Print Report
A3640 Abies lasiocarpa - Picea engelmannii - Pinus flexilis Dry-Mesic Rocky Mountain Krummholz Alliance
Type Concept Sentence: Shrublands at or above treeline in the subalpine zones of the Rocky Mountains and intermountain ranges of the Great Basin dominated by Abies lasiocarpa, Picea engelmannii, and Pinus flexilis singly or in combination.
Common (Translated Scientific) Name: Subalpine Fir - Engelmann Spruce - Limber Pine Dry-Mesic Rocky Mountain Krummholz Alliance
Colloquial Name: Rocky Mountain Dry-Mesic Subalpine Fir - Engelmann Spruce - Limber Pine Krummholz
Hierarchy Level: Alliance
Type Concept: Stands of this alliance are a mosaic of dense patches of dwarfed evergreen conifer trees usually less than 2 m tall. The woody canopy is dominated by stunted Abies lasiocarpa, Picea engelmannii, and Pinus flexilis singly or in combination. Other woody species include shrubs and dwarf-shrubs, such as Kalmia polifolia, Phyllodoce glanduliflora, Ribes montigenum, Salix brachycarpa, Salix glauca, Salix planifolia, Vaccinium membranaceum, and Vaccinium scoparium, that may be present to codominant. The herbaceous layer is sparse under dense shrub canopy, or may be dense where the shrub canopy is open or absent. It is often dominated by mesic or xeric alpine forb and graminoid species, but may include subalpine species, especially in protected areas. Characteristic species may include forbs Antennaria spp., Artemisia scopulorum, Geum rossii, Polemonium pulcherrimum ssp. delicatum, Potentilla diversifolia, Sedum lanceolatum, Sibbaldia procumbens, Thalictrum occidentale, Trifolium dasyphyllum, and graminoids Calamagrostis purpurascens, Carex spp., Festuca brachyphylla, Kobresia myosuroides, Poa spp., and Trisetum spicatum. These dwarf-tree shrublands are a matrix type in the upper treeline areas of the Rocky Mountains and intermountain ranges of the Great Basin. Elevations range from 3600 m in the southern Rocky Mountains down to 2000 m in northern Montana and Alberta. Climate is cold temperate often with heavy winter snow, short cool summers, and windswept most of the year. Sites are nearly level to steeply sloping, often on more mesic northern aspects. Soils are shallow, lithic gravelly or sandy loams typically derived from granite or schist. Rock outcrop is common.
Diagnostic Characteristics: This alliance is distinguished by stunted, shrubby conifers such as Abies lasiocarpa, Picea engelmannii, and Pinus flexilis singly or in combination. Cover may be open to dense. Understories are variable and may be forb- or graminoid-dominated. Understory cover is typically sparse except in canopy gaps.
Rationale for Nominal Species or Physiognomic Features: No Data Available
Classification Comments: This is currently a placeholder alliance for all krummholz vegetation within this ecological group.
Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: These shrublands are dominated by patches of dwarfed, needle-leaved evergreen trees usually less than 2 m in height. Deciduous and evergreen broad-leaved shrubs and dwarf-shrubs may also be present to codominant. Woody canopy cover of these conifer patches is usually dense. The herbaceous layer is sparse under the woody canopy, but may be dense between the shrub patches depending on whether the interstices are wet meadow, dry turf or fell-field. The herbaceous layer may be dominated by perennial graminoids or forbs.
Floristics: Stands are a mosaic of dense patches of dwarfed evergreen conifer trees usually less than 2 m tall. The woody canopy is dominated by stunted Abies lasiocarpa, Picea engelmannii, and Pinus flexilis singly or in combination. Other woody species include shrubs and dwarf-shrubs such as Kalmia polifolia, Phyllodoce glanduliflora, Ribes montigenum, Salix brachycarpa, Salix glauca, Salix planifolia, Vaccinium membranaceum, and Vaccinium scoparium. The herbaceous layer is sparse under dense shrub canopy, or may be dense where the shrub canopy is open or absent. It is often dominated by mesic or xeric alpine forb and graminoid species, but may include subalpine species especially in protected areas. Characteristic species may include forbs Antennaria spp., Artemisia scopulorum, Geum rossii, Polemonium pulcherrimum ssp. delicatum, Potentilla diversifolia, Sedum lanceolatum, Sibbaldia procumbens, Thalictrum occidentale, Trifolium dasyphyllum, and graminoids Calamagrostis purpurascens, Carex spp., Festuca brachyphylla, Kobresia myosuroides, Poa spp., and Trisetum spicatum.
Dynamics: In the harsh windswept environment where these shrublands occur, trees are stunted and flagged from wind damage. The stands or patches often originate when Picea engelmannii colonizes a sheltered site such as the lee side of a rock. Abies lasiocarpa then can colonize in the shelter of the Picea engelmannii, and may form a dense canopy by branch layering (Habeck 1969, Zwinger and Willard 1996). Sexual reproduction and the role of disturbances from frost heaving and small mammal burrows that expose mineral soil need further investigation (Habeck and Choate 1963).
Environmental Description: Elevations range from 3600 m in the southern Rocky Mountains down to 2000 m in the northern Rocky Mountains. Climate is cold temperate often with heavy winter snow, short cool summers, and windswept most of the year. Sites are nearly level to steeply sloping, often on more mesic northern aspects. Soils are shallow, lithic gravelly or sandy loams typically derived from granite or schist. Rock outcrops are common.
Geographic Range: These shrublands occur near treeline in the Rocky Mountains and intermountain ranges of the Great Basin. Stands have only been described from Colorado, Nevada, Utah, Wyoming, Montana, and Alberta, Canada, but likely occur in similar habitat in adjacent states.
Nations: CA,US
States/Provinces: AB, CO, MT, NV, UT, WY
Plot Analysis Summary:
http://vegbank.org/natureserve/ELEMENT_GLOBAL.2.899698
Confidence Level: Low
Confidence Level Comments: No Data Available
Grank: GNR
Greasons: No Data Available
Concept Lineage: A.811
Predecessors: No Data Available
Obsolete Names: No Data Available
Obsolete Parents: No Data Available
Synonomy: >< Mesic Krummholz (Peet 1981)
>< Xeric Krummholz (Peet 1981)
>< Xeric Krummholz (Peet 1981)
- Faber-Langendoen, D., J. Drake, M. Hall, G. Kittel, S. Menard, C. Nordman, M. Pyne, M. Reid, M. Russo, K. Schulz, L. Sneddon, K. Snow, and J. Teague. 2013-2019b. Screening alliances for induction into the U.S. National Vegetation Classification: Part 1 - Alliance concept review. NatureServe, Arlington, VA.
- Habeck, J. R. 1969. A gradient analysis of a timberline zone at Logan Pass, Glacier Park, Montana. Northwest Science 43(2):65-73.
- Habeck, J. R., and C. M. Choate. 1963. An analysis of krummholz communities at Logan Pass, Glacier National Park. Northwest Science 37:165-166.
- Peet, R. K. 1981. Forest vegetation of the Colorado Front Range. Vegetatio 45:3-75.
- Zwinger, A. H., and B. E. Willard. 1996. Land above the trees: A guide to American alpine tundra. Johnson Books, Boulder, CO. 425 pp.