluction, and cryoturbation; permafrost can occur. Wind exposure has a strong influence on site conditions by varying exposure, snow depth, and soil moisture. Although this is a very cold climate environment, daylight is long during much of the growing season due to latitude.
Diagnostic Characteristics: Characteristic species include Artemisia arctica, Carex microchaeta, Cassiope tetragona, Dryas integrifolia, Festuca altaica, and Salix reticulata. Further review of these diagnostic species is needed.
Rationale for Nominal Species or Physiognomic Features:
Classification Comments: Arctic Dry-Moist Tundra Macrogroup (M173) presently includes subarctic alpine, which may be difficult to differentiate from the boreal alpine of this macrogroup (M404). Alpine tundra grading into arctic tundra on Alaska's north slope is why M173 includes both. There is insufficient data from Yukon subarctic alpine to compare to the arctic tundra and boreal alpine; at this time, subarctic alpine is included with boreal alpine in Yukon. The compositional similarity of Arctic, subarctic and boreal alpine dwarf-shrub and tussock tundra groups has led us to describe these groups exclusively under M173. Western Boreal Alpine Dwarf-shrubland Group (G613) is retained under M404 as it is distinctly boreal in its distribution (L. Flagstad pers. comm. 2015).
Similar NVC Types:
M099 Rocky Mountain-Sierran Alpine Tundra, note: "occurs on interior mountains to the south in temperate continental climates and has a ""southern"" flora with Dryas octopetala instead of Dryas integrifolia; graminoids include Calamagrostis breweri, Carex elynoides, Carex helleri, Carex filifolia, Carex rupestris, and Kobresia myosuroides; heath species are mostly Phyllodoce empetriformis and Cassiope mertensiana; forbs and dwarf woody plants include Geum rossii, Erigeron peregrinus, Potentilla diversifolia, and Salix nivalis."
M173 Arctic Dry-Moist Tundra, note: "occurs to the north and characterizes Arctic tundra, not boreal alpine, although the alpine of subarctic regions of Alaska grades into the arctic tundra and is included."
M101 Vancouverian Alpine Tundra, note: "occurs on coastal mountains to the west in maritime climate regions and is characterized by alpine heath vegetation with species such as Cassiope mertensiana, Cassiope tetragona, Empetrum nigrum, Harrimanella stelleriana, Luetkea pectinata, Phyllodoce aleutica, Phyllodoce empetriformis, and Phyllodoce glanduliflora."
Physiognomy and Structure: Dwarf woody shrubs with mixed graminoids and perennial forbs; meadows dominated by perennial forbs; sparse vegetation with scattered perennial forbs and cushion plants; some shrublands to 1 m in height.
Floristics: Alpine tundra vegetation characterizes this macrogroup. On sites of average moisture and snow conditions, Salix reticulata and Carex microchaeta dominate, with Artemisia arctica, Festuca altaica, Senecio lugens, Silene acaulis, and some bryophytes, such as Hylocomium splendens, Polytrichum spp., and Stereocaulon spp., and lichens, such as Flavocetraria nivalis (= Cetraria nivalis). At higher elevations, Salix polaris and Flavocetraria nivalis predominate, with some of the species of lower elevations. Drier climate areas or sites are characterized by Festuca altaica and Anthoxanthum monticola ssp. alpinum (= Hierochloe alpina), as well as Carex bigelowii (= Carex consimilis) and Carex microchaeta; other associated vascular species include Artemisia arctica, Festuca brachyphylla, Luzula spicata, Polygonum viviparum, Potentilla diversifolia, and Sibbaldia procumbens. Nonvascular species include Polytrichum spp. and Cladonia spp. In the driest climate areas or in the Rocky Mountains where limestone-influenced soils occur, Dryas integrifolia predominates; Dryas octopetala may also occur in some areas, e.g., Alaska, Yukon, northwestern British Columbia and the Chilcotin area.
Alpine heath occupies snowbed sites. Cassiope mertensiana - Luetkea pectinata heath communities are common in the south; Cassiope tetragona dominates in northern areas, often associated with Salix Polaris, or with an ericaceous mix of Vaccinium vitis-idaea, Vaccinium uliginosum, Empetrum nigrum, and Arctostaphylos alpina. On unstable scree and talus below snowbeds, Oxyria digyna occurs, sometimes associated with Silene acaulis or Carex pyrenaica. Meadows are characterized by Aconitum delphiniifolium, Artemisia arctica, Carex macrochaeta, Festuca altaica, Geranium erianthum, Myosotis asiatica, Parnassia fimbriata or Parnassia kotzebuei, Ranunculus occidentalis, Sanguisorba canadensis, Senecio triangularis, Valeriana sitchensis, and/or Veronica wormskjoldii. Windblown sites are mostly characterized by species such as Dryas integrifolia, Kobresia myosuroides, Oxytropis podocarpa, Potentilla nana, Saxifraga oppositifolia, Saxifraga tricuspidata, Silene acaulis, and lichens such as Flavocetraria nivalis. On high alpine ridges with some snow cover, Silene acaulis dominates, with Artemisia arctica, Luzula spicata, Poa alpina, and Polytrichum spp. On cool aspects, with permafrost, vegetation characterized by Salix reticulata and Dryas integrifolia occurs. Carex membranacea and Saxifraga hirculus can also be found on these sites. They have a deep turfy moss layer of Hylocomium splendens and Rhytidium rugosum.
Low shrublands occur mostly at lower elevations in protected sites. Betula nana or Betula glandulosa is the most common shrub, although Salix arctica can also occur. Associated species include Festuca altaica, Artemisia arctica, Empetrum nigrum, and the feathermosses Hylocomium splendens and Pleurozium schreberi. Scattered trees may occur at lower elevations. Species include Abies lasiocarpa, Picea glauca, or Pinus contorta, depending upon the area.
Dynamics: Elevation, wind, gravity, and ice/frost action are the main factors influencing vegetation development. On the most wind-exposed sites, the wind removes soil and snow and creates extremely difficult environments for plant establishment. By moving snow, wind creates microhabitats of varying snow depths, influencing the length of snow-free periods and soil moisture conditions. Slopes are common and downslope movement of rocks, cobbles, soil and snow affects vegetation development. Freeze-thaw cycles churn the soil, mix organic matter, and sort rocks in the profile and on the ground surface. At the lower elevations, trees can occur and treeline is influenced by wind exposure as well as temperature (frost, growing season). At the highest elevations, vegetation can be mostly lichens on rock with scattered hardy vascular plants. A changing climate will alter the environment at these extremes and influence the vegetation development.
Environmental Description: This macrogroup occurs on gentle to steep slopes (5-50°) on mountaintops and high plateaus of boreal western North America, mostly from 1000-2000 m in elevation but as low as 100 m and as high as 2400 m (vegetation lower elevations range from 1600-2000 m in British Columbia; 600-1500 m in Yukon; 100-1000 m in Alaska). The climate is continental so snowpack tends to be light; the frost-free period is very short; in some locales, frost may occur at any time. Soils are typically shallow, well-drained, and stony, and can be subject to downslope movement, solifluction, and cryoturbation; permafrost can occur. Wind exposure has a strong influence on site conditions by varying exposure, snow depth, and soil moisture. Moist meadow sites can occur on gentle slopes with seepage; soils here are often deeper with considerable organic matter incorporation. Rock, ice and late-persisting snow characterize considerable portions of the landscape adjacent to this type. Although this is a very cold climate environment, daylight is long during much of the growing season due to latitude.
Geographic Range: This macrogroup occurs from interior Alaska, east to the Yukon and western edge of Northwest Territories, and south through the interior mountains of northern British Columbia. It also occurs on some high mountains of the Chilcotin Plateau of west central British Columbia.
Nations: CA, GL?, US
States/Provinces: AK, BC, NT, YT
|US Forest Service Ecoregions (2007)|
Confidence Level: Moderate
Confidence Level Comments:
Synonomy: = Boreal Altai Fescue Alpine Zone (MacKenzie 2005)
>< II.D.1.a - Dryas tundra (Viereck et al. 1992) [Dryas variant and Dwarf-shrub variant]
>< II.D.1.b - Dryas-sedge tundra (Viereck et al. 1992) [Dryas variant]
>< II.D.1.c - Dryas-lichen tundra (Viereck et al. 1992) [Dwarf-shrub - lichen variant]
>< II.D.2.a - Bearberry tundra (Viereck et al. 1992) [Dwarf-shrub variant, Dwarf-shrub - lichen variant, Ericaceous variant]
>< II.D.2.b - Vaccinium tundra (Viereck et al. 1992) [Dwarf-shrub variant, Dwarf-shrub - lichen variant, Ericaceous variant]
>< II.D.2.c - Crowberry tundra (Viereck et al. 1992) [Dwarf-shrub variant, Dwarf-shrub - lichen variant, Ericaceous variant]
>< II.D.2.e - Cassiope tundra (Viereck et al. 1992) [Dwarf-shrub variant and Ericaceous variant]
Concept Author(s): Faber-Langendoen et al. (2014)
Author of Description: D. Meidinger and G. Kittel
Version Date: 29Mar2017
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