Print Report
A4343 Arctic Tussock Sedge Tundra Alliance
Type Concept Sentence: This tundra alliance is defined by tussock-forming sedges often in combination with dwarf- or low shrubs developing over continuous, ice-rich permafrost throughout arctic and subarctic Alaska and Canada.
Common (Translated Scientific) Name: Arctic Tussock Sedge Tundra Alliance
Colloquial Name: Arctic Tussock Sedge Tundra
Hierarchy Level: Alliance
Type Concept: This tundra alliance is defined by tussock-forming sedges often in combination with dwarf- and low shrubs occurring in the arctic and subarctic regions of Alaska and Canada. The cottongrass Eriophorum vaginatum is the predominant tussock-former on older landscapes and acidic substrates. Tussock formation may transition to the sedge Carex bigelowii across younger landscapes, disturbance-prone landforms and circumneutral substrates. Carex bigelowii tussock tundra is considered a more productive type relative to mature Eriophorum vaginatum tussock tundra. Eriophorum vaginatum tussock tundra is characterized by high constancy of the dwarf-shrub Vaccinium vitis-idaea and the low shrub Betula nana, with the low shrub Ledum palustre ssp. decumbens and the forb Rubus chamaemorus indicating the type. By comparison, Carex bigelowii tussock tundra is characterized by high constancy of the dwarf-shrubs Salix reticulata, and Cassiope tetragona with the dwarf-shrub Dryas octopetala indicating the type. Where Eriophorum vaginatum and Carex bigelowii both contribute to tussock formation, the low shrub Vaccinium uliginosum and the dwarf-shrub Empetrum nigrum, and the forb Polygonum bistorta, have high constancy, with the shrub Salix pulchra indicating the type. For tussock tundra occurring in wet areas of Alaska''s Arctic Coastal Plain, shrub abundance appears to increase on microtopographic highs such as high-centered polygons. On a broader scale, low-shrub cover appears to increase in tussock tundra with increasing slope, with the occurrence of dwarf-shrubs increasing in the subalpine. The presence of continuous, ice-rich permafrost renders sites cold and poorly-drained. Shallow organics in the intertussock hollows are underlain by silty mineral soils. Patch size is small to matrix-forming.
Diagnostic Characteristics: This tundra alliance is defined by tussock-forming sedges developing over continuous, ice-rich permafrost throughout arctic and subarctic regions of Alaska and Canada.
Rationale for Nominal Species or Physiognomic Features: No Data Available
Classification Comments: Information in Komarkova and Webber (1980), Walker et al. (1994) and Jorgenson (2000) need to be incorporated into this description.
Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: This tundra alliance is represented by dense assemblages of tussock-forming sedges exceeding 20% cover often in combination with dwarf- and low shrubs, bryophytes and lichens. Mesotopographic relief may reach 50 cm from tussock top to hollow.
Floristics: Tussock tundra has >20% cover of sedges in a tussock growth form. Eriophorum vaginatum and Carex bigelowii (to a lesser extent) are the dominant tussock-formers. Eriophorum vaginatum tussock tundra is characterized by high constancy of the dwarf-shrub Vaccinium vitis-idaea and the low shrub Betula nana, with the low shrub Ledum palustre ssp. decumbens and the forb Rubus chamaemorus indicating the type. Sphagnum peatmosses are common in Eriophorum vaginatum tussock tundra and likely contribute to their high moisture and acidity. Within the Sphagnum genus, members of section Acutifolia often occupy hummock tops and sides, whereas members of section Cuspidata occupy the wetter hollows. True mosses such as Dicranum elongatum and Polytrichum strictum are more common on the drier tussock tops, whereas liverworts such as Ptilidium ciliare and Lophozia species are found in the wetter tussock hollows. By comparison, Carex bigelowii tussock tundra is characterized by high constancy of the dwarf-shrubs Salix reticulata, and Cassiope tetragona with the dwarf-shrub Dryas octopetala indicating the type. Here, bryophytes with affinities for more mineral-rich habitats are found, with Tomentypnum nitens and Aulacomnium acuminatum occupying the tussock sides and Aulacomnium turgidum and Calliergon species found in the wetter tussock hollows. Where Eriophorum vaginatum and Carex bigelowii both contribute to tussock formation, the low shrub Vaccinium uliginosum, the dwarf-shrub Empetrum nigrum, and the forb Polygonum bistorta have high constancy, with the shrub Salix pulchra and members of the Pedicularis genus indicating the type. Lichens are present in all tussock types with peak abundance reached at elevation or under more mesic conditions. Characteristic lichen species include Cladonia rangiferina (= Cladina rangiferina), Cladonia arbuscula ssp. mitis (= Cladina mitis), Cladonia stellaris (= Cladina stellaris), Dactylina arctica, Cetraria laevigata, Cetraria islandica, Flavocetraria cucullata, Flavocetraria nivalis, and Thamnolia vermicularis. The presence of shrubs with a more boreal-centric distribution, such as Dryas octopetala, Empetrum nigrum, Vaccinium uliginosum, increase in abundance towards the subarctic.
Dynamics: Permafrost aggradation and degradation, cryoturbation, solifluction and fire are the dominant processes for this alliance. This type, especially sites dominated by Eriophorum vaginatum, are thought to represent a stable, late-successional stage. It is unknown if Carex bigelowii tussock tundra is seral to Eriophorum vaginatum tussock tundra.
Environmental Description: Tussock tundra is common across lowlands, terraces and shallow slopes throughout arctic and subarctic Alaska and Canada. These sites are cold, poorly-drained, with a thin organic layer over silty mineral soils, which are saturated at depth. Sites are underlain by continuous, ice-rich permafrost at depths of 30-50 cm. Patch size is small to matrix-forming.
Geographic Range: This alliance occurs throughout arctic and subarctic Alaska and in western arctic and subarctic Canada. Its distribution in Canada needs review.
Nations: CA,GL,IS,NO,RU,US
States/Provinces: AK, LB, MB, NT, NU, QC, YT
Plot Analysis Summary:
http://vegbank.org/natureserve/ELEMENT_GLOBAL.2.1042181
Confidence Level: Low
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.2 Polar Tundra & Barrens Formation | F031 | 4.B.2 |
| Division | 4.B.2.Xa Arctic Tundra & Barrens Division | D044 | 4.B.2.Xa |
| Macrogroup | 4.B.2.Xa.2 Feltleaf Willow - Eight-petal Mountain-avens - Tussock Cottongrass Tundra Macrogroup | M173 | 4.B.2.Xa.2 |
| Group | 4.B.2.Xa.2.c Arctic Herbaceous Tundra Group | G898 | 4.B.2.Xa.2.c |
| Alliance | A4343 Arctic Tussock Sedge Tundra Alliance | A4343 | 4.B.2.Xa.2.c |
Concept Lineage: No Data Available
Predecessors: No Data Available
Obsolete Names: No Data Available
Obsolete Parents: No Data Available
Synonomy: > Dryado integrifoliae-Caricetum bigelowii (non-acidic moist tussock tundra) (Walker et al. 1994a) [The authors place this association in the Scheuchzerio-Caricetea nigrae class, which typically contains poor to medium fens, based on the Braun-Blanquet method.]
> Eriophorum vaginatum - Betula nana - Ledum decumbens - Vaccinium spp. (Tussock cottongrass - dwarf birch - marsh Labrador tea - blueberry) (Hanson 1953)
> Eriophorum vaginatum - Carex bigelowii - Ledum decumbens - Vaccinium vitis-idaea (Tussock cottongrass - Bigelow''s sedge - marsh Labrador tea - lingonberry) (Hanson 1950)
> Eriophorum vaginatum - Carex bigelowii (Tussock cottongrass - Bigelow''s sedge) (Churchill 1955)
> Eriophorum vaginatum (Tussock cottongrass) (Johnson et al. 1966)
> Sphagno-Eriophoretum vaginati (acidic moist tussock tundra) (Walker et al. 1994a) [The authors place this association in the Oxycocco-Sphagnetea class, which typically contains oligotrophic peatlands (bogs and wet heath), based on the Braun-Blanquet method.]
> Eriophorum vaginatum - Betula nana - Ledum decumbens - Vaccinium spp. (Tussock cottongrass - dwarf birch - marsh Labrador tea - blueberry) (Hanson 1953)
> Eriophorum vaginatum - Carex bigelowii - Ledum decumbens - Vaccinium vitis-idaea (Tussock cottongrass - Bigelow''s sedge - marsh Labrador tea - lingonberry) (Hanson 1950)
> Eriophorum vaginatum - Carex bigelowii (Tussock cottongrass - Bigelow''s sedge) (Churchill 1955)
> Eriophorum vaginatum (Tussock cottongrass) (Johnson et al. 1966)
> Sphagno-Eriophoretum vaginati (acidic moist tussock tundra) (Walker et al. 1994a) [The authors place this association in the Oxycocco-Sphagnetea class, which typically contains oligotrophic peatlands (bogs and wet heath), based on the Braun-Blanquet method.]
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